Equipment Maintenance

EQUIPMENT BASIC CARE

Fig. 1. The traditional bathtub curve illustrates machine life.

Fig. 2. With a condition monitoring program, the shape of the bathtub curve changes.

Fig. 3. This model may actually be considered a great condition-based maintenance success.

Basis for Condition Based MaintenancePoint Where Failure StartsPPoint Where Failure isDetectablePoint Where ithas FailedFTimeConditionP-F IntervalTime from Detection to Failure

Risk MatrixlWork is requiredNormally Scheduled Work is usually justified*Work is not required. Consider if cost effectiveNormally scheduled work may be justified. Tasks should be cost effective

EQUIPMENT BASIC CAREWHAT IS EQUIPMENT BASIC CARE?

Activities performed by Process to maintain optimum stable equipment operation and to increase equipment reliability at tag level.

EQUIPMENT BASIC CAREWhat can be achieved through the Program?

Ensure that Refinery meets Production Plans and competitive cost objectives via correct, optimum and stable operation of equipment

Proactive care of the Equipment at tag level to prevent deterioration and unpredicted breakdowns

Establish Unit, System and Tag Equipment, condition and Operating Envelope to run the Equipment in a reliable state

Prompt detection and correction of abnormalities and recognition of incipient failures

Prompt operational adjustment and/or minor servicing to maintain Equipment within acceptable Operating Envelope

Execution of Process Task generated via Equipment Strategy process

Communication and Documentation to Area Teams, to improve effectiveness of Selecting, Planning and executing Equipment repairs that are outside the capability of Process personnel

EQUIPMENT BASIC CARE WHAT NEEDS TO BE DONE

1. Operating EnvelopeDocument Max & Min Operating Limits for variables affecting Equipment Reliability

Plant System configured to monitor limits and alarm on infringement

Absence of data at Plant Information System, needs monitoring by Process Surveillance Rounds

Deviations vs Tag Reliability Operating Envelope shall be corrected through operational adjustment or minor servicing - all such actions needs to be logged

Prolonged Operating Envelope deviations shall be flagged as Operating Envelope Exceptions requiring follow up

EQUIPMENT BASIC CAREWHAT NEEDS TO BE DONE

2. EQUIPMENT CONDITION THRESHOLD MONITORING

Document Equipment condition Thresholds, Monitoring Task and associated intervals, Action Trigger level and required appropriate action should be defined for each Threshold

Establish system of visual clues which should include color coding and posting at the Equipment to facilitate efficient and effective Monitoring and Task Execution (e.g. Establish and mark Vibration Monitoring points)

Monitoring Task Document should indicate the When, Why, Who and How of each Task to foster repeatability and efficiency

All Task, including that generated through Equipment Strategy shall be included in a Task Management System when due , Task should be assigned, completed and signed off, documenting As found & As left conditions

Threshold Exceptions that cannot be corrected by Process shall be reported for follow up


3. PROCESS SURVEILLANCE

Document minimum expectation for Process Technician Surveillance rounds and Console Operator Surveillance

Develop standard for Equipment cleaning and Housekeeping that enables ongoing monitoring, exposure of defects and effective use of visual clues

Visual clues should be installed to assist Technicians Surveillance for efficiency and consistency

Abnormality detected by Surveillance should be corrected by Process if possible or reported for follow up


4. OTHERS

A System should be in place to quality assure Operating Envelope application, Equipment Condition Monitoring Task execution and Surveillance Activities to ensure requirements are met

The Process organization should own a Database of Deviation Respond and ensure that data is available to appropriate analytical group for inclusion in activities performed as part of Performance Evaluation & Improvement

Appropriate training shall be provided for Process to handle activities compatible with Process goals of improved reliability and control of the process

Activities that cannot be performed by Process are assigned to Mechanical by Work Request. In making this determination, training Skills, Work load and Safety are considered

EQUIPMENT BASIC CAREREPORTING

1.Compliance to Task (%)----------------------------------------------------MONTHLY

2. Failure Caused by gaps in Basic Operator Care (#)---------------------MONTHLY

3. Operating Envelope Exception (# with reliability objective)------------MONTHLY

4. Equipment Failure Avoided/Saved due to Basic Operator Care (#)---MONTHLY

EQUIPMENT BASIC CARE1. Standard Task 3a- Primary Walkabout Surveillance

Verify Oiler Level is correct (non Oil Mist & Purge Mist)

Verify Mist is showing from Telltale or collection Bottle (Pure Mist/Purge Mist)

Listen & feel for strange noise and vibration along pump row

If both spare & main operating, find out why

For auto-start pumps check line up

Check Seal flush line for flow and temperature-check seal pot level.

What Lubricant Must DoReduce friction by forming a film between rolling and sliding surfaces of Bearing

Prevent Wear and Corrosion

Guard against solid and liquid contamination

Remove heat

Minimum Viscosity change with temperature change (high VI)

Dont oxidize easily

Dont foam easily

Good load carrying ability

VISCOSITY:

Measurement of a fluids resistance to flow. The common metric unit of absolute viscosity is the poiseFor convenience, the centipoise (cp) one one-hundredth of a poise is the unit customarily used.

VISCOSITY INDEX (V.I.)

Empirical, unitless number indicating the effect of temperature change on the kinematic viscosity of an oil. Liquids change viscosity with temperature, becoming less viscous when heated; the higher the V.I. of an oil, the lower its tendency to change viscosity with temperature.LUBRICATION PROPERTIES

CONSTANT LEVEL OILER (TRICO)

a) Verify Oil Level is correctEQUIPMENT BASIC CARE

Bearing Oil LevelEQUIPMENT BASIC CARE

PUMP BEARING LOCATION & OIL RINGS

HOW OIL MIST SYSTEM WORKS Oil is atomized at the Mist Generator by high velocity air Baffles intercept large particles and return them back to Oil Reservoir Remaining smoke like suspension of minute oil particles is distributed through Piping, Tubes and Hoses The low pressure and velocity Mist flow is metered to each Lubrication point by application fittings 3 main type of fittings: Mist, Spray and Condensing Turbulence in and around Rolling Element Bearings cause oil to wet out from the mist directly on to Bearing Elements Spray & Condensing fittings Reclassify the dry mist into larger droplets Spray Fittings expel oil as fine wet spray while Condensing Fittings reclassify oil to larger drops which drip or run down adjacent surfaces

How Oil Mist is Generated

Oil Mist System & Application Fittings

ADVANTAGES OF OIL MIST SYSTEM2. PURGE MIST SYSTEM

Employed together with conventional system

In conjunction with the advantage of positive oil circulation created by Oil Rings

Bearing Housing under positive pressure-contaminant ingress prevented

Constant Level Oiler has overflow feature to prevent flooding of Bearings

PURGE MIST SYSTEM

ADAVANTAGES OF OIL MIST SYSTEM1.PURE MIST SYSTEMAir oil mist fed under pressure directly into Bearing Housing

No reservoir of oil in the housing & has no oil rings

Provide uncontaminated environment with oil deposited on to Bearing elements

Heat build up is eliminated

Needs pre oil film forming when oil mist system is down.

PURE MIST SYSTEM

Oil Mist Lubrication

Motor With Oil Mist Lubrication

TYPES OF LUBRICATION3 Types of Lubrication situations can exist between two surfaces separated by lubricant: 1. Hydrodynamic or Full Fluid Film Lubrication-surfaces are completely separated by lubricant

2. Boundary Lubrication-Lubricant too thin to provide total surface separation

3. Elastrohydrodynamic Lubrication-viscosity of lubricant has higher shear strength than metal surface resulting in metal surface deforming elastically and decrease effectiveness of Lubricant

1. HYDRODYNAMIC LUBRICATIONSliding and rolling materials are separated by thin film of Lubricant held in place by pressure created between surfaces.

2.BOUNDARY LUBRICATIONLubricant too thin to provide good total surface separation, resulting in contact and frictional heat generation at microscopic peaks. Protection is provided through chemical additives.TYPES OF LUBRICATION

3.ELASTROHYDRODYNAMIC LUBRICATION (EHD OR EHL)Load increased to high level where Lubricant shear strength is higher than supporting metal surface resulting in metal surface deform and decreased effect of Lubrication.TYPES OF LUBRICATION

EQUIPMENT BASIC CAREIrregularity in Bearings can be identified by listeningAbnormal noise can be traced to an individual machine component by an experienced OperatorA good operating Bearing produces a soft purring noiseGrinding, squeaking and other irregular noise points to poor operating conditionSqueaking noise inadequate lubricationMetallic tone- insufficient bearing clearanceIndentation at outer ring raceway cause vibration & smooth clear toneIntermittent noise may indicate damage to rolling elementGrinding noise dirt in bearingIrregular & loud noise indicate severe bearing damage

BEARING PROBLEMS Normal fatigue spalling The limiting criterion for fatigue damage is largely application dependent. For the purpose of establishing bearing dynamic ratings, it has been arbitrarily set as a spall size of 0.01 square inches in area.Abrasive wear Foreign material can enter the bearing through a damaged or worn seal or during cleaning, when water or other cleaning fluids contaminate the lubricant. This causes premature wear of the bearing. Pitting and bruising Larger metal clips or particles of dirt entering the bearing can cause pitting and bruising. Etching and corrosion Moisture in the bearing results in etching or corrosion. Causes include condensation from a humid environment or moisture passing through a damaged or worn seal.Scoring Inadequate lubrication of the rib face and roller end results in metal-to-metal contact and scoring.Cage breakage and peeling Cage breakage doesn't happen often. It can occur as a result of vibration, orbital rotation (in plant idler bearings), or rapid acceleration or deceleration of the bearing. Other factors are marginal lubrication systems or excessive end play in the bearings.

BEARING PROBLEMSBearing adjustment Bearing adjustment is a critical component of successful bearing operation. With excessive end play in the bearing, rollers are very loose out of the load zone, resulting in skidding and sliding and cause scalloped wear on the cup race.Misalignment Bearing misalignment results in reduced bearing life, depending on the amount of misalignments as well as the loads and speeds involved. If misalignment exceeds set limits, the load on the bearing is concentrated in one area on the bearing races, resulting in high edge stresses and subsequent fatigue spalling.False brinnelling/impact damage False brinelling is bearing surface wear. It occurs when the rollers slide axially back and forth on the race while the bearing is essentially stationary but subject to vibration. A groove is worn into the race by the roller's sliding action.Electric current When electric current passes through a bearing, arcing or burning occurs at the point of contact between the races and rollers. This may cause a single burn or appear as a line of small burns, called "fluting," along the line of contact of the rollers and the race.

IF YOU CANNOT HEAR OR SEE THIS YOU MUST BE DEAF & BLIND

CAUSES OF NOISE & VIBRATIONNOISEUnusual noise is a sign of : - Bearing problem - Pump Cavitation - Loose connections/fittings - Leak - Overload/under load - Rub - Operating outside of design envelope - Resonance - Improper fitting (not meeting tolerances) - Change in flow - Generally indicating something is not right

Suction Cavitations occurs when the pump suction is under a low pessure/high vacuumcondition where the liquid turns into a vapor at the eye of the pump impeller. This vapor iscarried over to the discharge side of the pump where it no longer sees vacuum and iscompressed back into a liquid by the discharge pressure. This imploding action occurs violently and attacks the face of the impeller. An impeller that has been operating under a suction cavitations condition has large chunks of material removed from its face causingpremature failure of the pump.

PUMP SUCTION CAVITATIONS

PUMP DISCHARGE CAVITATIONS

Discharge Cavitations occurs when the pump discharge is extremely high. It normally occurs in a pump that is running at less than 10% of its best efficiency point. The high discharge pressure causes the majority of the fluid to circulate inside the pump instead of being allowed to flow out the discharge. As the liquid flows around the impeller it must pass through the small clearance between the impeller and the pump cutwater at extremely high velocity. This velocity causes a vacuum to develop at the cutwater similar to what occurs in a venturi and turns the liquid into a vapor. A pump that has been operating under these conditions shows premature wear of the impeller vane tips and the pump cutwater. In addition due to the high pressure condition premature failure of the pump mechanical seal and bearings can be expected and under extreme conditions will break the impeller shaft.

EFFECT OF CAVITATIONFig 1- Initial Bubble Fig 2- Initiation of CollapseFig 3- Forming of liquid jetFig 4- Impact & Metal Extrusion

CAUSES OF NOISE & VIBRATIONVibrationUnusual Vibration is a sign of : - Bearing problem - Loose connections/fittings - Overload/under load - Rub - Operating outside of design envelope - Resonance - Improper fitting (not meeting tolerances) - Imbalance - Misalignment - Pump/valve cavitations - Foundation problem - Flow changes

- Generally indicating something is not right

VIBRATION TELERANCE CHART (ISO 23720I = Small (up to 15Kw)II = Medium (15 to 17Kw)III = Large (Prime movers on heavy foundation)IV = Large (Prime movers on light foundation)

PROCESS CONDITIONS REQUIRING PUMP PARALLEL OPERATIONMaking up for design shortfall

Making up for individual Pump inefficiency

Correcting Process upset conditions

Operating condition change (system head increased)

Increased throughput

Startup

IDENTICAL PUMPS PARALLEL OPERATIONSingle Pump (Pt. A): Head=85Ft, Flow= 470 gpmParallel Operation (Pt. B): Head=105Ft, Flow=660 gpm

PARALLEL OPERATION-DIFFERENT PUMPS3 Pump (A) : Head=70 Ft , Flow= 300 gpm4 Pump (B) : Head=87.5 Ft , Flow= 410 gpmBoth Running: Head=87.5 Ft , Flow= 460 gpm

PROBLEMS ENCOUNTED WITH PARALLEL OPERATIONEither or both pumps operating below recommended minimum continuous flowHigher system head

Possible lower efficiency

No contingency spare

Higher life cycle cost

Increased load on condition monitoring activity

Suction/Discharge piping not similar-both pumps operating point not similar

AUTO CUT IN LINE UP Auto cut-in switches needs to be set for spare to cut in

Markings and tags must clearly indicate spare and running equipment

EQUIPMENT BASIC CARE2. Standard Task 3b Supplementary Walkabout Surveillance

Drain water from Bearing Housing or BracketFeel Bearing Housing for heat and vibration

Water Contamination in Lubrication Oil and its effect

EQUIPMENT BASIC CARE2. Standard Task 3b Supplementary Walkabout Surveillance

Drain water from Bearing Housing or BracketFeel Bearing Housing for heat and vibration

EFFECT OF HIGH TEPERATURE ON LUBRICATION OIL

EFFECT OF TEMPERATURE ON MINERAL OILSAt temperatures above 90C (195F), Mineral Oil can oxidize rapidly

VISCOSITY CHANGE WITH TEMPERATURE

COMMON CAUSES OF BEARING OVERHEATING Inadequate lubrication (Wrong type of grease or oil)Insufficient Lubrication (Low oil level loss of lubricant through seal)Insufficient Bearing Clearance (Wrong fit selection)Bearing pinched in the housing (Bore out of round)Oil Gauge breather hole is clogged (indicate incorrect oil level)Constant oil level cup (incorrect level)Incorrect positioning of flingers (Rubbing against cover)

((Bearing diameter in inches x breadth in inches) x 1.29) / 7) = Daily cc's of lube Oil lubrication:Preference is given to oil lubrication, when the speed of rotation or operating temperature makes it impossible to use grease, when heat has to be removed from the bearingassembly by the lubricant and of course when the bearings are mounted in an oil-lubricated construction, for example a gearbox.Grease lubrication:Grease lubrication is usually chosen for applications in which the bearing operates under normal speed and temperature conditions. Grease has a number of advantagesover oil. For example, it enables simpler (i.e. cheaper) installation, offers better adhesion and provides protection against damp and impurities. Most bearing assemblies aregreased

Required Grease Quantity For Regreasing

EQUIPMENT BASIC CARE3. Standard Task 3c, 4a, 8a Manual Vibration Data CollectionData collected with Handheld monitor for ascertaining that vibration is tolerable.

Monitor will be calibrated to show Good, Tolerable, Bad and Shutdown levels

When at Bad level Maintenance reliability team will be alerted to do a Diagnostic vibration data collection

At very high Shutdown levels arrangement must be made to have the machine shutdownData should be taken whenever Walkabout surveillance show machine vibration is higher than normal

CAUSES OF NOISE & VIBRATIONVibrationUnusual Vibration is a sign of : - Bearing problem - Loose connections/fittings - Overload/under load - Rub - Operating outside of design envelope - Resonance - Improper fitting (not meeting tolerances) - Imbalance - Misalignment - Pump/valve cavitations - Foundation problem - Flow changes

- Generally indicating something is not right

Comparing Circular and Sinusoidal Motion As a point rotates counterclockwise around a circular path in the complex plane the real component (blue line) oscillates back and forth along the real axis as a cosine function. Meanwhile, the height of the imaginary component (red line) oscillates up and down as a sine function. (By Dan Russell)

Peak-to-Peak is mostly used as a basis for displacement units (sometimes referred to as Zero-to-Peak) Peak is used as a basis for velocity units (sometimes referred to as Zero-to-Peak) Rms refers to terms of root-mean-square used to mathematically determine its value

VIBRATION MEASUREMENTS

There are two general classes of vibrations - free and forced.

Free vibration takes place when a system oscillates under the action of forces inherent in the system itself, and when external impressed forces are absent. The system under free vibration will vibrate at one or more of its natural frequencies, which are properties of the dynamic system established by its mass and stiffness distribution.

Forced Vibration takes place under the excitation of external forces. When the excitation is oscillatory, the system is forced to vibrate at the excitation frequency. If the frequency of excitation coincides with one of the natural frequencies of the system, a condition of resonance is encountered, and dangerously large oscillations may result.

Resonance can possibly cause the failure of major structures such as bridges, buildings, or airplane wings. Thus, the calculation of the natural frequencies is of major importance in the study of vibrations.TYPES OF VIBRATION & RESONANCE

VIBRATION MEASUREMENTSDisplacement is a distance, usually measured in mils ( 1 mil=0.001 inch) or in microns (1 micron= 1 millionth of a meter). Displacement is usually the preferred unit for low frequency vibrations of machines with running speeds < 1000 rpm.

Velocity is the rate of change of displacement, usually measured in in/sec or mm/sec. Used for higher frequency measurements.

Acceleration is the rate of change of velocity with units of in/sec or mm/sec. Used for analysis of high frequency (gearmesh vibrations)

Frequency

The repetition rate of a periodic vibration, per unit of time, determined by taking the reciprocal of the period (T). Frequency is expressed in three ways: -Hz (how many cycles per second) - cpm (how many cycles per minute) -Orders (how many cycles per shaft turning speed [TS])

Frequency is also the x-axis of the vibration spectrum; it identifies the source of the vibration.

BEARING FAULT FREQUENCIESBearing Frequencies

Faults in any of the four bearing components will generate specific frequencies dependent upon the bearing geometry and rotating speed.

BPFO - Ball Pass Frequency, Outer Race (generated by balls or rollers passing over defective outer races)

BPFI - Ball Pass Frequency, Inner Race (generated by balls or rollers passing over defective inner races)

BSF - Ball Spin Frequency (generated by ball or roller defect)

FTF - Fundamental Train Frequency (generated by cage defect or improper movements)

BEARING ELEMENTS

FAULT ANALYSIS BASED ON VIBRATION FREQUENCYUnbalance is the most common fault associated with rotating shaft.

Unbalance vibration is mainly radial. On overhung rotors, axial components may be present as well.

High 1X is commonly considered as the unbalance symptom, however it can be misalignment, bent rotor or cracked shaft, and further investigation of what may cause the defect is often necessary.

VIBRATION TELERANCE CHART

ISO2372 ( BS 4675 , VDI 2056 )

EQUIPMENT BASIC CARE4. Standard Task 3e- Spare Pump Swap

Pump swapping activity is more for Confidence building

Too frequent swapping has been known to cause increased failures

Equipment Strategy recommended swapping intervals to be followed

All normal pump starting check list to be followed-detailed written startup procedure for each pump

Swapping activity is preferably done during day hours where Maint. Personnel are available

A Spare Pump Operating procedure will be in place process run plan in place to maximize reliability of spare pump when main pump is under repair ( for critical pumps)

EQUIPMENT BASIC CARE5. Standard Task 3g- Visual Oil Quality Check

Check Oiler Bulb for oil colour- cloudy oil is a sign of contamination

Unusually dark oil also indicate deterioration

Change the oil if it shows sign of contamination or deterioration

Oil misted equipment check vent and drain line for plugging

Drain a small amount oil and check for contaminant-also feel the oil a rough viscosity check

EQUIPMENT BASIC CARE6. Standard Task 3i- Bearing re-greasing

Re-grease Bearings (greased Bearings) as per Equipment Strategy Schedule

Only the Grease in the Bearing should be replaced

Re-greased amount depends on Bearing size and a chart needs to be established

Use only recommended Grease

Make sure all Greasing equipment are kept clean

Make sure Grease gets to the Bearing (check tubing for plugging and rupture)

EXAMPLE OF GREASE NOT GETTING TO BEARING Figure 1. Pillow block bearing from fan assembly.Figure 2. Bearing partiallyremoved from housing.Figure 3. Bearing offsetrelative to fitting.Figure 4. Inside of the pillow block.

EFFECT OF OVERGREASINGFigure 2. End bell with bearing shield that has become dislodged from the bearing. Figure 1.This was a control rod drive (CRD) fan motor at Watts Bar Nuclear Plant. The bearing experienced a ball cage failure due to the bearing shield (Figure 2) being pushed down on the ball cage due to over pressurization of the grease cavity.

Always make sure the dispensing nozzle of the grease gun is clean before using.USING A GREASE GUN

EQUIPMENT BASIC CARE7. Standard Task 3j Change Lube Oil Oil change as per recommended interval as per Equipment Strategy When changing oil on running equipment, need to stay clear of moving parts It is best that some oil is being poured in while draining so that all sludge is removed. Care should be taken to not to overfill or underfill ascertain constant level oiler is set properly and is controlling oil level in bearing housing Make sure oil used is the correct type and proper container is used Good practice to collect and check quality of drained oil Maintain good housekeeping and dispose used oil properly

CHOOSING THE CORRECT LUBRICATIONThe right lube oil is determined by following factors:The type of lubrication in the application

Manufacturers recommendations-most important as they know their machine best

The viscosity and correct additive in the oil for the srvice

The ambient and operating temperature of the application

The loading or abnormal pressure and speed of the application if changed from original design

Best to do some research to confirm lubrication currently used is correct type

CHOOSING THE CORRECT LUBRICATION

2. Viscosity and Additives Viscosity is the resistance to flow or how thick the oil is at given temperature High pressure additives added to enhance performance Oxidation inhibition additives to improve oil life Rust-inhibitor additive to prevent rusting through moisture condensation

Sometimes the most creative ideas are the wrong ideas. Open top-up containers like this are magnets for contaminants and can wreak havoc when used on small sumps.USING PROPER LUBRICATION OIL CONTAINERS

LUBE OIL STORAGE & CONSUPTION


8. Standard Task 3u- Develop rigid Operating Envelope including alarms

Establish Normal flow, Max flow, Minimum flow for pumps

Normal startup/shutdown procedure

Emergency startup/shutdown procedure

Normal vibration and temperature limits

Process run plan for critical equipment when spare is operating


9. Standard Task 3x- Develop special procedure for Seal leak/Emission control/fire risk

For severe HSE concern, have written procedure to mitigate risk

Signage at critical location with instruction is prefered

Drills exercise will help


10. Standard Task 4e-Check Fan Blade Pitch

Fan pitch or tilt angle is given by manufacturer for the required duty

For adjustable pitch, the pitch can be adjusted for higher or lower duty

Pitch angles are directly proportional to power consumption and this can be used as a guide

Pitch can be checked using special Protector (supplied by Fan manufacturer)

Adjusting the pitch is an economical way of operating the cooler

For Fans with Pitch control device indicators will be provided to indicate pitch


11. Standard Task 4i Check Belt wear on Belt driven equipment

Belts should be properly ventilated as higher temperatures lower belt life

Belts should be properly tensioned a tension gauge should be used to check tension

Rule of thumb- a V-belt drive should give its thickness for every 4 feet span

Too much tension can cause wear on bearings

Belts should be replaced as a set


12. Standard Task 4j Check critical instrumentation

All instruments on Double Seal Pots should be checked as per Equipment Strategy.

THANK YOU

Equipment Maintenance

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