Applying Condition Based Monitoring Approach in Engineering Management Services
Applying Condition Based Monitoring Approach in FacilityManagement Services by Ismail Yusof
CONTENTS Maintenance Strategies Condition Based Maintenance (CBM) Condition Based Maintenance Cycle Spectrum of CBM Detection Method in CBM Mortality of Machinery & Bathtub Type of CBM IR/VA/OA/PQA/US Benefits The Challenges
Condition Based Maintenance A predictive approach can be applied to any equipment problem if, A physical parameter like vibration, temperature, pressure, voltage, current, or resistance can be measured. An engineering limit for the measured physical parameter must be, established so a problem can be detected during routine monitoring. The limit should be low enough to detect the problem before excessive damage occurs. Correcting of the root problem is the key to most predictive efforts.
Condition Based Maintenance Cycle Condition Based or Periodic Monitoring CorrectiveMaintenance no (Schedule) yes OpenCorrective AnalyzeWork Order Problem
Spectrum of CBM With CBM technology, a vast number of equipment failures can be predicted. Vibration measurement on rotating equipment & InfraRed Thermography is probably the best known of current CBM applications, but other categories of industrial equipment also benefit from a CBM approach.
Detection Method in CBM Spectrum of CBMEquipment Equipment Failure Mode Failure Cause DetectionCategory Types MethodRotating Machinery Pumps, Motors, Premature Bearing Excessive Force Vibration and Lube Compressors, Blowers Loss Analysis Lubrication Failure Over, Under, Spectrographic & or Improper Lube; Heat Ferrographic Analysis and MoistureElectrical Equipment Motors, Cable, Insulation Failure Heat, Moisture Time I Resistance Starters, Transformers Tests, IR Scans and Oil Analysis Corona Discharge Moisture Splice Ultrasound MethodsHeat Transfer Exchangers, Fouling Sediment I Material Heat TransferEquipment Condensers Buildup CalculationsContainment and Tanks, Piping, Corrosion Chemical Attack Corrosion Meters,Transfer Equipment Reactors Thickness Checks Stress cracks Metal Fatigue Acoustic Emission
The mortality of machinery There is a definite pattern of life spans. In practice, this pattern manifests itself when a collection of machinery is subjected to rigorous operation. The plot of typical life spans is shown in the so-called bathtub curve. There is a rather high incidence of early failures, called infant mortalities. Most equipment that survives infancy will continue to perform with few failures occurring. In time, however, the failures begin to increase until the last of the group succumbs.
Bathtub Curve Normal Aging Infant MortalitiesMachineFailures Random Failures Machine Life - Years
Type of Condition Based Maintenance o Infra Red Thermography o Vibration Analysis o Oil Analysis o Power Quality Analysis o Ultrasound
InfraRed Thermography (IR) Infrared thermography, thermal imaging, thermographic imaging, or thermal video, is a type of infrared imaging science. Thermographic cameras detect radiation in the infrared range of the electromagnetic spectrum (roughly 900–14,000 nanometers or 0.9– 14 µm) and produce images of that radiation, called thermograms. Since infrared radiation is emitted by all objects near room temperature, according to the black body radiation law, thermography makes it possible to "see" ones environment with or without visible illumination. The amount of radiation emitted by an object increases with temperature, therefore thermography allows one to see variations in temperature. When viewed by thermographic camera, warm objects stand out well against cooler backgrounds; humans and other warm- blooded animals become easily visible against the environment, day or night. As a result, thermographys extensive use can historically be ascribed to the military, security services and Condition Based Maintenance.
Sample of IR ImagesInfrared Image Photo AR01 151.5°CLI01 140 120 AR02 LI02 100 80 SP01 60 SP02 40 33.3°C Thermal Profile °C IR01 150 100 50 Line Min Max Cursor li01 37.6°C 125.9°C - li02 36.2°C 58.9°C - li03 - - -
VIBRATION ANALYSIS (VA) Vibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road Rotating machinery has a characteristic vibration pattern depending on the location the vibration data is collected. Characteristic vibrations are produced at different frequencies for similar equipment. Any change to these vibration patterns will indicate the nature and severity of a defect such as misalignment of shafts, bearings and footing etc. In vibration analyses a transducer converts mechanical motion (vibration) to electrical signals. These electrical signals are then plotted on amplitude versus frequency plots, which then is analyzed to predict the source of vibration.
Defining VA Limits Many engineered limits have already been established for equipment by manufacturers, professional societies and industrial groups. Vibration Institute, a not-for-profit professional organization, and other organizations have established levels of equipment health as a function of vibration velocity based on experiments. A simplification of this equipment health data for ‘Rotating machinery ratings.‘ This table is useful for categorizing vibration levels on most industrial equipment operating between 600 rpm and 3600 rpm.
Vibration Limits Rotating Machinery RatingsRating Vibration Level Necessary ActionGood Less than .15 ips Continue to trendFair .15 ips to .30 ips Continue to trendPoor .30 ips & above Analyze & Correct
Using Ultrasound & Vibration In the past, ultrasound and vibration technologies have been used independently to monitor ball bearings in plant equipment. However, it is becoming more common to use ultrasonic inspection interfaced with vibration analysis to support CBM maintenance programs for periodic inspection of critical bearings to monitor wear and predict failure.
Oil Analysis Oil analysis (OA) is the sampling and laboratory analysis of a lubricants properties, suspended contaminants, and wear debris. OA is performed during routine preventive maintenance to provide meaningful and accurate information on lubricant and machine condition. By tracking oil analysis sample results over the life of a particular machine, trends can be established which can help eliminate costly repairs. The study of wear in an machinery is called tribology. Tribologists often perform or interpret oil analysis data. The sample sent to Accredited Lab for analysis.
Oil Analysis OA can be divided into three categories: Analysis of oil properties including those of the base oil and its additives. Analysis of contaminants. Analysis of wear debris from machinery.
Oil Analysis Comparing the OA results of new and used oil, a tribologist can determine when an oil must be replaced. Careful analysis might even allow the oil to be "sweetened" to its original additive levels by either adding fresh oil or replenishing additives that were depleted.
BENEFITS OF APPLYING CONDITION BASED MAINTENANCE Increase Your Profitability by: • Reducing capital costs. • Reducing maintenance costs. • Reducing energy costs. Reduces the risk of: • Costly business interruption. • Fire/ life safety. • Code violations.
The Challenges Ahead !!!! First and most important of all, the initial cost of CBM is high. It requires improved instrumentation of the equipment. Often the cost of sufficient instruments can be quite large, especially on equipment that is already installed. Next introducing CBM will invoke a major change in how maintenance is performed, and potentially to the whole maintenance organization in a company. Organizational changes are in general very difficult. The technical side of it is not always as simple. Even if some types of equipment can easily be observed by measuring simple values as vibration (displacement or acceleration), temperature or pressure, it is not trivial to turn this measured data into actionable knowledge about health of the equipment. Also Limited Maintenance/resources budgets (insufficient manpower, tools, training and skilled staff). Lastly Obsolete systems & equipment.