This document discusses various modes of failure for components in industrial power transmission gear drives, including gears, shafts, bearings, and seals. It describes different types of gear failures such as surface fatigue (pitting), wear, plastic flow, and breakage. Pitting is subdivided into initial, destructive, and normal pitting. The document explains the causes and appearances of each failure mode with diagrams and photos. Recommendations are provided for preventing or reducing failures based on their causes.
WPSAmerica.com provides online welding software and services to support various welding codes. Their services offer benefits like savings from using prequalified welding procedures and avoiding costly tests. The software is continuously updated to meet the latest code versions. Practical weld data and expert presentations help users save time and money compared to expensive training courses. The document discusses the scope and applications of the AASHTO/AWS D1.5M/D1.5 Bridge Welding Code.
In a perfect world, there would be zero defects in steel. In the real world, however, with the myriad of steelmaking processes, raw material inputs, numerous finishing lines, and various grades and thicknesses, some imperfections are bound to occur.
Finding, quarantining, and reporting defects helps assure that products are up to the standard our customers and partners expect from us, and keeps the manufacturing world running smoothly. For this reason, quality assurance is a top priority for Pacesetter.
Here are some common flat-roll steel defects we watch out for.
Este documento describe los diferentes tipos de rodamientos y sus aplicaciones. Explica cómo se clasifican los rodamientos por carga, número de hileras y forma de los cuerpos rodantes. Detalla los rodamientos más comunes como los radiales de bolas, de rodillos cilíndricos y cónicos, y oscilantes. Cada tipo se utiliza mejor para soportar cargas radiales, axiales o combinadas en diferentes condiciones.
This document provides a classification and overview of common welding defects. It divides defects into three main categories: planar defects, linear volumetric defects, and non-planar defects. Examples of each type of defect are given. The document also describes specific defect types such as cracks, inclusions, lack of fusion, porosity, overlap, undercut and provides potential causes of each.
Este documento presenta los elementos y símbolos utilizados para representar soldaduras y pruebas no destructivas en planos e ingeniería mecánica. Describe los componentes básicos de un símbolo de soldadura como la posición, longitud, proceso y especificaciones. Luego proporciona ejemplos detallados de símbolos comunes de soldadura, biselado y pruebas no destructivas.
The document discusses various welding defects that can be visually detected, including cracks, lack of solid metal, lack of fusion, lack of smoothly blended surfaces, and miscellaneous defects. It provides details on different types of each defect, their causes, and methods for prevention. It also discusses welding repairs, noting that repairs require authorization and testing to ensure defects have been fully removed before performing the repair weld.
Este documento presenta información sobre soldadura y procesos de soldadura, incluyendo electrodos recomendados para diferentes materiales y aplicaciones. Describe la clasificación y especificaciones de varios electrodos, así como sus propiedades mecánicas y posiciones de soldadura apropiadas. También incluye información sobre cursos de capacitación en soldadura y gases utilizados en procesos de corte y soldadura.
Este documento presenta el catálogo técnico de productos de Reinike Hermanos S.A., una compañía chilena especializada en la fabricación de pernos especiales y productos de maestranza. El catálogo incluye 7 capítulos que describen los servicios, campos industriales, y especificaciones técnicas de pernos, espárragos, tuercas, golillas y otros productos.
WPSAmerica.com provides online welding software and services to support various welding codes. Their services offer benefits like savings from using prequalified welding procedures and avoiding costly tests. The software is continuously updated to meet the latest code versions. Practical weld data and expert presentations help users save time and money compared to expensive training courses. The document discusses the scope and applications of the AASHTO/AWS D1.5M/D1.5 Bridge Welding Code.
In a perfect world, there would be zero defects in steel. In the real world, however, with the myriad of steelmaking processes, raw material inputs, numerous finishing lines, and various grades and thicknesses, some imperfections are bound to occur.
Finding, quarantining, and reporting defects helps assure that products are up to the standard our customers and partners expect from us, and keeps the manufacturing world running smoothly. For this reason, quality assurance is a top priority for Pacesetter.
Here are some common flat-roll steel defects we watch out for.
Este documento describe los diferentes tipos de rodamientos y sus aplicaciones. Explica cómo se clasifican los rodamientos por carga, número de hileras y forma de los cuerpos rodantes. Detalla los rodamientos más comunes como los radiales de bolas, de rodillos cilíndricos y cónicos, y oscilantes. Cada tipo se utiliza mejor para soportar cargas radiales, axiales o combinadas en diferentes condiciones.
This document provides a classification and overview of common welding defects. It divides defects into three main categories: planar defects, linear volumetric defects, and non-planar defects. Examples of each type of defect are given. The document also describes specific defect types such as cracks, inclusions, lack of fusion, porosity, overlap, undercut and provides potential causes of each.
Este documento presenta los elementos y símbolos utilizados para representar soldaduras y pruebas no destructivas en planos e ingeniería mecánica. Describe los componentes básicos de un símbolo de soldadura como la posición, longitud, proceso y especificaciones. Luego proporciona ejemplos detallados de símbolos comunes de soldadura, biselado y pruebas no destructivas.
The document discusses various welding defects that can be visually detected, including cracks, lack of solid metal, lack of fusion, lack of smoothly blended surfaces, and miscellaneous defects. It provides details on different types of each defect, their causes, and methods for prevention. It also discusses welding repairs, noting that repairs require authorization and testing to ensure defects have been fully removed before performing the repair weld.
Este documento presenta información sobre soldadura y procesos de soldadura, incluyendo electrodos recomendados para diferentes materiales y aplicaciones. Describe la clasificación y especificaciones de varios electrodos, así como sus propiedades mecánicas y posiciones de soldadura apropiadas. También incluye información sobre cursos de capacitación en soldadura y gases utilizados en procesos de corte y soldadura.
Este documento presenta el catálogo técnico de productos de Reinike Hermanos S.A., una compañía chilena especializada en la fabricación de pernos especiales y productos de maestranza. El catálogo incluye 7 capítulos que describen los servicios, campos industriales, y especificaciones técnicas de pernos, espárragos, tuercas, golillas y otros productos.
El documento trata sobre el análisis de fractografía de materiales ferrosos. Explica los diferentes tipos de fractura como frágil, dúctil y por fatiga, así como sus características microscópicas y macroscópicas. También describe las causas de cada tipo de fractura y cómo se ven afectadas por las condiciones de carga y el material. Finalmente, detalla el mecanismo y etapas de una fractura por fatiga.
O documento discute os principais defeitos que podem ocorrer no lingotamento contínuo de aço, divididos em defeitos de forma, superficiais e internos. São descritos defeitos como romboidade, convexidade, empeno e suas possíveis causas como problemas no molde, refrigeração ou velocidade de produção."
Este documento proporciona información sobre fracturas en metales. Explica los tres tipos principales de fracturas (frágil, dúctil y fatiga), sus características distintivas y causas. También describe factores que afectan la resistencia de los metales como concentradores de esfuerzo, temperatura y carga aplicada. El documento incluye imágenes que ilustran las características de cada tipo de fractura.
Este manual proporciona información sobre aceros inoxidables y soldadura, incluyendo las ventajas del acero inoxidable, su clasificación, corrosión, soldabilidad y recomendaciones para soldar diferentes tipos. Además, presenta detalles sobre electrodos INDURA para soldadura manual, MIG, TIG y tubular de aceros inoxidables.
O documento descreve uma dissertação de mestrado sobre a caracterização de fases e análise de trincas em junta soldada de Inconel 625 e aço 9Cr-1Mo após envelhecimento térmico. O trabalho caracterizou as fases presentes no Inconel 625 depositado na união após exposição a temperaturas entre 500°C e 700°C por períodos de 10 a 1000 horas, analisando a evolução microestrutural e propriedades.
HOT ROLLING MILL - BILLETS Split ends and cracking problem ANIL KUMAR SHARMA
Several defects can occur during the metal rolling process. Surface defects such as impurities, scale, rust, or dirt are common if adequate surface preparation is not performed before rolling. More serious internal defects like edge cracks, center cracks, and wavy edges can result from improper material distribution in the final product. Other defects include alligatoring, where the material splits during rolling, and cracking or tearing from non-uniform heating of the workpiece in hot rolling. Process parameters like roll bending force, billet movement speed, roller clearance, and alloy composition can also influence defect formation.
Origem de defeitos superficiais em tarugos de aços ao carbono e de baixa ligaJorge Madias
O trabalho revisa o tema dos defeitos superficiais em tarugos de diversas qualidades de aços ao carbono e de baixa liga obtidos por lingotamento com jato aberto ou válvula submersa e lubrificação com azeite ou pó fluxante.
Utiliza-se a observação visual e mediante microscópio estéreo do defeito; o estudo metalográfico; o estudo das variáveis de processo e equipamento que influem na geração dos defeitos; a análise da bibliografia sobre o problema, a evolução do defeito durante a laminação e a influência no produto laminado.
Entre os defeitos superficiais comuns na produção de tarugos, discute-se a porosidade superficial, as trincas transversais, as depressões e trincas longitudinais, a dupla pele, a escória, etc. Recentemente, também se presta atenção à interação entre qualidade superficial, interna e de forma, visando obter uma casca ou camada chill de espessura importante e uniforme.
A identificação precisa das características dos defeitos facilita a compreensão das causas que os originam, permite a aplicação de medidas corretivas certas, e senta as bases para evitar no futuro a recorrência do problema sob novas condições.
This document provides a handbook for visual inspection of welds. It includes sections on visual inspection responsibilities and techniques, definitions and images of common weld defects such as cracks, underfill, burn through, incomplete fusion, roughness, overlap, undersized fillets, incomplete penetration, undercut, corner melt, and end melt. Preventive and corrective actions are provided for each defect. The handbook also includes sections on measuring fillet weld size, types of weld joints, parts of a weld, welding symbols and joint numbering systems. It is intended to provide basic information for visual inspection of welds and is not a replacement for work procedures or other technical documents.
Catalogo sobre ganchos y swivels marca crosby, entre los que se incluyen Ganchos swivels y destorcedores. Todas herramientas y accesorios muy indispensables en la industria
The document summarizes ASME Section VIII Division 1 code requirements for material identification, repair of material defects, Charpy impact testing of production test coupons, weld joint categories, radiographic and ultrasonic examination, welding requirements, and acceptance standards for non-destructive examination. Key points include requirements for original material markings, testing procedures that vary based on joint category and position, examination types based on joint size and material thickness, welder identification, pre-welding surface preparation, and imperfection acceptance criteria.
The document provides an overview of welding inspection. It discusses the roles and duties of welding inspectors, including verifying qualifications and documentation, ensuring proper joint preparation and fit-up, monitoring welding processes, and performing post-weld inspections. It also covers common welding defects, inspection of weld size and shape, and examples of problems that can arise from incorrect joint fit-up such as incomplete fusion or burnthrough. The document aims to give insight into basic welding inspection practices and defect prevention.
Este manual proporciona información sobre diferentes aspectos de la soldadura, incluyendo la identificación de materiales, propiedades de metales y aleaciones, tipos de uniones y posiciones, detalles sobre soldadura con electrodo y procesos TIG y MIG, así como consejos para obtener buenas soldaduras. El manual ofrece una guía básica sobre conceptos y procedimientos clave de la soldadura para apoyar a personas que se dedican a esta actividad.
Steel Making and Rolling (Metalworking): Process & Applications, Rod and Bar...Ajjay Kumar Gupta
The steel industry has taken note of the continued growth in steel imports and a number of projects have been planned and are under implementation.In rolling mills, intermediate steel products are given their final shape and dimension in a series of shaping and finishing operations. Rolling of steel is one of the most important manufacturing processes for steel. It is usually the first step in the processing of steel after it is made and cast either in Ingot or continuous cast product in a steel melting shop.
See more
http://goo.gl/lUUh86
http://goo.gl/fSIHG7
http://goo.gl/4os7IE
http://www.entrepreneurindia.co/
Tags
Business guidance for steel rolling industry, Business Plan for a Startup Business, Business plan for steel rolling mill, Business start-up, Fusion welding processes, Great Opportunity for Startup, Hot rolled steel properties, Hot rolling mill process, Hot Rolling Mill, Hot Rolling mill, Hot Strip Mill, How is Steel Produced, How to Start a Steel Production Business, How to start a successful steel rolling business, How to start steel mill industry, How to Start Steel rolling Industry in India, How to start steel rolling mill, Indian Steel Industry, Industrial steel rolling mill, Modern steel making technology, Most Profitable Steel Business Ideas, New small scale ideas in Steel rolling industry, Opportunity Steel Rolling Mill, Plate Mill, Process & Applications, Process of steelmaking, Profitable small and cottage scale industries, Progress and Prospect of Rolling Technology, Project for startups, Rod and Bar Rolling, Rod and bar rolling, Rolling Metalworking, Rolling Mill for Steel Bars, Rolling process, Setting up and opening your steel rolling Business, Small scale Commercial steel rolling business, Small Scale Steel rolling Projects, Small Start-up Business Project, Start a Rolling Mill Industry, Start steel rolling mill in India, Starting a Steel Business, Starting a Steel rolling Business, Starting Steel Mini Mill, Start-up Business Plan for steel rolling, Startup Project for steel rolling business, Steel and hot rolling Business, Steel Based Profitable Projects, Steel Based Small Scale Industries Projects, Steel business plan, Steel hot rolling process, Steel Industry in India, Steel making and rolling, Steel making Projects, Steel making technology, Steel Making, Steel manufacturing process, Steel mill process, Steel mill, Steel production process, Steel rerolling mill feasibility start up, Steel rolling Industry in India, Steel rolling machine factory, Steel rolling mill industry demand, Steel rolling mill industry overview, Steel rolling mill industry, Steel rolling mill market forecast, Steel rolling mill market growth, Steel rolling mill market, Steel rolling mill size, Steel rolling mill starts production, Steel rolling mill, Steel Rolling Technology, Steelmaking, Steelmaking Processes, Types of rolling mills
1) Analysis of casting data over three months found higher incidence of slivers on some specific casting dates, possibly due to process variability in the plant.
2) Slivers were more common in lower slab widths and at higher ramping positions due to higher surface velocity of steel in the mould in those conditions.
3) Running the electromagnetic brake (EMBR) reduced sliver occurrence compared to when it was off, while higher argon flow induced more turbulence and resulted in more slivers.
O documento discute os tipos de ferro fundido, como são produzidos e classificados. Existem quatro principais tipos: ferro fundido cinzento, branco, maleável e nodular. Cada tipo tem propriedades e usos específicos, como resistência mecânica ou à abrasão, dependendo de sua composição química e tratamento térmico. Os ferros fundidos são normalizados por normas técnicas que especificam suas propriedades mecânicas.
This document discusses common forging defects, their causes, and remedies. It begins by defining forging as a metalworking process that shapes solid metal using compressive forces from dies. The main defects covered are underfilling, mismatch, scale pits, cold shuts, surface cracking, overlapping, and dents. Each defect is explained with diagrams showing potential root causes such as improper die design, incorrect billet temperature, presence of scale, and careless handling. Remedies focus on selecting the proper die design, preheating dies, controlling billet temperature, and improving the forging process. The conclusion emphasizes that defects can originate from issues with materials, design, processing, fabrication, or service conditions, and proper investigation is needed to
O documento discute os principais elementos de fixação e transmissão em máquinas, como pinos, cavilhas, rebites, roscas, parafusos, porcas, arruelas, molas, mancais e eixos. O objetivo é fornecer conhecimentos sobre esses componentes para que profissionais de manutenção possam executar suas atividades de forma eficiente e segura.
1) O documento descreve as etapas básicas do processo de fundição por areia, incluindo a preparação do molde e vazamento do metal.
2) Inclui também informações sobre os diferentes tipos de modelos usados no processo de fundição e seus respectivos materiais e características.
3) Finalmente, discute inovações recentes no setor de fundição, como a prototipagem rápida e softwares de simulação do processo.
This document provides a 10-step overview of the cold rolling process for steel in a 4 Hi mill. The key steps include: 1) Pickling the hot rolled coil to remove impurities, 2) Water washing, 3) Applying a rust-protective emulsion, 4) Sizing coils to an ideal diameter for rolling, 5) Cold rolling the steel through multiple passes to reduce thickness, 6) Annealing to improve strength, 7) A final "skin pass" rolling, 8) Slitting coils to customer specifications, 9) Applying a protective coating, and 10) Packaging the finished cold rolled steel for shipping. The cold rolled steel can be used for automotive and appliance manufacturing.
Este manual fornece informações técnicas sobre os produtos de aço da Gerdau, incluindo faixas de bitolas produzidas, bitolas padrões, tolerâncias dimensionais, composições químicas, propriedades mecânicas, classificações e seleção de materiais.
An investigation and rectification on failure of bearings of casting shakeout...eSAT Journals
Abstract This project deals with investigation and rectification on failure of bearing of casting shakeout, required in foundry industries to separate solidified casting and sand from mould box. The failure of bearings is mainly due to brinelling tends to create cavities on the bearing raceway. This result in roller and inner races surface of spherical bearing get damage. The rectification of existing system uses four bearings as modified setup of existing system to distribute the load acting on shakeout aims at reducing this frequent breakdown, increases life of bearings and increases the productivity of plant. The software Pro-E wildfire 4 is used for modeling. Keywords: Brinelling, Casting shakeout, Spherical Roller bearing, and Bearing life
This document discusses gear failure analysis. It begins by introducing different types of gears and common failure modes like fatigue, wear, and plastic deformation. Tooth bending and surface contact fatigue are identified as two of the most common fatigue failures. The document then discusses preparing for an inspection, including collecting background information and preserving evidence. Key steps in the inspection process are outlined such as visual examination, measuring gear geometry, and selecting specimens for laboratory testing. Finally, the document analyzes different failure modes in depth, such as bending fatigue, contact fatigue, wear, scuffing, and provides conclusions on preventing gear failure through proper design and alignment.
El documento trata sobre el análisis de fractografía de materiales ferrosos. Explica los diferentes tipos de fractura como frágil, dúctil y por fatiga, así como sus características microscópicas y macroscópicas. También describe las causas de cada tipo de fractura y cómo se ven afectadas por las condiciones de carga y el material. Finalmente, detalla el mecanismo y etapas de una fractura por fatiga.
O documento discute os principais defeitos que podem ocorrer no lingotamento contínuo de aço, divididos em defeitos de forma, superficiais e internos. São descritos defeitos como romboidade, convexidade, empeno e suas possíveis causas como problemas no molde, refrigeração ou velocidade de produção."
Este documento proporciona información sobre fracturas en metales. Explica los tres tipos principales de fracturas (frágil, dúctil y fatiga), sus características distintivas y causas. También describe factores que afectan la resistencia de los metales como concentradores de esfuerzo, temperatura y carga aplicada. El documento incluye imágenes que ilustran las características de cada tipo de fractura.
Este manual proporciona información sobre aceros inoxidables y soldadura, incluyendo las ventajas del acero inoxidable, su clasificación, corrosión, soldabilidad y recomendaciones para soldar diferentes tipos. Además, presenta detalles sobre electrodos INDURA para soldadura manual, MIG, TIG y tubular de aceros inoxidables.
O documento descreve uma dissertação de mestrado sobre a caracterização de fases e análise de trincas em junta soldada de Inconel 625 e aço 9Cr-1Mo após envelhecimento térmico. O trabalho caracterizou as fases presentes no Inconel 625 depositado na união após exposição a temperaturas entre 500°C e 700°C por períodos de 10 a 1000 horas, analisando a evolução microestrutural e propriedades.
HOT ROLLING MILL - BILLETS Split ends and cracking problem ANIL KUMAR SHARMA
Several defects can occur during the metal rolling process. Surface defects such as impurities, scale, rust, or dirt are common if adequate surface preparation is not performed before rolling. More serious internal defects like edge cracks, center cracks, and wavy edges can result from improper material distribution in the final product. Other defects include alligatoring, where the material splits during rolling, and cracking or tearing from non-uniform heating of the workpiece in hot rolling. Process parameters like roll bending force, billet movement speed, roller clearance, and alloy composition can also influence defect formation.
Origem de defeitos superficiais em tarugos de aços ao carbono e de baixa ligaJorge Madias
O trabalho revisa o tema dos defeitos superficiais em tarugos de diversas qualidades de aços ao carbono e de baixa liga obtidos por lingotamento com jato aberto ou válvula submersa e lubrificação com azeite ou pó fluxante.
Utiliza-se a observação visual e mediante microscópio estéreo do defeito; o estudo metalográfico; o estudo das variáveis de processo e equipamento que influem na geração dos defeitos; a análise da bibliografia sobre o problema, a evolução do defeito durante a laminação e a influência no produto laminado.
Entre os defeitos superficiais comuns na produção de tarugos, discute-se a porosidade superficial, as trincas transversais, as depressões e trincas longitudinais, a dupla pele, a escória, etc. Recentemente, também se presta atenção à interação entre qualidade superficial, interna e de forma, visando obter uma casca ou camada chill de espessura importante e uniforme.
A identificação precisa das características dos defeitos facilita a compreensão das causas que os originam, permite a aplicação de medidas corretivas certas, e senta as bases para evitar no futuro a recorrência do problema sob novas condições.
This document provides a handbook for visual inspection of welds. It includes sections on visual inspection responsibilities and techniques, definitions and images of common weld defects such as cracks, underfill, burn through, incomplete fusion, roughness, overlap, undersized fillets, incomplete penetration, undercut, corner melt, and end melt. Preventive and corrective actions are provided for each defect. The handbook also includes sections on measuring fillet weld size, types of weld joints, parts of a weld, welding symbols and joint numbering systems. It is intended to provide basic information for visual inspection of welds and is not a replacement for work procedures or other technical documents.
Catalogo sobre ganchos y swivels marca crosby, entre los que se incluyen Ganchos swivels y destorcedores. Todas herramientas y accesorios muy indispensables en la industria
The document summarizes ASME Section VIII Division 1 code requirements for material identification, repair of material defects, Charpy impact testing of production test coupons, weld joint categories, radiographic and ultrasonic examination, welding requirements, and acceptance standards for non-destructive examination. Key points include requirements for original material markings, testing procedures that vary based on joint category and position, examination types based on joint size and material thickness, welder identification, pre-welding surface preparation, and imperfection acceptance criteria.
The document provides an overview of welding inspection. It discusses the roles and duties of welding inspectors, including verifying qualifications and documentation, ensuring proper joint preparation and fit-up, monitoring welding processes, and performing post-weld inspections. It also covers common welding defects, inspection of weld size and shape, and examples of problems that can arise from incorrect joint fit-up such as incomplete fusion or burnthrough. The document aims to give insight into basic welding inspection practices and defect prevention.
Este manual proporciona información sobre diferentes aspectos de la soldadura, incluyendo la identificación de materiales, propiedades de metales y aleaciones, tipos de uniones y posiciones, detalles sobre soldadura con electrodo y procesos TIG y MIG, así como consejos para obtener buenas soldaduras. El manual ofrece una guía básica sobre conceptos y procedimientos clave de la soldadura para apoyar a personas que se dedican a esta actividad.
Steel Making and Rolling (Metalworking): Process & Applications, Rod and Bar...Ajjay Kumar Gupta
The steel industry has taken note of the continued growth in steel imports and a number of projects have been planned and are under implementation.In rolling mills, intermediate steel products are given their final shape and dimension in a series of shaping and finishing operations. Rolling of steel is one of the most important manufacturing processes for steel. It is usually the first step in the processing of steel after it is made and cast either in Ingot or continuous cast product in a steel melting shop.
See more
http://goo.gl/lUUh86
http://goo.gl/fSIHG7
http://goo.gl/4os7IE
http://www.entrepreneurindia.co/
Tags
Business guidance for steel rolling industry, Business Plan for a Startup Business, Business plan for steel rolling mill, Business start-up, Fusion welding processes, Great Opportunity for Startup, Hot rolled steel properties, Hot rolling mill process, Hot Rolling Mill, Hot Rolling mill, Hot Strip Mill, How is Steel Produced, How to Start a Steel Production Business, How to start a successful steel rolling business, How to start steel mill industry, How to Start Steel rolling Industry in India, How to start steel rolling mill, Indian Steel Industry, Industrial steel rolling mill, Modern steel making technology, Most Profitable Steel Business Ideas, New small scale ideas in Steel rolling industry, Opportunity Steel Rolling Mill, Plate Mill, Process & Applications, Process of steelmaking, Profitable small and cottage scale industries, Progress and Prospect of Rolling Technology, Project for startups, Rod and Bar Rolling, Rod and bar rolling, Rolling Metalworking, Rolling Mill for Steel Bars, Rolling process, Setting up and opening your steel rolling Business, Small scale Commercial steel rolling business, Small Scale Steel rolling Projects, Small Start-up Business Project, Start a Rolling Mill Industry, Start steel rolling mill in India, Starting a Steel Business, Starting a Steel rolling Business, Starting Steel Mini Mill, Start-up Business Plan for steel rolling, Startup Project for steel rolling business, Steel and hot rolling Business, Steel Based Profitable Projects, Steel Based Small Scale Industries Projects, Steel business plan, Steel hot rolling process, Steel Industry in India, Steel making and rolling, Steel making Projects, Steel making technology, Steel Making, Steel manufacturing process, Steel mill process, Steel mill, Steel production process, Steel rerolling mill feasibility start up, Steel rolling Industry in India, Steel rolling machine factory, Steel rolling mill industry demand, Steel rolling mill industry overview, Steel rolling mill industry, Steel rolling mill market forecast, Steel rolling mill market growth, Steel rolling mill market, Steel rolling mill size, Steel rolling mill starts production, Steel rolling mill, Steel Rolling Technology, Steelmaking, Steelmaking Processes, Types of rolling mills
1) Analysis of casting data over three months found higher incidence of slivers on some specific casting dates, possibly due to process variability in the plant.
2) Slivers were more common in lower slab widths and at higher ramping positions due to higher surface velocity of steel in the mould in those conditions.
3) Running the electromagnetic brake (EMBR) reduced sliver occurrence compared to when it was off, while higher argon flow induced more turbulence and resulted in more slivers.
O documento discute os tipos de ferro fundido, como são produzidos e classificados. Existem quatro principais tipos: ferro fundido cinzento, branco, maleável e nodular. Cada tipo tem propriedades e usos específicos, como resistência mecânica ou à abrasão, dependendo de sua composição química e tratamento térmico. Os ferros fundidos são normalizados por normas técnicas que especificam suas propriedades mecânicas.
This document discusses common forging defects, their causes, and remedies. It begins by defining forging as a metalworking process that shapes solid metal using compressive forces from dies. The main defects covered are underfilling, mismatch, scale pits, cold shuts, surface cracking, overlapping, and dents. Each defect is explained with diagrams showing potential root causes such as improper die design, incorrect billet temperature, presence of scale, and careless handling. Remedies focus on selecting the proper die design, preheating dies, controlling billet temperature, and improving the forging process. The conclusion emphasizes that defects can originate from issues with materials, design, processing, fabrication, or service conditions, and proper investigation is needed to
O documento discute os principais elementos de fixação e transmissão em máquinas, como pinos, cavilhas, rebites, roscas, parafusos, porcas, arruelas, molas, mancais e eixos. O objetivo é fornecer conhecimentos sobre esses componentes para que profissionais de manutenção possam executar suas atividades de forma eficiente e segura.
1) O documento descreve as etapas básicas do processo de fundição por areia, incluindo a preparação do molde e vazamento do metal.
2) Inclui também informações sobre os diferentes tipos de modelos usados no processo de fundição e seus respectivos materiais e características.
3) Finalmente, discute inovações recentes no setor de fundição, como a prototipagem rápida e softwares de simulação do processo.
This document provides a 10-step overview of the cold rolling process for steel in a 4 Hi mill. The key steps include: 1) Pickling the hot rolled coil to remove impurities, 2) Water washing, 3) Applying a rust-protective emulsion, 4) Sizing coils to an ideal diameter for rolling, 5) Cold rolling the steel through multiple passes to reduce thickness, 6) Annealing to improve strength, 7) A final "skin pass" rolling, 8) Slitting coils to customer specifications, 9) Applying a protective coating, and 10) Packaging the finished cold rolled steel for shipping. The cold rolled steel can be used for automotive and appliance manufacturing.
Este manual fornece informações técnicas sobre os produtos de aço da Gerdau, incluindo faixas de bitolas produzidas, bitolas padrões, tolerâncias dimensionais, composições químicas, propriedades mecânicas, classificações e seleção de materiais.
An investigation and rectification on failure of bearings of casting shakeout...eSAT Journals
Abstract This project deals with investigation and rectification on failure of bearing of casting shakeout, required in foundry industries to separate solidified casting and sand from mould box. The failure of bearings is mainly due to brinelling tends to create cavities on the bearing raceway. This result in roller and inner races surface of spherical bearing get damage. The rectification of existing system uses four bearings as modified setup of existing system to distribute the load acting on shakeout aims at reducing this frequent breakdown, increases life of bearings and increases the productivity of plant. The software Pro-E wildfire 4 is used for modeling. Keywords: Brinelling, Casting shakeout, Spherical Roller bearing, and Bearing life
This document discusses gear failure analysis. It begins by introducing different types of gears and common failure modes like fatigue, wear, and plastic deformation. Tooth bending and surface contact fatigue are identified as two of the most common fatigue failures. The document then discusses preparing for an inspection, including collecting background information and preserving evidence. Key steps in the inspection process are outlined such as visual examination, measuring gear geometry, and selecting specimens for laboratory testing. Finally, the document analyzes different failure modes in depth, such as bending fatigue, contact fatigue, wear, scuffing, and provides conclusions on preventing gear failure through proper design and alignment.
IRJET- Analysis of Static Load Bearing Capacity of the Ball Bearing – A ReviewIRJET Journal
The document summarizes research analyzing the static load bearing capacity of ball bearings. It discusses using finite element analysis to determine capacity without destructive testing. The research found a linear relationship between the deviation of capacity results from finite element vs practical testing and the bearing size. A linear interpolation equation was developed relating deviation to bearing size. Laboratory testing on bearings of different sizes validated the relationship and showed deformation increasing with load. The research concludes the equation can be used to determine static capacity from bearing size.
This document discusses Flygt's methods for analyzing and dimensioning the rotating systems of pumps and mixers. It focuses on shaft and bearing calculations. Bearings are key components that determine service intervals, so understanding failure factors is important. A correctly dimensioned shaft is also fundamental for smooth operation without issues like fatigue failures or natural frequency disturbances. Complex calculations are needed to model loads, geometries, stresses and lifetimes to create a robust design that can withstand unpredictable conditions. The document outlines Flygt's approaches to failure analysis, modeling, load calculations, stress analysis, and bearing lifetime predictions to enable long-lasting product performance.
Conditioning Monitoring of Ball Bearing Using Vibrational AnalysisIRJET Journal
This document provides an overview of condition monitoring of ball bearings using vibrational analysis. It discusses how ball bearings work and common failure modes. Vibration analysis is explored as a way to identify bearing defects by analyzing vibration signatures from sensors. Signal processing techniques like Fourier analysis are used to extract information from vibration signals and identify distinctive frequencies associated with different defect types. Continuous vibration monitoring allows early identification of defects, enabling prompt maintenance and increasing bearing lifespan.
How black oxide coated bearings can make an impact on cutting o&m costs for w...Mans199
Black oxide-coated bearings can help reduce operating and maintenance costs for wind turbines. Black oxide coating provides benefits like improved corrosion resistance, better performance in low lubrication, and reduced damage from cracking, smearing, and surface distress. Testing by SKF found failure rates of black oxide-coated bearings were 0.1% compared to 40-70% for standard bearings. By extending bearing life, black oxide coating can lower repair and downtime costs for wind turbines.
Different types of gear & maintenance By Md. Raijul IslamMd Raijul Islam
This document provides information about different types of gears and gear maintenance. It begins with an introduction to gears, their functions, and key characteristics. It then describes various types of gears including spur gears, helical gears, bevel gears, worm gears, and others. The document discusses good maintenance practices for gears such as regular inspection and cleaning oil filters. It also outlines different modes of potential gear failure including wear, scoring, pitting, and abrasive wear and their causes and remedies.
Different types of gear & maintenance By Md. Raijul IslamMd Raijul Islam
This document provides an overview of different types of gears and maintenance practices for gear drives. It discusses various gear types including spur gears, helical gears, bevel gears, and worm gears. It also describes common gear failures such as wear, scoring, pitting, and abrasive and corrosive wear. Proper maintenance like routine inspection, cleaning oil filters, and ensuring proper lubrication can prevent failures and extend the life of gear drives. Regular maintenance and preventing overloading of gears are emphasized for optimal gear performance.
Analysis of Bearing and Shaft Failures in Motors.pdfZiad Salem
This document discusses bearing and shaft failures in electric motors. It provides details on bearing stresses, fundamentals, loading principles, lubrication, failure analysis methodology and common failure modes. The key points are:
- Bearing failures account for 50-65% of motor failures, with improper lubrication, contamination, excessive loads and vibration being common causes.
- Proper lubrication and avoiding contamination are critical for bearing life. Grease is most common for small/medium motors, with polyurea greases suitable for higher temperatures.
- A methodology is presented to accurately diagnose bearing failures which considers the failure mode, pattern, appearance, application and maintenance history. The most common failure modes result from fatigue, fret
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
Wear In Hydrodynamic Journal Bearings: A ReviewIJMER
The importance of friction and wear control cannot be overemphasized for economic reasons
and long-term reliability. This paper presents the reviews of different works in the area of wear and
friction in hydrodynamic journal bearings and tries to find out latest developments and trends available in
industries and other fields in order to minimize the total equipment cost, minimize damages and maximize
the safety of machines, structures and materials. This paper helps us to find out the parameters on which a
hydrodynamic journal bearing is selected for different conditions i.e. dry as well as lubricated conditions.
Impact of Bearing Vibration on yarn quality in Ring Frameiosrjce
IOSR Journal of Polymer and Textile Engineering (IOSR-JPTE) is ambitious to disseminate information and experience in education, practice and investigation between polimer, fibric and all the sciences involved in textile.
This document provides information on various repair methods for machine elements and components. It discusses repair techniques for machine beds including riveting and clamping cracks. It also covers repair of slideways through scraping, grinding and machining. Methods for repairing gears, bearings and other components are described. Failure analysis techniques like fault tree analysis and event tree analysis are also summarized.
Review of Fault Detection in Rolling Element BearingAM Publications
Defective bearings are the source of vibrations in machines. Due to constructional features of bearing, they generate
vibrations. As the condition of bearings changes during use, the nature of vibrations also changes and it has a definite
characteristics depending upon the cause. This characteristic feature of bearing makes them suitable for vibration
monitoring. This is a review paper for fault detection technique in rolling element bearing, it covers rolling element
bearing components and its geometry, bearing failure modes, bearing condition monitoring techniques, time domain
and frequency domain techniques.
The document discusses using ultrasound to monitor plain bearings. It begins by introducing plain bearings and their advantages over rolling-contact bearings, such as withstanding shocks and damping vibration. It then discusses using ultrasound to monitor three failure modes in plain bearings: normal operation, hard contamination, and oil starvation. Ultrasound readings can detect these failures by analyzing static ultrasound data across multiple measurement points on the bearing and looking at time waveforms. Ultrasound is presented as an effective technique for condition monitoring of plain bearings.
A mechanical seal is a sealing device which forms a running seal between rotating and stationary parts. They were developed to overcome the disadvantages of compression packing. Leakage can be reduced to a level meeting environmental standards of government regulating agencies and maintenance costs can be lower.
Development of Process for Replacement of Mill RollerIRJET Journal
1) The document describes a numerical analysis conducted using ANSYS software to study the separation conditions for shrink fitting of an existing mill roller.
2) A 3D model of the mill roller shaft and shell was created in ANSYS based on technical drawings. Mesh refinement was performed to improve mesh quality metrics like skewness and orthogonal quality.
3) The analysis involves cooling the shaft to -10°C and heating the shell to 400°C, then determining the temperatures at which the shrink fitting is released to separate the assembly. Results will be validated using analytical methods.
Study on Hard Shifting of Gears in Transmission Box Assembly and Analysis of ...IRJET Journal
This document summarizes a study on hard shifting of gears and abnormal noise from the transmission box of four-wheeler vehicles under varying loads and speeds. The study found that hard shifting and a "kat-kat" noise were caused by worn synchronizer rings in the transmission. Replacing the synchronizer rings resolved the issues. Improper driving techniques like shifting gears at inappropriate times can accelerate wear and lead to transmission problems. Maintaining vehicles properly and avoiding water contact with the gear box can extend the life of the transmission components.
IRJET- Optimization Technique of Epicyclic Gear Train and Failure of Gears: A...IRJET Journal
This document reviews optimization techniques for epicyclic gear trains and common failures of gears. It discusses how finite element analysis and optimization tools can be used to optimize gearbox design and reduce weight. Some key points:
- Epicyclic gear trains have advantages like high torque capacity, compact size, and efficiency, but also have challenges like high bearing loads.
- Common gear failures include surface wear, cracking, pitting, and corrosion due to factors like loading, lubrication issues, and material defects.
- Optimization techniques aim to minimize weight and number of components while improving load capacity and efficiency. This includes using finite element analysis to optimize housing design.
- Proper design, material selection, lubrication
IRJET- Review paper on Stator and Rotor Fault Diagnosis of 3-Phase Induct...IRJET Journal
This document reviews methods for diagnosing faults in 3-phase induction motors. It discusses the main types of faults including stator faults, rotor faults, bearing failures, eccentricity, and mechanical vibrations. Various techniques are presented for fault detection such as vibration analysis, current and voltage monitoring, temperature measurements, and spectral analysis. The review emphasizes the need for effective fault diagnosis methods to improve reliability and prevent catastrophic motor failures.
Similar to failure-analysis-gears,-shafts,-bearings,-seals-maintenance-manual (20)
DEEP LEARNING FOR SMART GRID INTRUSION DETECTION: A HYBRID CNN-LSTM-BASED MODELijaia
As digital technology becomes more deeply embedded in power systems, protecting the communication
networks of Smart Grids (SG) has emerged as a critical concern. Distributed Network Protocol 3 (DNP3)
represents a multi-tiered application layer protocol extensively utilized in Supervisory Control and Data
Acquisition (SCADA)-based smart grids to facilitate real-time data gathering and control functionalities.
Robust Intrusion Detection Systems (IDS) are necessary for early threat detection and mitigation because
of the interconnection of these networks, which makes them vulnerable to a variety of cyberattacks. To
solve this issue, this paper develops a hybrid Deep Learning (DL) model specifically designed for intrusion
detection in smart grids. The proposed approach is a combination of the Convolutional Neural Network
(CNN) and the Long-Short-Term Memory algorithms (LSTM). We employed a recent intrusion detection
dataset (DNP3), which focuses on unauthorized commands and Denial of Service (DoS) cyberattacks, to
train and test our model. The results of our experiments show that our CNN-LSTM method is much better
at finding smart grid intrusions than other deep learning algorithms used for classification. In addition,
our proposed approach improves accuracy, precision, recall, and F1 score, achieving a high detection
accuracy rate of 99.50%.
Gas agency management system project report.pdfKamal Acharya
The project entitled "Gas Agency" is done to make the manual process easier by making it a computerized system for billing and maintaining stock. The Gas Agencies get the order request through phone calls or by personal from their customers and deliver the gas cylinders to their address based on their demand and previous delivery date. This process is made computerized and the customer's name, address and stock details are stored in a database. Based on this the billing for a customer is made simple and easier, since a customer order for gas can be accepted only after completing a certain period from the previous delivery. This can be calculated and billed easily through this. There are two types of delivery like domestic purpose use delivery and commercial purpose use delivery. The bill rate and capacity differs for both. This can be easily maintained and charged accordingly.
Advanced control scheme of doubly fed induction generator for wind turbine us...IJECEIAES
This paper describes a speed control device for generating electrical energy on an electricity network based on the doubly fed induction generator (DFIG) used for wind power conversion systems. At first, a double-fed induction generator model was constructed. A control law is formulated to govern the flow of energy between the stator of a DFIG and the energy network using three types of controllers: proportional integral (PI), sliding mode controller (SMC) and second order sliding mode controller (SOSMC). Their different results in terms of power reference tracking, reaction to unexpected speed fluctuations, sensitivity to perturbations, and resilience against machine parameter alterations are compared. MATLAB/Simulink was used to conduct the simulations for the preceding study. Multiple simulations have shown very satisfying results, and the investigations demonstrate the efficacy and power-enhancing capabilities of the suggested control system.
Rainfall intensity duration frequency curve statistical analysis and modeling...bijceesjournal
Using data from 41 years in Patna’ India’ the study’s goal is to analyze the trends of how often it rains on a weekly, seasonal, and annual basis (1981−2020). First, utilizing the intensity-duration-frequency (IDF) curve and the relationship by statistically analyzing rainfall’ the historical rainfall data set for Patna’ India’ during a 41 year period (1981−2020), was evaluated for its quality. Changes in the hydrologic cycle as a result of increased greenhouse gas emissions are expected to induce variations in the intensity, length, and frequency of precipitation events. One strategy to lessen vulnerability is to quantify probable changes and adapt to them. Techniques such as log-normal, normal, and Gumbel are used (EV-I). Distributions were created with durations of 1, 2, 3, 6, and 24 h and return times of 2, 5, 10, 25, and 100 years. There were also mathematical correlations discovered between rainfall and recurrence interval.
Findings: Based on findings, the Gumbel approach produced the highest intensity values, whereas the other approaches produced values that were close to each other. The data indicates that 461.9 mm of rain fell during the monsoon season’s 301st week. However, it was found that the 29th week had the greatest average rainfall, 92.6 mm. With 952.6 mm on average, the monsoon season saw the highest rainfall. Calculations revealed that the yearly rainfall averaged 1171.1 mm. Using Weibull’s method, the study was subsequently expanded to examine rainfall distribution at different recurrence intervals of 2, 5, 10, and 25 years. Rainfall and recurrence interval mathematical correlations were also developed. Further regression analysis revealed that short wave irrigation, wind direction, wind speed, pressure, relative humidity, and temperature all had a substantial influence on rainfall.
Originality and value: The results of the rainfall IDF curves can provide useful information to policymakers in making appropriate decisions in managing and minimizing floods in the study area.
AI for Legal Research with applications, toolsmahaffeycheryld
AI applications in legal research include rapid document analysis, case law review, and statute interpretation. AI-powered tools can sift through vast legal databases to find relevant precedents and citations, enhancing research accuracy and speed. They assist in legal writing by drafting and proofreading documents. Predictive analytics help foresee case outcomes based on historical data, aiding in strategic decision-making. AI also automates routine tasks like contract review and due diligence, freeing up lawyers to focus on complex legal issues. These applications make legal research more efficient, cost-effective, and accessible.
Introduction- e - waste – definition - sources of e-waste– hazardous substances in e-waste - effects of e-waste on environment and human health- need for e-waste management– e-waste handling rules - waste minimization techniques for managing e-waste – recycling of e-waste - disposal treatment methods of e- waste – mechanism of extraction of precious metal from leaching solution-global Scenario of E-waste – E-waste in India- case studies.
Software Engineering and Project Management - Introduction, Modeling Concepts...Prakhyath Rai
Introduction, Modeling Concepts and Class Modeling: What is Object orientation? What is OO development? OO Themes; Evidence for usefulness of OO development; OO modeling history. Modeling
as Design technique: Modeling, abstraction, The Three models. Class Modeling: Object and Class Concept, Link and associations concepts, Generalization and Inheritance, A sample class model, Navigation of class models, and UML diagrams
Building the Analysis Models: Requirement Analysis, Analysis Model Approaches, Data modeling Concepts, Object Oriented Analysis, Scenario-Based Modeling, Flow-Oriented Modeling, class Based Modeling, Creating a Behavioral Model.
Digital Twins Computer Networking Paper Presentation.pptxaryanpankaj78
A Digital Twin in computer networking is a virtual representation of a physical network, used to simulate, analyze, and optimize network performance and reliability. It leverages real-time data to enhance network management, predict issues, and improve decision-making processes.
VARIABLE FREQUENCY DRIVE. VFDs are widely used in industrial applications for...PIMR BHOPAL
Variable frequency drive .A Variable Frequency Drive (VFD) is an electronic device used to control the speed and torque of an electric motor by varying the frequency and voltage of its power supply. VFDs are widely used in industrial applications for motor control, providing significant energy savings and precise motor operation.
Prediction of Electrical Energy Efficiency Using Information on Consumer's Ac...PriyankaKilaniya
Energy efficiency has been important since the latter part of the last century. The main object of this survey is to determine the energy efficiency knowledge among consumers. Two separate districts in Bangladesh are selected to conduct the survey on households and showrooms about the energy and seller also. The survey uses the data to find some regression equations from which it is easy to predict energy efficiency knowledge. The data is analyzed and calculated based on five important criteria. The initial target was to find some factors that help predict a person's energy efficiency knowledge. From the survey, it is found that the energy efficiency awareness among the people of our country is very low. Relationships between household energy use behaviors are estimated using a unique dataset of about 40 households and 20 showrooms in Bangladesh's Chapainawabganj and Bagerhat districts. Knowledge of energy consumption and energy efficiency technology options is found to be associated with household use of energy conservation practices. Household characteristics also influence household energy use behavior. Younger household cohorts are more likely to adopt energy-efficient technologies and energy conservation practices and place primary importance on energy saving for environmental reasons. Education also influences attitudes toward energy conservation in Bangladesh. Low-education households indicate they primarily save electricity for the environment while high-education households indicate they are motivated by environmental concerns.
1. CONTENTS
Page
Part 1 Introduction.· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 1
Part 2 Gear Distress and Failure Modes · · · · · · · · · · · · · · 2
Surface Fatigue – Pitting · · · · · · · · · · · · · · · · · · · · 3
– Spalling · · · · · · · · · · · · · · · · · · · 5
Wear · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 6
– Degrees of Wear · · · · · · · · · · · · · 7
– Types of Wear · · · · · · · · · · · · · · · 8
– Miscellaneous Wear Modes · · · · · 9
Plastic Flow · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 10
Breakage · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 11
Failure Associated with Processing · · · · · · · · · · · · · 13
Part 3 Shaft Distress and Failure Modes · · · · · · · · · · · · · 14
Part 4 Anti-Friction Bearing Failures · · · · · · · · · · · · · · · · 16
Part 5 Failure of Contact Oil Seals · · · · · · · · · · · · · · · · · 18
1 - INTRODUCTION
The function of the industrial power transmission gear drive is
to reliably transmit torque and rotary motion between a prime
mover and a driven piece of equipment at acceptable levels of
noise, vibration and temperature. When one or more of the
preceding operating characteristics exceeds allowable limits,
the drive and its application should be examined to determine
the cause of the problem. Gear drive components most
commonly subject to distress are the gears, shafts, bearings
and seals. The purpose of this paper is to describe a number
of distress and failure modes of each of these components
and to indicate probable causes and possible remedies for
these failure modes.
For drives that are properly designed and manufactured,
abnormal distress or failure can result from misapplication or
poor installation or poor maintenance.
Continuous steady state overloads can result from erroneous
initial power requirement calculations, over motoring,
increased output demands, etc. Such loading should be
detectable by motor overheating or from electrical meter
readings on the driving motor.
Momentary or transient peak loads are of such short duration
that electrical meters do not respond accurately to them. In
such cases torquemeter readings of instantaneous loads, as
shown in Figure 1.1 may be necessary to determine actual
torque loads.
Rexnord Industries, LLC, Gear Group 108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131 August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.com Replaces 690801
Failure Analysis • Installation & Maintenance
Gear – Shafts – Bearings – Seals (Page 1 of 20)
ZERO TORQUE
ZERO TORQUE
RUNNING TORQUE VARIATION
LESS THAN 5%TIME
PEAK TORQUE
RUNNING TORQUE
=7.0
PEAK TORQUE
RUNNINGSTARTING
HIGH TORQUE STARTING - UNIFORM LOAD
TORQUE
RUNNING TORQUE
VARIATION LESS
THAN 5%
TIME
PEAK TORQUE
RUNNING TORQUE
=1.2
PEAK TORQUE
TORQUE
EASY STARTING UNIFORM LOAD
RUNNINGSTARTING
FIG. 1.1 (253-2) TORQUE METER RECORD
FIG. 1.2 (253-1) TORQUE METER RECORD
TORQUE
TORQUE
TIME
RESILIENT COUPLINGNON-RESILIENT COUPLING
TIME
TYPICAL TORQUE IN STEEL MILL DRIVE
FLUCTUATING LOAD-TWO CYLINDER GAS COMPRESSOR
TORQUE
ZERO TORQUE
TIME
FAILURE ANALYSIS
GEARS-SHAFTS-BEARINGS-SEALS
2. Vibratory loads, or system dynamic loads depend on the
interrelation of the components in the entire system with one
another and torquemeter readings or a study of the system is
required to assess instantaneous loads. From properly
obtained torquemeter readings, see Figure 1.2, the load
characteristics of the system can be determined including
steady state loads, peak loads, accelerating loads, reversing
and vibratory loads and other dynamic effects that may exist.
Once the nature of the load within a system has been
established, the manner in which the load affects each of the
drive components must then be assessed.
Unexpected environmental conditions affecting gear drive
performance can be grouped into three categories:
1 – ambient temperature, either high or low
2 – airborne abrasive material
3 – corrosive materials of gaseous, liquid or solid form
Ambient temperatures that are too high may result in lube
temperatures so high that ineffective oil films are formed,
while too low a temperature may thicken oil so much that flow
is restricted and certain parts may be starved of lubricant. In
either case, abnormal wear may result. Ingress of airborne
abrasive material can cause premature bearing failure,
abnormal gear wear and can damage shaft journals for oil
seals. Infiltration of corrosive gases, liquids (including water)
or solids can result in corrosive chemical reactions on bearing,
gear and seal contact surfaces that can cause premature
failure or abnormally high wear rates.
Last but not least, installation, care and maintenance
procedures can influence gear drive performance. Units
improperly installed or maintained can result in such things as
poor tooth contact, preloaded bearings, damaged bearings
and improper or poor lubrication and lubrication leakage.
A gear drive is one part of a power system which has certain
load characteristics peculiar to the specific application. The
gear drive package itself is a subsystem within the overall
system and in addition to transmitting the load demands of the
overall system, it is subject to additional load variations
generated or contained within itself.
The elastic deflection of the gears, shafts, bearings and their
supporting structures determine to a large degree the manner
in which mating gears will be aligned to one another under
operating loads. These deflections along with manufacturing
tolerances result in loads being non-uniformly distributed
across the gear tooth surface, thus stressing some areas of the
tooth more highly than others. In the AGMA rating formulas,
which are in wide use today, this effect is recognized by the
incorporation of a load distribution factor, designated Cm or
Km. The numerical value of this factor is the ratio of the
maximum load intensity on the tooth to the load intensity for a
uniformly distributed load. Figure 1.3 shows several contact
patterns that might be observed on loaded teeth. Load
intensity diagrams along with values of load distribution
factors are shown for each case. Other more complex intensity
distributions often prevail, but for most well designed gear
sets, the load distribution factors vary from 1.2 to 1.7.
The AGMA rating formulas also recognize a tooth loading
effect which is velocity dependent, but is largely independent
of the system transmitted load. It is the dynamic impact
loading a tooth encounters as it picks up its share of the load
as it enters the zone of tooth action at the mesh. The AGMA
formulas account for the usual accuracies of today’s
manufacturer, but if exaggerated errors are present, from
whatever cause, dynamic loads can be a source of tooth
surface distress or tooth fracture.
2 — GEAR DISTRESS AND FAILURE MODES
Distress or failure of gears may be classified into four
categories:
1 – surface fatigue (pitting),
2 – wear,
3 – plastic flow
4 – breakage.
The appearance of the various distress and failure modes can
differ between gears that have through hardened teeth and
those that have surface hardened teeth. These differences result
from the different physical characteristics and properties and
from the residual stress characteristics associated with the
surface hardened gearing. Where appropriate, examples of
distress of both through and surface hardened gears are shown
and discussed.
Rexnord Industries, LLC, Gear Group108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.comReplaces 690801
Installation & Maintenance • Failure Analysis
(Page 2 of 20) Gear – Shafts – Bearings – Seals
FF/2
TIP
PITCH
LINE
ROOT
K = 4.0K = 2.0K = 1.2
SHADED AREA IS PROFILE CONTACT
F F
1
2
3
4
1
2
3
4
1
2
3
4
ACTUAL LOAD
DISTRIBUTION
ACTUAL LOAD
DISTRIBUTION
ACTUAL LOAD
DISTRIBUTION
UNIFORM LOAD
DISTRIBUTION UNIFORM LOAD
DISTRIBUTION
UNIFORM LOAD
DISTRIBUTION
LOADINTENSITY
LOADINTENSITY
LOADINTENSITY
m m m
F
FIG. 1.3 (253-3) CONTACT PATTERNS AND LOAD DISTRIBUTION
ss
z
S =
ó
ó
ó
ó
ó
S
RADIUS OF CURVATURE
OF TOOTH
x
–.393b
x
z
y
y
óx
z
–.25b
4P
b
TENSION
COMPRESSION
A B C
.434b .434b
SHEAR STRESS
AT A=±0.25 S
AT B= 0.30 Scm
cm
cm
cm
b
y
FIG. 2.1 (312-10) HERTZIAN STRESSES
3. FIG. 2.2 (312-6) VARIATION OF STRESS BELOW SURFACE
SURFACE FATIGUE
Surface fatigue is the failure of a material as a result of
repeated surface or sub-surface stresses beyond the endurance
limit of the material. Figure 2.1 indicates the theoretical mutual
Hertzian stresses occurring when a gear and pinion mesh. There
are compressive stresses at the surface and unidirectional and
bi-directional sub-surface shear stresses. Figure 2.2 indicates
the magnitude of these stresses.
PITTING
Pitting is a form of surface fatigue which may occur soon after
operation begins and may be of three types:
1 - initial (corrective)
2 - destructive
3 - normal
INITIAL PITTING is caused by local areas of high stress due to
uneven surfaces on the gear tooth. This type pitting can
develop within a relatively short time, reach a maximum and
with continued service polish to a lesser severity. Initial pitting
shown in Figure 2.3 usually occurs in a narrow band at the
pitchline or just slightly below the pitchline. It is most
prominent with through-hardened gears and is sometimes
seen with surface-hardened gears.
The shape of a classical pit is shown in Figure 2.4. It appears
as an arrowhead pointing in the direction of on coming
contact. Starting at the surface of the tip of the arrowhead, the
fracture proceeded inward at a shallow angle to the surface.
Simultaneously, the crack broadened forming the arrowhead.
The back side of the pit has a steep side. The magnified pit
shown in Figure 2.4 is shown with the remaining portions of
the tooth in Figure 2.5. Although there were several large pits
on the tooth surface, this pitting was corrective since it
progressed no further with continued operation.
For most through-hardened industrial type gears, initial pitting
is considered normal and no remedial action is required.
Where necessary, initial pitting can be reduced by special
tooth finishing means and sometime by a careful break-in at
reduced loads and speeds. In some special critical
applications, teeth are copper or silver plated to prevent or
reduce initial pitting.
Rexnord Industries, LLC, Gear Group 108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131 August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.com Replaces 690801
Failure Analysis • Installation & Maintenance
Gear – Shafts – Bearings – Seals (Page 3 of 20)
0
01.0 0.5
0.5 b
1.0 b
1.5 b
2.0 b
2.5 b
3.0 b
DEPTHBELOWSURFACE
STRESS ALONG x AXIS
STRESS ALONG y AXIS
STRESS ALONG z AXIS
SHEAR STRESS PLANE xy
y
yCONTACT STRESS -
b
y
xx
y
cmS
cmS
FIG. 2.3 (683-2) INITIAL (CORRECTIVE) PITTING
FIG. 2.4 (683-9) INITIAL (CORRECTIVE) PITTING ENLARGED
PHOTO
FIG. 2.5 (697-4) INITIAL (CORRECTIVE) PITTING
4. DESTRUCTIVE OR PROGRESSIVE PITTING on the other hand
usually starts below the pitch line, in the dedendum portion of
the tooth and progressively increases in both the size and
number of pits until the surface is destroyed. Destructive pitting
can appear to be as severe as corrective pitting at the
beginning of operation, however, as time goes on the severity
of destructive pitting sharply increases and far surpasses the
severity of corrective pitting as shown in Figure 2.6. Figure
2.7 illustrates this type pitting on a through-hardened gear.
Figure 2.8 shows destructive pitting of a surface hardened
gear.
Destructive pitting usually results from surface overload
conditions that are not alleviated by initial pitting. If tooth
surface hardness is within specified values, system overloads
are usually the cause of such pitting. To see a finely pitted
gear, with several large pits is no cause for alarm since it can
be of a corrective nature, see Figure 2.9.
NORMAL DEDENDUM PITTING DEDENDUM WEAR) of fully
loaded through-hardened gears manifests itself as small or
modest size pits, covering the entire dedendum portion of the
tooth flanks. Continued operation results in pit rims being
worn away with virtually no further pitting occurring. Figure
2.10 shows the tooth appearance in the pitting phase, prior to
pit rim wear. Figure 2.11 illustrates a dedendum pitted gear
tooth after pit rims have been worn away.
Dedendum pitting results when loads are at or close to maximum
allowable surface loading values. The dedendums are most
vulnerable to this phenomenon because of the preferential
orientation of the surface microcracks along the tooth profile.
Figure 2.12 illustrates this. The orientation of the cracks in the
dedendum of both pinion and gear are such that oil is
Rexnord Industries, LLC, Gear Group108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.comReplaces 690801
Installation & Maintenance • Failure Analysis
(Page 4 of 20) Gear – Shafts – Bearings – Seals
DESTRUCTIVE
PITTING
INITIAL
PITTING
CYCLES
PITTINGSEVERITY
FIG. 2.6 (2342-1C) PITTING SEVERITY
FIG. 2.7 (828-1) DESTRUCTIVE (PROGRESSIVE) PITTING
THRU HARDENED GEARS
FIG. 2.8 (2342-2C) DESTRUCTIVE (PROGRESSIVE) PITTING
FIG. 2.10 (2342-4C) NORMAL DEDENDUM WEAR
5. readily trapped in them as the contact rolls over the surface
openings. These then propagate rapidly into pits by hydraulic
pressure. In the addendum, the oil is forced out of the
microcracks before the contact progresses far enough to seal
the surface openings off, hence hydraulic propagations of the
crack is almost nil and few pits are formed in this region.
At loadings currently used for industrial surface hardened
gears, pitting is much less prevalent than with
through-hardened gears. When it does occur, the appearance
may be similar to that of through-hardened gears, but it often
looks different.
MICRO-PITTING (FROSTING). Figure 2.13 shows a
micro-pitted carburized tooth as it appears to the naked eye
and Figure 2.14 shows the surface and micro-pitting enlarged
430 times. This type of pitting is considered to be normal.
SPALLING
SPALLING is a term used to describe a large or massive area
where surface material has broken away from the tooth. In
through-hardened and softer material, it appears to be a
massing of many overlapping or interconnected large pits in
one locality. See Figures 2.15 and 2.16. In surface hardened
material it manifests itself as the loss of a single or several
large areas of material. The visual pit like attributes are not
observed, see Figure 2.17. Frequently the bottom of the spall
appears to run along the case-core interface.
Spalling is caused by high contact stresses possibly associated
with proud areas of the tooth surface. With surface-hardened
gear teeth, surface or subsurface defects or excessive internal
stresses from improper heat treatment also can cause spalling.
CASE CRUSHING is another form of spalling associated with
heavily loaded case-hardened gears. It appears as long
longitudinal cracks on the tooth surface which may
subsequently break away. It often occurs suddenly, without
Rexnord Industries, LLC, Gear Group 108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131 August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.com Replaces 690801
Failure Analysis • Installation & Maintenance
Gear – Shafts – Bearings – Seals (Page 5 of 20)
FIG. 2.11 (683-i6) NORMAL DEDENDUM WEAR
FIG. 2.12 (2342-5C) TOOTH SURFACE MICROCRACKS
FIG. 2.13 (683-12) MICRO-PITTING (FROSTING)
Driven Gear
Driving Gear
Diagonal microscopic cracks,
with directions as shown, are often
observed on surfaces of gear teeth.
FIG. 2.14 (2342-6C) MICRO-PITTING (ENLARGED PHOTO)
FIG. 2.15 (13-162) SPALLING (THRU HARDENED GEAR)
6. warning signs, on only one or two teeth of the pinion or gear.
The cracks differ from those of pits in that they not only extend
below the hard case, but most of its depth is in the softer core
material. The cracks in the case, generally are perpendicular
to the surface. Figure 2.18 shows an example of this failure
mode. Failure may be due to insufficient case depth,
insufficient core hardness or high residual stresses or too high
loading.
WORM GEAR endurance tests have been performed by Falk
during the past several years. The tests have run to
approximately 20,000 hours and from these tests varying
degrees of surface destruction may be severe when compared
with that of a helical gear, the worm gears nevertheless
survived the test. From this experience we can conclude that
worm wheels incurring this amount of destruction can still
perform satisfactorily. Figures 2.19 and 2.20 illustrate this
surface deterioration.
WEAR
Wear is a general term describing loss of material from the
contacting surface of a gear. There are varying degrees of
wear, which can be measured in terms of thousandths of an
inch, per million or 10 million contact cycles, ranging from
light to moderate to excessive wear.
Rexnord Industries, LLC, Gear Group108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.comReplaces 690801
Installation & Maintenance • Failure Analysis
(Page 6 of 20) Gear – Shafts – Bearings – Seals
FIG. 2.16 (2342-7C) SPALLING (THRU HARDENED GEAR)
FIG. 2.17 (828-2) SPALLING (SURFACE HARDENED GEAR
FIG. 2.18 (2342-8C) CASE CRUSHING
FIG. 2.19 (1169-16) WORM GEAR PITTING)
FIG. 2.20 (596-2) WORM GEAR PITTING)
7. DEGREES OF WEAR
POLISHING OR LIGHT WEAR, Figures 2.21 and 2.22 is the
slow loss of metal at a rate that will little affect satisfactory
performance of the gears within the life of the gears. It is a
normal, very slow wear-in process in which asperities of the
contacting surfaces are gradually worn until very fine, smooth,
conforming surfaces develop. Polishing or light wear can
occur by either abrasive or adhesive mechanisms when thin oil
films or what is known as boundary lubrication conditions
prevail usually on slow speed applications.
MODERATE WEAR, sometimes called normal wear, progresses
at a rate slow enough that it will little affect satisfactory
performance of the gears within their expected life. Tooth
contact patterns indicate that metal has been removed from
the entire tooth surface, but generally more from the
dedendum areas. The operating pitch line begins to show as
an unbroken line. Surface-hardened gears, because of their
high surface hardness manifest less wear than do
through-hardened gears.
The judgment of moderate wear is somewhat subjective
because performance requirements and expectations vary over
the broad spectrum of industrial gear drive applications.
Figure 2.23 illustrate wear observed on gears early in their
operational history. Subsequently, these gears continued in
operation to give years of additional satisfactory service.
Moderate or normal wear depends on the lubrication regime,
the nature of the load, the surface hardness and roughness,
and on the contaminants present in the lubricating oil which
might promote abrasive or corrosive wear. The limitations of
usable oil viscosities and the speed requirements of the
application often dictate that the gears must operate in the
boundary lubrication regime where metal-to-metal contact
occurs and wear takes place.
Moderate wear is normal and usually no remedial action is
required other than normal maintenance of the lube system. If
contaminants are present, filtering or more frequent lube
changes are appropriate.
EXCESSIVE OR DESTRUCTIVE WEAR, see Figure 2.24, is
surface destruction that has changed the tooth shape to such
an extent that smoothness of meshing action is impaired and
life is appreciably shortened. Continued operation results in
still greater wear and may eventually lead to tooth breakage.
Rexnord Industries, LLC, Gear Group 108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131 August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.com Replaces 690801
Failure Analysis • Installation & Maintenance
Gear – Shafts – Bearings – Seals (Page 7 of 20)
FIG. 2.21 (697-7) INITIAL PITTING AND LIGHT WEAR
FIG. 2.22 (2342-9C) POLISHING (SURFACE HARDENED GEAR)
1 YEAR s
4 YEARS s
FIG. 2.24 (747-1) EXCESSIVE WEAR
11/2 YEARS s
FIG. 2.23 (697-10) TYPICAL TOOTH SURFACE APPEARANCE
8. The occurrence of such wear early in the operational history,
can be caused by excessive loads, contaminated oil or too
light an oil viscosity. Excessive wear incurred over a long
period of operational history would be considered an
advancement of normal wear from the moderate to the
excessive degree and may not be detrimental to the operation
of the gear drive.
TYPES OF WEAR
Wear types can be classified in two major categories:
1 - abrasive
2 - adhesive
ABRASIVE WEAR, sometimes called cutting wear occurs when
hard particles slide and roll under pressure, across the tooth
surface. Hard particle sources are: dirt in the housing, sand or
scale from castings, metal wear particles from gear teeth or
bearings, particles introduced into housing when filling with
lube oil and particles infiltrating into unit in service. Figure
2.25 shows abrasive wear of a through-hardened gear caused
by massive loss of hard surface material from tapered bearing
surfaces. Gear teeth surfaces hardened after cutting sometimes
have rough surface that may wear softer mating teeth. Figure
2.26 shows through hardened teeth that were worn away in just
a few hours from the flame-hardened teeth which had rough
surfaces due to a sand blast cleaning operation.
SCRATCHING is a form of abrasive wear, characterized by
short scratch-like lines in the direction of sliding. This type of
damage is usually light and can be stopped by removing the
contaminants that caused it. See Figure 2.27.
ADHESIVE WEAR results from high attractive forces of the
atoms composing each of two contacting, sliding surfaces.
Teeth contact at random asperities and a strong bond is
formed. The junction area grows until a particle is transferred
across the contact interface. In subsequent encounters, the
transferred fragment fractures or fatigues away, forming a
wear particle.
Adhesive wear depends upon the bond strength, which relates
to the physical chemistry of the contact material and lubricant,
on the load and on the material hardness. Figures 2.28 and
2.29 show typical surfaces of through hardened and
surface-hardened gears respectively that have undergone
adhesive wear.
SCUFFING WEAR is the Falk term for an adhesive type wear
occurring at normal temperatures where smooth burnished
appearing radial striations are observed in the direction of
sliding on the tooth surfaces. The texture of lower hardness
through-hardened teeth is more coarse than that of higher
hardness through hardened or surface-hardened teeth, see
Figures 2.28 and 2.29. It can appear where tooth pressures
are high and oil films are in the boundary regime and where
speeds are slow enough that high contact temperatures do not
occur. This type wear can be reduced by increased oil
viscosities where applicable or by reduced load.
Rexnord Industries, LLC, Gear Group108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.comReplaces 690801
Installation & Maintenance • Failure Analysis
(Page 8 of 20) Gear – Shafts – Bearings – Seals
FIG. 2.25 (942-3) ABRASIVE WEAR (THRU HARDENED GEAR)
THRU HARDENED PINIONS(350-390 BHN
RUN AGAINST FLAME HARDENED GEARS
GEAR SANDBLASTED
5 HRS.
.025 WEAR
GEAR SANDBLASTED
50 HRS.
.070 WEAR
FIG. 2.27 (2342-10C) SCRATCHING
FIG. 2.28 (2342-11C) ADHESIVE WEAR (THRU HARDENED GEAR)
FIG. 2.29 (2342-12C) ADHESIVE WEAR (SURFACE
HARDENED GEAR)
FIG. 2.26 (749-1) ABRASIVE WEAR (THRU HARDENED GEAR)
9. SCORING, Figure 2.30, is the smearing and rapid removal
of material from the tooth surface resulting from the tearing
out of small particles that become welded together as a result
of oil film and high temperature metal-to-metal contact in the
tooth mesh zone. After welding occurs, sliding forces tear the
metal from the surface producing a minute cavity in one
surface and a projection on the other. The wear initiates
microscopically, however, it progresses rapidly.
Scoring is sometimes referred to as galling, seizing or scuffing.
The term scoring is preferred.
Scoring most frequently occurs in localized areas on the tooth
where high contact pressure exists or at the tip or root where
sliding velocities, and hence contact temperatures, are high.
This mode of wear is usually associated with high pitch line
velocities and is not common in the lower hardness
through-hardened gears running at normal commercial
speeds.
The direct causes of scoring are high contact temperature and
pressure and marginal lubrication. Scoring can sometimes be
prevented by use of more viscous oil or by an EP type oil.
Localize high contact pressure can be relieved by improved
finishing of tooth surfaces. Sometimes profile or face
modifications are required on highly loaded teeth to minimize
high localized pressures.
WELDING is a hybrid form of scoring and pitting, where pit
cracks are formed on the gear member with pit bodies
subsequently adhering or welding to the pinion member. The
two then run together with the profile formed by the original
involute and the resultant pits bodies and pit cavities, see
Figure 2.31. This phenomena is thought to occur at high load
low speed and at marginal lubrication condition where high
contact temperature prevail, but classical scoring doesn’t
occur. Increased oil viscosities or EP lubricants may help.
Reduced loads will aid. Care must be exercised that axial
displacement of the mating pinion and gear does not occur as
high localized pressure can result from the mismatching of
high and low profile spots which could cause fracture. If
gearing is disassembled and reassembled, the tooth surfaces
should be dressed to remove proud bumps.
MISCELLANEOUS WEAR MODES
WAVY TOOTH WEAR is occasionally observed on gears. Teeth
can be observed to have wavy or undulating surfaces either by
light reflection or by profile and lead checks. The crests and
valleys of the waves usually lie parallel to the inclined lines of
helical contact. See Figure 2.32. This wear pattern is thought
to be caused by vibratory loads occurring in the system in
which the gears are operating.
SURFACE BUMPS are occasionally experienced as shown in
Figure 2.33. The cause of such phenomena has not yet been
defined. As with welding, axial movement could cause
localized high tooth pressures which could fracture teeth. The
tooth surfaces should be dressed to remove proud bumps.
WEAR PADS. Pinion elements of a gear set are frequently
made slightly wider than the gear element. As wear occurs,
unworn pads are left at the tooth ends of the pinion, Figure
2.34. These cause no problem as long as axial positioning of
gears is properly maintained. If unit is disassembled for some
reason and subsequently reassembled, these pads on the ends
of the pinion should be ground flush to the worn surface to
assure that heavy contact, and possible tooth fracture, does
not occur from this source.
Rexnord Industries, LLC, Gear Group 108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131 August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.com Replaces 690801
Failure Analysis • Installation & Maintenance
Gear – Shafts – Bearings – Seals (Page 9 of 20)
FIG. 2.30 (683-1) SCORING
GEAR s
PINION s
FIG. 2.31 (683-13) WELDING (METAL TRANSFER GEAR TO
PINION)
FIG. 2.32(2342-13C) WAVEY TOOTH WEAR
10. FIG. 2.33 (2342-14C) SURFACE BUMPS
FIG. 2.34 (2342-15C) WEAR PADS
FURROWING has been observed on the working tooth
surfaces of coarse textured, low DP, “as hobbed” mill pinion
teeth shortly after being put into service. To the unaided eye, it
appears as a lattice of fine hair lines oriented generally in the
root-to-tip direction. They are aligned in rows across the face
of the tooth in an order consistent with the hobbing texture
pattern, see Figure 2.35.
FIG. 2.35 (2342-16C FURROWING
The cause of furrowing has not been definitely established.
Under the microscope, they appear as round bottom channels
looking as if they were formed by hydraulic erosion. At present
there are no recognized problems emanating from furrowing.
It is thought to be prevented by minimizing localized contact
pressure and by maintaining adequate lube films.
PLASTIC FLOW
Plastic flow is the cold working of the tooth surfaces, caused
by high contact stresses and the rolling and sliding action of
the mesh. It is a surface deformation resulting from the
yielding of the surface and subsurface material, and is usually
associated with the softer gear materials, although it can
occur in heavily loaded case-hardened gears as well.
COLD FLOW occurs when the surface and subsurface
material show evidence of metal flow. Often surface material
has been worked over the tips and ends of the gear teeth,
giving a finned appearance. See Figure 2.36. This is
sometimes called ROLLING or WIRE EDGING. Sometimes the
tooth tips are heavily rounded-over and a depression appears
on the contacting tooth surface. PEENING, another form of
plastic flow as shown in Figure 2.37, is caused by excessive
loading due to impact loading.
FIG. 2.36 (683-6) PLASTIC FLOW (ROLLING)
FIG. 2.37 (683-11) PLASTIC FLOW (PEENING)
Under heavy load, the rolling and peening action of the mesh
cold-works the surface and subsurface material. The sliding
action tends to push or pull the material in the direction of
sliding, if the contact stresses are high enough. The dents and
battered appearance of the surface are a result of dynamic
loading due to operation while the profile is in the process of
deteriorating from a combination of cold-working and wear.
Failures of this type can be eliminated by reducing the contact
stress and by increasing the hardness of the contacting surface
and subsurface material. Increasing the accuracy of
tooth-to-tooth spacing and reducing profile deviations will give
better tooth action and reduce dynamic loads. If the high-
Rexnord Industries, LLC, Gear Group108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.comReplaces 690801
Installation & Maintenance • Failure Analysis
(Page 10 of 20) Gear – Shafts – Bearings – Seals
11. contact stress is caused by mounting deflections or helix-angle
error, these conditions should be corrected.
RIPPLING is a periodic wave-like formation at right angles to
the direction of sliding or motion, Figure 2.38. It has a
fish-scale appearance and is usually observed on surface
hardened gear surfaces, although it can occur on softer tooth
surfaces under certain conditions. Rippling is not always
considered a surface failure, unless it has progressed to an
advanced stage.
FIG. 2.38 (2342-17C) RIPPLING
High contact stresses under cyclic operation tend to roll and
knead the surface causing the immediate Surface material to
ripple. This type of failure is usually associated with slow speed
operation and an inadequate oil film thickness. The
combination of high contact stress, repeated cycles, and an
inadequate lubricating film will produce a rippled surface.
Although rippling can be produced as a wear phenomenon, it
most often is associated with a considerable amount of plastic
flow.
If the gear material is soft, rippling can be prevented by
case-hardening the tooth surface. Also, reduction in contact
stress will reduce the tendency of the surface to ripple. Since
the lubricating film is marginal, an extreme-pressure additive
in the oil and an increase in oil viscosity may be beneficial. An
increase in rubbing speed is sometimes helpful.
RIDGING is the formation of deep ridges by either wear or
plastic flow of surface and subsurface material, Figure 2.39.
It shows definite peaks and valleys or ridges across the tooth
surface in the direction of sliding. Ridging is caused by wear
or plastic flow of surface and subsurface material due to high
contact compressive stresses and low sliding velocities. It is
often present on heavily loaded worm and worm gear
FIG. 2.39 (2342-18C) RIDGING
drives and on hypoid pinion and gear drives. Ridging may
occur on low-hardness materials and may also occur in
high-hardness materials if the contact stresses are high, such
as in case-hardened hypoid gear sets.
Ridging can be prevented by reducing the contact stress,
increasing the hardness of the material, and using a more
viscous lubrication oil with extreme pressure additives. In
drives that do not have circulating systems, it is also helpful to
change the oil often and to ensure that no foreign particles
remain in the lubricant.
BREAKAGE
Breakage is the ultimate type of gear failure. Bending loads
on gear teeth usually cause the highest stresses at the root
fillets and at the tooth profile/root fillet junctions. A gear tooth
is a cantilever plate with tensile stresses on the contact side of
the tooth and compressive stresses on the opposite side. If the
tensile stresses at the critical location are allowed to exceed
the endurance strength of the tooth material, fatigue cracks
will eventually develop and with continued operation, will
ultimately progress to the point where the tooth will break
away from the rim material.
CLASSICAL TOOTH ROOT FILLET FATIGUE FRACTURE is the
most common fatigue breakage mode. It is illustrated in
Figure 2.40. The crack originates at the root fillet on the
tensile side of the tooth and slowly progress to complete
fracture either along or across the tooth. The face of these
fractures are usually characterized by a series of contour lines
or “beach marks” caused by the progressing crack “front”.
They indicate the position of the advancing crack front at a
given time. As the section gradually weakens, the crack
progresses further with each load cycle and the beach marks
become more coarse. The focal point of these marks often
locates the origin of the fracture.
FIG. 2.40 (683-5) TOOTH FRACTURE (ROOT FILLET FATIGUE)
Fatigue fractures result from repeated bending stress above
the endurance limit of the material. If the tooth contact pattern
appears even across the entire face, system overloads would
be suspect. If the contact pattern is confined or “heavy” in the
region of the fracture and at one end of the tooth, an
alignment problem of the gearing would be suspect. When
contact is good, system load must be reduced, or increased
strength rating of the gearing is needed. If contacts indicate
localized loading, gear alignment or face modifications
should be examined.
Rexnord Industries, LLC, Gear Group 108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131 August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.com Replaces 690801
Failure Analysis • Installation & Maintenance
Gear – Shafts – Bearings – Seals (Page 11 of 20)
12. LOW CYCLE FATIGUE OR IMPACT FRACTURES are due to a
low number of high load fatigue cycles or to a single very high
load. Figure 2.41 illustrates such fractures. With lower
hardness, more ductile materials, the fracture face is coarse,
fibrous and torn in appearance. With harder, less ductile
material, the appearance may be smooth or silky looking.
FIG. 2.41 (683-7) TOOTH FRACTURE (LOW CYCLE FATIGUE)
In some cases, a single overload may break out a tooth or
several teeth. A more common occurrence is the plastic
yielding of a group of teeth in one load zone from a high
impact load. The plastic yielding displaces the pitch on this
group of teeth with respect to the other teeth on the gears,
thus subjecting them to abnormally high dynamic loads in
subsequent operation. These teeth then develop very rapidly
progressing fatigue cracks which soon lead to tooth breakage.
This type failure is prevented by protecting the gearing from
high impact or transient loadings. This may involve the use of
controlled torque or resilient couplings in the connected drive
train or it may require better control by the customer at the
process being performed by the driven equipment.
PIT ASSOCIATED FRACTURES occasionally originate in
severely pitted areas since pits can act as stress raisers and
can be crack origins. Figure 2.42 illustrated such a fracture.
FIG. 2.42 (697-9) FATIGUE FRACTURE EMANATING FROM PIT
TOOTH TIP CHIPPING is a fracture mode where the top of a
tooth will break away from lower portion, see Figures 2.43
and 2.44. Failures of this kind may be caused by deficiencies
in the gear tooth, which results in a high stress concentration
at a particular area. Sometimes flaws or minute grinding
cracks will propagate under repeated stress cycling and a
fracture will eventually develop. Foreign material passing
through the gear mesh will also produce short-cycle failure of
a small portion of a tooth. High residual stresses due to
improper heat treatment can cause local fractures that do not
originate in the tooth root section.
FIG. 2.43 (2342-19C) TIP CHIPPING (THRU HARDENED GEAR)
FIG. 2.44 (2342-20C) TIP CHIPPING (SURFACE HARDENED GEAR)
It is difficult to prevent failures of this type except by good
design and manufacturing practices. If trouble is encountered,
the gear surfaces should be checked for possible previous
damage that may have contributed to local stress risers. The
history of heat treatment and manufacturing techniques should
be reviewed to ensure that proper processing was carried out
during all steps of the manufacturing cycle. Cleanliness of the
gear material should also be examined.
WORM WHEEL FRACTURES are occasionally encountered.
Figure 2.45 shows a tooth root-rim fracture on a bolt-on type
worm wheel. Such failures are rare and are indicative of
overloading.
FRACTURE DUE TO FAILURE OF ASSOCIATED PARTS.
Sometimes a severe load maldistribution of load on gear teeth
can occur from damage to associated parts. Figure 2.46
illustrates a pinion run for a time after a severe bearing
failure. Load shifted to one end of the teeth and they
subsequently broke away. The process repeated itself two
more times before the element was finally removed from
service. Similar fractures could occur from shaft that is severely
bent or broken.
Rexnord Industries, LLC, Gear Group108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.comReplaces 690801
Installation & Maintenance • Failure Analysis
(Page 12 of 20) Gear – Shafts – Bearings – Seals
13. FIG. 2.45 (2342-21C) WORM WHEEL TOOTH FRACTURE
FIG. 2.46 (683-14) TOOTH FRACTURE FROM BEARING FAILURE
FAILURES ASSOCIATED WITH PROCESSING
QUENCHING CRACKS can develop with some materials during
heat treatment and after quenching of the gear blank in a
quenching medium. Often these cracks are visible to the naked
eye, Figure 2.47. They may run across the top land of the tooth
or be radial in direction at the ends of the teeth. When these are
found, the material and heat treat specifications should be
reviewed and the processing procedures reexamined.
FIG. 2.47 (2342-22C) QUENCH CRACKS (THRU HARDENED
MATERIAL)
GRINDING CRACKS may form on the gear tooth surfaces due
to process grinding, Figures 2.48 and 2.49. These surface
cracks are usually in a definite pattern or network and often
have the appearance of a series of short cracks laying parallel
to each other. Grinding cracks may also have the appearance
of a chicken wire mesh. The cause may be excessive grinding
pressures or may be a metallurgical structure which is prone to
cracking.
Sometimes grinding cracks are latent and do not show up until
after several hours of shelf life or after operation under load.
When found an examination of the processing procedures is
in order.
FIG. 2.48 (2342-23C) GRINDING CRACKS (ENLARGED)
FIG. 2.49 (2342-24C) GRINDING CRACKS
SUMMARY
In this section, many of the distress and failure modes
encountered with today’s industrial gearing have been
described. The various modes, however, have been treated as
separate entities whereas in actual situations, several modes
are often found together and the reader is advised that the
determination for actual causes may require experienced
experts who are familiar with the subtleties of the gear drive
design and with the load characteristics of the particular
application. The information does, though, provide some
understanding and nomenclature useful in communicating
information regarding specific problems.
Rexnord Industries, LLC, Gear Group 108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131 August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.com Replaces 690801
Failure Analysis • Installation & Maintenance
Gear – Shafts – Bearings – Seals (Page 13 of 20)
14. 3 - SHAFT DISTRESS AND FAILURE MODES
The performance of a gear set is dependent on the shafting
for the gear elements. The shafting must be rigid enough to
prevent excessive deflection that would result in abnormal
load distribution on the gear teeth. The fits between the shafts
and the bearings and between the shaft and the mounted
gears must be proper so that mounted members are not too
loose nor too tight as either condition can contribute to shaft
failure. The shafts must be strong enough to resist permanent
yield from shock loads and they must be strong enough to
resist the reverse bending fatigue loads that are superimposed
on the transmitted torsional loads.
In many cases a careful inspection of the shaft surface and the
face of the fracture will reveal clues as to the probable cause
of failure. When the clues are not obvious, it is helpful to
know the function of the shaft in the drive system and to know
the type of service in order to assess the primary cause of
fracture.
In general, fractures resulting from bending stresses are
perpendicular to the shaft axis, see Figure 3.1, whereas
fracture resulting from fatigue type torsional stresses most
frequently are disposed at a 45° angle to the shaft axis, see
Figure 3.2.
FIG. 3.1 (2342-25C) BENDING FRACTURE
The most common type of shaft fracture encountered with
gear drives is that resulting from the alternating bending stress
that occur as the shaft rotates while transmitting a
unidirectional torque load. The fatigue cracks almost always
start at some stress raiser on the shaft such as sharp cornered
fillets, snap ring grooves, fit corners, fretted areas, key or
keyway ends, or tool or stamp marks.
SYMMETRICAL STRESS RAISERS. In cases where the fracture is
caused by a stress riser that is symmetrical to the axis of the
shaft, several things can be learned about the loading and the
severity of the stress raiser. If the shaft is subjected to a low
nominal stress, the crack usually starts from a single source
and the final fracture area progresses from the surface
towards the center of the shaft. If the shaft is subject to high
nominal stresses, many crack origins are found at the surface
and the final fracture area is also near the shaft center.
The fracture face sometimes reveals the direction of rotation
by noting the location of the final fracture area with respect to
crack origin. The final fracture area is offset from the crack
origin in the direction opposed to the shaft rotation.
FIG. 3.2 (2342-26C) TORSIONAL FRACTURE
Figure 3.3 illustrates three types of shaft fractures. The one
on the left resulted from bending fatigue due to a high stress
raiser at a fillet. Note the many rachet marks around the
periphery at the fillet location indicating multiple crack starts.
The fracture of the center shaft was due to bending fatigue,
essentially having started at one location and propagating to
shaft center when final fracture occurred. The fracture of the
shaft shown on the right was primarily due to torsional fatigue
originating at the left of the keyway, This crack propagated in
the counterclockwise direction, but final fracture, to the right
of the keyway was caused by bending. The small area of the
final fracture zone indicates that the nominal stress was low.
FIG. 3.3 (548-7) SHAFT FRACTURES
KEYS AND KEYWAYS. Some fatigue fractures start from a
combination of stress raisers such as a keyway and the end of
a key. Figure 3.4 shows such a failure. The strength of a
keyed joint is affected by the distribution of the load along the
keyway. The strength of the shaft at the keyway depends on
position of the key in the hub, the accuracy of the key and the
keyway, the geometric shape of the end of the keyway and the
location relative to shaft shoulder fillets and the magnitude of
the interference fit.
Rexnord Industries, LLC, Gear Group108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.comReplaces 690801
Installation & Maintenance • Failure Analysis
(Page 14 of 20) Gear – Shafts – Bearings – Seals
15. FIG. 3.4 (548-1) SHAFT FRACTURE (KEY AND KEYWAY
ASSOCIATED)
FIG. 3.5 (548-6) SHAFT FAILURE (PEELING)
A keyway fracture can be normal to the shaft axis as shown in
Figure 3.4 or it can peel circumferentially as shown in Figure
3.5. This latter type fracture occurs in a loosely fitted joint where
nearly all the torque is transmitted through the key. Fatigue starts
in the bottom of the keyway and progresses around the shaft axis.
TORSIONAL FAILURES. Gear drive shafting failures are seldom
due to pure torsion. However, when they do occur marked
characteristics are exhibited. Torsional cracks may follow
transverse or longitudinal shear planes, or they may follow
diagonal planes of maximum tensile stress and various
combinations of these modes are possible. For this reason
torsional fractures are more complex to analyze than bending
fractures. Fracture due to a single overload in a ductile material
may develop along the longitudinal shear plane, but in a brittle
material the crack may develop on a 45° spiral angle
perpendicular to the principal tensile stress. Torsional fatigue
cracks may grow because of shear or tensile stresses or both.
Figure 3.6 shows a torsional fatigue failure originating at the
keyway and progressing as a result of a reversing torque in the
system due to dynamic effects. The final fracture zone is typical
of a torsional failure occurring along a plane approximately
45° to the axis of the shaft.
FRETTING CORROSION occurs where minute relative
movement of tightly fitted parts occurs such as at bearing,
gear and coupling hub seats. As fretting progresses, minute
cracks form at the surface of the shaft which form stress raisers
which can become origins for fatigue cracks. Figure 3.7
illustrates such a situation. Fits must be designed properly and
manufactured accurately to assure proper fit pressure to
prevent fretting. On taper bore fits, locknuts which hold the
gear in place must be properly torqued.
FIG. 3.6 (548-5) SHAFT FRACTURES
FIG. 3.7 (2342-27C) FRETTING CORROSION
SUMMARY
The successful operation of a shaft can be hampered by the
creation of unexpected stress raisers formed in the processing
of a shaft or during the operation of the gear drive. There may
be other situations where an unexpected dynamic load may be
imposed on the shaft which may be two to three times greater
than the operating load. Situations sometimes occur where
causes for a shaft failure cannot be determined, however it is
expected that experience gained by Falk and others will, in
time, offer better insights into such cases.
Rexnord Industries, LLC, Gear Group 108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131 August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.com Replaces 690801
Failure Analysis • Installation & Maintenance
Gear – Shafts – Bearings – Seals (Page 15 of 20)
16. 4 - ANTI-FRICTION BEARING FAILURES
The selection of bearings is usually based on a specified
bearing life under specific conditions of load. The life is based
on the fatigue resistance of the contacting surfaces. However,
experience indicates that 80% of installed anti-friction
bearings fail to attain their expected service life. Most bearings
fail at an early age for one or more of the following reasons.
1 - corrosion
2 - contamination of the lubricant
3 - overheating
4 - inadequate internal clearance
5 -unexpected vibratory loads
6 - misalignment
7 - inadequate lubrication
There are excellent publications printed by bearing manufacturers
(1) (2) (3) (4) (5)* that illustrate the more common failures.
However, no matter how many pictures of failures are in
existence, it seems that the failure in hand never quite matches,
hence the purpose of this section of the Falk failure paper is to
supplement existing illustrations with failures encountered by Falk.
CORROSION
A bearing can be failed before it is placed into service, if the unit
in which it is mounted is improperly stored prior to installation.
The damage done to a bearing due to corrosion manifests itself
by a surface that appears to be stained. Under magnification, this
area contains a series of pits which serve as a nucleus for a spall
which leads to a complete failure shortly after the unit is placed in
service. Figure 4.1 which is the race of a large thrust bearing
illustrates this type of failure. If a spalled bearing race is not
excessively damaged, it is possible to get a clue as to whether
corrosion was the basic cause by noting if the spalled areas are
spaced approximately the same as the roller spacing. In Figure
4.1 note the definition of the roller spacing.
FIG. 4.1 (2342-28C) FAILURE INDUCED BY CORROSION
CONTAMINANTS IN LUBRICANT
Solid contaminants in the lubricant can produce a denting of
the rollers, balls, or races of a bearing. These dents then
become a stress raiser from which a pit will be formed. See
Figure 4.2.
On some occasions the contaminant in the oil may be very fine
and the oil will have the appearance of silver paint and the races
will experience a lapping severe enough to increase the bearing
clearance by .010 to .020". Under these conditions the shafts will
become misaligned and the bearing cages may break.
The presence of water in the lubricant is not uncommon. The
oil companies indicate that most industrial oils will contain
dissolved water in the range of 50 to 500 parts per million
(ppm). Research data indicates that water accelerated fatigue
takes place when water concentration exceeds 100 ppm which
can reduce bearing life from 30 to 80%. (6) (7)
The effects of contaminants can be minimized by either
preventing the ingress of the contaminant, or by changing oil
at the recommended change intervals.
FIG. 4.2 (2342-29C) DEBRIS DENTING
OVERHEATING AND INTERNAL CLEARANCES
Periodically, on start up, bearings have been reported to run
hot. The overheating can be caused by insufficient internal
clearance or insufficient lubrication. Insufficient clearance is
usually the cause. There have been instances where the
thermal expansion of the bearing elements is greater than the
internal clearances and the bearings will load themselves and
the heat will become intense enough to weld the rollers to the
races as shown in Figure 4.3.
FIG. 4.3 (2342-30C) WELDING OF ROLLERS
Rexnord Industries, LLC, Gear Group108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.comReplaces 690801
Installation & Maintenance • Failure Analysis
(Page 16 of 20) Gear – Shafts – Bearings – Seals
* Numbers in parentheses designate references on page 20.
17. If a ball bearing has run for a period of time with insufficient
internal clearance, there could be a wear band or a series of
bands on the ball as shown in Figure 4.4.
FIG. 4.4 (2342-31 C) BALL BANDING
CAGE BREAKAGE-VIBRATORY LOADS
MISALIGNMENT
Bearing cages guide the rollers or balls in a bearing. They are
usually lightly loaded. However, when a bearing is severely
misaligned or when it is subjected to a vibratory load, or when
the bearing is lightly loaded, the cage can be heavily loaded.
The loads are caused by either the impact forces between the
cage and the rollers, or the forces generated when the balls or
rollers attempt to move out of their prescribed position. Lightly
loaded rollers tend to skew and assume a position
approximately 90° to their operating position.
These loads can cause the cage to break as shown in Figure
4.5. If there are stress raisers present either from the
processing of the cage or from the geometry of the part, the
cage will break at these stress raisers. Figure 4.6 illustrates
the effect that a notch and a reduced section can have on the
cage strength and Figure 4.7 illustrates the cracks present at a
sharp edge that was not removed after machining. In either
case the result is the same, a failed bearing.
FIG. 4.5 (2342-32C) CAGE BREAKAGE
FIG. 4.6 (2342-33C) CAGE BREAKAGE AT NOTCH AND
REDUCED SECTION
FIG. 4.7 (2342-34C) CRACKS IN CAGE FROM NOT REMOVING
SHARP EDGE
FIG. 4.8 (2342-35C) CAGE WEAR AND ROLLER END WEAR
INADEQUATE LUBRICATION
Inadequate lubrication is defined today as either a lack of
lubricant or the inability of the bearing to form an adequate film
thickness. Lubrication damage is characterized by damaged roller
ends and cages. The damage usually manifests itself as cage
wear and wear on the roller ends. See Figure 4.8.
SUMMARY
The failures described here are only a few of the ways that a
bearing can malfunction. If a bearing is properly installed and
maintained and operated under loads for which it was
designed, the bearing should exceed its expected life.
Rexnord Industries, LLC, Gear Group 108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131 August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.com Replaces 690801
Failure Analysis • Installation & Maintenance
Gear – Shafts – Bearings – Seals (Page 17 of 20)
18. 5 - FAILURE OF CONTACT OIL SEALS
Contact oil seals are used in Falk products as shown in Figure
5.1. They are used singularly or in combination with another
seal or sealing media such as grease. The oil seal functions by
either preventing oil from leaking from an enclosed drive or by
preventing the ingress of dirt. The seal consists of a synthetic
component bonded to a steel casing. A spring maintains
pressure on the lip. The seal will malfunction for one or more of
the following reasons, all of which will be explored in this paper.
1 - Damage to seal in handling or mounting.
2 - Hardening and cracking due to heat or chemical
attack.
3 -Improperly prepared or damaged shaft journal.
The shelf life of a seal can be considered indefinite if stored in
accordance with the seal manufacturer’s recommendation. Rarely
has a failure in a Falk product been traced to a deterioration caused
by improper storage or storage for too long a period of time.
FIG. 5.1 (2342-36C) SEAL ARRANGEMENT
CAUSES OF LEAKAGE
CUT SEAL LIP. In the handling and in the mounting of a contact
seal, it is very possible to cut or nick the seal lip as it is slipped
over a burr, keyway or spline. The use of proper mounting tools
as defined by the seal manufacturer will prevent a cut lip. When a
lip is cut, leakage is detected within several minutes after startup.
A typical cut lip is shown in Figure 5.2.
FIG. 5.2 (2342-37C) CUT AND TURNED UNDER LIP
TURNED-UNDER LIP. In mounting a seal, the lip may turn
under due to either an improperly designed or manufactured
lead chamfer. The use of proper mounting tools and
procedures will minimize the occurrence of a turned-under lip.
See Figure 5.2.
DAMAGED SPRING. The spring which maintains pressure on
the seal lip can become damaged or can “pop out” of the
groove provided in the seal. This can occur during the
handling and mounting of a seal, therefore it can be avoided
by exercising care in handling and in mounting the seal.
DAMAGED OR DISTORTED SEAL CASE. A damaged seal
case as shown in Figure 5.3 can be encountered due to
careless handling and mounting. Using care and the proper
mounting tool will prevent this from occurring. A distorted seal
cage can be caused by a seal outside diameter too large for
the bore.
SCORED OUTSIDE DIAMETER OF SEAL CAGE. A seal with a
scored outside diameter may leak around the O.D. This is
usually caused from a burr or other machining imperfection in
the housing bore that receives the seal.
PAINT OR SEALANT ON SHAFT OR SEAL ELEMENT. Paint or
the sealant used on the outside diameter of the seal,
deposited on either the shaft or seal lip, can contribute to
leakage. This can be avoided by the proper masking of the
seal and adjacent shaft before painting and exercising care in
applying the sealant to the outside diameter of the seal.
FIG. 5.3 (2342-38C) DAMAGED SEAL CASE
Rexnord Industries, LLC, Gear Group108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.comReplaces 690801
Installation & Maintenance • Failure Analysis
(Page 18 of 20) Gear – Shafts – Bearings – Seals
19. HARDENING AND CRACKING OF THE SEAL LIP. Elastomers
harden, crack and chip at the lip-shaft interface due to
excessive heat, exposure to certain extreme pressure lubricants
or exposure to chemicals. The cracking is shown in Figure
5.4. Chipping is shown in Figure 5.5. Laboratory tests have
indicated that a Nitrile seal (most commonly used in a Falk
drive) heated to 320° F will harden to the consistency of a
phonograph record within 15 minutes. Another failure mode
associated with heat is the formation of blisters on the sealing
lip as shown in Figure 5.6.
FIG. 5.4 (2342-39C) HEAT CRACKING
FIG. 5.5 (2342-40C) CHIPPING OF SEAL LIP
FIG. 5.6 (2342-41C) BLISTERS ON SEAL LIP
Published values indicate the following maximum service
temperatures for various seal materials, however, nothing is
stated regarding the expected seal life at these temperatures.
Material Maximum Service Temperature
Natural Rubber · · · · · · · · · · · · · · · · · · · · · · · · · · · · 212°F
Chloroprene (Neoprene) · · · · · · · · · · · · · · · · · · · · · · 250
Nitrile · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 250
Silicone · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 550
Fluoroelastomers · · · · · · · · · · · · · · · · · · · · · · · · · · · 600
(Teflon, Viton, Nylon)
The availability of some seal materials is limited and prevents
easy substitution. Before considering an al ternate material, its
availability should be checked and all its properties studied to
determine suitability for the environment and application.
The chemical action of some EP lubricants will cause a seal to
harden, the rate of hardening increases wit temperature. The EP
lubricants shown in Falk Service Manual 128-010 are compatible
with Nitrile seals Tests are conducted periodically at Falk by
submerging an oil seal in a tank of lubricant maintained at 200°I
and inspecting the seal at frequent intervals to deter mine the
effects of the lubricant on the seal material
ELEMENT CRACKING-NO HARDENING. Tests con ducted by
Falk indicate that when Nitrile seals are exposed to an
atmosphere of 9-11 parts per million (ppm) of ozone, they will
exhibit radial and circumferential cracks without any evidence
of hardening. Them cracks are shown in Figure 5.7. When an
atmosphere containing this amount of ozone is encountered,
either the seal should be protected by another media such as
grease, or the seal material should be changed.
FIG. 5.7 (2342-42C) RADIAL AND CIRCUMFERENTIAL
CRACKS DUE TO OZONE
EXCESSIVE LIP WEAR. The width of the wear band of a
normally wearing seal is .010-.030" depending on size of
seal. If the band width is wide on one side and narrow
diametrically opposite, it is possible that the shaft is
misaligned to the bore. Initial leakage will generally occur in
the area which shows little to no wear due to inadequate lip
contact. As the worn side is hardened from excessive pressure
and heat, it may crack and cause additional leakage.
SHAFT JOURNAL. Shaft journals used by Falk are plunge
ground to a surface finish of 16 micro-inches (RMS). The
hardness of the journal is the same hardness of the shaft. It
has been Falk’s experience that these specifications have
worked well. The scratches are circumferential and have no
lead. If a seal leaks in only one direction of rotation, it is
possible that oil is passing along a scratch or a tool mark
that has a lead.
The width of the seal path on a shaft should vary from
.010" to .030" and be only a few thousandths deep. See
Rexnord Industries, LLC, Gear Group 108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131 August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.com Replaces 690801
Failure Analysis • Installation & Maintenance
Gear – Shafts – Bearings – Seals (Page 19 of 20)
20. Figure 5.8. If the wear path is wider than .030" or deeper
than what you can feel with your fingernail, leakage may be
encountered. The causes of this condition can be abrasive
conditions, eccentricity between seal and shaft, cocked seal or
axial motion between seal and shaft. A shaft surface with this
degree of wear will leak, hence should be resurfaced or the
seal should be relocated along the shaft in order to provide a
new shaft surface.
FIG. 5.8 (2342-43C) JOURNAL WEAR
SEAL LIFE
Seal manufacturers today will not make a public statement
regarding seal life. However, statements made several years
ago in the literature (8) indicates that “long life” is considered
to be more than 1000 hours before leakage results, that
“medium life” is defined as leakage beginning at 400-600
hours of operation and that “short life” is 100 hours. In
another paper (9) it is pointed out that a Nitrile material
“withstands temperatures of 100-200E at surface speeds of
200 fpm for approximately 3000 hours. Viton would last
longer possibly up to 10,000 hours. Information given to Falk
in 1965 by Chicago Rawhide indicated that the seal life for a
Nitrile seal at 200E was 3000 hours. Apparently their studies
did not consider seal life at lower temperatures. A more recent
paper (10) reveals data regarding seal tests where it is
indicated that a criteria of success is to operate without
leakage for a period of 100 to 500 hours, and that from a
test of 10 seals they all leaked within 1100 hours. The
following statement made in this paper can best summarize
the performance of contact seals:
“All seals will leak if run long enough at a given set of
conditions. Material, process, design and test variations
will result in variations in time to leakage.”
SEAL LEAKAGE
Information regarding degree of leakage is impossible to
obtain from seal manufacturers. The only definitive
information uncovered (8) indicates that most synthetic seals
(about 80%) leak .002 grams/hr. or approximately one drop
every 11 hours. This is not considered to be troublesome by
some persons. About 15% of synthetic seals leak .002-0.100
grams/hr. (approximately 1 drop per 11 hours to 1 drop per
11 minutes), a rate which is considered borderline. If the
leakage rate is in excess of 0.10 grams/hour the seal can be
considered defective, misapplied or misspecified.
SUMMARY
Precise performance criteria for contact seals is impossible to
obtain from seal manufacturers. The following statement is
based on the years of experience that Falk has had with the
application of contact oil seals in their products and must be
regarded as a tentative standard by which to measure seal
performance.
All contact type oil seals used in enclosed gear drives will leak
if operated long enough. The variation in time before leakage
occurs will depend on the material of the seal, the operating
temperature of the gear drive and lubricant, the type of
lubricant used, the quality of the seal-shaft surface interface
and the environment in which the gear drive operates. A
wetting of the surface may commence shortly after the startup
of a gear drive and may then progress to the formation of
droplets. Unusual operating conditions would accelerate the
leakage.
REFERENCES
(1) “Analysis of Tapered Roller Bearing Damage”, Widner
and Wolfe, American Society for Metals, Report
C-7-11.1, October 1967.
(2) “How to Recognize and Prevent Tapered Roller Bearing
Damage”, The Timken Company, Canton, Ohio, 1970.
(3) “Bearing Failures and Their Causes”, SKF Industries,
King of Prussia, Pa., 1968.
(4) “Spherical Roller Bearing Service Damage and Causes”,
The Torrington Co., South Bend, Indiana, 1960.
(5) “How to Prevent Ball Bearing Failures”, the Fafnir
Bearing Company, Form 493.
(6) “Fatigue Prevention by Lubricant Chemistry”,Mobil Oil
Corporation Publication.
(7) “The Effect of Water in Lubricating Oil on Bearing
Fatigue Life”, Richard Cantley, ASLE Paper
76-AM-713-1, May 1976.
(8) 1973-1974 Seals Reference Issue - Machine Design,
September 13, 1973, page 22, Penton Press, Cleveland,
Ohio.
(9) “The Fluoroelastomer Seal: A Stronger Link”, Daniel B.
Jackson, (Manager R & D, Parker Seal Company), Power
Transmission Design, July 1971.
(10) “Statistical Interpretation of Shaft Seal Performance”,
Leslie Horve, SAE Paper 741044, October 1974.
Rexnord Industries, LLC, Gear Group108-010
3001 W. Canal St., Milwaukee, WI 53208-4200 USA Telephone: 414-342-3131August 1978
Fax: 414-937-4359 e-mail: info@rexnord.com web: www.rexnord.comReplaces 690801
Installation & Maintenance • Failure Analysis
(Page 20 of 20) Gear – Shafts – Bearings – Seals