Gear Pumps & Motors Failure Analysis Guide

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1. 1. The heart of a hydrauliThe heart of a hydraulic system is c system is thethe
hydraulic pumphydraulic pump. . The pump is The pump is the componentthe component
that converts mechanical energy into fluidthat converts mechanical energy into fluid
energy. energy. A healthy pA healthy pump will ump will allow theallow the
hydraulic system on mobile equipment tohydraulic system on mobile equipment to
’’ vv vv
FFAAIILLUURE RE AANNAALLYSYSIISS//
TROUBLESHOOTINGTROUBLESHOOTING
FAILURE ANALYSIS/FAILURE ANALYSIS/
TROUBLESHOOTINGTROUBLESHOOTING
11
..
Without a healthy pump, the system will be lessWithout a healthy pump, the system will be less
responsive and rob the machine of performanceresponsive and rob the machine of performance
and productiviand productivity. ty. A properly mA properly maintainedaintained
hydraulic system provides insurance that thehydraulic system provides insurance that the
equipment will deliver the work it is designed toequipment will deliver the work it is designed to
do. do. A good A good preventative mainpreventative maintenance programtenance program
affords the operator hundreds of hours of affords the operator hundreds of hours of 
GGEEAAR R PPUMUM PPS S & & MM OOTORSTORSGGEEAAR R PPUMUM PPS S & & MM OOTORSTORS
trouble free operation.trouble free operation.
Unfortunately, the hydraulic system does notUnfortunately, the hydraulic system does not
always perform at itsalways perform at its’ specified level. ’ specified level. It is atIt is at
these times that we need these times that we need to troubleshoot theto troubleshoot the
system and system and pinpoint pinpoint the cause. the cause. A properA proper
diagnosis is critical to diagnosis is critical to providing renewedproviding renewed
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
11
performance and extended life. performance and extended life. This booklet is This booklet is designed to help you prodesigned to help you properly identify theperly identify the
. . --
Commercial Intertech’s gear pumps and motors.Commercial Intertech’s gear pumps and motors.
Commercial Intertech is a worldwide manufacturer Commercial Intertech is a worldwide manufacturer of fixed displacement hydraulic gearof fixed displacement hydraulic gear
pumps and motors. With facilities pumps and motors. With facilities on four continents Commercial is on four continents Commercial is positioned to providepositioned to provide
product and service to the global market place. For the past 75 years product and service to the global market place. For the past 75 years CommercialCommercial
Intertech has been the product of choice for Intertech has been the product of choice for meeting the needs of tough mobilemeeting the needs of tough mobile
applications.applications.
’’. . e e eaeart rt o to t e e yy rarauu c c ssysysttemem, , oommmmerercc a a ntnterertetecc s s exexteternrna sa spupur r ggeaear r pupummppss
are a fixed displacement design. are a fixed displacement design. For every complete revolution oFor every complete revolution of the gear shaft the pumpf the gear shaft the pump
displaces a fixed amount of oil. displaces a fixed amount of oil. Pump output flow is proportiPump output flow is proportional to the engine speed.onal to the engine speed.
There are three casting components that maThere are three casting components that make up the exterior pump capsule: ke up the exterior pump capsule: shaft end,shaft end,
gear housing, and port end cover. gear housing, and port end cover. A tandem pump will A tandem pump will have a fourth casting component,have a fourth casting component,
the bearing carrier. the bearing carrier. Various casting materials are used includinVarious casting materials are used including gray iron (the mostg gray iron (the most
common), compacted graphite, ductile common), compacted graphite, ductile iron, and aluminum.iron, and aluminum.
ear ear and and drdr ve ve shasha ts ts are are cut cut rom rom aa oy oy stestee e and and thethen n cascase he hardardeneened. d. he he momost st comcommomonn
gear shaft is the gear shaft is the integral, where the drive sintegral, where the drive shaft and gear are one piece. haft and gear are one piece. The integral gearThe integral gear
shaft provides exceptionshaft provides exceptional torque carrying capabilities. al torque carrying capabilities. The other type is the “continThe other type is the “continental”ental”
shaft and drive gear or the two piece. shaft and drive gear or the two piece. The “continental” shaft is machiThe “continental” shaft is machined with drivened with drive
GEAR PUMPGEAR PUMP
ThrustThrust
PlatesPlates Port EndPort End
extensions on both ends of the shaft; extensions on both ends of the shaft; anan
external drive (splined or keyed) and a smallerexternal drive (splined or keyed) and a smaller
splined ensplined end for internal d for internal drive. drive. The driveThe drive
End CoverEnd Cover Lip SealLip Seal
DriveDrive
SplineSpline
Drive GearDrive Gear
RollerRoller
BearingsBearings
MountingMounting
FlangeFlange
inserting the small end of the shaft inserting the small end of the shaft into the hubinto the hub
of an internally splined drive gear.of an internally splined drive gear.
No matter what type of gear shaft used, theNo matter what type of gear shaft used, the
gear journals must be supported by bearings gear journals must be supported by bearings oror
sleeve type busleeve type bushings. shings. The roller bearinThe roller bearingg
pumps require the use of ring seals to preventpumps require the use of ring seals to prevent
the hthe hii h presh pressure oisure oil thal that lubrt lubricateicates thes the
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Out BoardOut Board
BearingBearing
Ring SealRing Seal
(High Pressure)(High Pressure)
Gear HousingGear Housing
Inlet PortInlet Port
Idler GearIdler Gear
bearings from traveling down the shaft.bearings from traveling down the shaft.
Bushing pumps do not need ring seals as Bushing pumps do not need ring seals as thethe
bushings are lubricated with low pressure oil.bushings are lubricated with low pressure oil.
To insure maximum pumping efficiencyTo insure maximum pumping efficiency
Commercial Intertech’s pump and Commercial Intertech’s pump and motormotor
products employ the use of pressure products employ the use of pressure balancebalance
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TANDEM GEAR PUMPTANDEM GEAR PUMP
BearingBearing carriercarrier
BushingsBushings
3. 3. Tandem pumTandem pumps are needed when ps are needed when there arethere are
multiple functions, functions that requiremultiple functions, functions that require
different flows and where a single section candifferent flows and where a single section can
vv ..
tandem pump shows the fourth castingtandem pump shows the fourth casting
component, the bearing carrier.component, the bearing carrier.
4. 4. Both pumpBoth pumps and motors s and motors employ a pressureemploy a pressure
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
33
Pumping SectionsPumping Sections
..
hydraulically balances the thrust plates andhydraulically balances the thrust plates and
squeezes them against the two gear faces. Thesqueezes them against the two gear faces. The
squeeze provides a seal between the gear facesqueeze provides a seal between the gear face
and the thrust plate surface preventing highand the thrust plate surface preventing high
pressure oil from slipping back to the pressure oil from slipping back to the lowlow
pressure sipressure side ode of the f the pump. pump. Mechanical Mechanical sealsseals
are used behind the thrust plate to block oilare used behind the thrust plate to block oil
GEAR PUMP CUTAWAYGEAR PUMP CUTAWAY
OUTOUT
from slipping between the plate and from slipping between the plate and adjoiningadjoining
casting.casting.
In the roller bearing units these seals are calledIn the roller bearing units these seals are called
pocket seals and are pocket seals and are shown in the illustration.shown
in the illustration.
The sleeve bearing (bushing) units use aThe sleeve bearing (bushing) units use a
different kind of seal called a channel seal.different kind of seal called a channel seal.
ININ
Pressure Pressure Balanced Balanced Thrust Thrust PlatesPlates
5. 5. A cross sectionA cross sectional view of tal view of the pumpinhe pumpingg
chambers illustrates the flow path of chambers illustrates the flow path of thethe
hydraulic oil thhydraulic oil through the gear pumrough the gear pump. p. As theAs the
gears counter rotate the separating gear teethgears counter rotate the separating gear teeth
create a vacuum drawing oil create a vacuum drawing oil into the inlinto the inlet. et. OilOil
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
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THRUST PLATE VIEWTHRUST PLATE VIEW
is picked up by each tooth and carried aroundis picked up by each tooth and carried around
the outside of the outside of the gear, oil is nthe gear, oil is notot drawndrawn
through tthrough the center. he center. The pockets bThe pockets between theetween the
gear teeth and the housing are referred to asgear teeth and the housing are referred to as
pumping pumping chambers. chambers. As the geAs the gear teeth mesh oar teeth mesh onn
the outlet side, oil is forced out of the pocketsthe outlet side, oil is forced out of the pockets
and exits the pump.and exits the pump.
FFoorrccee FFoorrccee
OUTPUTOUTPUT
ownstream ownstream resres stance stance to to the the output output owow
causes an increase in causes an increase in pressure. pressure. High presHigh pressuresure
on the outlet side of the on the outlet side of the housing forces thehousing forces the
gears to deflect into the low pressure (inlet)gears to deflect into the low pressure (inlet)
side. side. The tips The tips of the gear tof the gear teeth contact theeeth contact the
housing preventing high pressure output oilhousing preventing high pressure output oil
from leaking back to the low pressure inlet.from leaking back to the low pressure inlet.
AAlltthhoouu hh nneecceessssarar tthhiiss ttooootthh ttoo hhoouussiinn
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
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OIL FLOWOIL FLOW
contact can generate cast contact can generate cast iron contaminantiron contaminant,,
particularly in particularly in new units. new units. Therefore,Therefore,
Commercial Intertech 100% tests all unitsCommercial Intertech 100% tests all units
before shipping, bringing them up to theirbefore shipping, bringing them up to their
operating operating pressure. pressure. Any coAny contaminantntaminant
generated is filtered out by our test stands.generated is filtered out by our test stands.
33
6. 6. Contamination Contamination is the singis the single largestle largest
contributor to hydraulic component failures.contributor to hydraulic component failures.
Contamination is considered to be anyContamination is considered to be any
CONTAMINATIONCONTAMINATIONCONTAMINATIONCONTAMINATION
specified by specified by the oil the oil producer. producer. Water, dirt,Water, dirt,
dust, air, etc.... dust, air, etc.... System cleanliness and regularSystem cleanliness and regular
preventative maintenance insure a long lasting,preventative maintenance insure a long lasting,
responsive hydraulic system.responsive hydraulic system.
7. 7. Particulate contamParticulate contamination is ination is measuredmeasured
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
66
across its largest diameter to determine size.across its largest diameter to determine size.
This chart shows some comparative sizes of This chart shows some comparative sizes of 
particles in microns (or particles in microns (or micrometers).micrometers).
Commercial suggests the use of a Commercial suggests the use of a 25 micron25 micron
return line filter in systems with a pressurereturn line filter in systems with a pressure
rating of 2500 psi (172 bar) or less. In systemsrating of 2500 psi (172 bar) or less. In systems
rated between 2500 (172 bar) and 3000 psirated between 2500 (172 bar) and 3000 psi
PARTICLE SIZESPARTICLE SIZES
SSUUBBSSTTAANNCCEE MMIICCRROONN IINNCCHH
GGrraaiin n oof f ssaalltt 110000 ..00003399
HHuummaan n hhaaiirr 7700 ..00002277
recommended. A 10 micron return line filter isrecommended. A 10 micron return line filter is
suggested for use with our P300 sleevesuggested for use with our P300 sleeve
bushing pumps.bushing pumps.
8. 8. Particle counting is Particle counting is the most comthe most commonmon
Lower limit of Lower limit of 
visibiltyvisibilty
4400 ..0000115588
WWhhiitte e bbllooood d cceellll 2255 ..000011
TTaallccuum m ppoowwddeerr 1100 ..0000003399
RReed d bbllooood d cceellll 88 ..00000033
method for determining cleanliness levels of method for determining cleanliness levels of 
hydraulic fluihydraulic fluids. ds. Powerful optical Powerful optical instrumentsinstruments
are used to count the number of particles in aare used to count the number of particles in a
specified voluspecified volume of fluime of fluid. d. There are severalThere are several
common cleanliness level standards, of these,common cleanliness level standards, of these,
thethe IInternationalnternational SStandardstandards OOrganization coderganization code
has gained wide acceptance.has gained wide acceptance.
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
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BBaacctteerriiaa 22 ..000000007788
ISO CODESISO CODES
he he code code conscons sts sts o to two wo ndex ndex numbnumbersers
referring to the number of particles greaterreferring to the number of particles greater
than 5 micrometers and 15 micrometers foundthan 5 micrometers and 15 micrometers found
in one milliliter of fluid.in one milliliter of fluid.
Maximum recommended contamination levelsMaximum recommended contamination levels
are a functioare a function of n of component component clearancesclearances andand
system opsystem operating pressure. erating pressure. As the sAs the systemystem
IISSO O CCOODDEE PPAARRTTIICCLLEESS/  /  
> 5> 5 mmicrometersicrometers
MILLILITERMILLILITER
> 15> 15 micrometersmicrometers
Fluid cleanlinessFluid cleanliness
required forrequired for
1188//1155 22,,550000 332200 FFlloow w ccoonnttrrool l vvaallvveess,,
cylinderscylinders
1177//1144 11,,330000 116600 GGeeaar r ppuummpps s aanndd
motorsmotors
1166//1133 664400 8800 DDiirreeccttiioonnaal l aanndd
pressure controlpressure control
pressure increases the oil pressure increases the oil film separating thefilm separating the
working parts become thinner making theworking parts become thinner making the
components more susceptible to damage bycomponents more susceptible to damage by
contaminant. contaminant. Microscopic pMicroscopic particles streamarticles streaminging
through the hydraulic components at highthrough the hydraulic components at high
velocities pound the wear surfaces velocities pound the wear surfaces weakeningweakening
and eroding and eroding material. material. Some partiSome particles getcles get
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
88
valvesvalves
1155//1122 332200 4400 VVaanne e aannd d ppiissttoonn
pumps/motorspumps/motors
1144//1111 116600 2200 SSeerrvvo o ccoonnttrrool l vvaallvveess
new components and remove metallic materialnew components and remove metallic material
from thfrom the wear surfaces. e wear surfaces. This This wear generateswear generates
additional contaminadditional contaminant in the ant in the system and leadssystem and leads
to leaks and a to leaks and a loss of component performance.loss of component performance.
Commercial gear pumps require filtration of Commercial gear pumps require filtration of 
ISO 17/14 or better.ISO 17/14 or better.
9. 9. Read sRead slide lide text.text.
CONTAMINATIONCONTAMINATION
44
•• Accelerated wearAccelerated wear
 –  – bearings, thrust plates,bearings, thrust plates,
housinghousing
•• Bearing / bushingBearing / bushing
failurefailure
•• Reduced pumpReduced pump
•• Improper filtrationImproper filtration
•• Low oil level - concentrationLow oil level - concentration
of contaminantof contaminant
•• Loose or lost breather capLoose or lost breather cap
•• Leaking fittings, seals,Leaking fittings, seals,
wwii eerrss
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
99
ee c ec ennccyy
•• Reduced lifeReduced life
•• HeatHeat
•• Internal leaksInternal leaks
•• Failed pumpFailed pump
•• Missing or collapsed inletMissing or collapsed inlet
strainerstrainer
•• Poor fill practicesPoor fill practices
•• Clogged Clogged filter filter - - by-passby-pass
10. 10. Nuts, bolts, Nuts, bolts, screws, washers, plasticscrews, washers, plastic
closures, shop rags, pieces of hose, etc.... closures, shop rags, pieces of hose, etc.... cancan
cause considerable damage cause considerable damage to hydraulic pumpsto hydraulic pumps
and other hydrauand other hydraulic componlic components. ents. Many timesMany times
the failures caused by large foreign objectsthe failures caused by large foreign objects
occurs instantaneously as the pump ingests theoccurs instantaneously as the pump ingests the
debris and catastrophic failure results.debris and catastrophic failure results.
FOREIGN OBJECTFOREIGN OBJECTFOREIGN OBJECTFOREIGN OBJECT
(( NNUUTS TS & & BBOOLLTSTS))(( NNUUTS TS & & BBOOLLTSTS))
11. 11. The damage that occuThe damage that occurred to this gear setrred to this gear set
was caused by a hardened foreign object such aswas caused by a hardened foreign object such as
a screw or nua screw or nut. t. Additional Additional debris has bdebris has beeneen
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
1010
FOREIGN OBJECTFOREIGN OBJECT
DAMAGEDAMAGE
generated by the broken gear teeth andgenerated by the broken gear teeth and
component component scoring. scoring. This type This type of failure canof failure can
contaminate the entire hydraulic contaminate the entire hydraulic system.system.
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
1111
12. 12. Particles too large to Particles too large to fit between the tighfit between the tightt
component tolerances will cause surface tocomponent tolerances will cause surface to
surface contact removing material from thesurface contact removing material from theLARGE PARTICLELARGE PARTICLELARGE PARTICLELARGE PARTICLE
55
..
surface, which provides a sealing surfacesurface, which provides a sealing surface
between the high and low pressure oil leads tobetween the high and low pressure oil leads to
leaks and a loss of performance.leaks and a loss of performance.
ContaminatioContamination in a n in a hydraulic system is self hydraulic system is self 
perpetuating. perpetuating. As damage As damage to internalto internal
components continues additional debris iscomponents continues additional debris is
generated by the wearing of the components.generated by the wearing of the components.
CONTAMINATIONCONTAMINATIONCONTAMINATIONCONTAMINATION
GearGear
MotionMotion
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
1212
Thrust plateThrust plate
Large particle contaminantLarge particle contaminant
13. 13. The pump thThe pump thrust plate is orust plate is one of the bestne of the best
places to look for evidence places to look for evidence contributing to thecontributing to the
pump failupump failure. re. The thrust platThe thrust plate is sometime is sometimeses
referred to as a referred to as a wear plate. wear plate. The score markThe score markss
on the above plate were caused by particleson the above plate were caused by particles
being dragged across the plate surface by thebeing dragged across the plate surface by the
hardened gear face.hardened gear face.
SCORED THRUST PLATESCORED THRUST PLATE
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
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SCORED THRUST PLATESCORED THRUST PLATE
14. 14. New components pNew components provide a smootrovide a smooth, evenh, even
surface allowing a continuous oil film to existsurface allowing a continuous oil film to exist
between the tbetween the thrust plate hrust plate and gear face. and gear face. WhenWhen
these surfaces become scored the oil filmthese surfaces become scored the oil film
dissipates into the grooves interrupting thedissipates into the grooves interrupting the
film. film. Metal to Metal to metal contact metal contact occurs, resultingoccurs, resulting
in an increase in friction and heat. Thein an increase in friction and heat. The
grooved plate surface can also provide angrooved plate surface can also provide an
escape route for high pressure oil to go back toescape route for high pressure oil to go back to
low pressure inlet, resulting in a loss of low pressure inlet, resulting in a loss of 
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
1414
..
15. 15. P300 series P300 series plate shows plate shows score marks fromscore marks from
large particle large particle contaminant.contaminant. SCORED THRUST PLATESCORED THRUST PLATE
66
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
1515
16. 16. Microscopic partMicroscopic particles the size oicles the size of airbornef airborne
dust can accumulate in the tiny tolerances of dust can accumulate in the tiny tolerances of 
FINE PARTICLEFINE PARTICLEFINE PARTICLEFINE PARTICLE
CONTAMINATIONCONTAMINATIONCONTAMINATIONCONTAMINATION
today's today's hydraulic cohydraulic components. mponents. TheThe
accumulation can form a wedge betweenaccumulation can form a wedge between
moving parts, increasing friction andmoving parts, increasing friction and
accelerating wear. accelerating wear. The velocitThe velocity of y of the tinythe tiny
particles striking the wear surfaces can erodeparticles striking the wear surfaces can erode
material weakening the wear surface andmaterial weakening the wear surface and
causing spallicausing spalling. ng. This erosion This erosion of metal leadsof metal leads
Fine particle contaminantsFine particle contaminants
adds additional contamination to the hydraulicadds additional contamination to the hydraulic
system. system. All this All this adds up to a redadds up to a reduction of uction of 
system efficiency causing the engine to work system efficiency causing the engine to work 
harder, increasing fuel harder, increasing fuel consumptioconsumption.n.
Roller bearings are more Roller bearings are more susceptible to finesusceptible to fine
particle contaminant than the particle contaminant than the bushing (sleevebushing (sleeve
type)type). . The The bushibushin n unitsunits, h, howevowever, are er, are mormoree
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
1616
rruus s pp aa eesusceptible to large contaminant than rollersusceptible to large contaminant than roller
bearings.bearings.
THRUST PLATE VIEWTHRUST PLATE VIEW
17. 17. As the gear teeth mesAs the gear teeth mesh and oil is h and oil is forcedforced
out of the pump outlet, a out of the pump outlet, a small amount of thesmall amount of the
oil is trapped by the oil is trapped by the meshing teeth in the toothmeshing teeth in the tooth
FFoorrccee FFoorrccee
OUTPUTOUTPUT
space root area (circled). space root area (circled). The trapped The trapped oil isoil is
forced at right angles into the faces of theforced at right angles into the faces of the
thrust plates. Relieved areas on the platesthrust plates. Relieved areas on the plates
called trapping grooves allow the highcalled trapping grooves allow the high
pressure oil to pressure oil to escape. escape. The high velThe high velocity of ocity of 
the oil moving at a right angle the oil moving at a right angle to the thrustto the thrust
plate will do serious damage to the plate will do serious damage to the thrust platethrust plate
vv
 © 1998 Commercial Intertech
Corp. © 1998 Commercial Intertech Corp.
1717
OIL FLOWOIL FLOW
contamination is being carried by the oil.contamination is being carried by the oil.
18. 18. The fine partiThe fine particles being carried by cles being carried by thethe
hydraulic fluid erodes the thrust plate surfacehydraulic fluid erodes the thrust plate surface
in the trapping groove on the in the trapping groove on the high pressurehigh pressure
FINE PARTICLEFINE PARTICLE
CONTAMINATIONCONTAMINATION
77
..
heaviest where the teeth mesh and thenheaviest where the teeth mesh and then
migrate towards the low pressure side migrate towards the low pressure side of theof the
plate. Over time, the wear cuts a plate. Over time, the wear cuts a channel intochannel into
the plates’ surface allowing the oil to leak back the plates’ surface allowing the oil to leak back 
to the pump inlet. The volumetric efficiency of to the pump inlet. The volumetric efficiency of 
the pump is reduced.the pump is reduced.
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
1818
19. 19. A closer inspection A closer inspection of the plate surface notof the plate surface not
only reveals the damage in the center of theonly reveals the damage in the center of the
plate but iplate but in the root sn the root seal area as well. eal area as well. A lightA light
ring around the I.D. root seal area ring around the I.D. root seal area developsdevelops
due to due to the very tighthe very tight clearances. t clearances. Fine particlesFine particles
wear the thrust plate surface leaving a polishedwear the thrust plate surface leaving a polished
SCORED THRUST PLATESCORED THRUST PLATE
..
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
1919
SCORED THRUST PLATESCORED THRUST PLATE
20. 20. This P300 tThis P300 thrust plate showhrust plate shows evidence of s evidence of 
fine particle contamination on the back side of fine particle contamination on the back side of 
the the thrust thrust late. late. Fine Fine erratic erratic tracks tracks are are cut cut intointo
the plate surface around the balancing holesthe plate surface around the balancing holes
and low pressure area.and low pressure area.
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
2020
21. 21. This thrust This thrust plate face shows plate face shows erosionerosion
damage in the areas of high oil velocity, suchdamage in the areas of high oil velocity, such
as the trapping groove and balance holes.as the trapping groove and balance holes.
SCORED THRUST PLATESCORED THRUST PLATE
88
 just bel just below the balance ow the balance hole. hole. The metalThe metal
removed from the wear surfaces adds to theremoved from the wear surfaces adds to the
contaminated condition.contaminated condition.
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
2121
Leakage in Hydraulic ComponentsLeakage in Hydraulic ComponentsLeakage in Hydraulic ComponentsLeakage in Hydraulic ComponentsLeakage in Hydraulic ComponentsLeakage in Hydraulic Components
++
22 Control of clearance criticalControl of clearance critical
22. 22. Internal leakage is Internal leakage is the primary cthe primary cause of aause of a
loss of performance in a hydraulic system. Of loss of performance in a hydraulic system. Of 
the three factors identified above, control of the three factors identified above, control of 
critical clearances have the most dramaticcritical clearances have the most dramatic
impact. Wear, accelerated impact. Wear, accelerated by contaminationby contamination,,
heat, or pressure, will act to increase heat, or pressure, will act to increase thesethese
critical clearances with disastrous results.critical clearances with disastrous results.
Q =flowQ =flow
(leakage)(leakage)
00
11
33
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
2222
•• eenng g o o eeaa
••Clearance 2Clearance 2
••Pressure 3Pressure 3
WORN DRIVESHAFTWORN DRIVESHAFT
23. 23. When contaminWhen contamination is ation is present two wpresent two wearear
bands will develop under the ring seals bands will develop under the ring seals on theon the
gear shaft of tgear shaft of the roller bearing he roller bearing pumps. pumps. TheseThese
bronze high pressure seals are designed tobronze high pressure seals are designed to
reduce the high pressure reduce the high pressure oil lubricating theoil lubricating the
bearings to low pressure before reaching thebearings to low pressure before reaching the
shaft seal. shaft seal. Tiny particlTiny particles, under high es, under high pressurepressure
and velocity, progressively wear the gearand velocity, progressively wear the gear
 journal surface until the ring seal is no longer journal surface until the ring seal is no longer
effective. effective. High pressHigh pressure jets under ture jets under the ringhe ring
seal pressurizing the shaft seal area.seal pressurizing the shaft seal area.
The oil pressure on the shaft seal can force The oil pressure on the shaft seal can force thethe
seal lip away from the journal or even dislodgeseal lip away from the journal or even dislodge
the seal from the the seal from the bore. bore. In both inIn both instances anstances an
external leak wouexternal leak would occur. ld occur. Pump shaft Pump shaft sealsseals
are typically rated for a are typically rated for a maximum pressmaximum pressure of ure of 
15 to 20 15 to 20 psi. psi. Shaft seals are sensitivShaft seals are sensitive to shafte to shaft
speed, an increase in speed can cause aspeed, an increase in speed can cause a
decrease in the maximum pressure rating of decrease in the maximum pressure rating of 
the seal.the seal. 2323
24. 24. When a seal When a seal leak is discoleak is discovered the firstvered the first
inclination for the mainteninclination for the maintenance staff can ance staff can be tobe to
replace the shaft seal. replace the shaft seal. This will This will not solve not solve thethe
robroblemlem. . The The ear ear set set and and rin rin seaseals ls ma ma alsalsoo
DRIVE SHAFT RING SEALDRIVE SHAFT RING SEAL
99
have to be have to be replaced. replaced. A rule of thA rule of thumb forumb for
determining excessidetermining excessive wear ve wear on the shaft is thaton the shaft is that
if you can feel the wear if you can feel the wear with your finger nail itwith your finger nail it
should be replaced.should be replaced.
Ring seals are not needed in the bushingRing seals are not needed in the bushing
pumps as the bushings are lubricated with lowpumps as the bushings are lubricated with low
pressure inlet oil.pressure inlet oil.
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
2424
25. 25. Contamination Contamination has caused wear bands has caused wear bands toto
develop on this roller bearing motor gear.develop on this roller bearing motor gear.
Closest to the spline end, the shaft Closest to the spline end, the shaft has beenhas been
grooved by dgrooved by dirt trapped under thirt trapped under the lip seal. e lip seal. AsAs
the damage progresses external shaft seal leaksthe damage progresses external shaft seal leaks
will develowill develop. p. Replacing the shaft sReplacing the shaft seal at thiseal at this
point will not correct the leak as the undercutpoint will not correct the leak as the undercut
MOTOR SHAFTMOTOR SHAFT
will prevent the proper squeeze of the seal onwill prevent the proper squeeze of the seal on
the shaft.the shaft.
Note: The contamination attacking the shaftNote: The contamination attacking the shaft
seal area could also been brought in from theseal area could also been brought in from the
outside environment.outside environment.
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
2525
CCAVITAAVITATTIIOON N &&CAVITATION &CAVITATION &
26. 26. Excessive noise iExcessive noise in a hydraulic systn a hydraulic system canem can
be caused by the presence of be caused by the presence
of air in theair in the
hydraulic oil. hydraulic oil. Air can be introduced inAir can be introduced into theto the
system two system two ways; ways; through cavitatthrough cavitation orion or
aeration. aeration. “Cavitation” o“Cavitation” occurs when tccurs when the pumphe pump
inlet flow can no longer inlet flow can no longer fill the pumpfill the pump
chambers created by the separation of the gearchambers created by the separation of the gear
teeth. teeth. The partial vacuThe partial vacuum vaporizes soum vaporizes some of me of 
the oil causing air and or water to come out of the oil causing air and or water to come out of 
solution.solution.
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
2626
Thrust plateThrust plate
aavv aa oonn s s tt e e oorrmmaatt oon n o o aa rr, , aan n wwaatteerr
or oil vapor bubbles in the or oil vapor bubbles in the hydraulic oil.hydraulic oil.
AerationAeration is a form of cavitation that occursis a form of cavitation that occurs
when outside air is drawn when outside air is drawn into the hydraulicinto the hydraulic
system due to a loose fitting or low system due to a loose fitting or low oil level inoil level in
the reservoir.the reservoir.
27. 27. As the buAs the bubbles, created by bbles, created by cavitation andcavitation and
aeration, are carried aeration, are carried around to the pump outlet,around to the pump outlet,
the increase in pressure squeezes the bubbles.the increase in pressure squeezes the bubbles.
CAVITATION &CAVITATION &CAVITATION &CAVITATION &
1010
An implAn implosionosion occurs when thoccurs when the pressuree pressure
becomes too great and becomes too great and the bubbles collapsethe bubbles collapse
inward.inward.
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
2727
Thrust plateThrust plate
28. 28. When the air bubbles When the air bubbles implode inimplode intensetense
shock waves bombard the surface of the wearshock waves bombard the surface of the wear
plates. plates. The shock wThe shock waves erode the paves erode the plates’lates’
surfaces on the high pressure side and trappingsurfaces on the high pressure side and trapping
groove area. groove area. The sealing The sealing capability of capability of thethe
plate is reduced resulting in a plate is reduced resulting in a loss of outputloss of output
flow.flow.
CCAVIAVITTATATIIOON N &&CCAVITAAVITATTIIOON N &&
AERATIONAERATIONAERATIONAERATION
The presence of air can The presence of air can also reduce the volumealso reduce the volume
of oil available to carry away heat that isof oil available to carry away heat that is
produced by produced by mechanical frictionmechanical friction. . VacuumVacuum
conditions created in the pump rob oil from conditions created in the pump rob oil from thethe
bearing and thrust plate areas. The loss of oilbearing and thrust plate areas. The loss of oil
in bearing bore upsets the in bearing bore upsets the loading which canloading which can
result in result in premature bearing premature bearing failure. failure. ThrustThrust
Thrust lateThrust late
pp aatteess, , rree yy nng g oon n tt e e o o tto o mmaa nnttaa n n tt ee rr
balance become unbalanced, resulting in abalance become unbalanced, resulting in a
milling of the plate surface.milling of the plate surface.
Physical damage can also be seen on the gearPhysical damage can also be seen on the gear
housing bore in the form of a rough surface inhousing bore in the form of a rough surface in
the gear wipe area.the gear wipe area.
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
2828
CAVITATION DAMAGECAVITATION DAMAGECAVITATION DAMAGECAVITATION DAMAGE
•• NoiseNoise
•• HeatHeat
•• Accelerated wearAccelerated wear
 –  – thrust plates / housingthrust plates / housing
•• Internal leaksInternal leaks
•• Reduced umReduced um
- Inlet restriction- Inlet restriction
•• Clogged inlet strainer /Clogged inlet strainer /
breatherbreather
•• Inlet strainer too smallInlet strainer too small
•• Inlet line too longInlet line too long
•• Inlet line bore too smallInlet line bore too small
29. 29. Read slidRead slide texte text..
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
2929
efficiencyefficiency
•• Erratic actuatorErratic actuator
performanceperformance
•• Failed pumpFailed pump
•• Excessive engine speedExcessive engine speed
•• Collapsed inlet hoseCollapsed inlet hose
•• Suction head too greatSuction head too great
•• Oil too viscous (Oil too viscous (cold weathercold weather))
30. 30. Read sliRead slide texde text.t.
AERATION DAMAGEAERATION DAMAGEAERATION DAMAGEAERATION DAMAGE
1111
•• NoiseNoise
•• HeatHeat
•• Accelerated wearAccelerated wear
 –  – thrust plates / housingthrust plates / housing
•• Internal leaksInternal leaks
•• Erratic actuatorErratic actuator
erformanceerformance
- Air enters oil- Air enters oil
•• Low oil levelLow oil level
•• Vortexing of oil aboveVortexing of oil above
strainer - whirlpoolstrainer - whirlpool
•• Loose inlet fittingsLoose inlet fittings
•• Worn pump shaft sealWorn pump shaft seal
••
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
3030
•• Reduced pumpReduced pump
efficiencyefficiency
•• Failed pumpFailed pump
•• Foam suspended in oil dueFoam suspended in oil due
to sloshing in the reservoirto sloshing in the reservoir
CAVITATED THRUST PLATECAVITATED THRUST PLATE
31. 31. This plate This plate has been damaged has been damaged byby
cavitation. cavitation. As the gAs the gear teeth come arouear teeth come around tond to
the discharge side of the pump (outlet) the oilthe discharge side of the pump (outlet) the oil
is exposed to the outlet pressure collapsing theis exposed to the outlet pressure collapsing the
large air bubbles.large air bubbles.
OUTLETOUTLET
INLETINLET
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
3131
CAVITATED THRUST PLATECAVITATED THRUST PLATE
32. 32. A close up of A close up of the plate shows the plate shows the severitythe severity
of the pittiof the pitting. ng. The damage is hThe damage is heaviest in theeaviest in the
root seal area where the clearance between theroot seal area where the clearance between the
plate and the gplate and the gear face is the tightest. ear face is the tightest. ThisThis
damage allows high pressure oil to escapedamage allows high pressure oil to escape
down the gear journal into the bearing ordown the gear journal into the bearing or
bushing.bushing.
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
3232
33. 33. Motor cavitatMotor cavitation occurs when ion occurs when thethe
supply pump cannot produce enough flowsupply pump cannot produce enough flow
to keep up with the speed of the motor. Theto keep up with the speed of the motor. The
CAVITATED MOTORCAVITATED MOTOR
THRUST PLATETHRUST PLATE
1212
motor then bmotor then begins to act as a pegins to act as a pump. ump. ThisThis
M75 series motor plate has cavitationM75 series motor plate has cavitation
damage on both damage on both sides of the platsides of the plate. e. ThisThis
condition occurs when a motor is cavitatedcondition occurs when a motor is cavitated
in both directions of rotation.in both directions of rotation.
The damage to this plate is The damage to this plate is heaviest in theheaviest in the
trapping groove areas because thetrapping groove areas because the
ccaavv ttaatt oon n uu ees s ccrreeaatte e oon n tt e e ppuummp p ss ee
of the motor are carried to the of the motor are carried to the outlet sideoutlet side
and are and are mechanically imploded by themechanically imploded by the
meshing of the gear teeth.meshing of the gear teeth.
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
3333
34. 34. Again, a close up sAgain, a close up shows the severity hows the severity of of 
the damage.the damage. CAVITATED MOTORCAVITATED MOTOR
THRUST PLATETHRUST PLATE
35. 35. A loss of lubriA loss of lubrication in the cation in the pump canpump can
also cause rifling of the gears and thrustalso cause rifling of the gears and thrust
plates. plates. Air in Air in the system the system creates ancreates an
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
3434
RIFLED GEARRIFLED GEAR
& THRUST PLATE& THRUST PLATE
come in harder over one gear come in harder over one gear than the other.than the other.
The gears try to separate and walk towardsThe gears try to separate and walk towards
opposite ends opposite ends of the pump. of the pump. The effect is aThe effect is a
milling of the plates behind the idler gear atmilling of the plates behind the idler gear at
one end of the pump and the drive gear one end of the pump and the drive gear onon
the other end. the other end. The torque needed to The torque needed to drive thedrive the
pump increases dramatically and the pumppump increases dramatically and the pump
becomes heated. becomes heated. The removal The removal of thrust of thrust plateplate
material will contaminate the material will contaminate the hydraulichydraulic
system.system.
Note: The problem described above has beenNote: The problem described above has been
largely eliminated in the P300 series largely eliminated in the P300 series bushingbushing
pumps because of the new pumps because of the new thrust platethrust plate
design. design. However, all pumHowever, all pumps with ps with an integralan integral
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
3535
rr vve e ss aa t t nncc uu nng g tt e e sseerr ees s aarree
susceptible to rifling if an external force issusceptible to rifling if an external force is
applied to the drive shaft applied to the drive shaft (push or pulling(push or pulling
force). force). An example oAn example of this f this is an intis an interferenceerference
fit between the drive shaft and its drivefit between the drive shaft and its drive
coupling.coupling.
36. 36. Milling Milling damage is evident damage is evident at the center of at the center of 
this thrusthis thrust plate. t plate. Not as obvious Not as obvious is theis the
cavitation erosion on the plate at three o’clock.cavitation erosion on the plate at three o’clock.
RIFLED THRUST PLATERIFLED THRUST PLATE
1313
37. 37. The milling The milling has not erased the has not erased the tell taletell tale
erosion damaged caused by the erosion damaged caused by the cavitation.cavitation.
When the damage has When the damage has progressed to this pointprogressed to this point
the entire hydraulic system should be flushedthe entire hydraulic system should be flushed
and the filters and strainers checked.and the filters and strainers checked.
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
3636
38. 38. Pressure and hydraulPressure and hydraulic shock are alic shock are alsoso
causes of pumcauses of pump failure. p failure. Pumps opPumps operatingerating
under a continuous heavy load, (highunder a continuous heavy load, (high
pressure), and extended duty cycle arepressure), and extended duty cycle are
susceptible to prematususceptible to premature wear re wear and failure.and failure.
RIFLED THRUST PLATERIFLED THRUST PLATE
ororceces s gegenenerarate te y y tt e e pupump mp ououtt et et prpresessusurere
and gear area causes a deflection of the gears.and gear area causes a deflection of the gears.
This This stresses the bearings stresses the bearings or bushings or bushings thatthat
support the support the gear journals. gear journals. The oil film The oil film neededneeded
to lubricate and cushion the pump elementsto lubricate and cushion the pump elements
becomes thinner and thinner with the increasebecomes thinner and thinner with the increase
in pressure until direct contact is made.in pressure until direct contact is made.
loading fractures the hardened surfaces of theloading fractures the hardened surfaces of the
needle bearings, bearing race, and gearneedle bearings, bearing race, and gear
 journals.  journals. These These fractures, over fractures, over time, time, lead to lead to aa
breakdown of breakdown of the surface mthe surface material. aterial. SmallSmall
pieces of material break away leaving a pieces of material break away leaving a roughrough
running running surface. surface. The rough The rough surface can nosurface can no
longer support the film of oil needed longer support the film of oil needed toto
 © 1998 Commercial Intertech Corp. © 1998 Commercial Intertech Corp.
3737
lubricate and cushion the lubricate and cushion the pump components.pump components.
The damage quickly accelerates until aThe damage quickly accelerates until a
catastrophic failure occurs spreadingcatastrophic failure occurs spreading
contaminant throughout the hydraulic system.contaminant throughout the hydraulic system.
The bushing pumps rely more heavily on theThe bushing pumps rely more heavily on the
film of oil to support the loaded gear film of oil to support the loaded gear journal.journal.
Clearances between the journal and bushingClearances between the journal and bushing
PRPREESSSSUURE RE DDAAMM AAGEGE
REPEATEDREPEATED
HEAVYHEAVY
sursur ace ace are are greatgreater ter than han the the cc earance earance n n thethe
bearing pumps. bearing pumps. This is nThis is necessary to supportecessary to support
the thicker the thicker oil filmoil film. . When subjected When subjected toto
repeated heavy loads a breakdown of the oilrepeated heavy loads a breakdown of the oil
film allows direct contact of film allows direct contact of the bushing andthe bushing and
 journal.  journal. The PTFE The PTFE coating, that coating, that protects theprotects the
bushing I.D., wears away and an increase bushing I.D., wears away and an increase inin
frictfriction ion and and heat heat occuroccurs. s. The The bushbushin in surfasurfacece
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.3838
becomes rough and the oil film can becomes rough and the oil film can no longerno longer
be be supported. supported. Under Under continued continued operation operation andand
friction becomes severe and friction becomes severe and the bushing maythe bushing may
start spinninstart spinning in the g in the bore. bore. Again a catastrophicAgain a catastrophic
failure results contaminating the entirefailure results contaminating the entire
hydraulic system.hydraulic system.
39. 39. Read slidRead slide texte text..
PRESSURE DAMAGEPRESSURE DAMAGEPRESSURE DAMAGEPRESSURE DAMAGE
1414
•• Improper relief valve settingImproper relief valve setting
•• Relief valve malfunctionedRelief valve malfunctioned
•• Slow acting relief valveSlow acting relief valve
•• Absence of a relief valveAbsence of a relief valve
••
•• Accelerated wearAccelerated wear
•• Cracked housingsCracked housings
•• Excessive housing cut-outExcessive housing cut-out
•• Reduced efficiencyReduced efficiency
•• Internal leakageInternal leakage
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.
downstream of the valvedownstream of the valve
affecting the relief valveaffecting the relief valve
performanceperformance
•• eeaarr nng g uuss nng g aa uurree
•• Thrust plates coined,Thrust plates coined,
warped or crackedwarped or cracked
•• Broken drive / connectingBroken drive / connecting
shaftshaft
3939
BEARING FAILUREBEARING FAILURE
40. 40. Extended operation Extended operation under high under high pressurespressures
has caused the spalling of the needle bearingshas caused the spalling of the needle bearings
in this in this bearing. bearing. Surface cracks have lead to Surface cracks have lead to aa
fracturing of fracturing of the needle the needle bearing materialbearing material. . AnAn
increase in system noise and heat could alertincrease in system noise and heat could alert
the operator to this type of the operator to this type of problem.problem.
 ©1998 Commercial
Intertech Corp. ©1998 Commercial Intertech Corp.4040
BEARING FAILUREBEARING FAILURE
41. 41. This slide sThis slide shows the inner race of thows the inner race of thehe
bearing and the damage caused by excessivebearing and the damage caused by excessive
loading.loading.
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.4141
42. 42. As the beariAs the bearing wears the gear jng wears the gear journalournal
becomes damaged by the direct contact of thebecomes damaged by the direct contact of the
 journal to the needle bearings. journal to the needle bearings.
BEARING FAILUREBEARING FAILURE
1515
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.4242
43. 43. The system The system pressure deflects thpressure deflects the gears intoe gears into
the low presthe low pressure inlet side of tsure inlet side of the pump. he pump. If theIf the
system pressure increases above the system pressure increases above the pressurepressure
rating of the pump, then the gears deflect too farrating of the pump, then the gears deflect too far
and the gear and the gear housing cut-out becomes excessive.housing cut-out becomes excessive.
Internal slip increases and the Internal slip increases and the pump becomespump becomes
less efficient. less efficient. The contamiThe contaminant created by tnant created by thehe
PRESSURE DAMAGEDPRESSURE DAMAGED
GEAR HOUSINGGEAR HOUSING
cut-out can foul relief valves and other systemcut-out can foul relief valves and other system
components. components. If the housinIf the housing cut-out g cut-out exceedsexceeds
.005” (.007” for a bushing pump gear housing).005” (.007” for a bushing pump gear housing)
the gear housing should be replaced.the gear housing should be replaced.
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.4343
PRESSURE DAMAGEDPRESSURE DAMAGED
44. 44. Hydraulic shock Hydraulic shock loads can cause loads can cause anan
immediate componenimmediate component failure in t failure in your hydraulicyour hydraulic
system. Sudden pressure spikes that exceed thesystem. Sudden pressure spikes that exceed the
housing at the port location and bolt hole areashousing at the port location and bolt hole areas
of the castof the casting. ing. A slow A slow acting oracting or
malfunctionmalfunctioning relief valve can ing relief valve can causecause
excessive pressure spikes in the system.excessive pressure spikes in the system.
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.4444
45. 45. Commercial Commercial Intertech’s engiIntertech’s engineeringneering
department sets maximum pressure limits fordepartment sets maximum pressure limits for
all pumps by calculating bearing loads andall pumps by calculating bearing loads and
vv
PRESSURE DAMAGEDPRESSURE DAMAGED
GEAR HOUSINGGEAR HOUSING
1616
. . ,,
size in the gear housing the weaker the casting.size in the gear housing the weaker the casting.
The larger port requires the removal of aThe larger port requires the removal of a
greater percentage of casting material and agreater percentage of casting material and a
reduction in reduction in the safety the safety factor. factor. ContinuousContinuous
operating pressures above the pump rating canoperating pressures above the pump rating can
lead to cracked housings due to fatigue.lead to cracked housings due to fatigue.
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.4545
PRESSURE DAMAGEDPRESSURE DAMAGED
THRUST PLATETHRUST PLATE
46. 46. Thrust plates Thrust plates can also be can also be damaged bydamaged by
excessive pressure. The above plate splitexcessive pressure. The above plate split
through the middle due to excessive loads. Thethrough the middle due to excessive loads. The
thrust plates used in the roller thrust plates used in the roller bearing productbearing product
are most susceptible to damage between are most susceptible to damage between thethe
two gear borestwo gear bores. . A small A small bleed hole, bleed hole, neededneeded
for balancing pressures in the bearing bores, isfor balancing pressures in the bearing bores, is
machined on the back side of the plate in thismachined on the back side of the plate in this
area. area. Couple thiCouple this with s with fact that the fact that the greatestgreatest
pressure in the pump occurs at the center of pressure in the pump occurs at the center of 
the plate wthe plate where the gear teeth here the gear teeth mesh. mesh. TheThe
oblong bores in the above plate are due to aoblong bores in the above plate are due to a
bearing failure.bearing failure.
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.4646
HEAVILY COINED THRUSTHEAVILY COINED THRUST
47. 47. Excessive pressExcessive pressures can also ures can also causecause
coining damcoining damage to the thrust age to the thrust plate. plate. This is aThis is a
deformation of material on the low deformation of material on the low pressurepressure
vv..
pushes the plate into the gear pushes the plate into the gear housing withhousing with
enough force to cause a enough force to cause a bulging of material inbulging of material in
the relieved edge the relieved edge of the platof the plate. e. The major OThe major O.D..D.
is flattened.is flattened.
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.
COININGCOINING
4747
48. 48. Hydraulic shock Hydraulic shock and excessive presand excessive pressuresure
can also cause failures to the pump drive line.can also cause failures to the pump drive line.
Many times the drive coupling or pump driveMany times the drive coupling or pump drive
vv
PRESSURE DAMAGEDPRESSURE DAMAGED
DRIVE SHAFTDRIVE SHAFT
1717
. . ,,
drive shaft broke where the shaft diameter isdrive shaft broke where the shaft diameter is
the smallest. The drive shaft was the smallest. The drive shaft was not strongnot strong
enough to withstand the torque load generatedenough to withstand the torque load generated
by the high pressure.by the high pressure.
Each section of a Each section of a multiple pump or motormultiple pump or motor
should be regarded as a single unit withshould be regarded as a single unit with
correcorresponspondin din delidelivery anvery and powed power inpur inputt
requirements. requirements. Since the Since the entire inputentire input
horsepower required to drive the pump is fedhorsepower required to drive the pump is fed
through a common drive shaft, the powerthrough a common drive shaft, the power
delivered to or from the delivered to or from the unit is limited by theunit is limited by the
physical strengphysical strength of the shaft. th of the shaft. This limiThis limit ist is
defined as a defined as a “PL” factor; “PL” factor; “P” being t“P” being thehe
maximum operatinmaximum operating pressure and g pressure and “L” the“L” the
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.4848
““ ””..
maximum operating pressuremaximum operating pressure by theby the gear widthgear width..
Each style or type of shaft has a unique “PL” ratingEach style or type of shaft has a unique “PL” rating. . Tables are provided in each of theTables are provided in each of the
pump/mopump/motor product catalogs defining ttor product catalogs defining the “PL” rating for each shaft type. he “PL” rating for each shaft type. If the “PL”If the “PL”
factor exceeds the catalog rating of your shaft choice factor exceeds the catalog rating of your shaft choice select a new shaft type with anselect a new shaft type with an
adequate “PL” rating.adequate “PL” rating.
PL= Pressure X Total Gear WidthPL= Pressure X Total Gear Width
Torsional fatigueTorsional fatigue can also cause a can also cause a shaft to fail, having a similar appearance to the aboveshaft to fail, having a similar appearance to the above
shaft. shaft. With torsional fatigWith torsional fatigue failure, however, the core of the shaft across the break has aue failure, however, the core of the
shaft across the break has a
smeared appearance caused by repeated forces and a gradusmeared appearance caused by repeated forces and a gradual wearing out of tal wearing out of the shaft. he shaft. (A(A
sudden break is characterisudden break is characterized by a rough granular shaft cozed by a rough granular shaft core.) re.) Torsion forces acting Torsion forces acting onon
the shaft in the same direction tend to cause a break at the shaft in the same direction tend to cause a break at a 45a 4500 angle to the shaft axis.angle to the shaft axis.
PRESSURE DAMAGEDPRESSURE DAMAGED
CONNECTING SHAFTCONNECTING SHAFT
49. 49. The connecting shaft iThe connecting shaft in a tandem pumn a tandem pumpp
has the smallest diameter in the pump drivehas the smallest diameter in the pump drive
line, many times making it the weak link.line, many times making it the weak link.
In multiple units the “PL” must be calculatedIn multiple units the “PL” must be calculated
for thfor the firse first connt connectin ectin shaft shaft as welas well as thel as the
drive shaft. drive shaft. When calculatinWhen calculating the “PL” for g the “PL” for thethe
connectingconnecting shafts, the shafts, the drive gear drive gear is notis not
included. included. The calculation The calculation is made frois made from them the
first connecting shaft back.first connecting shaft back.
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.4949
50. 50. Drive line mDrive line misalignment isalignment can cause thecan cause the
pump shaft to flex with each pump shaft to flex with each revolution, oftenrevolution, often
resulting in a clean break at a resulting in a clean break at a 909000 angle to theangle to the
ROTATIONAL BENDINGROTATIONAL BENDING
FATIGUE FAILUREFATIGUE FAILURE
1818
..
areas where stresses are concentrated, such as,areas where stresses are concentrated, such as,
holes, grooholes, grooves, and ves, and reduced diameters. reduced diameters. AA
rough spot on therough spot on the
smooth shaft core is where the shaft finallysmooth shaft core is where the shaft finally
severed.severed.
51. 51. Heat is generated Heat is generated in a hydraulin a hydraulic systemic system
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.5050
whenever oil dumps from an area of highwhenever oil dumps from an area of high
pressure to low pressure pressure to low pressure without doingwithout doing
mechanical work. Oil blowing over a relief mechanical work. Oil blowing over a relief 
valve or flowing through piping, a valve, valve or flowing through piping, a valve, aa
clogged filter or strainer all are examples of clogged filter or strainer all are examples of 
sources of sources of heat. heat. Proper reservoir Proper reservoir size cansize can
dissipate much of the heat generated in adissipate much of the heat generated in a
HEATHEATHEATHEATHEATHEAT
..
must be added to sufficiently cool the must be added to sufficiently cool the oil.oil.
Other factors, such as, Other factors, such as, contamination,contamination,
cavitation/aeration, improper oil viscosity cancavitation/aeration, improper oil viscosity can
add to the heating problems of a hydraulicadd to the heating problems of a hydraulic
system.system.
Heat build-up causes the hydraulic oil to Heat build-up causes the hydraulic oil to looseloose
its its visviscoscosity ity resresultultin in in ain an oil n oil thathat no lt no lonon erer
•• THINS THE SYSTEM OILTHINS THE SYSTEM OIL
-- increasing frictionincreasing friction
•• ACCELERATES THE BREAKDOWN OF THE OILACCELERATES THE BREAKDOWN OF THE OIL
-- causing sludge to formcausing sludge to form
•• CAN BE CAUSED BY CAN BE CAUSED BY WORN COMPONENTSWORN COMPONENTS
•• EVERY 1EVERY 18°8°FF RISE IRISE IN OIL TEMN OIL TEMPERAPERATURETURE
-- doubles the rate of corrosion on exposed surfacesdoubles the rate of corrosion on exposed surfaces
meets specificatimeets specification. on. This greatlThis greatly reduces they reduces the
lubricating effects of the oil on the closelubricating effects of the oil on the close
tolerance parts. tolerance parts. The heated The heated oil oxidoil oxidizes,izes,
encouraging corrosion, leakage, and theencouraging corrosion, leakage, and the
development odevelopment of sludge. f sludge. Sludge can cloSludge can clog filtersg filters
and strainers and strainers compounding system problems.compounding system problems.
leading to cavitation and additional heating of leading to cavitation and additional heating of 
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.5151
tt e e oo ..
The close running tolerances of theThe close running tolerances of the
pump/motpump/motor components makes or components makes themthem
susceptible to susceptible to heat damage. heat damage. Add the Add the fact thatfact that
the thrust plates are being squeezed against thethe thrust plates are being squeezed against the
gear faces with hgear faces with hydraulic pressureydraulic pressure; ; a loss of a loss of 
lubrication between the two surfaces canlubrication between the two surfaces can HEAT DAMAGEHEAT DAMAGEHEAT DAMAGEHEAT DAMAGE
friction.friction.
•• Low oil levelLow oil level
•• Cavitation / aeration / waterCavitation / aeration / water
•• ContaminationContamination
•• Inlet restrictionInlet restriction
•• Relief valveRelief valve
•• Incorrect fluidIncorrect fluid
•• Breakdown of oilBreakdown of oil
•• Loss of lubricityLoss of lubricity
•• Accelerated wearAccelerated wear
•• Reduced efficiencyReduced efficiency
•• LeakageLeakage
52. 52. Read slidRead slide texte text..
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.
•• Poor reservoir designPoor reservoir design
•• Undersized fittings, hoses,Undersized fittings, hoses,
componentscomponents
•• Internal seal destructionInternal seal destruction
•• SeizureSeizure
5252
53. 53. With the loWith the loss of lubricatiss of lubrication the thrust on the thrust plateplate
becomes heated rapidbecomes heated rapidly. ly. If the conditiIf the condition persiston persistss
the plates will become so heated that lead in thethe plates will become so heated that lead in the
1919
alloy will be drawn out of the plate.alloy will be drawn out of the plate.
MotionMotionMotionMotionMotionMotionLeadLead
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.
Thrust plateThrust plate
GearGearGearGearGearGear
5353
54. 54. As the lead comes to As the lead comes to the surface the trailingthe surface the trailing
gear tooth smears the lead over the surface gear tooth smears the lead over the surface of theof the
plate. plate. The plate wiThe plate will become bll become blackened by thelackened by the
lead oxidation.lead oxidation.
HEAT DAMAGEHEAT DAMAGEHEAT DAMAGEHEAT DAMAGE
GearGear
MotionMotion
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.
Thrust plateThrust plate
5454
HEAT DAMAGED THRUSTHEAT DAMAGED THRUST
PLATEPLATE
55. 55. The thrust platThe thrust plate in this sle in this slide has beenide has been
subjected to extreme heat causing the lead to besubjected to extreme heat causing the lead to be
drawn to drawn to the surface. the surface. A blackened A blackened surface andsurface and
thermal cracks in the plate can result.thermal cracks in the plate can result.
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.5555
5566.. EExxcceessssiivvee hheeaatt ccaann ccaauussee aa tthhrruusstt ppllaattee
mamateteririalal toto bebecocomeme brbritittltlee anandd crcracack.k. HEAT DAMAGED THRUSTHEAT DAMAGED THRUST
2020
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.5656
HEAT DAMAGED THRUSTHEAT DAMAGED THRUST
PLATEPLATE
57. 57. This P300 This P300 series thrust plate hseries thrust plate has beenas been
damaged by extreme heat due to a loss of damaged by extreme heat due to a loss of 
lubrication. lubrication. The surface iThe surface is blackeneds blackened
 ©1998 Commercial Intertech Corp.
©1998 Commercial Intertech Corp.5757
HEAT DAMAGED THRUSTHEAT DAMAGED THRUST
58. 58. Temperatures of Temperatures of 400 degrees 400 degrees FahrenheitFahrenheit
will melt the glass filled nylon channel sealwill melt the glass filled nylon channel seal
..
the two piece channel seal and the buna pocketthe two piece channel seal and the buna pocket
seal will be damaged at a much lowerseal will be damaged at a much lower
temperature.temperature.
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.5858
59. 59. With excessive heat tWith excessive heat the ends of the gearhe ends of the gear
teeth near the gear face teeth near the gear face become discolored.become discolored.
The high heat causes a bluing of the teeth.The high heat causes a bluing of the teeth.
WW
HEAT DAMAGED GEARHEAT DAMAGED GEAR
2121
thrust platthrust plate will start to e will start to weld together. weld together. TheThe
continued motion of the gear tears continued motion of the gear tears thrust platethrust plate
material from material from the plates the plates surface. surface. The frictionThe friction
can generate enough heat that the pump couldcan generate enough heat that the pump could
eventually seize up.eventually seize up.
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.5959
HEAT DAMAGED THRUSTHEAT DAMAGED THRUST
PLATEPLATE
60. 60. Welding betwWelding between the gear face and teen the gear face and thehe
thrust plate has occurred resulting in a thrust plate has occurred resulting in a rippingripping
of material from the plate surface.of material from the plate surface.
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.6060
61. 61. Fretting is a Fretting is a condition thcondition that occurs betweenat occurs between
the drive shaft extension and the the drive shaft extension and the drivedrive
coupling. coupling. These parts These parts are commoare commonlynly
lubricated lubricated with a with a heavy grease. heavy grease. FrettingFretting
CouplingCoupling
Small amplitudeSmall amplitude
vibrationvibration
damage occurs when the grease picks up gritdamage occurs when the grease picks up grit
and the small amplitude vibration makes and the small amplitude vibration makes thethe
contaminated contaminated grease act likgrease act like sandpaper. e sandpaper. AsAs
the wear progresses the clearance the wear progresses the clearance between thebetween the
parts becomes greater allowing more shaftparts becomes greater allowing more shaft
coupling coupling movement. movement. The wear acceleratesThe wear accelerates
until there is not enough engagement to carryuntil there is not enough engagement to carry
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.
ContaminantContaminant
suspendedsuspended
in greasein grease
Drive splineDrive spline
6161
..
the coupling will spin on the shaft stopping thethe coupling will spin on the shaft stopping the
revolution of the pump gears and revolution of the pump gears and thus pumpthus pump
flow. flow. The couplinThe coupling and g and the pumthe pump gear p gear setset
will have to be replaced.will have to be replaced.
62. 62. This splined This splined drive shaft has been worn bdrive shaft has been worn byy
fretting corrosifretting corrosion. on. To prevent To prevent this damthis damage theage the
drive coupling should be cleaned regularlydrive coupling should be cleaned regularly
2222
FRETTED DRIVESHAFTFRETTED DRIVESHAFT
synthetic grease.synthetic grease.
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.6262
REBUILD ERRORSREBUILD ERRORSREBUILD ERRORSREBUILD ERRORS
63. 63. Commercial Commercial Intertech performs Intertech performs a break-ina break-in
test on 100% test on 100% of it’s factory built of it’s factory built pumps. pumps. AnyAny
pump repaired and rebuilt should also bepump repaired and rebuilt should also be
tested. tested. This gives tThis gives the unit a prophe unit a proper break-iner break-in
and insures that it is performing toand insures that it is performing to
specification. specification. The unit The unit should alshould also beso be
inspected for external leakinspected for external leaks at this tims at this time. e. TheThe
recommended test/break-in procedure isrecommended test/break-in procedure is
described in all the Commercial Intertechdescribed in all the Commercial Intertech
pump servpump service manuals. ice manuals. Fact, 99% of Fact, 99% of allall
rebuild errors can be found at the rebuild errors can be found at the test stand.test stand.
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.6363
POTENTIAL ASSEMBLYPOTENTIAL ASSEMBLYPOTENTIAL ASSEMBLYPOTENTIAL ASSEMBLY
64. 64. Read slidRead slide texte text..
•• Improper bolt torqueImproper bolt torque
•• Nicked lip sealNicked lip seal
•• Pinched / fretted sectionPinched / fretted section
sealseal
•• Improper installation ofImproper installation of
•• HeatHeat
•• Extruded section sealExtruded section seal
•• External leakExternal leak
•• Internal leakInternal leak
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.
thrust platethrust plate
•• Pinched pocket /Pinched pocket /
channel sealchannel seal
•• Reduced efficiencyReduced efficiency
6464
65. 65. Pinched or Pinched or fretted section sfretted section seals can lead toeals can lead to
external leaks. external leaks. If the section If the section seal is notseal is not
properly installed the seal can be flattenedproperly installed the seal can be flattened
vv
PINCHED & FRETTEDPINCHED & FRETTED
SEALSSEALS
2323
..
leak path for oil to escape.leak path for oil to escape.
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.6565 ©1998 Commercial Intertech Corp.©1998 Commercial Intertech Corp.
66. 66. Your approach to Your approach to system msystem maintenance willaintenance will
either give you a reliable, relatively troubleeither give you a reliable, relatively trouble
free system or a system that is a constantfree system or a system that is a constant
maintenance nightmare.maintenance nightmare.
The best advise we can offer is to meet orThe best advise we can offer is to meet or
exceed theexceed the OOriginalriginal EEquipmentquipment
’’
SYSTEM MAINTENANCESYSTEM MAINTENANCESYSTEM MAINTENANCESYSTEM MAINTENANCE
MAINTENANCEMAINTENANCE
ananuu acactuturererr s s rerecocommmmenen atat onons s onon
maintenance intervals, and follow hismaintenance intervals, and follow his
recommendations when replacing criticalrecommendations when replacing critical
system components.system components.
The OEM has engineered and assembled aThe OEM has engineered and assembled a
hydraulic system which has been thoroughlyhydraulic system which has been thoroughly
tested and proven to give the besttested and proven to give the best
..
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.6666
THTHEE SYSYSTSTEMEMTHE SYSTEMTHE SYSTEM
67. 67. These are critical sThese are critical system comystem components.ponents.
INCLUDES:INCLUDES:
•• Hydraulic OilHydraulic Oil
•• Hoses/tubingHoses/tubing
•• FittingsFittings
•• Hydraulic PumpHydraulic Pump
•• Directional ValveDirectional Valve
•• ActuatorActuator
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.
•• FiltersFilters  –  – motormotor
 –  – cylindercylinder
6767
68. 68. Careless substitution Careless substitution of any critical systemof any critical system
component with a substandard replacementcomponent with a substandard replacement
will lead to extended downtime andwill lead to extended downtime and SUBSTITUTIONSSUBSTITUTIONSSUBSTITUTIONSSUBSTITUTIONS
2424
..
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.6868
69. 69. Read slidRead slide texte text..
HYDRAULIC OILHYDRAULIC OILHYDRAULIC OILHYDRAULIC OIL
closely as possibleclosely as possible
•• UnnecessaUnnecessary additives may ry additives may bebe
detrimentaldetrimental
•• Do not mix
and matchDo not mix and match
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.6969
WHEN REPLACINGWHEN REPLACINGWHEN REPLACINGWHEN REPLACING
70. 70. Read slidRead slide texte text..
,,,,
Use products with the same:Use products with the same:
 –  –  SizeSize
 –  –  MaterialMaterial
 –  –  LengthLength
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.
 –  –  reressssurure re raa nngg
as the original equipmentas the original equipment
7070
71. 71. Using Using “after market” “after market” hydraulichydraulic
components can be a components can be a dangerous proposition.dangerous proposition.HYDRAULICHYDRAULICHYDRAULICHYDRAULIC
COMPONENTSCOMPONENTSCOMPONENTSCOMPONENTS
2525
After market substitutions may lack proper:After market substitutions may lack proper:
•• TolerancesTolerances
•• TestingTesting
•• Pressure ratingPressure rating
•• Safety factorSafety factor
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.
•• aa eerr aa
•• DesignDesign
7171
72. 72. SUBSTITUTES SUBSTITUTES CAN CAN COSTCOST
YOU BIG:YOU BIG:
•• added downtime!added downtime!
•• additional repairs !!additional repairs !!
•• additional cost!!!additional cost!!!
SUBSTITUTIOSUBSTITUTIONS CAN NS CAN DEALDEALSUBSTITUTIOSUBSTITUTIONS CAN NS CAN DEALDEAL
YOU A LOSING HANDYOU A LOSING HANDYOU A LOSING HANDYOU A LOSING HAND
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.7272
73. 73. Replacing a worn Replacing a worn or failed pumor failed pump/motorp/motor
without taking the proper precautions canwithout taking the proper precautions can
lead to rapid failead to rapid failure of the new unit. lure of the new unit. TheThe
PPUMUMP P / / MM OOTTOORRPPUMUM P P / / MM OOTTOORR
RREEPLPLAACECEMM EENNTTREREPLPLAACECEMM EENNTT
tight factory tolerances of a new unit make ittight factory tolerances of a new unit make it
more susceptible to the same conditions thatmore susceptible to the same conditions that
caused the first unicaused the first unit to fail. t to fail. Flushing tFlushing thehe
hydraulic system, changing filters, andhydraulic system, changing filters, and
replacing used oil with new can insure properreplacing used oil with new can insure proper
component component life. life. The relief valve and The relief valve and thethe
governor should be reset prior to governor should be reset prior to resumingresuming
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.7373
..
AALLWWAAYYSS UUSSEE AANN AACCCCUURRAATTEE GGAAGGEE
WWHHEENN AADDJJUUSSTTIINNGG TTHHEE RREELLIIEEFF
VAVALVELVE PRPRESSESSUREURE SETSETTINTING.G.
74. 74. Before installing a new oBefore installing a new or rebuilt pumr rebuilt pump orp or
motor, back off the main relief valve until themotor, back off the main relief valve until the
spring tension on the adjusting screw is relieved.spring tension on the adjusting screw is relieved.
vv
RECOMMENDED START-UPRECOMMENDED START-UPRECOMMENDED START-UPRECOMMENDED START-UP
FOR NEW OR REBUILT PUMP/ FOR NEW OR REBUILT PUMP/ FOR NEW OR REBUILT PUMP/ FOR NEW OR REBUILT PUMP/ 
2626
damage to the replacement unit in the event thatdamage to the replacement unit in the event that
the relief valve setting had been increasedthe relief valve setting had been increased
beyond the recommended operating pressurebeyond the recommended operating pressure
prior to removing the old unit.prior to removing the old unit.
Before connecting any lines to the pump orBefore connecting any lines to the pump or
motor, fill all ports with clean oil to motor, fill all ports with clean oil to provideprovide
initial lubinitial lubrication. rication. This is partThis is particularly importanticularly important
MOTORMOTORMOTORMOTOR
•• Insure system cleanlinessInsure system cleanliness
•• Back-off relief valve Back-off relief valve pressure and reset governorpressure and reset governor
•• Fill unit Fill unit with clean oil before connecting lineswith clean oil before connecting lines
•• Connect the lines and mount unitConnect the lines and mount unit
•• Operate the unit at zero pressure for a minimum ofOperate the unit at zero pressure for a minimum of
where the unit is located above the oil reservoir.where the unit is located above the oil reservoir.
During the break-in period, the During the break-in period, the unit should rununit should run
free and not develop an excessive amount of free and not develop an excessive amount of 
heat. heat. Commercial’s pumCommercial’s pump/valve units sp/valve units should behould be
started up in the shift tstarted up in the shift to raise position. o raise position. This willThis will
insure a good prime and prevent heat damage.insure a good prime and prevent heat damage.  ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.
two mtwo minutes ainutes at lowt low speedspeed
•• Gradually increase speed and pressure to normalGradually increase speed and pressure to normal
operating conditions - approximately 5 minutesoperating conditions - approximately 5 minutes
•• Reset the main relief valve while the unit is operatingReset the main relief valve while the unit is operating
at maximum operating speedat maximum operating speed
7474
’’,,
manufacturers of hydraulic components for themanufacturers of hydraulic components for the
mobile market, has brought you this training programmobile market, has brought you this training program
on Failure Analysis. If you have any further questionson Failure Analysis. If you have any further questions
on this subject or any of our hydraulic products,on this subject or any of our hydraulic products,
please contact your Commercial Intertech Salesplease contact your Commercial Intertech Sales
Representative or your nearest AuthorizedRepresentative or your nearest Authorized
Distributor.Distributor.
 ©1998 Commercial Intertech Corp. ©1998 Commercial Intertech Corp.7575