Terry Harris Reliable Process RW
Reliable Process Solutions It Can Operate Forever
Equipment Failure Modes Training A study of how components fail and how we can make them last forever!
Terry Harris, CMRP Certified RCM facilitator Predictive/proactive maintenance training Lubrication audits Lubrication excellence training programs Detailed equipment failure modes training Training programs for oilseeds industry Asset criticality software, assessment, training Environmental, health and safety software/assessment Maintenance audits Reliable installation project management services Cost-effective training articles/PowerPoints Exam director for SMRP
The Future of Manufacturing • • •
Operational excellence is a must Assets must be available and reliable We must operate at the lowest cost We must do the right maintenance on the right equipment
Equipment Reliability Everything in your plant is going to fail!
Potential Failure Curve S
PF Interval
FF S – The point in time when failure can first be detected. FF – Functional Failure* * See RCM Terms
Reactive 10-15
Equipment Performance
Time
FF
Reactive Maintenance
Reactive Maintenance
Can things be fixed correctly when they are done in the reactive mode?
Maintenance is a Reliability Function Not a Repair Function
BUT, Reliability is not just about maintenance
Reactive 10-15
Equipment Performance
Time
FF
Reactive Issues Affecting Efficiency -Inability to perform precision maintenance -More spare parts -Expediting of spare parts -Unplanned maintenance -Unplanned downtime -Quality issues -E,H,&S issues -Inefficient use of maintenance time -Inefficient use of operations time -Extremely short equipment life Work practices don’t extend equipment life
Behavioral Cycle of Despair
2469
Ref: DT, S. Thomas
Predictive
Reactive
30-50
10-15
Equipment Performance Time
FF
Predictive Maintenance • 90% of all failures can be predicted! • 90% of all bearing failures can be predicted six months before failure! • 90% of all motor failures can be predicted 6-12 months before failure!
Predictive Maintenance 9 Reduces collateral damage 9 Time to plan the work 9 Time to do the correct maintenance 9 Time to have correct parts (no expediting) 9 Time to do precision maintenance 9 Less spare parts – 30% less 9 More efficient use of maintenance time 9 Less emergency downtime 9 Repair work can extend equipment life 9 Safer work conditions
Reliability What can we do while the equipment is running at its peak performance or when it is new? Can being proactive extend equipment life cycles?
Proactive 70-100 PP
Predictive 30-50
Reactive 10-15
Equipment Performance
Lubrication Excellence Precision Maintenance Alignment, Balance, etc. Select Suppliers Supplier Specifications Metrics Equipment Ranking RCM TPM RCA/FMEA RCD Training Programs Written Procedures Job Planning/Scheduling CMMS System
Time
FF RCA
Proactive Maintenance ¾ Maximizes precision work techniques ¾ Minimum spare parts, 50% reduction ¾ Maximum runtime, minimal downtime ¾ 80% of maintenance tasks proactive ¾ Minimal EH&S exposure ¾ Very low quality issues ¾ Maximum equipment life ¾ Lower MRO costs ¾ Reduction of predictive maintenance costs ¾ Elimination of equipment failure modes ¾ Allows you to perform “lean maintenance”
Proactive 70-100 PP
Predictive 30-50
Reactive 10-15
Equipment Performance
Lubrication Excellence Precision Maintenance Alignment, Balance, etc. Select Suppliers Supplier Specifications Metrics Equipment Ranking RCM TPM RCA/FMEA RCD Training Programs
PM Tasks
Written Procedures Job Planning/Scheduling CMMS System
Time
FF RCA
What Did Your Shoes Cost You?
Pump Components
Pump Component Failures ANSI states: Average life of centrifugal pumps in U.S. industrial plants is 18 months.
Operations with Few Failures
What are the Factors of Equipment Life Cycle Improvement? ¾ Engineering ¾ Design ¾ Fabrication ¾ Installation ¾ Operations ¾ Maintenance
Engineering/Design 25-35% of equipment reliability issues are engineering and design related. ¾ Poor equipment selection ¾ Motors, pumps, couplings, equipment options, pump bases, gear reducers, fans, conveyors, packing equipment, etc.
¾ ¾
Improper sizing of equipment/components Improper piping design practices ¾ Elbows on inlet flanges ¾ Pipe strain on equipment ¾ Torque methods on fasteners
¾ ¾
Poor base/foundation designed/structures Understanding of factory alignment/balance
Engineering/Design ¾ Who ¾ Who ¾ Who ¾ Who ¾ Who ¾ Who ¾ Who
makes makes makes makes makes makes makes
the the the the the the the
best best best best best best best
motor? pump? bearings? roll mills? actuators/valves? coupling? pump base?
Knowing the answer to these questions is what adds life and reliability to the equipment.
HSB Risk Study at a Petrochemical Plant
2344
Ref: Oliverson, HSB
Mechanical Seals How long should a mechanical seal last? How long do mechanical seals last?
Sealing Points
Mechanical Seals Failure Modes: ¾ Improper storage and handling ¾ Improper installation ¾ Failure of shaft O-ring ¾ Inability to adjust for wear ¾ Seal cover O-ring failure ¾ Failure of spring tension component ¾ Fails due to coupling misalignment ¾ Fails due to impeller imbalance
Sealing Points
Mechanical Seals Failure Modes: ¾ Fails due to bearing wear ¾ Fails due to shaft deflection ¾ Fails due to operating with no fluid film ¾ Fails due to foreign material ¾ Fails due to broken drive pin ¾ Fails due to overpressure
Shaft Deflection
Shaft Deflection Rule: Always verify the shaft length/diameter rule: L3/D4 constant should never be over “50” Length to the 3rd divided by diameter to the 4th Example: Pump is 7” from bearing to impellor Shaft diameter is 1 7/8” L3 = 343, D4 = 12.36 = 27.8 Shaft cut down to 1.5” for a sleeved shaft = 68.6
Seal O-ring Failures
Chemical Attack
Chemical Attack
Mechanical Failure
Thermal Failure
Thermal Failure
When a seal fails, don’t just replace it. Determine the real cause of failure. Some causes for failures, which are often ignored, are listed below. 1. Misalignment of components 2. Poor bearing lubrication (little bearing wear with oil mist) 3. Vibration of rotating components 4. Contaminated fluid (water, acids or particulate) 5. Twisting condition due to “soft foot” at mounting pads 6. Poor component base plate grouting or mounting 7. Rotor imbalance or shaft whip 8. Inadequate flushing procedures during commissioning or start-up after repairs
9. Poor, or careless seal or bearing installation 10. Piping strains, due to misalignment or temperature variations 11. Looseness of bolts and brackets 12. Addition of incompatible fluid 13. An increase in temperature (or a dramatic change in temperature) 14. Unclean operating conditions (causing dirt ingression) 15. A change in filtration practices Selecting the correct seal is only the beginning of sound equipment operation. Ongoing predictive condition monitoring using vibration and fluid analysis, a regular review of equipment operating logs and the implementation of a sound preventive maintenance program will ensure the long life of seals, eliminating leaks and environmental damage, and will add millions of dollars to the bottom line.
Impact on Mechanical Seal Life 12
With Oil Mist
8 6 4
Without Oil Mist 2
Se p01
Ju l-0 1
ay -0 1 M
ar -0 1 M
Ja n01
N
ov -0 0
0 Se p00
Years
10
• Oil mist contributes to higher mechanical seal MTBF
Reliability-Centered Maintenance
What is RCM?
Preventive Maintenance
Maintenance performed on time base or condition-based strategy.
Preventive Maintenance Everyone has a PM program. What are the types of PM programs? ¾ Time based ¾ Condition based ¾ Failure finding ¾ OEM directed (Recommended) ¾ Hand me down (Experience) ¾ Regulatory, EPA, OSHA ¾ Risk
Activities of Preventive Maintenance ¾ Routine functions performed at regular intervals of time or life cycles of use ¾ Lubricating ¾ Cleaning ¾ Inspection; visual or by measurement ¾ Adjustments to specifications ¾ Replacement of parts due to ordinary wear ¾ Early identification of potential problems ¾ Documentation of work performed
PM Optimization The reverse of RCM: PM optimization is the study of each PM task to prove it adds value and life to your component life cycle.
PM Optimization 1. 2. 3.
4. 5.
Select equipment or component for PM Make a list of the current PM tasks and frequency. Ask the question: Is this task necessary? a. Does this task help identify an onset to failure? (inspections, PDM, calibrations) b. Does it help avoid failure or extend life? (lubrication tasks, filter change out) c. Is it related to a known, consistent failure mode? (belt life, dc motor brushes) d. Does the PM task help me find/avoid a significant failure? Can the PM task be eliminated? Does the task have adequate specifications, so if we have a failure, we can take corrective action? Example: “Check the belts” Or: Check the belts to assure good condition, no slipping or flipping. If can be isolated, check to assure proper tension of no more than 1-inch deflection with a 5-pound load.
PM Optimization 6. What is the process for the current PM task/frequency? Known failure rate Equipment history data files or analysis Statistical analysis (Weibull) Best judgment Regulatory requirement 7. For each PM task, always consider the consequence of the failure. High consequence may increase the frequency of the PM or PdM tasks. 8. Based on the above information, should frequency be increased or decreased for any current tasks? 9. What has the task found in the past year to indicate the task is obtaining results? 10. What failure mode has been eliminated by using this task? 11. Where possible, look at PM that are intrusive and may result in infant mortality issues.
PM Optimization 12. Could any of the scheduled rebuild tasks be deferred or eliminated by using a PdM method for early detection? 13. Could any of the items such as tightening, adjusting, lubricating, cleaning or inspecting be done by an operator? Operators can, in many cases, perform these tasks on higher frequencies and reduce failures. What are the issues that can must be considered: training, safety, plant culture, unions, environment? 14. Can PMs be consolidated by covering them all at one downtime or service visit? 15. Are there any failures or known failure modes that are not being covered during PMs. Are there any hidden failures that need to be added to the PM program? 16. This optimization program should be reviewed every year for continuous improvement. 17. Don’t assume OEM (vendor PMs) are correct, and don’t assume everything you are now doing is correct.
Components Components: The parts and pieces that make up our equipment and processes. Some companies want to be trained on individual detailed components; some want to be trained on equipment pieces.
Motor Housing Failure Modes: Fails due to: Improper installation Physical damage Corrosion Material buildup
Motor Housing We would not think of the motor housing “failing to perform” would cause any problems, but there are failure modes and they affect other component functions and failures. Improper installation such as not correcting soft foot will lead to failure of bearings, broken feet and shaft bending.
Soft Foot Examples
Motor Soft Foot Failures
Motor Soft Foot Effects
Motor Housing Material build up on the housing? How can this be a failure mode of the motor? Keeping the housing clean and clear of buildup can reduce operating temperature and extend motor life. I once cleaned a motor housing and reduce the temperature by 35 degrees F.
Motor Stator The motor stator houses the stator core and windings. The stator core consists of many layers of laminated steel, which is used to help create the magnetic field.
Motor Stator Failure Modes: Fails due to: Physical damage Contamination Corrosion High temperature Voltage imbalance Broken supports Rewind burnout procedures
Motor Stator Stator fails due to rewind burn out of windings. Windings in motors are often burned out for before the motor can be rewound. This process on emergency repair motors can damage the stator structure by weakening or cracking the supports. The stator can also deform and cause problems with the rotor and motor efficiencies.
Motor Rotor Failure Modes: Fails due to: Physical damage Imbalance Broken rotor bar Contamination Improper installation
Motor Rotor
Motor Rotor Imbalance of motor rotors is quite normal and
usually causes problems for other components like the bearings. But the imbalance will eventually lead to the rotor making contact with the stator and creating a failure. Overheating during rebuild can still occur damaging the rotor components. Establish precision balance standards.
Motor Bearings Failure Modes: Fails due to: Improper handling Improper storage Improper installation Misalignment Improper lubricant Over-lubrication/under-lubrication Contamination Overhung load
Motor Bearings Bearing failure due to misalignment. This misalignment of the coupling can reduce bearing life by three to five times. Studies from NASA and the petrochemical industries indicate these statistics. Motor coupling alignment should be under .003 in all three planes after thermal expansion.
Grease Cavity
Proper Lubrication
Motor Bearing Seals Failure Modes: Fails due to: Over-lubrication Improper installation
Bearing Housing Seal
Bearing Housing Failure Modes: Fails due to: Improper installation Corrosion Improper tolerance
Motor Fan Failure Modes: Fails due to: Physical damage Ice build-up Foreign material Corrosion
Motor Fan Guard Failure Modes: Fails due to: Physical damage Plugging
Motor Insulation/Windings Failure Modes: Fails due to: Contamination Overheating Improper storage Moisture Insulation breakdown Cycling/flexing AC drive stress
Insulation/Windings Insulation breakdown
will cause the windings to short out. This will often be noticeable with MCE testing and thermography.
Motor Shaft Failure Modes: Fails due to: Physical damage Improper manufacturing Improper installation Corrosion
Preventive Maintenance for Motors Preventive Maintenance: Grease motors as needed based on service with the proper motor rated grease. Change oil in lubricated bearings often based on temperature or analysis. Perform hands on inspections weekly. Keep motors clean with good air flow. Store motors correctly away from moisture. Keep moisture and chemicals away from motors.
Precision Maintenance for Motors Precision Maintenance: Always align motors to under .003 in all 3 planes and eliminate soft foot. Always specify precision balance of the rotor to .05 inch/second. Use certified motor rebuild shops for all motors. Buy or rebuild?
Predictive Maintenance for Motors Predictive Maintenance: Motor circuit evaluation to detect nearly all motor failures. Vibration analysis for many motor failures. Mechanical ultrasound for bearings, rotor bar, some electrical. Oil analysis on sleeve bearings.
Proactive Maintenance for Motors Purchase precision motors for critical applications. Use certified motor rebuild shops with specifications. Make sound decisions on rebuild or new. Motor rebuild decision tree. Use precision maintenance on installation, alignment, balance and lubrication.
Asset Criticality What are your most critical assets? How do we know for sure?
BEARING LIFE EXTENSION Understanding Why Bearings Fail
Bearings Don’t Just Fail, They Are Murdered!
Bearing Failure
Reliabi lity Solutions
16
Murdered Bearing
Bearing Failure Modes
Bearings Bearings, Fatigue and Life Fatigue is the work hardening of the
bearing surfaces to the point where the metal fatigues.
Bearings Failure Modes: Transportation failures Storage failures Handling failures Installation failures Overheating/Undercooling Improper crossover Imbalance Misalignment Lubrication
Storage Failures Storage of bearings will assure that the bearing has no defects when it is ready for use. Bearings should: Never be dropped/mishandled Lay flat Be stored on wood/rubber Be stored with minimal vibration Be stored in a clean area Be stored in a climate controlled area.
Installation Failures
What is the best method for installing mounted bearings? SHAFT PREPARATION: Wipe the shaft clean and remove any burrs that could cause the bearing’s inner race to deform when the setscrews are tightened down. Proper shaft diameter is CRITICAL. Check the shaft diameter against the specifications in the “Shaft Fit” table; if it’s not within those tolerances, its use may lead to premature bearing failure. MOUNTING: Slide the bearing (and collar, if applicable) onto the shaft in the desired position. DO NOT use anti-seize lubricant on the shaft or bearing. Leave the setscrews (and collar, if applicable) loose. BASE PREPARATION: Make sure the base of the mounted bearing and the support surface are clean and flat. Any unevenness in the surface can deform proper bearing fits and lead to premature failure. Securely fasten the mounted bearing to the support surface using the machinery manufacturer’s recommendations. TIGHTENING: Setscrew lock: Begin tightening both setscrews down alternately with the proper torque, until both setscrews are locked to the shaft at the proper torque. Eccentric collar lock: Place the eccentric collar on the bearing’s inner race and turn rapidly in the direction of rotation, until the eccentric grooves engage the collar to the bearing. Use a drift or punch in the hole of the collar and drive it sharply with a hammer in the direction of the shaft’s rotation. This will help to ensure the lock on the shaft. Tighten the collar’s setscrew using the proper torque.
Imbalance Failures The effects of imbalance of impellors, fan rotors, motor rotors and other rotating equipment has a dramatic effect on bearing life. Use precision balance as one your proactive maintenance practices and greatly extend bearing life.
F = Force m = imbalance (lbs) r = radius of imbalance (in) f = rotational speed (Hz) g = 386.4 in/sec2 Substitute 1 oz. (1/16 lb.), 12", 3600 RPM (60 Hz):
Thus, 1 ounce of imbalance on a 12-inch radius at 3,600 RPM creates an effective centrifugal force of 275 pounds. Now calculate the effect of this weight on bearing life. Suppose that the bearings were designed to support a 1,000-pound rotor. The calculated bearing life is less than 50% of the design life as shown below.
Precision Balance can be affected by not cutting keyways in shafts the correctly. The correct method is as follows using the drawing below. Measure from the end of the shaft to the edge of the taper of the keyway slot. This is “A”. Measure the length of the coupling, this is “B”. A + B / 2 is the proper length of the key.
You are trying to replace only the weight of the remove metal in the keyway slot.
Misalignment Failures A study in the petrochemical industry realized the following results: • Average bearing life increases by a factor of 8.0. • Maintenance costs decrease by 7%. • Machinery availability increases by 12%.
Chemical Composition of Bearing Steel Carbon
0.98
Chromium
1.3-1.6
Iron
Balance
Maganese
0.25
Phosphorus
0.025 max
Silicon
0.15-0.35
Sulphur
0.025 max
Shaft Sealing
How can I get the longest life out of my bearings? CHECK YOUR FITS FIRST. A loose shaft or housing fit will let the bearing wobble or creep and cause uneven wear. A tight shaft or housing fit will reduce internal clearance and prevent grease or oil from lubricating the bearing properly. CHECK YOUR LOAD. Overloading will greatly accelerate metal fatigue and shorten the bearing life. Underloading will cause rolling elements to skid rather than roll, damaging the running surfaces. INSTALL WITH CARE. To press into a housing, make sure you press on the outer race; to press onto a shaft, press on the inner race. If installing by hand, avoid sharp blows; use a block of wood or a piece of pipe between the hammer and bearing, and tap it in at various points around the bearing. LUBRICATION PROCESS. Over-lubrication, under-lubrication, wrong lube, wrong additive, mixed lubes, etc. All these lead to shortened component life. KEEP THEM CLEAN. Contaminants can get embedded in the running surfaces and do irreparable damage to the rolling elements. Even tiny amounts of water can get trapped in the grease and lead to internal rust. KEEP THEM ALIGNED. Misalignment between the shaft and housing forces the rolling elements into an oval path, rather than circular, leading to uneven wear and possibly destroying the retainer. DAMPEN VIBRATION. Vibration from elsewhere in the machine causes the bearing to chatter and damages the running surfaces. Vibration may be caused by misalignment of a drive component, or a component being out of balance.
Gear Reducers Failure Modes: Lubrication practices Installation and rebuild practices Overloading Improper sizing
Gearbox Failure
Gearbox Failure
Gearbox Failure
A gearbox inspection and a homemade gasket lead to failure of this gear reducer. Gasket blocked the vent hole, box over-pressured, overheated, blew bottom seal. Lubricant lost and gearbox failure.
Gear Reducers Gearbox Best Practices: ¾ Size for higher rating or larger units ¾ No dip sticks to check oil level Use a sightglass for oil level ¾ Quick-connects on drain and fill ports ¾ Desiccant breather on the vent ¾ External filter system ¾ Filter from bottom of the unit ¾ Use good judgment on viscosity
Centrifugal Pumps Centrifugal pump life failures: Balanced impellers Good lube practices Precision bearing bores High tolerance straight shafts Good lube oil seals Consider oil mist in critical applications
Bearing Lube
Belts
V-Belt Failure Modes Failure Modes: Fails due to improper storage Fails due to misalignment Fails due to improper tension Fails due to over temperature Fails due to improper installation Fails due to improper matching
Belt Failure Modes Proper storage of belts can add years to the life of the belt. Keep Keep Keep Keep Keep
belts belts belts belts belts
storage out of direct sunlight stored away from heat sources stored away from chemicals stored away from moisture stored away from abrasive dust
V-BELT TENSION FORCES Manufacturers’ Recommended V-belt Tension Levels Belt Cross Sect.
Deflection Force-lbs.*
Shaft Forces-lbs.
Plain
Notched
Plain
Notched
A
3.5
4.5
112
144
B
5.1
6.5
163
208
C
12.0
14.0
384
448
D
25.0
26.0
800
832
3V
4.0
5.0
128
160
5V
10.5
13.0
336
416
8V
28.0
32.0
896
1024
*Approximate average for all sheave sizes and manufacturers
Calculated L10 Bearing Life Direct Drive vs. Belt Drive Fans
Direct Drive: Motor bearings proper alignment: L10 200,000 hrs = 22.6 yrs
Belt Drive: Motor bearings radial load: L10 40,000 hrs = 4.57 yrs or 10 times the chance of motor failure
Pillow block bearings: L10 40,000 hrs = 4.57 yrs or 10 times more change of bearings or shaft
Overall: A belt drive fan has a 10 times greater chance of motor or bearing change with belt drive over direct drive. Data based on actual historical data provided by an independent motor manufacturer. Some direct drive applications were over 25 years.
V-Belts and Temperatures For every 18 degree F increase in belt temperature, the belt’s life is cut in half.
OR For every 36 degree F increase in ambient temperature, the belt’s life is cut in half. Minimum cold start-up temperature is -30 degrees F.
Data above courtesy of Gates Rubber Company
DriveN
DriveR
Larger sheaves mean lower tension and more than 4 times the life!
C
TPeak TBending
T Tight Side D
A
B
Position
C
TLoose Side A
D
A
D
DriveN
DriveR
B
18” sheaves
TPeak
T Tight Side D
A
Cycles to Failure
C
Belt Tension
Comparing larger and smaller sheaves with the same rpm, same number of cycles and power requirements
Belt Tension
B
12” sheaves Peak Belt Tension
D
B
Position
C
D
A
Peak Tension
Changes
A
Cycles to Failure
Belt Life Strategy ¾ Proper alignment and proper tension ¾ Enclosed guards only if needed ¾ When sizing add a belt or increase belt size ¾ Use good storage methods ¾ Used power band belts if possible ¾ Modify equipment to achieve precision alignment ¾ Use sheave gauges on each belt change ¾ Use balanced sheaves/precision bored ¾ Reduce heat from slipping or ambient
Belt Failures Caused by slipping of the belt on pulley Turning around a small pulley or flexing Oil or contamination Foreign material or damaged pulley wall Forces over pulley edge, excessive strain, physical damage
Equipment Failure Modes Training A study of how components fail and how we can make them last forever!
Terry Harris, CMRP Certified RCM facilitator Predictive/proactive maintenance training Lubrication audits Lubrication excellence training programs Detailed equipment failure modes training Training programs for oilseeds industry Asset criticality software, assessment, training Environmental, health and safety software/assessment Maintenance audits Reliable installation project management services Cost-effective training articles/PowerPoints Exam director for SMRP
The Future of Manufacturing • • •
Operational excellence is a must Assets must be available and reliable We must operate at the lowest cost We must do the right maintenance on the right equipment
Equipment Reliability Everything in your plant is going to fail!
Potential Failure Curve S
PF Interval
FF S – The point in time when failure can first be detected. FF – Functional Failure* * See RCM Terms
Reactive 10-15
Equipment Performance
Time
FF
Reactive Maintenance
Reactive Maintenance
Can things be fixed correctly when they are done in the reactive mode?
Maintenance is a Reliability Function Not a Repair Function
BUT, Reliability is not just about maintenance
Reactive 10-15
Equipment Performance
Time
FF
Reactive Issues Affecting Efficiency -Inability to perform precision maintenance -More spare parts -Expediting of spare parts -Unplanned maintenance -Unplanned downtime -Quality issues -E,H,&S issues -Inefficient use of maintenance time -Inefficient use of operations time -Extremely short equipment life Work practices don’t extend equipment life
Behavioral Cycle of Despair
2469
Ref: DT, S. Thomas
Predictive
Reactive
30-50
10-15
Equipment Performance Time
FF
Predictive Maintenance • 90% of all failures can be predicted! • 90% of all bearing failures can be predicted six months before failure! • 90% of all motor failures can be predicted 6-12 months before failure!
Predictive Maintenance 9 Reduces collateral damage 9 Time to plan the work 9 Time to do the correct maintenance 9 Time to have correct parts (no expediting) 9 Time to do precision maintenance 9 Less spare parts – 30% less 9 More efficient use of maintenance time 9 Less emergency downtime 9 Repair work can extend equipment life 9 Safer work conditions
Reliability What can we do while the equipment is running at its peak performance or when it is new? Can being proactive extend equipment life cycles?
Proactive 70-100 PP
Predictive 30-50
Reactive 10-15
Equipment Performance
Lubrication Excellence Precision Maintenance Alignment, Balance, etc. Select Suppliers Supplier Specifications Metrics Equipment Ranking RCM TPM RCA/FMEA RCD Training Programs Written Procedures Job Planning/Scheduling CMMS System
Time
FF RCA
Proactive Maintenance ¾ Maximizes precision work techniques ¾ Minimum spare parts, 50% reduction ¾ Maximum runtime, minimal downtime ¾ 80% of maintenance tasks proactive ¾ Minimal EH&S exposure ¾ Very low quality issues ¾ Maximum equipment life ¾ Lower MRO costs ¾ Reduction of predictive maintenance costs ¾ Elimination of equipment failure modes ¾ Allows you to perform “lean maintenance”
Proactive 70-100 PP
Predictive 30-50
Reactive 10-15
Equipment Performance
Lubrication Excellence Precision Maintenance Alignment, Balance, etc. Select Suppliers Supplier Specifications Metrics Equipment Ranking RCM TPM RCA/FMEA RCD Training Programs
PM Tasks
Written Procedures Job Planning/Scheduling CMMS System
Time
FF RCA
What Did Your Shoes Cost You?
Pump Components
Pump Component Failures ANSI states: Average life of centrifugal pumps in U.S. industrial plants is 18 months.
Operations with Few Failures
What are the Factors of Equipment Life Cycle Improvement? ¾ Engineering ¾ Design ¾ Fabrication ¾ Installation ¾ Operations ¾ Maintenance
Engineering/Design 25-35% of equipment reliability issues are engineering and design related. ¾ Poor equipment selection ¾ Motors, pumps, couplings, equipment options, pump bases, gear reducers, fans, conveyors, packing equipment, etc.
¾ ¾
Improper sizing of equipment/components Improper piping design practices ¾ Elbows on inlet flanges ¾ Pipe strain on equipment ¾ Torque methods on fasteners
¾ ¾
Poor base/foundation designed/structures Understanding of factory alignment/balance
Engineering/Design ¾ Who ¾ Who ¾ Who ¾ Who ¾ Who ¾ Who ¾ Who
makes makes makes makes makes makes makes
the the the the the the the
best best best best best best best
motor? pump? bearings? roll mills? actuators/valves? coupling? pump base?
Knowing the answer to these questions is what adds life and reliability to the equipment.
HSB Risk Study at a Petrochemical Plant
2344
Ref: Oliverson, HSB
Mechanical Seals How long should a mechanical seal last? How long do mechanical seals last?
Sealing Points
Mechanical Seals Failure Modes: ¾ Improper storage and handling ¾ Improper installation ¾ Failure of shaft O-ring ¾ Inability to adjust for wear ¾ Seal cover O-ring failure ¾ Failure of spring tension component ¾ Fails due to coupling misalignment ¾ Fails due to impeller imbalance
Sealing Points
Mechanical Seals Failure Modes: ¾ Fails due to bearing wear ¾ Fails due to shaft deflection ¾ Fails due to operating with no fluid film ¾ Fails due to foreign material ¾ Fails due to broken drive pin ¾ Fails due to overpressure
Shaft Deflection
Shaft Deflection Rule: Always verify the shaft length/diameter rule: L3/D4 constant should never be over “50” Length to the 3rd divided by diameter to the 4th Example: Pump is 7” from bearing to impellor Shaft diameter is 1 7/8” L3 = 343, D4 = 12.36 = 27.8 Shaft cut down to 1.5” for a sleeved shaft = 68.6
Seal O-ring Failures
Chemical Attack
Chemical Attack
Mechanical Failure
Thermal Failure
Thermal Failure
When a seal fails, don’t just replace it. Determine the real cause of failure. Some causes for failures, which are often ignored, are listed below. 1. Misalignment of components 2. Poor bearing lubrication (little bearing wear with oil mist) 3. Vibration of rotating components 4. Contaminated fluid (water, acids or particulate) 5. Twisting condition due to “soft foot” at mounting pads 6. Poor component base plate grouting or mounting 7. Rotor imbalance or shaft whip 8. Inadequate flushing procedures during commissioning or start-up after repairs
9. Poor, or careless seal or bearing installation 10. Piping strains, due to misalignment or temperature variations 11. Looseness of bolts and brackets 12. Addition of incompatible fluid 13. An increase in temperature (or a dramatic change in temperature) 14. Unclean operating conditions (causing dirt ingression) 15. A change in filtration practices Selecting the correct seal is only the beginning of sound equipment operation. Ongoing predictive condition monitoring using vibration and fluid analysis, a regular review of equipment operating logs and the implementation of a sound preventive maintenance program will ensure the long life of seals, eliminating leaks and environmental damage, and will add millions of dollars to the bottom line.
Impact on Mechanical Seal Life 12
With Oil Mist
8 6 4
Without Oil Mist 2
Se p01
Ju l-0 1
ay -0 1 M
ar -0 1 M
Ja n01
N
ov -0 0
0 Se p00
Years
10
• Oil mist contributes to higher mechanical seal MTBF
Reliability-Centered Maintenance
What is RCM?
Preventive Maintenance
Maintenance performed on time base or condition-based strategy.
Preventive Maintenance Everyone has a PM program. What are the types of PM programs? ¾ Time based ¾ Condition based ¾ Failure finding ¾ OEM directed (Recommended) ¾ Hand me down (Experience) ¾ Regulatory, EPA, OSHA ¾ Risk
Activities of Preventive Maintenance ¾ Routine functions performed at regular intervals of time or life cycles of use ¾ Lubricating ¾ Cleaning ¾ Inspection; visual or by measurement ¾ Adjustments to specifications ¾ Replacement of parts due to ordinary wear ¾ Early identification of potential problems ¾ Documentation of work performed
PM Optimization The reverse of RCM: PM optimization is the study of each PM task to prove it adds value and life to your component life cycle.
PM Optimization 1. 2. 3.
4. 5.
Select equipment or component for PM Make a list of the current PM tasks and frequency. Ask the question: Is this task necessary? a. Does this task help identify an onset to failure? (inspections, PDM, calibrations) b. Does it help avoid failure or extend life? (lubrication tasks, filter change out) c. Is it related to a known, consistent failure mode? (belt life, dc motor brushes) d. Does the PM task help me find/avoid a significant failure? Can the PM task be eliminated? Does the task have adequate specifications, so if we have a failure, we can take corrective action? Example: “Check the belts” Or: Check the belts to assure good condition, no slipping or flipping. If can be isolated, check to assure proper tension of no more than 1-inch deflection with a 5-pound load.
PM Optimization 6. What is the process for the current PM task/frequency? Known failure rate Equipment history data files or analysis Statistical analysis (Weibull) Best judgment Regulatory requirement 7. For each PM task, always consider the consequence of the failure. High consequence may increase the frequency of the PM or PdM tasks. 8. Based on the above information, should frequency be increased or decreased for any current tasks? 9. What has the task found in the past year to indicate the task is obtaining results? 10. What failure mode has been eliminated by using this task? 11. Where possible, look at PM that are intrusive and may result in infant mortality issues.
PM Optimization 12. Could any of the scheduled rebuild tasks be deferred or eliminated by using a PdM method for early detection? 13. Could any of the items such as tightening, adjusting, lubricating, cleaning or inspecting be done by an operator? Operators can, in many cases, perform these tasks on higher frequencies and reduce failures. What are the issues that can must be considered: training, safety, plant culture, unions, environment? 14. Can PMs be consolidated by covering them all at one downtime or service visit? 15. Are there any failures or known failure modes that are not being covered during PMs. Are there any hidden failures that need to be added to the PM program? 16. This optimization program should be reviewed every year for continuous improvement. 17. Don’t assume OEM (vendor PMs) are correct, and don’t assume everything you are now doing is correct.
Components Components: The parts and pieces that make up our equipment and processes. Some companies want to be trained on individual detailed components; some want to be trained on equipment pieces.
Motor Housing Failure Modes: Fails due to: Improper installation Physical damage Corrosion Material buildup
Motor Housing We would not think of the motor housing “failing to perform” would cause any problems, but there are failure modes and they affect other component functions and failures. Improper installation such as not correcting soft foot will lead to failure of bearings, broken feet and shaft bending.
Soft Foot Examples
Motor Soft Foot Failures
Motor Soft Foot Effects
Motor Housing Material build up on the housing? How can this be a failure mode of the motor? Keeping the housing clean and clear of buildup can reduce operating temperature and extend motor life. I once cleaned a motor housing and reduce the temperature by 35 degrees F.
Motor Stator The motor stator houses the stator core and windings. The stator core consists of many layers of laminated steel, which is used to help create the magnetic field.
Motor Stator Failure Modes: Fails due to: Physical damage Contamination Corrosion High temperature Voltage imbalance Broken supports Rewind burnout procedures
Motor Stator Stator fails due to rewind burn out of windings. Windings in motors are often burned out for before the motor can be rewound. This process on emergency repair motors can damage the stator structure by weakening or cracking the supports. The stator can also deform and cause problems with the rotor and motor efficiencies.
Motor Rotor Failure Modes: Fails due to: Physical damage Imbalance Broken rotor bar Contamination Improper installation
Motor Rotor
Motor Rotor Imbalance of motor rotors is quite normal and
usually causes problems for other components like the bearings. But the imbalance will eventually lead to the rotor making contact with the stator and creating a failure. Overheating during rebuild can still occur damaging the rotor components. Establish precision balance standards.
Motor Bearings Failure Modes: Fails due to: Improper handling Improper storage Improper installation Misalignment Improper lubricant Over-lubrication/under-lubrication Contamination Overhung load
Motor Bearings Bearing failure due to misalignment. This misalignment of the coupling can reduce bearing life by three to five times. Studies from NASA and the petrochemical industries indicate these statistics. Motor coupling alignment should be under .003 in all three planes after thermal expansion.
Grease Cavity
Proper Lubrication
Motor Bearing Seals Failure Modes: Fails due to: Over-lubrication Improper installation
Bearing Housing Seal
Bearing Housing Failure Modes: Fails due to: Improper installation Corrosion Improper tolerance
Motor Fan Failure Modes: Fails due to: Physical damage Ice build-up Foreign material Corrosion
Motor Fan Guard Failure Modes: Fails due to: Physical damage Plugging
Motor Insulation/Windings Failure Modes: Fails due to: Contamination Overheating Improper storage Moisture Insulation breakdown Cycling/flexing AC drive stress
Insulation/Windings Insulation breakdown
will cause the windings to short out. This will often be noticeable with MCE testing and thermography.
Motor Shaft Failure Modes: Fails due to: Physical damage Improper manufacturing Improper installation Corrosion
Preventive Maintenance for Motors Preventive Maintenance: Grease motors as needed based on service with the proper motor rated grease. Change oil in lubricated bearings often based on temperature or analysis. Perform hands on inspections weekly. Keep motors clean with good air flow. Store motors correctly away from moisture. Keep moisture and chemicals away from motors.
Precision Maintenance for Motors Precision Maintenance: Always align motors to under .003 in all 3 planes and eliminate soft foot. Always specify precision balance of the rotor to .05 inch/second. Use certified motor rebuild shops for all motors. Buy or rebuild?
Predictive Maintenance for Motors Predictive Maintenance: Motor circuit evaluation to detect nearly all motor failures. Vibration analysis for many motor failures. Mechanical ultrasound for bearings, rotor bar, some electrical. Oil analysis on sleeve bearings.
Proactive Maintenance for Motors Purchase precision motors for critical applications. Use certified motor rebuild shops with specifications. Make sound decisions on rebuild or new. Motor rebuild decision tree. Use precision maintenance on installation, alignment, balance and lubrication.
Asset Criticality What are your most critical assets? How do we know for sure?
BEARING LIFE EXTENSION Understanding Why Bearings Fail
Bearings Don’t Just Fail, They Are Murdered!
Bearing Failure
Reliabi lity Solutions
16
Murdered Bearing
Bearing Failure Modes
Bearings Bearings, Fatigue and Life Fatigue is the work hardening of the
bearing surfaces to the point where the metal fatigues.
Bearings Failure Modes: Transportation failures Storage failures Handling failures Installation failures Overheating/Undercooling Improper crossover Imbalance Misalignment Lubrication
Storage Failures Storage of bearings will assure that the bearing has no defects when it is ready for use. Bearings should: Never be dropped/mishandled Lay flat Be stored on wood/rubber Be stored with minimal vibration Be stored in a clean area Be stored in a climate controlled area.
Installation Failures
What is the best method for installing mounted bearings? SHAFT PREPARATION: Wipe the shaft clean and remove any burrs that could cause the bearing’s inner race to deform when the setscrews are tightened down. Proper shaft diameter is CRITICAL. Check the shaft diameter against the specifications in the “Shaft Fit” table; if it’s not within those tolerances, its use may lead to premature bearing failure. MOUNTING: Slide the bearing (and collar, if applicable) onto the shaft in the desired position. DO NOT use anti-seize lubricant on the shaft or bearing. Leave the setscrews (and collar, if applicable) loose. BASE PREPARATION: Make sure the base of the mounted bearing and the support surface are clean and flat. Any unevenness in the surface can deform proper bearing fits and lead to premature failure. Securely fasten the mounted bearing to the support surface using the machinery manufacturer’s recommendations. TIGHTENING: Setscrew lock: Begin tightening both setscrews down alternately with the proper torque, until both setscrews are locked to the shaft at the proper torque. Eccentric collar lock: Place the eccentric collar on the bearing’s inner race and turn rapidly in the direction of rotation, until the eccentric grooves engage the collar to the bearing. Use a drift or punch in the hole of the collar and drive it sharply with a hammer in the direction of the shaft’s rotation. This will help to ensure the lock on the shaft. Tighten the collar’s setscrew using the proper torque.
Imbalance Failures The effects of imbalance of impellors, fan rotors, motor rotors and other rotating equipment has a dramatic effect on bearing life. Use precision balance as one your proactive maintenance practices and greatly extend bearing life.
F = Force m = imbalance (lbs) r = radius of imbalance (in) f = rotational speed (Hz) g = 386.4 in/sec2 Substitute 1 oz. (1/16 lb.), 12", 3600 RPM (60 Hz):
Thus, 1 ounce of imbalance on a 12-inch radius at 3,600 RPM creates an effective centrifugal force of 275 pounds. Now calculate the effect of this weight on bearing life. Suppose that the bearings were designed to support a 1,000-pound rotor. The calculated bearing life is less than 50% of the design life as shown below.
Precision Balance can be affected by not cutting keyways in shafts the correctly. The correct method is as follows using the drawing below. Measure from the end of the shaft to the edge of the taper of the keyway slot. This is “A”. Measure the length of the coupling, this is “B”. A + B / 2 is the proper length of the key.
You are trying to replace only the weight of the remove metal in the keyway slot.
Misalignment Failures A study in the petrochemical industry realized the following results: • Average bearing life increases by a factor of 8.0. • Maintenance costs decrease by 7%. • Machinery availability increases by 12%.
Chemical Composition of Bearing Steel Carbon
0.98
Chromium
1.3-1.6
Iron
Balance
Maganese
0.25
Phosphorus
0.025 max
Silicon
0.15-0.35
Sulphur
0.025 max
Shaft Sealing
How can I get the longest life out of my bearings? CHECK YOUR FITS FIRST. A loose shaft or housing fit will let the bearing wobble or creep and cause uneven wear. A tight shaft or housing fit will reduce internal clearance and prevent grease or oil from lubricating the bearing properly. CHECK YOUR LOAD. Overloading will greatly accelerate metal fatigue and shorten the bearing life. Underloading will cause rolling elements to skid rather than roll, damaging the running surfaces. INSTALL WITH CARE. To press into a housing, make sure you press on the outer race; to press onto a shaft, press on the inner race. If installing by hand, avoid sharp blows; use a block of wood or a piece of pipe between the hammer and bearing, and tap it in at various points around the bearing. LUBRICATION PROCESS. Over-lubrication, under-lubrication, wrong lube, wrong additive, mixed lubes, etc. All these lead to shortened component life. KEEP THEM CLEAN. Contaminants can get embedded in the running surfaces and do irreparable damage to the rolling elements. Even tiny amounts of water can get trapped in the grease and lead to internal rust. KEEP THEM ALIGNED. Misalignment between the shaft and housing forces the rolling elements into an oval path, rather than circular, leading to uneven wear and possibly destroying the retainer. DAMPEN VIBRATION. Vibration from elsewhere in the machine causes the bearing to chatter and damages the running surfaces. Vibration may be caused by misalignment of a drive component, or a component being out of balance.
Gear Reducers Failure Modes: Lubrication practices Installation and rebuild practices Overloading Improper sizing
Gearbox Failure
Gearbox Failure
Gearbox Failure
A gearbox inspection and a homemade gasket lead to failure of this gear reducer. Gasket blocked the vent hole, box over-pressured, overheated, blew bottom seal. Lubricant lost and gearbox failure.
Gear Reducers Gearbox Best Practices: ¾ Size for higher rating or larger units ¾ No dip sticks to check oil level Use a sightglass for oil level ¾ Quick-connects on drain and fill ports ¾ Desiccant breather on the vent ¾ External filter system ¾ Filter from bottom of the unit ¾ Use good judgment on viscosity
Centrifugal Pumps Centrifugal pump life failures: Balanced impellers Good lube practices Precision bearing bores High tolerance straight shafts Good lube oil seals Consider oil mist in critical applications
Bearing Lube
Belts
V-Belt Failure Modes Failure Modes: Fails due to improper storage Fails due to misalignment Fails due to improper tension Fails due to over temperature Fails due to improper installation Fails due to improper matching
Belt Failure Modes Proper storage of belts can add years to the life of the belt. Keep Keep Keep Keep Keep
belts belts belts belts belts
storage out of direct sunlight stored away from heat sources stored away from chemicals stored away from moisture stored away from abrasive dust
V-BELT TENSION FORCES Manufacturers’ Recommended V-belt Tension Levels Belt Cross Sect.
Deflection Force-lbs.*
Shaft Forces-lbs.
Plain
Notched
Plain
Notched
A
3.5
4.5
112
144
B
5.1
6.5
163
208
C
12.0
14.0
384
448
D
25.0
26.0
800
832
3V
4.0
5.0
128
160
5V
10.5
13.0
336
416
8V
28.0
32.0
896
1024
*Approximate average for all sheave sizes and manufacturers
Calculated L10 Bearing Life Direct Drive vs. Belt Drive Fans
Direct Drive: Motor bearings proper alignment: L10 200,000 hrs = 22.6 yrs
Belt Drive: Motor bearings radial load: L10 40,000 hrs = 4.57 yrs or 10 times the chance of motor failure
Pillow block bearings: L10 40,000 hrs = 4.57 yrs or 10 times more change of bearings or shaft
Overall: A belt drive fan has a 10 times greater chance of motor or bearing change with belt drive over direct drive. Data based on actual historical data provided by an independent motor manufacturer. Some direct drive applications were over 25 years.
V-Belts and Temperatures For every 18 degree F increase in belt temperature, the belt’s life is cut in half.
OR For every 36 degree F increase in ambient temperature, the belt’s life is cut in half. Minimum cold start-up temperature is -30 degrees F.
Data above courtesy of Gates Rubber Company
DriveN
DriveR
Larger sheaves mean lower tension and more than 4 times the life!
C
TPeak TBending
T Tight Side D
A
B
Position
C
TLoose Side A
D
A
D
DriveN
DriveR
B
18” sheaves
TPeak
T Tight Side D
A
Cycles to Failure
C
Belt Tension
Comparing larger and smaller sheaves with the same rpm, same number of cycles and power requirements
Belt Tension
B
12” sheaves Peak Belt Tension
D
B
Position
C
D
A
Peak Tension
Changes
A
Cycles to Failure
Belt Life Strategy ¾ Proper alignment and proper tension ¾ Enclosed guards only if needed ¾ When sizing add a belt or increase belt size ¾ Use good storage methods ¾ Used power band belts if possible ¾ Modify equipment to achieve precision alignment ¾ Use sheave gauges on each belt change ¾ Use balanced sheaves/precision bored ¾ Reduce heat from slipping or ambient
Belt Failures Caused by slipping of the belt on pulley Turning around a small pulley or flexing Oil or contamination Foreign material or damaged pulley wall Forces over pulley edge, excessive strain, physical damage
