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202999415-1-Pressure-Packing for compressor

This document discusses pressure packings used for piston compressors. It provides information on the basic understanding, ring theory, and typical types of pressure packings. Main pressure packings seal the compression chamber from the distance piece around the piston rod, while intermediate packings seal between distance pieces. Segmented rings are used with garter springs or gas pressure to create a seal around the piston rod, which allows for rod movement. Common ring types include single acting, double acting, and those with backup rings for higher pressures.

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Main Pressure Packing Intermediate Packing PRESSURE PACKINGS FOR PISTON COMPRESSORS
Contents • Basic Understanding • Ring Theory • Housing Theory • Leakage Control • Cooling Systems for Packings • Typical Packing Types • Associated Products - Piston Rods Main Pressure Packing Intermediate Packing PRESSURE PACKINGS
Basic Understanding • Task and Types • Function • Sealing System • Design PRESSURE PACKINGS
Task and Types of Pressure Packings Task : Create a positive seal at the piston rod Types : Main Pressure Packing - Intermediate Packing Double Distance Piece Double Acting Cylinder Crosshead Crankcase BASIC UNDERSTANDING
Seals the inboard compression chamber to distance piece in the area of the piston rod. Can be lube or non lube. Pressure range from vacuum to 3000 bar. Main Pressure Packing Ring sets O-Rings Flange Cups or Containers Tie rods Purge inlet Cooling Design example Flange bolts and nuts Piston rod BASIC UNDERSTANDING
Intermediate Packings seal the first distance piece to the second distance piece in the area of the piston rod. Usually they are not lubricated and not water cooled. Intermediate Packing Flange Cups or Containers Ring sets Tie rods Purge (plugged) Flange bolts and nuts Design example Piston rod BASIC UNDERSTANDING
• Seal gas or oil – in compression chamber – in intermediate piece • Maintain a positive seal at the piston rod even though there is lateral movement of the rod e n d c l e a r a n c e Function of Pressure Packings axial clearance piston rod piston rod radial clearance lateral axial BASIC UNDERSTANDING
• The rings segments are held together by garter springs until the gas pressure is such that they are forced on to the rod to create the seal. • Sealing rings are pegged together so that the gaps between the ring segments of one ring are covered by the ring segments of the other to reduce leakage. • Rings can float axially and radially in the grooves of the cups to compensate for rod movement. Function of Pressure Packings piston rod garter springs seal rings BASIC UNDERSTANDING
Sealing System for Piston Rods of Compressors Segmented rings Housing Piston rod Garter springs Radial cut ring Tangential cut ring BASIC UNDERSTANDING
Sealing System for Piston Rods of Compressors Segmented rings Housing Piston rod Garter springs Gas pressure loads the ring segments, forcing them onto the rod and against the housing crank end cylinder end BASIC UNDERSTANDING
Sealing System for Piston Rods of Compressors When the packing is not pressurized by gas, the garter springs hold the ring segments in place around the piston rod. BASIC UNDERSTANDING
Axial and radial clearance allow the rings to float in the housing , thus leakage is prevented by always maintaining a positive seal. Sealing System for Piston Rods of Compressors If lip seals were used they would not conform to the rod as it would not compensate for the rod movement. For this reason segmental rings are used. BASIC UNDERSTANDING
Gaps of one ring are covered by the face of the other ring. Rings are positioned by a pin Sealing System for Piston Rods of Compressors BASIC UNDERSTANDING
Sealing System for Piston Rods of Compressors End clearance between ring segments allows worn rings to compensate for wear automatically. Tangential cut rings act like a camera lens. BASIC UNDERSTANDING
Gaps of one ring are covered by the face of the other ring. Rings are positioned by a pin Axial and radial clearance allow the rings to float in the housing , thus leakage is prevented by always maintaining a positive seal. When the packing is not pressurized by gas, the garter springs hold the ring segments in place around the piston rod. Gas pressure loads the ring segments, forcing them on to the rod and housing Sealing System for Piston Rods of Compressors If lip seals were used they would not conform to the rod as it would not compensate for the rod movement. For this reason segmental rings are used. End clearance between ring segments allows worn rings to compensate for wear automatically. Tangential cut rings act like a camera lens. BASIC UNDERSTANDING
Sealing System for Piston Rods of Compressors Stepwise pressure reduction by each packing ring group: Rule of the thumb for packings: Each recess of a new packing will reduce the pressure by half. If one ring pair is worn, the pressure has to be reduced by the remaining ring pairs. The pressure profile will differ then from the pictured profile. The last sealing ring group is responsible for the leakage to the outside. packing ring groups atmospheric pressure pressure p packing assembly Piston rod Piston rod leakage discharge pressure pressure profile BASIC UNDERSTANDING
Design Criteria • Differential pressure - Number of ringsets, with or without cooling • Temperature - Cooling, ring material • Speed of the rod - Cooling , ring material • Gas type and - Vent, ring type,ring material gas condition • Lube - ring material, number of lube points • Rod material - ring material • Rod surface - ring material • Customer’s demand - materials and design • Expected life time - material, design • Costs - design and material BASIC UNDERSTANDING
Number of Ring Groups of Main Pressure Packings Pressure range of HRP filled TFE packings for compressors pressure (bar) uncooled not vented 4 sets 5 sets 6 sets 7 sets (Air) uncooled vented 5 sets 6 sets 7 sets 8 sets (Gas) cooled not vented 4 sets 5 sets 6 sets 7 sets 8 sets 9 sets (Air) cooled vented 5 sets 6 sets 7 sets 8 sets 9 sets 10 sets (Gas) All packings above 70 bar whether vented or unvented must be cooled and should be lubricated. 0 - 12 12.5 - 21 21.5 - 35 35.5 - 70 70.5 - 316 316.5 up 1 lube point 2 lube points BASIC UNDERSTANDING
Components of Pressure Packings Flange Flange Plates Plates Soft metal gasket (joint) to seal on stuffing box Soft metal gasket (joint) to seal on stuffing box Sealing Ring Sets Sealing Ring Sets Containers (Cups) Containers (Cups) etc. etc. etc. O-Rings O-Rings etc. Crank end Cylinder end BASIC UNDERSTANDING
Contents • Function • Single Acting Ring Groups • Double Acting Ring Groups • Side Loaded Ring Groups • Special Rings • Pressure Breakers • Clearance figures RING THEORY
Function Classification of rings according to their functions: • Seal ring • Pressure breaker – reduces the pressure by throttling the gas flow • Anti-extrusion ring - usually called “backup ring” – for pressures higher than approx. 15 bar – made out of stronger material than the seal rings – located on low pressure side, with a gap between the ring and the rod smaller than the gap between the housing and the rod • Ring set: consists of several rings RING THEORY
Function of a Single Acting Ring Pair Side clearance in the cups and radial cut ring gaps avoid gas traps. They allow the gas inside the cups to return to the cylinder. Gas enters the cup via the side clearance in the cups and gaps in radial cut ring and loads tangent cut ring onto piston rod. Tangent cut ring gaps are sealed by radial cut ring Cylinder end Crank end Cylinder end Crank end Axial movement of piston rod Axial movement of piston rod Axial movement of piston rod Axial movement of piston rod tangential ring radial ring RING THEORY
Single Acting Ring Group Type 0342 Description: Rings located relative to each by a peg in tangential cut ring mating hole in radial cut ring. By this gaps of tangential cut rings are covered by radial cut ring. Task: Seals only, when the crank end of the cylinder is compressing gas Application: Standard ring set for low to medium pressures Wear limit: Gaps decrease to zero when ring wears. Rings without gap are worn out and must be exchanged. Tangential cut ring Radial cut ring Pressure ring type 0306 ring type 0304 gap gap RING THEORY
Description: Radial cut ring combined with 6 piece design, instead of 3-piece design tangential cut ring. Task: Tangential cut is continued across the segment creating “ Bridge Pieces “ Application: for brittle ring materials , for pressures above 150 bar with metal Bridge Pieces Single Acting Ring Group Type 0353 Pressure 6-piece tangential cut ring Radial cut ring ring type 0322 ring type 0304 RING THEORY
Description: Single acting standard ring pair with backup ring. Backup ring is bored to have 0.1 to 0.2 mm clearance on the piston rod and hence no gaps when fitted. Application: Standard ring group for pressures above 21 bar Backup or anti-extrusion ring Radial cut seal ring Single Acting Ring Group Type 0371 Pressure Tangential cut seal ring ring type 0310 ring type 0304 ring type 0306 Bronze, Peek, PPS Bronze, Peek, PPS RING THEORY
Function of a Double Acting Ring Group Gaps in both tangent cut rings sealed because rings are pegged to prevent gaps aligning. Gas enters the cup via side clearance and loads tangent cut rings onto piston rod. Cylinder end Crank end On reverse stroke gas is sealed in the same manner as described for the crank stroke. Cylinder end Crank end Gas is trapped in the container. Axial movement of piston rod Axial movement of piston rod Axial movement of piston rod Axial movement of piston rod RING THEORY
Description: 2 tangential cut rings pegged together in such a way that the segments of one ring mask the end gaps of the other ring. Task: Seal in both strokes of the compression cycle. Application: Low pressures or vacuum, Intermediate Packing, pulsation seal in Wiper Packings, final or vent seal in Main Pressure Packings. Double Acting Ring Group Type 0344 ring type 0306 ring type 0308 Pressure RING THEORY
Description: Double acting ring set with backup ring Application: Standard set for pressures of less than 12 bar and higher temperatures Double Acting Ring Group Type 0372 Tangential cut seal ring Tangential cut seal ring Backup ring or anti-extrusion ring Pressure ring type 0310 ring type 0306 ring type 0308 RING THEORY
Description: Double acting ring pair consisting of two 4-segment radial cut rings pegged together, so that the segments of one ring masks the end gaps of the other. Application: Where brittle materials must be used, e.g. carbon Advantage: sturdy parts, frequently used with brittle materials Disadvantage: no wear limit, difficult to install Double Acting Ring Group Type 0347 Cut lines do not meet the centre ! ring type 0317 ring type 0316 Pressure RING THEORY
Description: always maintains a seal between tangential cut and container sealing face due to the inclined nature of the faces of the 2 radial cut rings and garter spring load. Application: Main Packings at low pressure side near vent and purge, also in Intermediate (Partition) Packings and Oil Tight Packings. Side Loaded Pressure Ring Group Type 0373 Radial cut ring with chamfered recess Radial cut ring with chamfered boss Tangential cut ring with peg Pressure ring type 0314 ring type 0313 ring type 0312 Pressure RING THEORY
Description: No direct leakage path beween the segments, needs no further ring for proper sealing. Application: Where small containers must be installed. Disadvantage: No wear restriction; possibility of damage to inboard feather edges if rod is inserted into assembled packing. Special Rings Type 0309 and 0328 Single acting tangential cut ring without wear restriction Double acting tangential cut ring without wear restriction ring type 0309 ring type 0328 Pressure Pressure RING THEORY
Single acting ring with relief slots in the middle of segments and chamfers on joint Description: Reduce pressure and throttle gas pressure pulsations but not to seal. Application: Pressures greater then 20 bar, used on their own filling a recess, or with backup ring when non metallics (PTFE). Pressure Breaker Rings 0301 and 1302 Double acting ring ring type 1302 ring type 0301 Pressure Pressure RING THEORY
Nomenclature of HRP Rings Ring radial thickness Recess dia Container (cup) outer dia Recess depth Container (cup) thickness Ring axial width Dimensions of standard rings are according to HRP standard TDSM 115 RING THEORY
Pressure and Intermediate Packings Flanges Flanges Containers Containers • Flanges, Containers (cups), Plates Types - Function - Clearance - Surface Quality - Materials • Other Parts Tie rods - O-rings - Static Sealing HOUSING THEORY
Types of Flanges and Containers Flanges Flanges T-Container (cup) L-Container (cup) Plate • vented • plain • cooled • lube • vented • plain • for purge Spigotted Flange HRP Standard Recessed Flange cannot be lapped Containers (cups) Containers (cups) Containers Containers HOUSING THEORY
Functions of Flanges and Containers Flange : Contains the connections for lube oil, cooling water, vent and purge. Containers are fixed with tie rods to flange. Container : Contains the ring sets and the holes (cup) for lube oil, cooling water, and vent. Plate : Contains the holes for vent. Masks the milled cooling water grooves. Compensates the thickness reduction of containers after reconditioning (by installing a thicker plate). Dimensions: Dimensions of flanges, containers, plates are according to HRP standard TDSM 182 HOUSING THEORY
FLANGES Spigot dia : Spigot dia. as Container (cup) outer diameter Recess dia : Recess dia = Stuffing box nom. bore +0 to 0.15 mm As recesses cannot be lapped effectively, recessed type flanges should be avoided. SEALING FACES on Containers, Flanges and Plates Surface finish low pressure: < 70 bar high pressure: > 70 bar and Flatness : uncooled Packings low MOL weight or cooled Packings 0.4 & 0.002 0.2 & 0.001 or Clearance and Surface Quality DETAILS - HOUSING THEORY
Standard : Grey iron BS1452 GR.250 Carbon steel BS970 GR 070M55 Stainless steel BS970 GR 316S16 Specials : As required by customers Materials Refer to TDSM213 for application details via HRP Intranet DETAILS - HOUSING THEORY
Details: O-Rings - Static Sealing High material and surface quality Captive rectangular section gasket (joint) from copper or soft iron O-ring material according to customer’s order Tie rod OTHER COMPONENTS
Details: Static Sealing Function The joint forms the only static seal as part of the main pressure packing, which seals against the bottom of the stuffing box in the compressor. It is important that the static seal is flat and parallel. It is also important that there is a good surface at the bottom of the stuffing box with no contamination. This is as important a seal as any of the sealing rings. OTHER COMPONENTS
• Calculation of Leakage Rates by HRP • Leakage Control System ECM LEAKAGE
Calculation of Leakage Rates to HRP Standards It is difficult to define exactly how much gas will leak through a pressure packing. A slight leakage is fundamental to the operation of the packing. Major factors influencing leakage are • the discharge pressure of the compressor, • the size of the piston rod • the molecular weight of the gas • any lubrication. Secondary factors include surface finish of the rod and the containers, gas contamination and machine misalignments. Compressors can suffer higher than normal leakage • if operated at very low pressures, • if running at partial or off-load, • if (new) packings have not bedded in. LEAKAGE
Vent and Purge Arrangement For dangerous gases or low emission values the containers near to the distance piece of Pressure and Intermediate Packing are purged. A flow of Nitrogen purge gas is inlet into the packing to stop possible leakage of dangerous gas into the crank case and further on into the compressor room. It could also contaminate oil and lower its flash point. Crankcase side Cylinder side Nitrogen IN Piped controlled leakage to dangerous gas/nitrogen vent Lubrication (on top) Nitrogen Oil drain Nitrogen Dangerous gas to distance piece vent LEAKAGE
Vent and Purge System, Pressures, Leakage flows to API 618 Vent Pressure - up to1.5 barg maximum to API 618, Appendix 1 depends on both the leakage flow escaping past the packing rings and the back pressure and flow restriction from vent / flare line system. If the vent line back pressure and restriction remains constant, then an increasing vent line pressure indicates increasing packaging leakage. Purge gas pressure - up to 2.5 barg. should be at least 1 bar above the Vent Pressure Purge Gas Flow (Leakage) Rates < 1 to 6 l /min for packing with rod and containers in good condition and new bedded-in wear parts with back to back SLP (WAT) rings. (Valid for purge systems fitted with SLP rings and AL (5 ring) sets). Recycling Vent Flows - to suction system of the compressor If the first stage suction pressure is < 1.5 barg, any leakage may be recycled to reduce the overall leakage (depending on installation). Intermediate Vent Connections - at higher pressures High pressure packings may be fitted with an intermediate HP vent connection as well as a low pressure vent connection for even break- down of pressure across all rings. LEAKAGE
Purge pressure and purge flow are controlled, consumption of purge gas (N2) is minimized. The equipment adjusts purge gas inlet pressure to compensate for increase in vent pressure and keeps the differential pressure of the purge to vent gas. If gas flow to flare exceeds a limiting value an alarm is switched on. Emission Control and Monitoring System ECM • Modular construction, up to 4 cylinders per cabinet • Satisfies emissions legislation to API618 & NACE • Optional flow controlled purge for valve unloaders, intermediate & wiper packings LEAKAGE
F1: Flowmeter (metallic type) Flow range 10 – 30 l/min F2: Flowmeter (rotameter) Flow range 0 – 10 l/min Purge Panel Diagram of the ECM Vent pressure Vent flow F1 VENT OUTLET TO FLARE NITROGEN PURGE TO PACKING Purge flow G3 F2 V4 G1 V5 Purge pressure V3 Purge Compensation Regulator, adjustable Gauge Regulator Shut Off NITROGEN SUPPLY max. 16 bar typ. 10 bar V2 V1 PURGED GASSES FROM PACKING max pressure 16 bar YYP range 1 – 3 bar G2 LEAKAGE
• HRP Cooling System • HRP Drilled Radial Flow Type Design of cooled packings is currently under review COOLING OF PRESSURE PACKINGS
HRP Cooling System Frictional heat has to be dissipated. For discharge pressures greater than 70 bar water cooling is necessary in general. For lower pressures water cooling is necessary only under special conditions. COOLING OF PRESSURE PACKINGS
HRP Cooling System Forced flow cooling by 340° milled groove gives: – improved water flow – no stagnancy – reduced pressure drop through packing cooling system water water outlet cooling water inlet water water outlet water inlet Required cooling water: pressure : 0.5 to 5 bar max. temperature: 40°C COOLING OF PRESSURE PACKINGS
HRP Drilled Radial Flow Type- conforms to API 618 • Better coolant flow with reduced losses • Meets API 618 revision 4 by eliminating “O” rings which surround the piston rod • Easier to change packing rings without removing the piston rod • Cooling passages can be cleaned by removal of plugs COOLING OF PRESSURE PACKINGS
• Main Characteristics • Typical Pressure Packing Types • HRP Stationary Gas Seal • Features of HRP Pressure Packings • Testing of Pressure Packings PRESSURE PACKING TYPES
Characteristics The main characteristics of Pressure Packings are: • lube or non-lube • with or without cooling • with or without vent • with vent and • with or without purge These characteristics are dependent upon: • discharge pressure • differential temperature. • piston speed • customer specification • process requirements Type and number of ring groups depend on the design criteria • see “Basic Understanding”. PRESSURE PACKING TYPES
Non lube, uncooled, not vented, not purged, for discharge pressures less than 10 bar Double acting ring groups are used 0308 0306 RING GROUP 0344 Crank end Cylinder end TYPICAL PACKING TYPES
Non lube, uncooled, not vented, not purged, RING GROUP 0371 0310 0304 0306 Crank end Cylinder end for discharge pressures less than 30 bar Pressure Breaker Ring Single acting ring groups RING GROUP 0349 0310 1302 TYPICAL PACKING TYPES
Lube Lube, uncooled, not vented, not purged, for discharge pressure from 30 bar to 70 bar Crank end Cylinder end oil oil from cylinder lube pump RING GROUP 0371 0310 0304 0306 Pressure Single acting Breaker Ring ring groups RING GROUP 0349 0310 1302 TYPICAL PACKING TYPES
Non lube, cooled, not vented, not purged - 170 bar Crank end Cylinder end For pressures greater than 70 bar cooled packings are recommended O-rings are used to prevent the process gas from entering the water channels and to also prevent water from leaving the water channels TYPICAL PACKING TYPES
Non lube, uncooled, vented, not purged - 70 bar Vented gas is piped to flare or to a lower pressure level of compressor. Gas vent SLP ring group: side load pressurized, behind vent For dangerous gases - toxic or explosive: For dangerous gases - toxic or explosive: Crank end Cylinder end RING GROUP 0373 0312 0314 0313 TYPICAL PACKING TYPES
Non lube, uncooled, vented and purged - 70 bar For very dangerous gases or low emission values For very dangerous gases or low emission values purge gas purge gas gas mixture Crank end Cylinder end gas Purge gas (mainly Nitrogen) is inlet in to the last container. Inlet pressure normally is 1 bar minimum above vent pressure. The mixture of dangerous gas and purge gas is piped to the vent collection TYPICAL PACKING TYPES
HRP Design Segmental Packing Rings only seal during dynamic reciprocating action. Piston energised Piston energised DYNAMIC : NO ROD CONTACT STATIC : ROD CONTACT Pneumatically operated externally, when the rod is stationary to prevent cylinder gas emission Cylinder end Stationary Gas Seal energises when the compressor is stopped Stationary Gas Seal energises when the compressor is stopped STATIONARY GAS SEAL
Segmental packing rings only seal during dynamic reciprocating action. Distance piece Cylinder end HRP Design Cartridge unit fitted to existing Packing increasing length For standstill additional parts are necessary STATIONARY GAS SEAL
Application Features TYPICAL WATER COOLED PRESSURE PACKING Face & outside dia connections make flange more serviceable. Thermocouple to detect increases in temperature Detachable flange to aid assembly Vent connection can be fitted with an off-line flow measurement device Facility for rod drop indicator to detect rider ring wear FEATURES OF HRP PRESSURE PACKINGS
Design Features Spiral wound Gasket, optional, to reduce static leakage Tee shaped Cup complete with`SLP' Rings & purge (API618) allows for sealing faces to be machine-lapped Milled groove Coolant Channels to reduce pressure drop to a minimum `O'-Ring design can be captive, totally eliminating possibility of gas leakage into water channels Fully lapped faces with O-Rings eliminate static leakage TYPICAL WATER COOLED PRESSURE PACKING FEATURES OF HRP PRESSURE PACKINGS
Standard and Extra Leakage Testing Procedures Standard test of water cooled packings: • Pressurised air (6 bar) is connected to cooling water inlet. • Air inlet valve will be closed. • Pressure drop is checked at the closed volume Standard bubble test • Pressurised air (6 bar) is connected to cooling water inlet. • Packings are submerged in water, bubbles indicate leakage. • After test packings are disassembled, cleaned, dried and reassembled. • Test do not show reasseambling errors. Extra test when required - all packings • Check of the gas tightness between the test flanges TESTING OF HRP PRESSURE PACKINGS
• Piston Rods ASSOCIATED PRODUCTS
Piston Rods Lube air compressor - unhardened 30 HRC, cut threads Process gas compr. - Induction hardened (occasionally nitrided) 50 to 55 HRC, rolled threads Coated rods - Thermal plasma sprayed, mostly to 65 - 70 HRC Materials Materials Surface Finish - hardened rods Ra : 0,2 - 0,4 µ µ µ µm - coated rods Ra : 0,2 - 0,25 µ µ µ µm Coating - Chromium oxide for reducing - Ceramics (Metco P130), produced rod wear and/or with plasma gun method (HVOF) reconditioning - Tungsten Carbide produced with plasma gun (HVOF) or “Detonation Gun” method Surface Finish Surface Finish - hardened rods Ra : 0,2 - 0,4 µ µ µ µm - coated rods Ra : 0,2 - 0,25 µ µ µ µm Coating - Chromium oxide for reducing - Ceramics (Metco P130), produced rod wear and/or with plasma gun method (HVOF) reconditioning - Tungsten Carbide produced with plasma gun (HVOF) or “Detonation Gun” method higher value of Ra preferred ASSOCIATED PRODUCTS
End of the Training File Pressure Packings END

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202999415-1-Pressure-Packing for compressor

  • 1.
    Main Pressure PackingIntermediate Packing PRESSURE PACKINGS FOR PISTON COMPRESSORS
  • 2.
    Contents • Basic Understanding •Ring Theory • Housing Theory • Leakage Control • Cooling Systems for Packings • Typical Packing Types • Associated Products - Piston Rods Main Pressure Packing Intermediate Packing PRESSURE PACKINGS
  • 3.
    Basic Understanding • Taskand Types • Function • Sealing System • Design PRESSURE PACKINGS
  • 4.
    Task and Typesof Pressure Packings Task : Create a positive seal at the piston rod Types : Main Pressure Packing - Intermediate Packing Double Distance Piece Double Acting Cylinder Crosshead Crankcase BASIC UNDERSTANDING
  • 5.
    Seals the inboardcompression chamber to distance piece in the area of the piston rod. Can be lube or non lube. Pressure range from vacuum to 3000 bar. Main Pressure Packing Ring sets O-Rings Flange Cups or Containers Tie rods Purge inlet Cooling Design example Flange bolts and nuts Piston rod BASIC UNDERSTANDING
  • 6.
    Intermediate Packings sealthe first distance piece to the second distance piece in the area of the piston rod. Usually they are not lubricated and not water cooled. Intermediate Packing Flange Cups or Containers Ring sets Tie rods Purge (plugged) Flange bolts and nuts Design example Piston rod BASIC UNDERSTANDING
  • 7.
    • Seal gasor oil – in compression chamber – in intermediate piece • Maintain a positive seal at the piston rod even though there is lateral movement of the rod e n d c l e a r a n c e Function of Pressure Packings axial clearance piston rod piston rod radial clearance lateral axial BASIC UNDERSTANDING
  • 8.
    • The ringssegments are held together by garter springs until the gas pressure is such that they are forced on to the rod to create the seal. • Sealing rings are pegged together so that the gaps between the ring segments of one ring are covered by the ring segments of the other to reduce leakage. • Rings can float axially and radially in the grooves of the cups to compensate for rod movement. Function of Pressure Packings piston rod garter springs seal rings BASIC UNDERSTANDING
  • 9.
    Sealing System forPiston Rods of Compressors Segmented rings Housing Piston rod Garter springs Radial cut ring Tangential cut ring BASIC UNDERSTANDING
  • 10.
    Sealing System forPiston Rods of Compressors Segmented rings Housing Piston rod Garter springs Gas pressure loads the ring segments, forcing them onto the rod and against the housing crank end cylinder end BASIC UNDERSTANDING
  • 11.
    Sealing System forPiston Rods of Compressors When the packing is not pressurized by gas, the garter springs hold the ring segments in place around the piston rod. BASIC UNDERSTANDING
  • 12.
    Axial and radial clearanceallow the rings to float in the housing , thus leakage is prevented by always maintaining a positive seal. Sealing System for Piston Rods of Compressors If lip seals were used they would not conform to the rod as it would not compensate for the rod movement. For this reason segmental rings are used. BASIC UNDERSTANDING
  • 13.
    Gaps of onering are covered by the face of the other ring. Rings are positioned by a pin Sealing System for Piston Rods of Compressors BASIC UNDERSTANDING
  • 14.
    Sealing System forPiston Rods of Compressors End clearance between ring segments allows worn rings to compensate for wear automatically. Tangential cut rings act like a camera lens. BASIC UNDERSTANDING
  • 15.
    Gaps of onering are covered by the face of the other ring. Rings are positioned by a pin Axial and radial clearance allow the rings to float in the housing , thus leakage is prevented by always maintaining a positive seal. When the packing is not pressurized by gas, the garter springs hold the ring segments in place around the piston rod. Gas pressure loads the ring segments, forcing them on to the rod and housing Sealing System for Piston Rods of Compressors If lip seals were used they would not conform to the rod as it would not compensate for the rod movement. For this reason segmental rings are used. End clearance between ring segments allows worn rings to compensate for wear automatically. Tangential cut rings act like a camera lens. BASIC UNDERSTANDING
  • 16.
    Sealing System forPiston Rods of Compressors Stepwise pressure reduction by each packing ring group: Rule of the thumb for packings: Each recess of a new packing will reduce the pressure by half. If one ring pair is worn, the pressure has to be reduced by the remaining ring pairs. The pressure profile will differ then from the pictured profile. The last sealing ring group is responsible for the leakage to the outside. packing ring groups atmospheric pressure pressure p packing assembly Piston rod Piston rod leakage discharge pressure pressure profile BASIC UNDERSTANDING
  • 17.
    Design Criteria • Differentialpressure - Number of ringsets, with or without cooling • Temperature - Cooling, ring material • Speed of the rod - Cooling , ring material • Gas type and - Vent, ring type,ring material gas condition • Lube - ring material, number of lube points • Rod material - ring material • Rod surface - ring material • Customer’s demand - materials and design • Expected life time - material, design • Costs - design and material BASIC UNDERSTANDING
  • 18.
    Number of RingGroups of Main Pressure Packings Pressure range of HRP filled TFE packings for compressors pressure (bar) uncooled not vented 4 sets 5 sets 6 sets 7 sets (Air) uncooled vented 5 sets 6 sets 7 sets 8 sets (Gas) cooled not vented 4 sets 5 sets 6 sets 7 sets 8 sets 9 sets (Air) cooled vented 5 sets 6 sets 7 sets 8 sets 9 sets 10 sets (Gas) All packings above 70 bar whether vented or unvented must be cooled and should be lubricated. 0 - 12 12.5 - 21 21.5 - 35 35.5 - 70 70.5 - 316 316.5 up 1 lube point 2 lube points BASIC UNDERSTANDING
  • 19.
    Components of PressurePackings Flange Flange Plates Plates Soft metal gasket (joint) to seal on stuffing box Soft metal gasket (joint) to seal on stuffing box Sealing Ring Sets Sealing Ring Sets Containers (Cups) Containers (Cups) etc. etc. etc. O-Rings O-Rings etc. Crank end Cylinder end BASIC UNDERSTANDING
  • 20.
    Contents • Function • SingleActing Ring Groups • Double Acting Ring Groups • Side Loaded Ring Groups • Special Rings • Pressure Breakers • Clearance figures RING THEORY
  • 21.
    Function Classification of ringsaccording to their functions: • Seal ring • Pressure breaker – reduces the pressure by throttling the gas flow • Anti-extrusion ring - usually called “backup ring” – for pressures higher than approx. 15 bar – made out of stronger material than the seal rings – located on low pressure side, with a gap between the ring and the rod smaller than the gap between the housing and the rod • Ring set: consists of several rings RING THEORY
  • 22.
    Function of aSingle Acting Ring Pair Side clearance in the cups and radial cut ring gaps avoid gas traps. They allow the gas inside the cups to return to the cylinder. Gas enters the cup via the side clearance in the cups and gaps in radial cut ring and loads tangent cut ring onto piston rod. Tangent cut ring gaps are sealed by radial cut ring Cylinder end Crank end Cylinder end Crank end Axial movement of piston rod Axial movement of piston rod Axial movement of piston rod Axial movement of piston rod tangential ring radial ring RING THEORY
  • 23.
    Single Acting RingGroup Type 0342 Description: Rings located relative to each by a peg in tangential cut ring mating hole in radial cut ring. By this gaps of tangential cut rings are covered by radial cut ring. Task: Seals only, when the crank end of the cylinder is compressing gas Application: Standard ring set for low to medium pressures Wear limit: Gaps decrease to zero when ring wears. Rings without gap are worn out and must be exchanged. Tangential cut ring Radial cut ring Pressure ring type 0306 ring type 0304 gap gap RING THEORY
  • 24.
    Description: Radial cutring combined with 6 piece design, instead of 3-piece design tangential cut ring. Task: Tangential cut is continued across the segment creating “ Bridge Pieces “ Application: for brittle ring materials , for pressures above 150 bar with metal Bridge Pieces Single Acting Ring Group Type 0353 Pressure 6-piece tangential cut ring Radial cut ring ring type 0322 ring type 0304 RING THEORY
  • 25.
    Description: Single actingstandard ring pair with backup ring. Backup ring is bored to have 0.1 to 0.2 mm clearance on the piston rod and hence no gaps when fitted. Application: Standard ring group for pressures above 21 bar Backup or anti-extrusion ring Radial cut seal ring Single Acting Ring Group Type 0371 Pressure Tangential cut seal ring ring type 0310 ring type 0304 ring type 0306 Bronze, Peek, PPS Bronze, Peek, PPS RING THEORY
  • 26.
    Function of aDouble Acting Ring Group Gaps in both tangent cut rings sealed because rings are pegged to prevent gaps aligning. Gas enters the cup via side clearance and loads tangent cut rings onto piston rod. Cylinder end Crank end On reverse stroke gas is sealed in the same manner as described for the crank stroke. Cylinder end Crank end Gas is trapped in the container. Axial movement of piston rod Axial movement of piston rod Axial movement of piston rod Axial movement of piston rod RING THEORY
  • 27.
    Description: 2 tangentialcut rings pegged together in such a way that the segments of one ring mask the end gaps of the other ring. Task: Seal in both strokes of the compression cycle. Application: Low pressures or vacuum, Intermediate Packing, pulsation seal in Wiper Packings, final or vent seal in Main Pressure Packings. Double Acting Ring Group Type 0344 ring type 0306 ring type 0308 Pressure RING THEORY
  • 28.
    Description: Double actingring set with backup ring Application: Standard set for pressures of less than 12 bar and higher temperatures Double Acting Ring Group Type 0372 Tangential cut seal ring Tangential cut seal ring Backup ring or anti-extrusion ring Pressure ring type 0310 ring type 0306 ring type 0308 RING THEORY
  • 29.
    Description: Double actingring pair consisting of two 4-segment radial cut rings pegged together, so that the segments of one ring masks the end gaps of the other. Application: Where brittle materials must be used, e.g. carbon Advantage: sturdy parts, frequently used with brittle materials Disadvantage: no wear limit, difficult to install Double Acting Ring Group Type 0347 Cut lines do not meet the centre ! ring type 0317 ring type 0316 Pressure RING THEORY
  • 30.
    Description: always maintainsa seal between tangential cut and container sealing face due to the inclined nature of the faces of the 2 radial cut rings and garter spring load. Application: Main Packings at low pressure side near vent and purge, also in Intermediate (Partition) Packings and Oil Tight Packings. Side Loaded Pressure Ring Group Type 0373 Radial cut ring with chamfered recess Radial cut ring with chamfered boss Tangential cut ring with peg Pressure ring type 0314 ring type 0313 ring type 0312 Pressure RING THEORY
  • 31.
    Description: No directleakage path beween the segments, needs no further ring for proper sealing. Application: Where small containers must be installed. Disadvantage: No wear restriction; possibility of damage to inboard feather edges if rod is inserted into assembled packing. Special Rings Type 0309 and 0328 Single acting tangential cut ring without wear restriction Double acting tangential cut ring without wear restriction ring type 0309 ring type 0328 Pressure Pressure RING THEORY
  • 32.
    Single acting ring withrelief slots in the middle of segments and chamfers on joint Description: Reduce pressure and throttle gas pressure pulsations but not to seal. Application: Pressures greater then 20 bar, used on their own filling a recess, or with backup ring when non metallics (PTFE). Pressure Breaker Rings 0301 and 1302 Double acting ring ring type 1302 ring type 0301 Pressure Pressure RING THEORY
  • 33.
    Nomenclature of HRPRings Ring radial thickness Recess dia Container (cup) outer dia Recess depth Container (cup) thickness Ring axial width Dimensions of standard rings are according to HRP standard TDSM 115 RING THEORY
  • 34.
    Pressure and IntermediatePackings Flanges Flanges Containers Containers • Flanges, Containers (cups), Plates Types - Function - Clearance - Surface Quality - Materials • Other Parts Tie rods - O-rings - Static Sealing HOUSING THEORY
  • 35.
    Types of Flangesand Containers Flanges Flanges T-Container (cup) L-Container (cup) Plate • vented • plain • cooled • lube • vented • plain • for purge Spigotted Flange HRP Standard Recessed Flange cannot be lapped Containers (cups) Containers (cups) Containers Containers HOUSING THEORY
  • 36.
    Functions of Flangesand Containers Flange : Contains the connections for lube oil, cooling water, vent and purge. Containers are fixed with tie rods to flange. Container : Contains the ring sets and the holes (cup) for lube oil, cooling water, and vent. Plate : Contains the holes for vent. Masks the milled cooling water grooves. Compensates the thickness reduction of containers after reconditioning (by installing a thicker plate). Dimensions: Dimensions of flanges, containers, plates are according to HRP standard TDSM 182 HOUSING THEORY
  • 37.
    FLANGES Spigot dia :Spigot dia. as Container (cup) outer diameter Recess dia : Recess dia = Stuffing box nom. bore +0 to 0.15 mm As recesses cannot be lapped effectively, recessed type flanges should be avoided. SEALING FACES on Containers, Flanges and Plates Surface finish low pressure: < 70 bar high pressure: > 70 bar and Flatness : uncooled Packings low MOL weight or cooled Packings 0.4 & 0.002 0.2 & 0.001 or Clearance and Surface Quality DETAILS - HOUSING THEORY
  • 38.
    Standard : Greyiron BS1452 GR.250 Carbon steel BS970 GR 070M55 Stainless steel BS970 GR 316S16 Specials : As required by customers Materials Refer to TDSM213 for application details via HRP Intranet DETAILS - HOUSING THEORY
  • 39.
    Details: O-Rings -Static Sealing High material and surface quality Captive rectangular section gasket (joint) from copper or soft iron O-ring material according to customer’s order Tie rod OTHER COMPONENTS
  • 40.
    Details: Static SealingFunction The joint forms the only static seal as part of the main pressure packing, which seals against the bottom of the stuffing box in the compressor. It is important that the static seal is flat and parallel. It is also important that there is a good surface at the bottom of the stuffing box with no contamination. This is as important a seal as any of the sealing rings. OTHER COMPONENTS
  • 41.
    • Calculation ofLeakage Rates by HRP • Leakage Control System ECM LEAKAGE
  • 42.
    Calculation of LeakageRates to HRP Standards It is difficult to define exactly how much gas will leak through a pressure packing. A slight leakage is fundamental to the operation of the packing. Major factors influencing leakage are • the discharge pressure of the compressor, • the size of the piston rod • the molecular weight of the gas • any lubrication. Secondary factors include surface finish of the rod and the containers, gas contamination and machine misalignments. Compressors can suffer higher than normal leakage • if operated at very low pressures, • if running at partial or off-load, • if (new) packings have not bedded in. LEAKAGE
  • 43.
    Vent and PurgeArrangement For dangerous gases or low emission values the containers near to the distance piece of Pressure and Intermediate Packing are purged. A flow of Nitrogen purge gas is inlet into the packing to stop possible leakage of dangerous gas into the crank case and further on into the compressor room. It could also contaminate oil and lower its flash point. Crankcase side Cylinder side Nitrogen IN Piped controlled leakage to dangerous gas/nitrogen vent Lubrication (on top) Nitrogen Oil drain Nitrogen Dangerous gas to distance piece vent LEAKAGE
  • 44.
    Vent and PurgeSystem, Pressures, Leakage flows to API 618 Vent Pressure - up to1.5 barg maximum to API 618, Appendix 1 depends on both the leakage flow escaping past the packing rings and the back pressure and flow restriction from vent / flare line system. If the vent line back pressure and restriction remains constant, then an increasing vent line pressure indicates increasing packaging leakage. Purge gas pressure - up to 2.5 barg. should be at least 1 bar above the Vent Pressure Purge Gas Flow (Leakage) Rates < 1 to 6 l /min for packing with rod and containers in good condition and new bedded-in wear parts with back to back SLP (WAT) rings. (Valid for purge systems fitted with SLP rings and AL (5 ring) sets). Recycling Vent Flows - to suction system of the compressor If the first stage suction pressure is < 1.5 barg, any leakage may be recycled to reduce the overall leakage (depending on installation). Intermediate Vent Connections - at higher pressures High pressure packings may be fitted with an intermediate HP vent connection as well as a low pressure vent connection for even break- down of pressure across all rings. LEAKAGE
  • 45.
    Purge pressure andpurge flow are controlled, consumption of purge gas (N2) is minimized. The equipment adjusts purge gas inlet pressure to compensate for increase in vent pressure and keeps the differential pressure of the purge to vent gas. If gas flow to flare exceeds a limiting value an alarm is switched on. Emission Control and Monitoring System ECM • Modular construction, up to 4 cylinders per cabinet • Satisfies emissions legislation to API618 & NACE • Optional flow controlled purge for valve unloaders, intermediate & wiper packings LEAKAGE
  • 46.
    F1: Flowmeter (metallictype) Flow range 10 – 30 l/min F2: Flowmeter (rotameter) Flow range 0 – 10 l/min Purge Panel Diagram of the ECM Vent pressure Vent flow F1 VENT OUTLET TO FLARE NITROGEN PURGE TO PACKING Purge flow G3 F2 V4 G1 V5 Purge pressure V3 Purge Compensation Regulator, adjustable Gauge Regulator Shut Off NITROGEN SUPPLY max. 16 bar typ. 10 bar V2 V1 PURGED GASSES FROM PACKING max pressure 16 bar YYP range 1 – 3 bar G2 LEAKAGE
  • 47.
    • HRP CoolingSystem • HRP Drilled Radial Flow Type Design of cooled packings is currently under review COOLING OF PRESSURE PACKINGS
  • 48.
    HRP Cooling System Frictionalheat has to be dissipated. For discharge pressures greater than 70 bar water cooling is necessary in general. For lower pressures water cooling is necessary only under special conditions. COOLING OF PRESSURE PACKINGS
  • 49.
    HRP Cooling System Forcedflow cooling by 340° milled groove gives: – improved water flow – no stagnancy – reduced pressure drop through packing cooling system water water outlet cooling water inlet water water outlet water inlet Required cooling water: pressure : 0.5 to 5 bar max. temperature: 40°C COOLING OF PRESSURE PACKINGS
  • 50.
    HRP Drilled RadialFlow Type- conforms to API 618 • Better coolant flow with reduced losses • Meets API 618 revision 4 by eliminating “O” rings which surround the piston rod • Easier to change packing rings without removing the piston rod • Cooling passages can be cleaned by removal of plugs COOLING OF PRESSURE PACKINGS
  • 51.
    • Main Characteristics •Typical Pressure Packing Types • HRP Stationary Gas Seal • Features of HRP Pressure Packings • Testing of Pressure Packings PRESSURE PACKING TYPES
  • 52.
    Characteristics The main characteristicsof Pressure Packings are: • lube or non-lube • with or without cooling • with or without vent • with vent and • with or without purge These characteristics are dependent upon: • discharge pressure • differential temperature. • piston speed • customer specification • process requirements Type and number of ring groups depend on the design criteria • see “Basic Understanding”. PRESSURE PACKING TYPES
  • 53.
    Non lube, uncooled,not vented, not purged, for discharge pressures less than 10 bar Double acting ring groups are used 0308 0306 RING GROUP 0344 Crank end Cylinder end TYPICAL PACKING TYPES
  • 54.
    Non lube, uncooled,not vented, not purged, RING GROUP 0371 0310 0304 0306 Crank end Cylinder end for discharge pressures less than 30 bar Pressure Breaker Ring Single acting ring groups RING GROUP 0349 0310 1302 TYPICAL PACKING TYPES
  • 55.
    Lube Lube, uncooled, notvented, not purged, for discharge pressure from 30 bar to 70 bar Crank end Cylinder end oil oil from cylinder lube pump RING GROUP 0371 0310 0304 0306 Pressure Single acting Breaker Ring ring groups RING GROUP 0349 0310 1302 TYPICAL PACKING TYPES
  • 56.
    Non lube, cooled,not vented, not purged - 170 bar Crank end Cylinder end For pressures greater than 70 bar cooled packings are recommended O-rings are used to prevent the process gas from entering the water channels and to also prevent water from leaving the water channels TYPICAL PACKING TYPES
  • 57.
    Non lube, uncooled,vented, not purged - 70 bar Vented gas is piped to flare or to a lower pressure level of compressor. Gas vent SLP ring group: side load pressurized, behind vent For dangerous gases - toxic or explosive: For dangerous gases - toxic or explosive: Crank end Cylinder end RING GROUP 0373 0312 0314 0313 TYPICAL PACKING TYPES
  • 58.
    Non lube, uncooled,vented and purged - 70 bar For very dangerous gases or low emission values For very dangerous gases or low emission values purge gas purge gas gas mixture Crank end Cylinder end gas Purge gas (mainly Nitrogen) is inlet in to the last container. Inlet pressure normally is 1 bar minimum above vent pressure. The mixture of dangerous gas and purge gas is piped to the vent collection TYPICAL PACKING TYPES
  • 59.
    HRP Design Segmental PackingRings only seal during dynamic reciprocating action. Piston energised Piston energised DYNAMIC : NO ROD CONTACT STATIC : ROD CONTACT Pneumatically operated externally, when the rod is stationary to prevent cylinder gas emission Cylinder end Stationary Gas Seal energises when the compressor is stopped Stationary Gas Seal energises when the compressor is stopped STATIONARY GAS SEAL
  • 60.
    Segmental packing ringsonly seal during dynamic reciprocating action. Distance piece Cylinder end HRP Design Cartridge unit fitted to existing Packing increasing length For standstill additional parts are necessary STATIONARY GAS SEAL
  • 61.
    Application Features TYPICAL WATERCOOLED PRESSURE PACKING Face & outside dia connections make flange more serviceable. Thermocouple to detect increases in temperature Detachable flange to aid assembly Vent connection can be fitted with an off-line flow measurement device Facility for rod drop indicator to detect rider ring wear FEATURES OF HRP PRESSURE PACKINGS
  • 62.
    Design Features Spiral wound Gasket, optional,to reduce static leakage Tee shaped Cup complete with`SLP' Rings & purge (API618) allows for sealing faces to be machine-lapped Milled groove Coolant Channels to reduce pressure drop to a minimum `O'-Ring design can be captive, totally eliminating possibility of gas leakage into water channels Fully lapped faces with O-Rings eliminate static leakage TYPICAL WATER COOLED PRESSURE PACKING FEATURES OF HRP PRESSURE PACKINGS
  • 63.
    Standard and ExtraLeakage Testing Procedures Standard test of water cooled packings: • Pressurised air (6 bar) is connected to cooling water inlet. • Air inlet valve will be closed. • Pressure drop is checked at the closed volume Standard bubble test • Pressurised air (6 bar) is connected to cooling water inlet. • Packings are submerged in water, bubbles indicate leakage. • After test packings are disassembled, cleaned, dried and reassembled. • Test do not show reasseambling errors. Extra test when required - all packings • Check of the gas tightness between the test flanges TESTING OF HRP PRESSURE PACKINGS
  • 64.
  • 65.
    Piston Rods Lube aircompressor - unhardened 30 HRC, cut threads Process gas compr. - Induction hardened (occasionally nitrided) 50 to 55 HRC, rolled threads Coated rods - Thermal plasma sprayed, mostly to 65 - 70 HRC Materials Materials Surface Finish - hardened rods Ra : 0,2 - 0,4 µ µ µ µm - coated rods Ra : 0,2 - 0,25 µ µ µ µm Coating - Chromium oxide for reducing - Ceramics (Metco P130), produced rod wear and/or with plasma gun method (HVOF) reconditioning - Tungsten Carbide produced with plasma gun (HVOF) or “Detonation Gun” method Surface Finish Surface Finish - hardened rods Ra : 0,2 - 0,4 µ µ µ µm - coated rods Ra : 0,2 - 0,25 µ µ µ µm Coating - Chromium oxide for reducing - Ceramics (Metco P130), produced rod wear and/or with plasma gun method (HVOF) reconditioning - Tungsten Carbide produced with plasma gun (HVOF) or “Detonation Gun” method higher value of Ra preferred ASSOCIATED PRODUCTS
  • 66.
    End of the TrainingFile Pressure Packings END