694Revised 8/96

Hydraulic Hints &Trouble Shooting Guide

Vickers®

General Product Support

2

General Hydraulic Hints 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Troubleshooting Guide & Maintenance Hints 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chart 1 Excessive Noise 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chart 2 Excessive Heat 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chart 3 Incorrect Flow 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chart 4 Incorrect Pressure 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chart 5 Faulty Operation 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Quiet Hydraulics 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Contamination Control 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hints on Maintenance of Hydraulic Fluid in the System 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Aeration 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Leakage Control 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hydraulic Fluid and Temperature Recommendations for Industrial Machinery 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hydraulic Fluid and Temperature Recommendations for Mobile Hydraulic Systems 19. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Oil Viscosity Recommendations 20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Pump Test Procedure for Evaluation of Antiwear Fluids for Mobile Systems 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Oil Flow Velocity in Tubing 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Pipe Sizes and Pressure Ratings 24. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Preparation of Pipes, Tubes and Fittings Before Installation in a Hydraulic System 25. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ISO/ANSI Basic Symbols for Fluid Power Equipment and Systems 26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Conversion Factors 29. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hydraulic Formulas 29. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3

General Hydraulic Hints

Good AssemblyPracticesMost important – cleanliness.

All openings in the reservoir should besealed after cleaning.

No grinding or welding operationsshould be done in the area wherehydraulic components are beinginstalled.

All cylinder, valve, pump and hoseconnections should be sealed and/orcapped until just prior to use.

Mineral spirits should be kept in safetycontainers.

Air hoses can be used to clean fittingsand other system components. However,the air supply must be filtered and dry toprevent contamination of the parts.

Examine pipe fittings and hoseassemblies prior to use to be certain thatburrs, dirt and/or scale are not present.

All pipe and tubing ends should bereamed to prevent restriction andturbulent flow.

Do not use Teflon tape on straightthread connections.

When installing pumps or motors,always align coupling halves as closelyas possible, within 0.007 inch.

When using flexible couplings, follow themanufacturer’s recommendations orallow 1/32 to 1/16 inch clearancebetween the coupling halves.

Do not drive couplings on pump ormotor shafts. They should be a slip fit,or shrunk on using hot oil.

Always use a dry spray-on lubricant onsplines when installing. This preventswear and adds to the life of the splines.

When using double universal jointcouplings, the shafts must be paralleland the yokes must be in line.

When installing V-belt pulleys on pumpsor motors, line up both pulleys as closelyas possible. Always install the pulleys witha minimum amount of overhang as closeto the pump or motor face as possible.This increases bearing service life.

PipesIron and steel pipes were the first kindsof plumbing used to conduct fluidbetween system components. Atpresent, pipe is the least expensive wayto go when assembling a system.Seamless steel pipe is recommendedfor use in hydraulic systems with thepipe interior free of rust, scale and dirt.

Early classifications of pipe wallthicknesses were: standard, extra heavyand double extra heavy.

Today, pipes are classified by schedulenumber as specified by the AmericanNational Standards Institute (ANSI). Theschedule numbers vary from 10 through160. The larger the number, the heavierthe wall thickness. The outer pipediameter stays the same for a given pipesize, while the inside opening becomessmaller as schedule number increases.

A comparison of early classificationsversus the ANSI classification follows:

Standard – Schedule 40Extra Heavy – Schedule 80

The double extra heavy classificationdoes not compare with a schedulenumber. However, the inside diameter ofa double extra heavy pipe isapproximately one half that of a schedule160 pipe.

In many cases, flanges are welded tothe pipe ends and gaskets or “O” ringsare used to seal the connections.Various pipe fittings are used to routethe piping to and from each systemcomponent. These fittings can bethreaded or welded in place as the needarises. Threaded connections are usedin low pressure applications and weldedconnections are used if high pressure,high temperature, or a severemechanical load exists.

All piping should be secured withclamps to prevent vibration andexcessive stress due to the weight ofthe fluid. Do not weld the clamps to thepipe as it may weaken the pipe andcause a stress crack.

Tubing Do’s And Don’tsDon’t take heavy cuts on thin wall tubingwith a tubing cutter. Use light cuts toprevent deformation of the tube end. Ifthe tube end is out or round, a greaterpossibility of a poor connection exists.

Ream tubing only for removal of burrs.DO NOT over ream tubing as it canweaken the connection.

Do not allow chips to accumulate in thetubing. They can be difficult to removeafter bending.

Follow the manufacturersrecommendations on the use of flaringtools. Don’t overtighten the feed screwhandle on a compression type flaring tool.Improper use of a tool can cause washoutand/or splitting of the flare connection.

Bend tubing instead of cutting and usinga fitting. This reduces pressure drop andminimizes system losses. The minimumradius of a tubing bend should be atleast three times the inside diameter ofthe tube. Larger bends are preferred.

Sketch the optimum tubing route beforebeginning the bending process. Be sureto use tubing with the proper temper toprevent wrinkles and flattened bends.

Most flares are made by hand or powertools that swage the tube end over asplit die. The standard flare angle is 37degrees from the centerline. For bestresults, heavy wall tubing should be cut,deburred, and flared and bent usingpower equipment.

For information on sealing technology, orhow to prevent leakage of hydraulic fluid,refer to “Leakage Control” in this catalog.

4

Troubleshooting Guide & Maintenance Hints

GeneralThe troubleshooting charts andmaintenance hints that follow are of ageneral system nature but shouldprovide an intuitive feeling for a specificsystem. More general information iscovered in the following paragraphs.Effect and probable cause chartsappear on the following pages.

System DesignThere is, of course, little point indiscussing the design of a system whichhas been operating satisfactorily for aperiod of time. However, a seeminglyuncomplicated procedure such asrelocating a system or changing acomponent part can cause problems.Because of this, the following pointsshould be considered:

1. Each component in the system mustbe compatible with and form anintegral part of the system. Forexample, an inadequate size filter onthe inlet of a pump can causecavitation and subsequent damage tothe pump.

2. All lines must be of proper size andfree of restrictive bends. Anundersized or restricted line results ina pressure drop in the line itself.

3. Some components must be mountedin a specific position with respect toother components or the lines. Thehousing of an in-line pump, forexample, must remain filled with fluidto provide lubrication.

4. The inclusion of adequate test pointsfor pressure readings, although notessential for operation, will expeditetroubleshooting.

Knowing the SystemProbably the greatest aid totroubleshooting is the confidence ofknowing the system. The construction andoperating characteristics of each oneshould be understood. For example,knowing that a solenoid controlleddirectional valve can be manually actuatedwill save considerable time in isolating adefective solenoid. Some additionalpractices which will increase your abilityand also the useful life of the systemfollow:

1. Know the capabilities of the system.Each component in the system has amaximum rated speed, torque orpressure. Loading the system beyondthe specifications simply increasesthe possibility of failure.

2. Know the correct operating pressures.Always set and check pressures with agauge. How else can you know if theoperating pressure is above themaximum rating of the components?The question may arise as to what thecorrect operating pressure is. If it isn’tcorrectly specified on the hydraulicschematic, the following rule should beapplied:

The correct operating pressure is thelowest pressure which will allowadequate performance of the systemfunction and still remain below themaximum rating of the componentsand machine.

Once the correct pressures have beenestablished, note them on the hydraulicschematic for future reference.

3. Know the proper signal levels,feedback levels, and dither and gainsettings in servo control systems. Ifthey aren’t specified, check themwhen the system is functioningcorrectly and mark them on theschematic for future reference.

Developing SystematicProceduresAnalyze the system and develop alogical sequence for setting valves,mechanical stops, interlocks andelectrical controls. Tracing of flow pathscan often be accomplished by listeningfor flow in the lines or feeling them forwarmth. Develop a cause and effecttroubleshooting guide similar to thecharts appearing on the following pages.The initial time spent on such a projectcould save hours of system down-time.

Recognizing TroubleIndicationsThe ability to recognize troubleindications in a specific system isusually acquired with experience.However, a few general troubleindications can be discussed.

1. Excessive heat means trouble. Amisaligned coupling places anexcessive load on bearings and canbe readily identified by the heatgenerated. A warmer than normaltank return line on a relief valveindicates operation at relief valvesetting. Hydraulic fluids which have alow viscosity will increase the internalleakage of components resulting in aheat rise. Cavitation and slippage in apump will also generate heat.

2. Excessive noise means wear,misalignment, cavitation or air in thefluid. Contaminated fluid can cause arelief valve to stick and chatter. Thesenoises may be the result of dirty filters,or fluid, high fluid viscosity, excessivedrive speed, low reservoir level, looseintake lines or worn couplings.

MaintenanceThree simple maintenance procedureshave the greatest effect on hydraulicsystem performance, efficiency and life.

1. Maintaining a clean sufficient quantityof hydraulic fluid of the proper typeand viscosity.

2. Changing filters and cleaningstrainers.

3. Keeping all connections tight, but notto the point of distortion, so that air isexcluded from the system.

GuidelinesThe following charts are arranged in fivemain categories. The heading of eachone is an effect which indicates amalfunction in the system. For example,if a pump is exceptionally noisy, refer toChart 1 titled Excessive Noise. Thenoisy pump appears in Column A underthe main heading. In Column A there arefour probable causes for a noisy pump.The causes are sequenced according tothe likelihood of happening or the easeof checking it. The first cause iscavitation and the remedy is “a”. If thefirst cause does not exist, check forcause number 2, etc.

5

Troubleshooting Guide & Maintenance Hints

Setting too low or tooclose to another valvesetting

Remedy: d

EXCESSIVE NOISE

Cavitation

Remedy: a

PUMP NOISY

Air in fluid

Remedy: b

Coupling Misaligned

Remedy: c

Pump worn ordamaged

Remedy: e

1.

2.

3.

4.

A

RELIEF VALVE NOISY

1.

C

Coupling misaligned

Remedy: c

MOTOR NOISY

Motor or couplingworn or damaged

Remedy: b

1.

2.

B

Worn poppet and seat

Remedy: e

2.

Chart 1

Remedies:

a. Any or all of the following:

Replace dirty filters; wash strainers insolvent compatible with system fluid;clean clogged inlet line; clean orreplace reservoir breather vent;change system fluid; change toproper pump drive motor speed;overhaul or replace superchargepump; fluid may be too cold.

b. Any or all of the following:

Tighten leaking connections; fillreservoir to proper level (with rareexception all return lines should bebelow fluid level in reservoir); bleedair from system; replace pump shaftseal (and shaft if worn at sealjournal).

c. Align unit and check condition ofseals, bearings and coupling.

d. Install pressure gauge and adjust tocorrect pressure.

e. Overhaul or replace.

6

Troubleshooting Guide & Maintenance Hints

Worn pump, valve, motor,cylinder or othercomponent

Remedy: e

Air in fluid

Remedy: b

Remedy: See column D

PUMP HEATED

Cavitation

Remedy: a

Relief or unloadingvalve set too high

Remedy: d

1.

2.

3.

4.

A

RELIEF VALVE HEATED

1.

C

Fluid heated

Remedy: See column D

MOTOR HEATED

Relief or unloadingvalve set too high

Remedy: d

1.

2.

B

Valve setting incorrect

Remedy: d

2.

Excessive load

Remedy: c

5.

Worn or damagedpump

Remedy: e

6.

FLUID HEATED

D

Excessive load

Remedy: c

Worn or damagedmotor

Remedy: e

3.

4.

Fluid heated

Remedy: See column D

Worn or damaged valve

Remedy: e

3.

System pressure toohigh

Remedy: d

1.

Unloading valve settoo high

Remedy: d

2.

Fluid dirty or low supply

Remedy: f

3.

Incorrect fluidviscosity

Remedy: f

4.

Faulty fluid coolingsystem

Remedy: g

5.

6.

EXCESSIVE HEATChart 2

Remedies:

a. Any or all of the following:

Replace dirty filters; clean cloggedinlet line; clean or replace reservoirbreather vent; change system fluid;change to proper pump drive motorspeed; overhaul or replacesupercharge pump.

b. Any or all of the following:

Tighten leaking connections; fillreservoir to proper level (with rareexception all return lines should bebelow fluid level in reservoir); bleedair from system; replace pump shaftseal (and shaft if worn at sealjournal).

c. Align unit and check condition ofseals and bearings; locate andcorrect mechanical binding; check forwork load in excess of circuit design.

d. Install pressure gauge and adjust tocorrect pressure (keep at least 125PSI difference between valvesettings).

e. Overhaul or replace.

f. Change filters and also system fluid ifimproper viscosity; fill reservoir toproper level.

g. Clean cooler and/or cooler strainer;replace cooler control valve; repair orreplace cooler.

7

Troubleshooting Guide & Maintenance Hints

Flow control set too high

Remedy: d

INCORRECT FLOW

Pump not receiving fluid

Remedy: a

NO FLOW

Pump to drive couplingsheared

Remedy: c

Pump drive motor turningin wrong direction

Remedy: g

1.

3.

4.

A

EXCESSIVE FLOW

1.

C

Flow control set too low

Remedy: d

LOW FLOW

Relief or unloadingvalve set too low

Remedy: d

1.

2.

B

Chart 3

Pump drive motor notoperating

Remedy: e

2. Yoke actuating deviceinoperative (variabledisplacement pumps)

Remedy: e

2.

Flow by-passing thrupartially open valve

Remedy: e or f

3.

External leak in system

Remedy: b

4.

RPM of pump drivemotor incorrect

Remedy: h

3.

4. Improper size pumpused for replacement

Remedy: h

Directional control set inwrong position

Remedy: f

5. Yoke actuating deviceinoperative (variabledisplacement pumps)

Remedy: e

5.

Entire flow passingover relief valve

Remedy: d

RPM of pump drivemotor incorrect

Remedy: h

6.6.

Damaged pump

Remedy: c

7. Worn pump, valve,motor, cylinder orother component

Remedy: e

7.

Improperly assembledpump

Remedy: e

8.

Remedies:

a. Any or all of the following:

Replace dirty filters; clean cloggedinlet line; clean or replace reservoirbreather vent; fill reservoir to properlevel; overhaul or replacesupercharge pump.

b. Tighten leaking connections.

c. Check for damaged pump or pumpdrive; replace and align coupling.

d. Adjust.

e. Overhaul or replace.

f. Check position of manually operatedcontrols; check electrical circuit onsolenoid operated controls; repair orreplace pilot pressure pump.

g. Reverse rotation.

h. Replace with correct unit.

8

Troubleshooting Guide & Maintenance Hints

Pressure relief pathexists

Remedy: See Chart 3,column A and B

No flow

Remedy: See Chart 3,column A

NO PRESSURE

1.

A

ERRATIC PRESSURE

1.

C

LOW PRESSURE

Pressure reducing valveset too low

Remedy: d

1.

2.

B

Worn relief valve

Remedy: e

2.

EXCESSIVEPRESSURE

D

Pressure reducingvalve damaged

Remedy: e

Damaged pump, motoror cylinder

Remedy: e

3.

4.

Air in fluid

Remedy: b

Contamination in fluid

Remedy: a

3.

Pressure reducing,relief or unloadingvalve misadjusted

Remedy: d

1.

Yoke actuating deviceinoperative (variabledisplacement pumps)

Remedy: e

2.

Pressure reducing,relief or unloadingvalve worn or damaged

Remedy: e

3.

INCORRECT PRESSUREChart 4

Accumulator defectiveor has lost charge

Remedy: c

4.

Worn pump, motor orcylinder

Remedy: e

5.

Remedies:

a. Replace dirty filters and system fluid.

b. Tighten leaking connections (fillreservoir to proper level and bleed airfrom system).

9

Troubleshooting Guide & Maintenance Hints

Low flow

Remedy: See Chart 3

No flow or pressure

Remedy: See Chart III

NO MOVEMENT

1.

A

ERRATIC MOVEMENT

1.

C

SLOW MOVEMENT

Fluid viscosity too high

Remedy: a

1.

2.

B

Air in fluid

Remedy: See Chart I

2.

EXCESSIVE SPEEDOR MOVEMENT

D

Insufficient controlpressure for valves

Remedy: See Chart 4

No lubrication of machineways or linkage

Remedy: g

3.

4.

Erratic pressure

Remedy: See Chart IV

Excessive flow

Remedy: See Chart 3

1.

Feedback transducermalfunctioning

Remedy: e

2.

Misadjusted ormalfunctioning servoamplifier

Remedy: c

3.

FAULTY OPERATIONChart 5

Erratic command signal

Remedy: f

4.

Misadjusted or malfunc-tioning servo amplifier

Remedy: c

5.

Limit or sequencedevice (mechanical,electrical or hydraulic)inoperative ormisadjusted

Remedy: e

2.

Mechanical bind

Remedy: b

3. No lubrication ofmachine ways orlinkage

Remedy: See Chart 4

3.

No command signalto servo amplifier

Remedy: f

4. Over-riding work load

Remedy: h

4.

Inoperative or mis-adjusted servo amplifier

Remedy: c

5. Misadjusted or malfunc-tioning servo amplifier

Remedy: c

5.

Inoperative servo valve

Remedy: c

6. Sticking servo valve

Remedy: c

6. Malfunctioning feedbacktransducer

Remedy: e

6.

Worn or damagedcylinder or motor

Remedy: e

7. Worn or damagedcylinder or motor

Remedy: e

7. Sticking servo valve

Remedy: d

7.

Worn or damagedcylinder or motor

Remedy: e

8.

Remedies:

a. Fluid may be too cold or should bechanged to clean fluid of correctviscosity.

b. Locate bind and repair.

c. Adjust, repair or replace.

d. Clean and adjust or replace; checkcondition of system fluid and filters.

e. Overhaul or replace.

f. Repair command console orinterconnecting wires.

g. Lubricate.

h. Adjust, repair or replacecounterbalance valve.

10

Quiet Hydraulics

Today, buyers are demanding quietmachines because of their concernabout meeting industry’s noise limits.Vickers is helping to meet this demandby supplying quiet hydrauliccomponents. Sound levels of somepumps today, for example, are fiftypercent lower than the same modelpumps of a few years ago.

Sound AdviceProducing quiet, hydraulically-actuatedmachines requires more than just theuse of quiet components.

Meeting the stringent sound-levelspecifications of today’s industrial hydraulicsystems and machines takes carefulengineering. The pump should beconsidered first. It not only produces sounddirectly but generates vibrations and fluidpulsations. These react with other machineparts which produce more sound.

Pump SelectionPumps generate more acoustic energyper unit of hydraulic power by running athigh speed rather than at low. For thisreason, a pump should operate at 1200RPM whenever sound is critical. Below3000 PSI, the trade-off between pressureand pump size for a given drive powerhas little effect on noise, so you are freeto select any combination of these factorsthat otherwise meet your needs.

Mechanical IsolationTo meet lower sound level limits, thepump should be mechanically isolatedfrom the rest of the machine usinganti-vibration mountings. This alsorequires that all connections to thepumps be made with flexible hose.

Flexible hose will often reduce noise evenwhere anti-vibration mountings are notused. It prevents vibrations from reachingother lines and components to keep themfrom becoming sound sources. In longlengths, this hose is, itself, a good soundgenerator so only short lengths should beused. For long runs, use solid pipes withshort hoses at the ends. All long lines mustbe supported every meter or so, preferablywith clamps providing vibration damping.Lines must not contact panels that aregood sounding boards. Where they passthrough such panels, allow sufficientclearance to prevent direct contact; neveruse bulkhead fittings in such cases.

Acoustic IsolationThe greatest sound level reductions areattained with the pump acoustically aswell as mechanically isolated. Thisrequires that the pump be completelyenclosed in a non-porous shell weighingat least 10 kg per square meter ofsurface. No openings can be toleratedand all joints must be sealed withresilient gaskets or moldings.

Grommets of rubber or other softmaterial should be used to closeopenings around piping and to preventmechanical contact between theenclosure and piping. It must beemphasized that while mechanicalisolation by itself can reduce noise,acoustic isolation can only be effectivewhen used in combination withmechanical isolation.

FluidsThe condition of the fluid being pumpedis also important in controlling sound.Fluid viscosity, temperature andvacuum by themselves have no effecton sound levels. It is important tocontrol them, however, to prevent theformation of entrained air or vaporbubbles that can double sound levels,and reduce pump life.

A combination of high fluidtemperature and inlet vacuumgenerates what are called cavitationbubbles. However, at lowtemperatures, a high viscosity fluid ina very long suction line can alsoproduce sufficient vacuum to causecavitation. Important methods ofsuppressing bubble formation include:Using short runs or large diameterinlet lines; keeping the reservoirelevation close to or above that of thepump; using low pressure-drop inletfilters that signal when they areproducing high vacuums and needchanging; and, providing adequatefluid controls. These are all goodhydraulic practices that becomeincreasingly important where youmust achieve low sound levels.

ReservoirsReservoirs provide the means forreleasing entrained bubbles. Thesecan come from sources other than thepump inlet and are usually present inthe fluid returning to the reservoir. It isimportant to note that low reservoirtemperatures reduce the rate ofbubble escape and may result inincomplete release. As pointed outearlier, high temperatures promotebubble formation. The best balancebetween these two alternatives isachieved by maintaining thetemperature of oil leaving thereservoir in the range of 120� to150�F and the temperature ofwater-based fluids between 100� and120�F.

A simple reservoir has to be largeto effect complete bubble release.By providing baffles to guide the fluidthrough a circuitous path and bylocating return and pump inlet linesas far apart as possible, a reservoirholding between two to three minutesof maximum pump flow can beadequate.

For Hydraulic Systems:– Provide fluid filter(s) in location(s) that assure the

required protection.– The ideal steady-state flow conditions through an

off-line filter make this a must for most applications.– Whenever possible, use filters having element

condition indicators.– Vented systems must be fitted with an air breather

appropriate to the environment(s) in which themachine is to be operated and the requirements ofthe system.

– Fit strainers to pump inlet lines if there is risk oflarge contaminant particles (i.e. string, rag, screws,etc.) entering the lines.

– Prevent air entering the system, particularly throughpump inlet lines. Ensure air-tight joints in anysub-atmospheric zone or pump inlet lines. Alsomake sure that those lines and all return and drainlines terminate below the minimum fluid level in thereservoir; pump inlet lines should be sufficientlybelow to prevent air entering through a vortex atlow fluid levels.

– Design for, and maintain, fluid temperatures atoptimum levels for the application. Apply coolers ifnecessary.

– Locate or screen hydraulic systems away from hightemperature sources (e.g. furnaces).

– Assemble system in clean conditions using cleanpractices.

– Pre-clean pipes and reservoir immediately beforeinstallation. Cap any ends that cannot immediatelybe connected to mating components (e.g. betweenshifts).

Preventive MeasuresSolid

Contam.High

Temp.Water Air

For Storage Drums:– Store in cool, dry location.– Ensure that closures fully seal in the fluid.– Wipe away any dirt and moisture from around the

closure before loosening and emptying.– Use a portable filtration and transfer unit for

emptying and refilling.

Fluid degradation by:

For Storage Tanks:– Install in cool, dry location.– Ensure that all covers and stop valves effectively

seal in the fluid.– Keep filling lines clean; cap ends when not in use.– Use a portable filtration unit for filling and emptying.

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11

Contamination Control

Contaminant in hydraulic systems isnow recognized as the most frequentcause of malfunction or failure ofhydraulic equipment. Dependent on thenature, size and/or amount ofcontaminant, it can cause:

– Reduced component service life.

– Machine malfunction, particularlywhen operating near maximumcapacity.

– Risk of frequent breakdowns underthe same conditions.

– Production rates below schedule.

– High product scrap rates and qualityfaults.

Nature of ContaminantContaminant can be either particlecontaminant or the product(s) of fluiddegradation.

Particle contaminant can be metal,rubber, plastic, dirt, dust, fibre, sand,paint, etc.; several types may be presentat any time. It can enter the fluid at anytime after the fresh clean fluid has beenproduced by the fluid manufacturer.There is usually little likelihood that freshfluid became contaminated during therefining and blending processes.

Fluid degradation results in:

– Oxidation and/or the formation ofgummy deposits and sludge from thecombined effects of hightemperatures, air, water and particlecontaminant. These can increaseviscosity, cause gummy deposits tocoat moving parts, clog orifices andsmall passages, thus impairingsmooth mechanical movements andform sludge.

– Unstable emulsions of poor lubricityformed when water accidentlyemulsifies with oil. These impair smoothmovements and promote wear.

– Aeration or air bubbles in the fluid,particularly at low pressures. Inexcess, they cause noise in pumpsand valves leading to erratic orspongy machine movements,premature wear and failure.

Control of ContaminationThe following table prescribespreventative measures relative to thedifferent common types and causes ofcontamination. For additional information,request Vickers Guide to SystemicContamination Control, catalog 561.

12

For Hydraulic Systems:– Remove protective caps only just before connecting

mating components.– Use a portable filtration and transfer unit to fill the

reservoir system.– Flush new systems, and those that have undergone

major repairs, before starting up. Temporarilyremove actuators and replace with flushingmanifolds or valves. Servo valves and similar highprecision units should also be replaced withflushing manifolds or valves for flushing operations.Make sure that actuators are clean internally beforeconnecting to the system.

– Make sure that air breathers and reservoir coversare at all times properly installed and tightlysecured.

– Stop any leakage of water into the system fromcoolers or other sources. Make a leak-tight repair.

– By planned maintenance, ensure that clean filterelements are applied (or metallic elements cleanedwhen appropriate) when indicators or visualinspection shows this to be necessary.

– Take fluid samples periodically and analyze todetermine whether effects of particle contaminant,heat, water and air indicate need for more control ofthose factors or replacement of the fluid.

– Whenever the reservoir is emptied, clean it outthoroughly and remove all residual contaminant. Ifnecessary, restore protective paint or other finishes.On completion, cap all openings unless the systemis to be refilled immediately.

Preventive MeasuresSolid

Contam.High

Temp.Water Air

Fluid degradation by:

�

�

� �

�

�

�

�

� �

�

� � �

� �

13

Hints On Maintenance Of Hydraulic Fluid In The System

Hydraulic Fluid ChangesGood maintenance procedures make itmandatory to keep the hydraulic fluidclean. A daily, weekly or monthly logshould be kept on the hydraulic fluidcondition.

No hard and fast rules can beestablished for changing the fluidbecause of the great variety of operatingconditions. However, we do know thatwhen filter elements are replacedfrequently, service life of a systemincreases. Periodic testing of the fluid bythe supplier is recommended to confirmsuitability for continued use and toestablish the correct fluid and filterelement replacement interval.

Some of the considerations affectinghydraulic fluid are: operatingtemperature, type of service,contamination levels, filtration, and thechemical composition of the fluid.

Fluid RecommendationsThe basic recommendations for fluidare stipulated in the Hydraulic Fluid andTemperature Recommendations forIndustrial Machinery in this catalog.The fluids recommended give theassurance of adequate wear protectionand excellent chemical stability underthe most adverse operating conditions.

On mobile applications, the viscositygrade of the fluid should be changed inspring and autumn as is done withautomotive engines. Hydrostatictransmissions and control mechanismsmay require a different viscosity fluid.Fluid requirements are normallyoutlined in the original equipmentmanufacturers operation andmaintenance manuals.

Draining The SystemThe system should be started and fluidheated before draining. This will lowerthe time it takes to drain the system andallow impurities suspended in the fluidto be removed. It is desirable to removeall fluid from the system. Bleeding ofthe fluid at the lowest point in thesystem will help in most cases.

Systems which have accumulateddeposits that were not removed duringdraining must be flushed with a lightviscosity fluid. The fluid should containa rust inhibitor to protect metal surfacesagainst rust formation after draining.

When hydraulic fluid is added toreplenish the system, it should bepumped through a 25 micron filter. Ifsuch a filter is not available, a funnelwith a fine wire screen (200 mesh or

finer) can be used. It is important thatfluid be clean and free of all substanceswhich will cause improper operation.

Fluid Contamination –Causes and EffectsContaminationA contaminated system can be the resultof several factors; system designinadequate, poor maintenance of thesystem, poor housekeeping of the systemand adverse operating conditions.

System Design Inadequate– Reservoirs which cannot be cleaned.– Breathers that permit abrasives

inherent in the atmosphere to enterthe system.

– Poor cylinder packing design (nowiper to clean dirt from the pistonrod).

– Improper piston rod design (pistonrods with poor wear characteristic).

– Improper valving (anti–cavitationchecks omitted from cylinder circuitswith rapid drop characteristics).

– Failure to provide adequate filtration.

Poor Maintenance of the System– Improper and unclean practices when

adding fluid to the system.– Failure to clean breathers.– Failure to change pitted cylinder rods

and worn cylinder packings.– Failure to use good cleanliness

practices when changing systemcomponents.

– Failure to change filter cartridgesand/or filter at proper intervals.

– Failure to purge debris from thesystem after a pump failure.

Poor Housekeeping of theSystemSurgical cleanliness is not required,however, ordinary clean practicesduring assembly will pay off inincreased service life of the equipment.

Excessive and improper use of pipethread sealer on lines and gaskets inthe system can cause pump failures.This is especially true when a type ofsealer is used that hardens.

Another source of contamination isfittings, hoses and lines which arereceived from a vendor uncapped. Theuse of brazed or welded fittings, andunpickled steel plating can alsocontribute to the contamination.

Preparation of pipes, tubes and fittingsin this catalog should be referred to andfollowed. This will lower the possibilityof premature failure due tocontamination of the system.

Adverse Operating Conditions

From experience, we have found thatmachines used in a very dustyatmosphere and in windy areas requirespecial components. For example,heavy duty breathers, chrome platedpiston rods, plus frequent changes ofthe filter cartridges are also required.

Effects of ContaminationContamination affects all types ofhydraulic equipment adversely.Precision high tolerance parts are verysusceptible to the effects ofcontamination. Dirty fluid causes wearwhich accelerates leakage and thedevelopment of heat in a system. Heatlowers the lubricity of a hydraulic fluidand causes additional wear.

If a hydraulic pump or motor should fail,the system becomes contaminated.Remove the unit for repair. Thereservoir must be drained, flushed, andcleaned. All hoses, lines, cylinders andvalves should be inspected for wearand particles of the unit that failed.Flush all components of the completesystem to remove metallic particles.

Replace filter elements. Dispose of thefluid removed from the system and fillthe reservoir with clean hydraulic fluid.Install a new or rebuilt unit and start-upthe system. Allow the system to run fora period of time to verify normaloperation. Filter elements should bechanged after 40 or 50 hours ofoperation. This guarantees that thesystem is essentially clean and free ofany residue of the failed unit.

A very good reference catalog oncontamination is available titled VickersGuide to Systemic ContaminationControl. This catalog describes typesand sources for contamination, effectsof types and sizes of particles,specifying contamination levels,selecting a filter, locating a filter, designsteps and worked examples of fluidsampling analysis. Order catalog 561from your local Vickers representative.

14

Aeration

AerationCausesThe following are candidates for theformation of air in a system.– Leaking inlet lines.– Control valve “O” rings leaking.– Shaft seal leakage.– Leaking cylinder packings caused

by cavitating cylinders.– Turbulence or sloshing in the

reservoir.– Vortexing fluid in the reservoir– Release of air suspended within

the fluid.

EffectsAeration can be in many forms; largebubbles, foam or in various degrees ofsuspension. It usually causes pump noise(cavitation). Small bubbles cause extremeand rapid ring wear, with correspondingvane tip wear. Larger bubbles cause vanesto collapse and pound. This poundingeffect develops rippling in the ring and thering will have a dull appearance. This ismore apparent on straight vane ringswhich are hardened cast iron. Withextreme aeration cases, the wear is sorapid that a ring and vanes can bedestroyed within an hour. In many cases, alarge step will be worn in the ring contourat the pressure quadrant. When the stepreaches a depth where the vane extendsand locks, the vane and/or ring will break.Also, the shaft can break where it entersthe rotor if the torque is great enough.

Cures

Leaking Inlet Lines– Pipe threaded fittings can be porous.

Use an approved type of pipe threadsealer on all pipe threads.

– If the pump inlet flange surface isrough, scored or mutilated, air leakagepast the “O” ring seal can result.

With any of the above defects, air canbe pulled into the system.

Control Valve “O” Rings Leaking

“O” rings are used to seal against portleakage in many control valves. Theseseals can be checked by applying heavygrease around the part to be checked. Ifthe noise stops, the trouble has beenlocated and repair can be initiated.

On systems which have been operatingat excessive high temperatures, the “O”rings can harden and take a set. If thisoccurs, air leakage can result. This istrue not only in a pump, but also in therest of the components of the system.Another factor enhancing air leakage isthe actual fluid composition. Fluids which

have a high sulphur content tend toaccelerate “O” ring hardness. This is oneof the principle reasons for keepingsystem operating temperatures down.Normal operating temperature of asystem is 90 degrees above ambient.When operating temperatures are inexcess of this value, trouble may result.Maximum operating temperatures shouldbe checked at the pump outlet port.

Shaft Seal Leakage

Most vane pumps are internally drained.The shaft seal cavity is connected to thepump inlet. Excessively high inletvacuums can cause air leakage at theshaft seal. The maximum vacuummeasured at the pump inlet should notexceed five inches of mercury.

Shaft misalignment can increase theprobability of air leakage past the shaftseal. Universal jointed couplings orsplined couplings can cause sealleakage if not properly aligned. Straight(direct) coupling should never be used.

The use of the wrong type of tools cancause distortion or mutilation of a shaftseal at installation. The outer diameter ofthe shaft should be lightly polished beforeinstallation to remove any burrs orroughness in the area of the shaft seal.

Shaft seals must be made of the correctmaterial for a given application. A materialthat is not compatible with system fluid candeteriorate and result in a leakageproblem.

Leaking Cylinder PackingsCaused By Cavitating Cylinders

On applications where a rapid raise andlower cycle is experienced, air can enterthe system through a cylinder rod seal.Vacuums in excess of 20 inches ofmercury have been recorded in systemswithout anti-cavitation check valves. This isenough to force dirt particles past the shaftseal into the system with the air. Ananti-cavitation check will allow flow fromthe reservoir to enter the rod area of thecylinder during a vacuum condition fromdeveloping. This will lower the possibility offluid contamination through the rod seal ofa working cylinder.

Turbulence or Sloshing in theReservoir

Return lines, if improperly located,can cause turbulence and aeration. APlexiglass window should be placedin the prototype reservoir to study flowconditions. Return lines emptyingabove the fluid level cause bubbles toform in the system. Return linesshould always be terminated belowthe fluid level. Vehicle movement cancause sloshing within the reservoir.

Reservoir must be deep enough toprevent aeration.

Vortexing Fluid in the Reservoir

If the fluid level in the reservoir is lowand the inlet demand is great, a vortexcondition can develop which pulls airinto the pump inlet. In a hydraulicsystem, vortexing is normally the resultof low fluid or poor reservoir design.

One of the best ways of curing avortex problem is to place ananti-cavitation plate over the outlet ofthe reservoir. This is a common pieceof sheet metal at lease 1/8 inch thickset over and above the outlet opening.This plate will allow flow into the outletfrom a horizontal direction andeffectively extends and enlarges thereservoir opening. This prevents thevortex condition from developing.

Release of Air Suspended in Fluid

There is considerable air suspended incold hydraulic fluid. As the fluid warms,air is released into the system. Areduction of fluid pressure will alsorelease air out of suspension. A simplerelief valve poppet can create an orificethat increases velocity of the fluid andlowers its pressure. The reducedpressure condition releases air out ofsuspension into the system. Relief valvesshould be returned below the fluid levelof the reservoir as far from the reservoiroutlet as possible. This allows time forthe air released by the relief valve to beremoved before leaving the reservoir andentering the inlet area of the pump.

In some cases, special return lineconfigurations are needed, or air bleedvalves used, to remove air from thesystem.

A special baffle made of 60 mesh screencan be installed into the reservoir. Thisbaffle should be positioned at a 30� anglein the reservoir so that inlet oil is above thescreen and outlet oil is below the screen.The top of the screen should be below thereservoir fluid level far enough to preventsurface foam from coming in contact withthe screen. Surface foam can penetratethrough the screen into the outlet area.The screen baffle will eliminate allbubbles except the very small onesfrom the fluid if designed properly.

15

Leakage Control

Cost Of LeakageConcern for safety at work and therapidly increasing cost of oil makesindustry sensitive to leakage.Leakage creates safety hazards,wastes costly oil, increases machinedown-time, decreases productionrates, generates product spoilage andincreases replacement partsinventory. The cost of effectiveleakage control is minor whencompared to the long term costs ofleakage.

Leak-Free DesignHydraulic systems do not need to leak.Today’s designer must create a moreleak resistant system, where staticseal leakage should not occur anddynamic seal leakage will becontrolled. Before presenting somedesign practices proved effective instopping leaks, we should consider thesources of most leaks.

Cause Of LeaksAlmost all hydraulic system leaksoccurring after extended service resultfrom three conditions:

– Loosening of fittings and connectorsby shock and vibration

– Wear of dynamic seals and matingparts especially in hydraulic cylinders

– Deterioration of the elastomerbecause of elevated fluidtemperatures or an incompatibility withthe hydraulic fluid

Combatting Shock AndVibrationMany things can be done to minimizeleakage from loose fittings andconnectors subject to shock andvibration:

1. Support all pipe lines with dampedmountings to absorb both shock andvibration.

2. Reduce shock with low-shock valvesor accumulators.

3. Use pressure controls with lowoverride and strategically placed toprotect all parts of the system.

4. Use a minimum number of fittings andconnectors. Use welded jointswherever practical.

5. Use parallel thread connectors, teesand elbows in place of tapered pipethreads.

6. Use manifolds instead of individuallines wherever possible.

7. Specify proper bolt and plug torquesfor expected peak pressures toprevent surface separation and staticseal nibbling.

8. Stress good workmanship to avoidpoorly assembled fittings andconnectors.

Reducing Dynamic SealWearMost dynamic seals are well designedand will provide long, relativelyleak-free service if given reasonablechance. Four things a designer can doto extend the life of dynamic seals are:

1. Eliminate side loads on cylinder rodand drive shaft seals.

2. Protect cylinder rods from abrasivedirt with scrapers, shields or rubbergaiters.

3. Provide the requisite filtration andeasily cleaned reservoirs to preventdirt build-up in the oil.

4. Keep cylinder rod and shaft speedsas low as possible.

Requirements ForStatic SealsA static seal retains fluid between rigid,stationary surfaces. The seal must becompressed as with a gasket ordeformed as with an “O” ring, to flowinto the microcrevices in the matingsurface and also raise the seal’sinternal stress level higher than thepressure to be sealed. When parts arenot rigid enough or bolt preload is nothigh enough, the mating surfaces willseparate under the action of fluidpressure, creating clearances ofenlarging those that might existbecause the sealing surfaces were notinitially flat enough. With movement ofmating surfaces, the static sealbecomes a dynamic seal. Roughsurfaces will wear the seal andchanging clearances nibble seal edges.

Mounting PlatesWhen valve packages or subplates arebolted to mounting plates, the conditionof the plate is important to obtain asatisfactory initial seal and preventextrusion and wear. Requirements are:

– Flat mounting surfaces

– Good sealing surface finish -64micro-inches with no radial scratches

– High enough bolt preload to preventsurface separation.

Preventing SealDeteriorationPremature deterioration of the seal canresult from other factors. A primaryfactor is excessive fluid temperature. Agood guide is that seal life is halved byevery 20� F. rise. The cure: Incorporatesufficient heat exchangers to keep fluidtemperatures below 150� F.

Another factor may be compatibility ofthe fluid with the seal material wherespecial fluids are used. If a doubt arises,contact your Vickers representative. Thefollowing brief review of seal materialsmay be helpful.

Nitrile (Buna N) is the most widely usedand best all around elastomer forpetroleum (mineral) oils, fuel andfire-resistant fluids – with the exceptionof phosphate esters.

Fluoroelastomer (Viton or Fluorel)costs more than Nitrile, can be usedinstead of Nitrile but has the addedadvantage of longer life when fluidtemperatures consistently run above150� F. It can be used with phosphateester fluids (except Skydrol).

Polyurethane shows extrusion andabrasion resistance superior to Nitrilein petroleum oils, fuel and silicateesters, but deteriorates ifcontaminated with hot water.

Refer to “Stop Leaks” bulletin 394 formore comprehensive coverage ofleakage control.

16

Hydraulic Fluid And TemperatureRecommendations For Industrial Machinery

Unit Type Viscosity Anti-wear Characteristicts

Inline Piston(Pumps & Motors)

� ViscosityGrades: 32-68 cSt (150-315 SUS) @ 40�C. (104�F)Running: 13-54 cSt (70-250 SUS)At Start Up: 220 cSt (1000 SUS) Max. Antiwear type hydraulic oils such as:

Angle PistonVane (Except MHT)Gear(Pumps & Motors)

� ViscosityGrades: 32-68 cSt (150-315 SUS) @ 40�C. (104�F)Running: 13-54 cSt (70-250 SUS)At Start Up: 860 cSt (4000 SUS) Max.

y y

automotive crankcase oils having APIletter designations “SE”, “SF”, “SG”, or“SH” per SAE J183

�MHT (High Torque/Low SpeedVane Motors

� ViscosityGrades: 32-68 cSt (150-315 SUS) @ 40�C. (104�F)Running: 13-54 cSt (70-250 SUS)At Start Up: 110 cSt (500 SUS) Max.

cSt: Centistokes

SUS:Saybolt Universal Seconds

� Adhere to the oil recommendations for MHTunits rather than the pumps involved.

� Viscosity Grades are the standard viscositygrades listed in ASTM D-2422 titled “ViscositySystem for Industrial Fluid Lubricants”, but anyintermediate viscosity is acceptable.

Selection Of Viscosity GradesUse the following tabulation todetermine the temperature extremesbetween which the viscosity gradescan be used to remain within Vickersstart–up and running viscosity rangerecommendations.

The SAE 10W grades fall betweenthe 32 cSt (150 SUS) and 46 cSt(215 SUS) grades and the SAE20–20W approximates the 68 cSt(315 SUS) grade.

ViscosityGrade

40�C (104�F)

Start Up860 cSt

(4000 SUS)

Start Up220 cSt

(1000 SUS)

Start Up110 cSt

(500 SUS)

Running54 cSt

(250 SUS) Max.

Running13 cSt

(70 SUS) Min.

32 cSt (150 SUS)46 cSt (215 SUS)68 cSt (315 SUS)

–12�C (11�F)–6�C (22�F)

0�C (32�F)

6�C (42�F)12�C (54�F)19�C (66�F)

14�C (58�F)22�C (72�F)29�C (84�F)

27�C (80�F)34�C (94�F)

42�C (108�F)

62�C (143�F)71�C (159�F)81�C (177�F)

General Data

Oil in hydraulic systems performs thedual function of lubrication andtransmission of power. It constitutes avital factor in a hydraulic system, andcareful selection should be made withthe assistance of a reputable supplier.Proper selection of oil assuressatisfactory life and operation of thesystem components with particularemphasis on hydraulic pumps andmotors. Generally, oil selected for usewith pumps and motors are acceptablefor use with valves. Critical servovalves may need special consideration.

Some of the factors especially importantin the selection of oil for use in anindustrial hydraulic system are:

1. The oil must contain the necessaryadditives to ensure high antiwearcharacteristics. Not all hydraulic oilscontain these in sufficient amounts.

2. The oil must have proper viscosity tomaintain adequate sealing andlubricating quality at the expectedoperating temperature of thehydraulic system.

3. The oil must have rust and oxidationinhibitors for satisfactory systemoperation.

Two specific types of oil meet therequirements of modern industrialhydraulic systems:

1. Antiwear type industrial hydraulic oils.A new generation of industrialhydraulic oils containing adequatequantities of antiwear compound isrecommended by VIckers for generalhydraulic service.

17

Hydraulic Fluid And TemperatureRecommendations For Industrial Machinery

These oils are generally developedand evaluated on the basis of pumpwear tests such as the Vickers35VQ25A and ASTM D-2882. Theseoils offer superior protection againstpump and motor wear and theadvantage of long service life. Inaddition, they provide gooddemulsibility as well as protectionagainst rust.

2. Automotive type crankcase oilshaving API letter designation “SE”,“SF”, “SG”, “SH”, per SAE J183.

The above classes of oils in the10W and 20-20W SAE viscosityranges are for severe hydraulicservice where there is little or nowater present. The only adverseeffect is that the “detergent”additive tends to hold water in atight emulsion and preventsseparation of water, even on longtime standing.

Automotive type crankcase oilsgenerally exhibit poorer shear stabilitywhich could result in some loss ofviscosity during their service life.More shear stable multiple viscosityindustrial grade hydraulic fluids willprovide improved viscosity control.

Over the years, Vickers hydraulic oilrecommendations have been based onoils that: (1) provide adequate wearprotection, (2) have proper viscosity, and(3) are sufficiently stable to withstand thechemical, thermal and mechanical stressesof severe hydraulic service. There areautomotive crankcase oils that are outsideof the API SE, SF, SG and SH classesthat meet the above basis ofrecommendation.

With these oils, it is highly desirable tohave acceptable data from pump weartests (35VQ25A and ASTM-D-2882). Inexceptional cases where the requirementsof speed, pressure, temperature andambient conditions exceed therecommendations for industrial machinery,please refer to the oil recommendations.These fluids must also pass the Vickers35VQ25 pump test.

ViscosityViscosity is the measure of the fluid’sresistance to flow. The selection of ahydraulic oil of specific viscosity rangemust be based on the needs of thesystem, limitations of critical components,or proper performance of specific types ofunits. Vickers recommends that certain

maximum and minimum viscosity rangesof the oil at start-up and during running bemaintained. (See chart) Very highviscosities at start-up temperatures cancause noise and cavitational damage topumps. Continuous operation atmoderately high viscosities will tend to holdair in suspension in the oil as well asgenerate higher operating temperatures.This can cause noise and early failure ofpumps, motors and erosion of valves. Lowviscosities result in decreased systemefficiency and impairment of dynamiclubrication which causes wear.

Choose the proper oil viscosity for yourparticular system so that over the entiretemperature range encountered, thestart-up viscosity and the runningviscosity range shown in the chart ismet. This is important, and assuranceshould be obtained from your oilsupplier that the viscosity of the oil beingused will not be less than the minimumrecommended at maximum oiltemperature encountered.

A number of antiwear hydraulic oilscontaining polymeric thickeners (V.I.improvers) are available and are used forlow temperature application. Thetemporary and permanent viscosity loss ofsome of these oils at operatingtemperature may adversely affect the lifeand performance of components. Becertain you know the extent of loss ofviscosity (shear stability) of polymercontaining oils under hydraulic servicebefore using them so that you do notoperate below the recommended minimumviscosity. The selection of an oil with goodshear stability, is recommended for lowtemperature applications.

TemperatureTo obtain optimum service life fromboth the oil and the hydraulic system,operate between 49�C (120�F) and54�C (130�F). The maximum oiltemperature normally recommendedis 66�C (150�F).

MHT motors are permitted to operate athigher temperatures, but this ispermissible by meeting specialapplication requirements. For thisservice, oils should have antiwearcharacteristics required to pass pumptest on page 20. Pumps can beapproved to operate MHT motors atthese higher temperatures. Contact yourVickers representative forrecommendations.

CleanlinessThorough precautions should always beobserved to ensure that the hydraulicsystem is clean.

1. Clean (flush) entire system to removepaint, metal chips, welding shot, lint,etc.

2. Filter each change of oil to preventintroduction of contaminant into thesystem.

3. Provide continuous oil filtration toremove sludge and products of wearand corrosion generated during thelife of the system.

4. Provide continuous protection ofsystem from entry of airbornecontamination by proper filtration ofair through breathers.

5. During usage, proper oil filling ofreservoir and servicing of filters,breathers, reservoirs, etc. cannot beover emphasized.

Sound LevelNoise can be an indication of systemproblems. Fluid selection and thecondition of that fluid in service willaffect the noise levels of your systems.

Some of the major factors affecting thefluid conditions that cause the loudestnoises in a hydraulic system are:

1. Very high viscosities at start-uptemperatures can cause pump noisesdue to cavitation.

2. Running with moderately highviscosity fluid will impede the releaseof entrained air. The fluid will not becompletely purged of such air in thetime it remains in the reservoir beforerecycling through the system.

18

3. Aerated fluid can be caused byingestion of air through the pipe jointsof inlet lines, high velocity dischargelines, cylinder rod packings, or byfluid discharging above the fluid levelin the reservoir. Air in the fluid willcause abnormal noise and wear inyour system.

4. Contamination fluids can causeexcessive wear of internal pumpparts which may result in increasedsound levels.

5. Systems using water based fluidsare susceptible to noise created byvaporization of the fluid if excessivevacuums and temperatures areencountered.

Fire Resistant FluidsHydraulic systems using fire resistantfluids require special engineeringconsiderations. For applications usingfire resistant fluids, consult VickersGuide to Alternative Fluids, Bulletin579, for the specific component beingused or contact your local Vickersrepresentative for assistance.

Proper design, operation andmaintenance of fluid power systems isof paramount importance to obtain theoptimum performance of fire resistantfluids such as synthetics, water glycoland water-in-oil emulsion types.

Additionally, you should consult your fluidsupplier for specific fluid maintenanceand application data on their fluid.

Water Based FluidsGeneral DataTo assure an effective emulsion orsolution, the water should not haveexcessive hardness or have an acidnature, and it should be distilled ordeionized with less than 300 parts permillion hardness.

Hard water containing excessive mineralcontent, such as calcium and iron, maycause deposits in the hydraulic systemor result in additive separation oremulsion breaking.

Proper maintenance of water containingfluids requires periodic testing for pH, oiland water concentrations. The pHshould be maintained at 8.0-9.5 inaccordance with the supplier’srecommendation. If the pH numberexceeds these limits, discard the fluid.Always use a premixed fluid to replenishthe system. The recommended storageor operating temperature range of watercontaining fluids is 4�C (39�F) to 49�C(120�F), unless otherwise specified bythe fluid supplier.

Types Of Water BasedFluidsInvert Emulsions

Invert emulsions are invertedwater-in-oil emulsions consisting of acontinuous oil phase surrounding finelydivided water droplets that are uniformlydispersed throughout the mixture.

Water-Glycol Fluids

Water-glycol fire-resistant fluids aretypically water and diethylene glycolmixtures. They have approximately 40%water content.

Oil-In-Water Fluids

Oil-in-water fluids are emulsions of oiland water. When preparing thesemixtures, the soluble oil should alwaysbe added to the water while maintaininggood fluid agitation. The water shouldnever be added to the soluble oil. Do notmix soluble oil brands.

Filters

Many Vickers standard indicating typeinlet filters and return line filters areapproved with water-based fluid types.

A reduction of predicted life of hydrauliccomponents should be expected whenusing water-based fluid types.

Synthetic Fluid TypePhosphate Ester

Phosphate ester type fluids aremanufactured from chemically producedesters. These types of fluids requirefluorocarbon seals. Consult your fluidsupplier for the types of seals which arecompatible.

Environmental Hydraulic Oil

If you have equipment that operates inenvironmentally sensitive areas, you mayconsider use of more environmentallyaware fluids. These fluids perform well inour hydraulic systems but may requireextra caution in order not to exceed theirperformance capabilities.

19

Hydraulic Fluid And TemperatureRecommendations For Mobile Hydraulic Systems

The oil in a hydraulic system serves asthe power transmission medium. It isalso the system’s lubricant and coolant.The selection of proper oil is arequirement for satisfactory systemperformance and life.

In most cases, use of theserecommendations will lead to selection ofa suitable oil. However, due to thecomplex nature of oil formulation, thevariety of oils available and peculiarities ofindividual hydraulic applications, there willbe rare instances where an oil selectedon the basis of these recommendationsmay yield unsatisfactory results. Vickerscannot be responsible for suchexceptions. In this respect, the customeris encouraged to consult his Vickersrepresentative or a reputable oil companywhen selecting an oil.

Important Factors InSelecting An OilAdditivesHydraulic fluids contain a number ofadditive agents which materially improvevarious characteristics of oil forhydraulic systems. These additives areselected to reduce wear, increasechemical stability, inhibit corrosion anddepress the pour point.

AntiwearPump performance and reliability aredirectly affected by the antiwear additiveformulation contained in the oil. Oilsproviding a high level of antiwearprotection are recommended foroptimum performance and long life.

ViscosityViscosity is the measure of the fluid’sresistance to flow. The oil selected musthave proper viscosity to maintain anadequate lubricating film at systemoperating temperature.

In addition to dynamic lubricatingproperties, oil must have sufficient bodyto provide an adequate sealing effectbetween working parts of pumps, valves,clylinders and motors, but not enough tocause pump cavitation or sluggish valveaction. Optimum operating viscosity ofthe oil should be between 16 cSt (80SUS) and 40 cSt (180 SUS).

“Viscosity Index” reflects the way viscositychanges with temperature. The smaller theviscosity change, the higher the viscosity

index. The viscosity index of hydraulicsystem oil should not be less than 90.Multiple viscosity oils, such as SAE10W-30, incorporate additives to improveviscosity index (polymer thickened). Theseoils should have a minimum viscosity indexof 120. Oils of this type generally exhibitboth a temporary and permanent decreasein viscosity due to oil shear encountered inthe operating hydraulic system. The actualviscosity can, therefore, be far less in theoperating hydraulic system than what isshown in normal oil data. Accordingly,when such oils are selected, it isnecessary to use those with high shearstability to insure that viscosity remainswithin recommended limits while in service.

Chemical StabilityOxidation and thermal stability areessential characteristics of oils for mobilehydraulic systems. The combination ofbase stocks and additives should bestable during the expected lifetime of theoil when exposed to the environment ofthese systems.

Suitable Types Of OilCrankcase OilOil having an API letter designation SE,SF, SG or SH per SAE J183. Note thatone oil may meet one or more of thesedesignations.

Antiwear Hydraulic OilThese oils are produced by all major oilsuppliers and should consist of goodquality base stocks compounded withantiwear, antioxidation, antifoam andantirust additives. These may bepetroleum, vegetable or synthetic base oil.

Due to the large number of differentantiwear hydraulic oils, it is impossiblefor Vickers to test its products with all ofthe available fluids. Because of this, anevaluation procedure was developed forfluid suppliers to establish the suitabilityof their products for use in Vickerscomponents. Refer to “Pump TestProcedure For Evaluation Of AntiwearHydraulic Fluids For Mobile Systems”,page 20, for details of the 35VQ25 testprocedure. It is the responsibility of youroil supplier to assure that their fluidsmeet Vickers requirements.

Environmental Hydraulic OilIf you have equipment that operates inenvironmentally sensitive areas, youmay consider use of moreenvionmentally aware fluids. Thesefluids perform well in our hydraulicsystems but may require extra caution inorder not to exceed their performancecapabilities. For further clarification,refer to Vickers Guide to AlternativeFluids, Bulletin 579.

Other OilsCertain other types of petroleum oil aresuitable if they meet the followingprovisions:

1. Contain the type and content ofantiwear additives found in the abovedesignated crankcase and antiwearhydraulic oils, and have passed thepump tests.

2. Have sufficient chemical stability formobile hydraulic system service.

3. Meet the viscosity requirementsshown in the following tables.

20

Oil Viscosity Recommendations

Oil Viscosity Recommendations

Crankcase Oils

Hydraulic SystemOperating Tem-perature Range1

SAE ViscosityDesignation

–23�C to 54�C(–10�F to 130�F)

5W, 5W-20,5W-30

–18�C to 83�C(0�F to 180�F)

10W

–18�C to 99�C(0�F to 210�F)

10W-30,10W-40

10�C to 99�C(50�F to 210�F)

20-20W

Antiwear Hydraulic Oils

Hydraulic SystemOperating Tem-perature Range1

ISO ViscosityGrade

–21�C to 60�C(–5�F to 140�F)

22

–15�C to 77�C(5�F to 170�F)

32

–9�C to 88�C(15�F to 190�F)

46

–1�C to 99�C(30�F to 210�F)

68

1 Temperatures shown are cold (ambient) start-up to maximum operating. During cold start-up,avoid high-speed operation of hydraulic components until the system is warmed up to provideadequate lubrication.

21

Pump Test Procedure For Evaluation OfAntiwear Fluids For Mobile Systems

Test Pump35VQ25A-11*20 (Cartridge Kit P/N413421)

Test ConditionsSpeed: 2350-2400 rpmOutlet Pressure: 205-210 bar gage

(2975-3025 psig)Inlet Pressure: 0-.15 bar gage

(0-2 psig) withflooded inlet

Inlet Temperature: 90-96�C(195-205�F)

Operating ModeSteady-state pressure at above ratedconditions for 50 hours. Terminate test ifflow degradation exceeds 7.5 L/min(2 gpm) prior to the completion of the50-hour test. Such terminations are notconsidered to be failures since this flowdegradation can be due to causes otherthan excessive wear, such as erosion onthe side plates resulting from insufficientinlet pressure.

Initial Fluid ConditionWater Content: .075% maximumContamination Level: ISO Code

18/16/14 or betterparticle count.Alternatively, 30mg/liter maximumgravimetric con-tamination (usingfilter membraneof 0.8 micrometerporosity).

Pump Break-InProcedure1. Increase pump speed to test level

and apply 70 bar gage (1000 psig)outlet pressure. When inlettemperature of approximately 50�C(125�F) is achieved, maintain it forelapsed time of 1/2 hour at pressure.

2. Increase pressure to 140 bar gage(2000 psig). When inlet temperatureof approximately 80�C (175�F) isachieved, maintain it for elapsed timeof 1/2 hour at pressure.

3. Increase pressure to 205-210 bargage (2975-3025 psig). Whentemperature stabilizes at 90-96�C(195-205�F), record operatingparameters, including flow. Terminatetest if flow is below 136 L/min (36gpm) after five hours of operation.With production tolerances, low flowsometimes occurs while pumpinglight fluids. This condition tends toincrease the wear rate.

Test DurationContinue operation of the unit for 50hours total (including break-in time),periodically monitoring operationparameters.

Number Of CartridgesEvaluation requires a minimum of threepump cartridges. The fluid should not bechanged during the total 150-hour testperiod.

Accept/Reject Guidelines1. Total weight loss of all vanes from

individual cartridge tested should beless than 15 mg (not includingintravanes).

2. Weight loss of ring from individualcartridge tested should be less than75 mg.

3. Regardless of weight lossmeasurements, the pump parts,especially the rings, should not haveevidence of unusual wear or stress incontact areas. There may beinstances when unsatisfactoryperformance is indicated even thoughthe weight loss is low; for example,galling or excessive burning wouldnot show as excessive weight lossbut would be unacceptable.

When any one cartridge out of threefails for any reason, two morecartridges should be tested. In this case,four of the five tested cartridges mustmeet the above accept/reject guidelines.

This procedure is offered only as a fluidscreening method. Successfulcompletion of this test does notconstitute endorsement or approval offluids by Vickers.

Test Circuit

M

1

23

4

5

7

8

9

102″ Line Size

6

Description of Components1. Reservoir (50 gallons minimum;

elevated above pump centerline toprovide gravity feed)

2. Temperature gage or thermocouple

3. Inlet pressure gage

4. Pump: 35VQ25A-11*20 (cartridge kitP/N 413421)

5. Electric motor (125 HP)

6. Outlet pressure gage

7. Pressure relief valve

8. Filter (10 micrometer nominal)

9. Cooler

10. Flow meter

22

Acceptable Rings Unacceptable Rings

23

Oil Flow Velocity In Tubing

Oil Flow Capacity OfTubingFigures in the chart are USgpm flowcapacities of tubing, and werecalculated from the formula:GPM = V � A � .3208,in which V = velocity of flow in feet persecond, and A is inside square incharea of tube.

Figures in Body of Chart are USgpm Flows

TubeO.D.

WallThick.

2Ft/Sec

4Ft/Sec

10Ft/Sec

15Ft/Sec

20Ft/Sec

30Ft/Sec

1/2�

.035

.042

.049

.058

.065

.072

.083

.905

.847

.791

.722

.670

.620

.546

1.81 1.631.581.441.341.241.09

4.52 4.233.953.613.353.102.73

6.79 6.355.935.415.034.654.09

9.05 6.477.917.226.706.205.46

13.612.711.910.810.19.308.16

5/8�

.035

.042

.049

.058

.065

.072

.083

.095

1.511.431.361.271.201.131.03.926

3.012.852.722.542.402.262.061.85

7.547.166.806.346.005.665.164.63

11.310.710.29.519.008.497.736.95

15.114.313.612.712.011.310.39.26

22.621.420.419.018.017.015.513.9

3/4�

.049

.058

.065

.072

.083

.095

.109

2.081.971.881.751.671.531.39

4.173.933.763.513.343.072.77

10.414.814.113.212.511.510.4

15.69.849.418.778.357.676.93

20.819.718.817.516.715.313.9

31.229.628.226.425.023.020.8

7/8�

.049

.058

.065

.072

.083

.095

.109

2.952.822.722.622.462.302.11

5.915.645.435.234.924.604.22

14.814.113.613.112.311.510.6

22.221.120.419.618.517.215.8

29.528.227.226.224.623.021.1

44.342.340.739.236.934.431.7

1�

.049

.058

.065

.072

.083

.095

.109

.120

3.983.823.703.593.403.213.002.83

7.967.657.417.176.816.426.005.65

19.919.118.517.917.016.115.014.1

29.928.727.826.925.524.122.421.2

39.838.237.035.934.032.129.928.3

59.757.455.653.851.148.244.942.4

24

Pipe Sizes And Pressure Ratings

Figures in Body of Chart are USgpm Flows

TubeO.D.

WallThick.

2Ft/Sec

4Ft/Sec

10Ft/Sec

15Ft/Sec

20Ft/Sec

30Ft/Sec

1-1/4�

.049

.058

.065

.072

.083

.095

.109

.120

6.50 6.296.146.005.755.505.215.00

13.0 12.612.312.011.511.010.410.0

32.5 31.530.730.028.827.526.125.0

48.7 47.246.044.943.141.239.137.4

64.9 62.961.459.957.555.052.150.0

97.4 94.492.189.886.382.578.274.9

1-1/2�

.065

.072

.083

.095

.109

.120

9.199.008.718.408.047.77

18.418.017.416.816.115.5

45.945.043.542.040.238.8

68.967.565.363.060.358.3

91.990.087.184.080.477.7

138135131126121117

1-3/4�

.065

.072

.083

.095

.109

.120

.134

12.812.612.311.911.511.210.7

25.725.224.623.823.022.321.5

64.263.161.459.657.455.853.7

96.394.792.189.386.183.780.6

128126123119115112107

193189184179172167161

2�

.065

.072

.083

.095

.109

.120

.134

17.116.916.516.015.515.214.7

34.233.732.932.131.130.329.4

85.684.382.380.277.775.873.4

128126123120117114110

171169165160155152147

257253247240233227220

Pipe Sizes And Pressure RatingsNominal

PipeSize

OutsideDiameterof Pipe

Numberof

Thre d

Lengthof

Effective

Schedule 40(Standard)

Schedule 80(Extra Heavy)

Schedule 160 DoubleExtra Heavy

Sizein.

of Pipein.

ThreadsPer Inch

EffectiveThreads

in.

PipeID-in.

BurstPres.PSI

PipeID-in.

BurstPres.PSI

PipeID-in.

BurstPres.PSI

PipeID-in.

BurstPres.PSI

1/8 0.405 27 0.26 – – – – – – – –

1/43/81/23/4

0.5400.6750.8401.050

18181414

0.400.410.530.55

.364

.493

.622

.824

16,00013,50013,20011,000

.302

.423

.546

.742

22,00019,00017,50015,000

––

.466

.614

––

21,00021,000

––

.252

.434

––

35,00030,000

11-1/41-1/2

1.3151.6601.900

11-1/211-1/211-1/2

0.680.710.72

1.0491.3801.610

10,0008,4007,600

.9571.2781.500

13,60011,50010,500

.8151.1601.338

19,00015,00014,800

.599

.8961.100

27,00023,00021,000

22-1/2

3

2.3752.8753.500

11-1/288

0.761.141.20

2.0672.4693.068

6,5007,0006,100

1.9392.3232.900

9,1009,6008,500

1.6892.1252.624

14,50013,00012,500

1.5031.771

–

19,00018,000

–

25

Preparation Of Pipes, Tubes, And FittingsBefore Installation In A Hydraulic System

General RequirementsWhen installing the various iron andsteel pipes, tubes, and fittings of ahydraulic system, it is necessary thatthey be absolutely clean, free fromscale, and all kinds of foreign matter.To attain this end, the following stepsshould be taken:

– Tubing, pipes and fittings should bebrushed with boiler tube wire brushor cleaned with commercial pipecleaning apparatus. The inside edgeof tubing and pipe should be reamedafter cutting to remove burrs. Alsoremove burrs from outside edge.

– Short pieces of pipe and tubing andsteel fittings should be sandblastedto remove rust and scale.Sandblasting is a sure and efficientmethod for short straight pieces andfittings. Sandblasting should not beused however, if there is theslightest possibility that particles ofsand will remain in blind holes orpockets in the work after flushing.

– In the case of longer pieces of pipe orshort pieces bent to complex shapeswhere is is not practical to sandblast, theparts should be pickled in a suitablesolution until all rust and scale isremoved. Preparation for picklingrequires thorough degreasing in arecommended vapor degreasing solvent.

– Neutralize pickling solution.

– Rinse parts and prepare for storage.

– Tubing must not be welded, brazed,or silver soldered after assembly asproper cleaning is impossible insuch cases. It must be accuratelybent and fitted so that it will not benecessary to spring it into place.

– If flange connections are used,flanges must fit squarely on themounting faces and be secured withscrews of the correct length. Screwsor stud-nuts must be drawn upevenly to avoid distortion in thevalve or pump body.

– Be sure that all openings into thehydraulic system are properlycovered to keep out dirt and metalslivers when work such as drilling,tapping, welding, or brazing is beingdone on or near the unit.

– Threaded fittings should beinspected to prevent metal sliversfrom the threads getting into thehydraulic system.

– Before filling the system withhydraulic oil, be sure that thehydraulic fluid is as specified andthat it is clean. DO NOT use clothstrainers or fluid that has beenstored in contaminated containers.

– Use at least a No. 120 mesh screenwhen filling the reservoir. Use of aVickers clean cart, porta filteringand transfer unit, is recommended.Operate the system for a short timeto eliminate air in the lines. Addhydraulic fluid if necessary.

– Safety precautions. Dangerouschemicals are used in the cleaningand pickling operations to bedescribed. They should be kept onlyin the proper containers andhandled with extreme care.

Pickling Process– Thoroughly degrease parts in

degreaser, using a recommendedvapor degreasing solvent.

– Tank No. 1 Solution. Use acommercially available derustingcompound in solution asrecommended by the manufacturer.The solution should not be used at atemperature exceeding thatrecommended by the manufacturer,otherwise the inhibitor willevaporate and leave a straight acidsolution. The length of time the partwill be immersed in this solution willdepend upon the temperature of thesolution and the amount of rust orscale which must be removed. Theoperator must use good judgementon this point.

– After pickling, rinse parts in coldrunning water and immerse in tankNo. 2. The solution in this tankshould be a neutralizer mixed withwater in a proportion recommendedby the manufacturer. This solutionshould be used at recommendedtemperatures and the parts shouldremain immersed in the solution forthe period of time recommended bythe manufacturer.

– Rinse parts in hot water

– Place in tank No. 3. The solution inthis tank should contain antirustcompounds as recommended by themanufacturer. Usually the parts beingtreated should be left to dry withantirust solution remaining on them.

If pieces are stored for any period oftime, ends of the pipes should beplugged to prevent the entrance offoreign matter. Do not use rags orwaste as they will deposit lint on theinside of the tube or pipe.Immediately before using pipes,tubes and fittings should bethoroughly flushed with suitabledegreasing solution.

26

ISO/ANSI Basic SymbolsFor Fluid Power Equipment And Systems

LinesLine, Working(Main)

Line, Pilot(For Control)

Line, Liquid Drain

HydraulicFlow, Direction of

Pneumatic

Lines Crossing or

Lines Joining

Line With FixedRestriction

Line, Flexible

Station, Testing,Measurement orPower Take-Off

�

Variable Component(run arrow throughsymbol at 45�

Pressure Compen-sated Units (arrowparallel to short sideof symbol)

Temperature Causeor Effect

VentedReservoir

Pressurized

Line, To ReservoirAbove Fluid Level

Below Fluid Level

Vented Manifold

PumpsHydraulic Pump

FixedDisplacement

VariableDisplacement

Motors and CylindersHydraulic

FixedDisplacement

VariableDisplacement

Cylinder, SingleActing

Cylinder, DoubleActing

Single End Rod

Double End Rod

AdjustableCushionAdvance Only

DifferentialPiston

Miscellaneous Units

Electric Motor M

Accumulator, SpringLoaded

Accumulator, GasCharged

Heater

Cooler

TemperatureController

Filter, Strainer

Pressure Switch

Pressure Indicator

TemperatureIndicator

ComponentEnclosure

Direction of ShaftRotation (assumearrow on near sideof shaft

Methods of OperationSpring

Manual

Push Button

27

Push-Pull Lever

Pedal or Treadle

Mechanical

Detent

PressureCompensated

Solenoid, SingleWinding

Servo Control ���

Pilot PressureRemote Supply

Internal Supply �

Valves

Check

On–Off(manual shut-off)

Pressure Relief

Pressure Reducing

Flow Control,Adjustable–Non-Compensated

Flow Control,Adjustable(temperature andpressurecompensated

Two PositionTwo Connection

Two PositionThree Connection

Two PositionFour Connection

Three PositionFour Connection

Two PositionIn Transition

Valves Capable OfInfinite Positioning(horizontal barsindicate infinitepositioning ability)

NoteAdditional symbols are shown inVickers Circuitool booklet available fora nominal charge. Ask for circuitooltemplate kit 352.

Color Code For FluidPower SchematicDrawingsFunction ColorIntensified Pressure Black. . Supply Red. . . . . . . . . . . . . . Charging Pressure Intermittent Red. . . Reduced Pressure Intermittent Red. . . . Pilot Pressure Intermittent Red. . . . . . . . Metered Flow Yellow. . . . . . . . Exhaust Blue. . . . . . . . . . . . . Intake Green. . . . . . . . . . . . . . . Drain Green. . . . . . . . . . . . . . . Inactive Blank. . . . . . . . . . . . .

Definition Of FunctionsFunction DefinitionIntensified Pressure Pressure in

excess of supplypressure which isinduced by abooster orintensifier.

Supply Pressure Power-actuatingfluid.

Charging Pressure Pump-inletpressure that ishigher thanatmosphericpressure.

Reduced Pressure Auxiliary pressurewhich is lowerthan supplypressure.

Pilot Pressure Control-actuatingpressure.

Metered Flow Fluid at controlledflow rate, otherthan pumpdelivery.

Exhaust Return of powerand control fluidto reservoir.

Intake Sub-atmosphericpressure, usuallyon intake side ofpump.

Drain Return of leakagefluid to reservoir.

Inactive Fluid which iswithin the circuit,but which doesnot serve afunctionalpurpose duringthe phase beingrepresented.

28

Conversion Factors

To convert Into Multiply by

Into To convert Divide by

Unit Symbol Unit Symbol Factor

Atmospheres Atm bar bar 1.013250

BTU/hour Btu/h kilowatts kW 0.293071 � 10–3

cubic centimeters cm3 liters 1 0.001

cubic centimeters cm3 milliliters ml 1.0

cubic feet ft3 cubic meters m3 0.0283168

cubic feet ft3 liters l 28.3161

cubic inches in3 cubic centimeters cm3 16.3871

cubic inches in3 liters l 0.0163866

degrees (angle) � radians rad 0.0174533

Fahrenheit �F Celsius �C �C=5 (�F–32) / 9

feet ft meters m 0.3048

feet of water ft H2O bar bar 0.0298907

fluid ounces, UK UK fl oz cubic centimeters cm3 28.413

fluid ounces, US US fl oz cubic centimeters cm3 29.5735

foot pounds f ft lbf joules J 1.35582

foot pounds/minute ft lbf/min watts W 81.3492

gallons, UK UK gal liters l 4.54596

gallons, US US gal liters l 3.78531

horsepower hp kilowatts kW 0.7457

inches of mercury in Hg millibar mbar 33.8639

inches of water in H2O millibar mbar 2.49089

inches in centimeters cm 2.54

inches in millimeters mm 2.54

kilogram force kgf newtons N 9.80665

kilogram f. meter kgf m newton meters Nm 9.80665

kilogram f. /sq. centimeter kgf/cm2 bar bar 0.980665

kilopascals kPa bar bar 0.01

kiloponds kp newtons N 9.80665

kilopond meters kp m newton meters Nm 9.80665

kiloponds/square centimeter kp/cm3 bar bar 0.980665

metric horsepower kilowatts kW 0.735499

microinches in microns m 0.0254

millimeters of mercury mm Hg millibar mbar 1.33322

millimeters of water mm H2O millibar mbar 0.09806

newtons/square centimeter N/cm2 bar bar 0.1

newtons/square meter N/m2 bar bar 10–5

29

Conversion Factors

To convert Into Multiply by

Into To convert Divide by

Unit Symbol Unit Symbol Factorpascals (newtons/sq meter) Pa bar bar 10–5

pints, UK UK pt liters l 0.568245pints, US US liq pt liters l 0.473163pounds (mass) lb kilograms kg 0.4536pounds/cubic foot lb/ft3 kilograms/cubic meter kg/m3 16.0185pounds/cubic inch lb/in3 kilograms/cubic centimeter kg/cm3 0.0276799pounds force lbf newtons N 4.44822pounds f feet lbf ft newton meters Nm 1.35582pounds f inches lbf in newton meters Nm 0.112985pounds f/square inch lbf/in2 bar bar 0.06894revolutions/minute r/min radians/second rad/s 0.104720square feet ft2 square meters m2 0.092903square inches in2 square meters m2 6.4516 � 10-4

square inches in2 square centimeters cm2 6.4516

Hydraulic Formulas

Horsepower:

Horsepower = GPM � PSI1714

Torque:Torque (lb. in.) = CU IN./REV. � PSI

2π

Torque (lb. in.) = HP � 63025RPM

Flow:Flow (gpm) = CU IN./REV. � RPM

231

Overall Efficiency:

Overall efficiency = Output HPInput HP

�100

Volumetric Efficiency:Volumetricefficiency =(pump)

Output GPMTheoretical GPM

�100

Volumetricefficiency =(motor)

Theoretical GPMInput GPM

�100

Conversion Factors:1 hp = 33,000 ft. lbs. per minute1 hp = 42.4 btu per minute1 hp = 0.746 kwhr (kilowatt hours)

1 U.S. gallon = 231 cubic inches.Pipe volume varies as the square of thediameter; volume in gallons = 0.0034 D2L

where: D = inside diameter of pipe ininches

L = length in inches

Velocity in feet per second =

0.408 � flow (gpm)D2

where: D = inside diameter of pipe ininches

Atmospheric pressure at sea level =14.7 PSI

Atmospheric pressure decreasesapproximately 0.41 PSI for each onethousand feet of elevation up to23,000 feet

Pressure (PSI) = feet head � 0.433 �specific gravity.

Specific gravity of oil is approximately 0.85.

Thermal expansion of oil isapproximately 1 cu.in. per 1 gal. per10�F rise in temperature.