MAKING MODERN LIVING POSSIBLE
Service Manual
Axial Piston Closed Circuit Pumps
Series 42
powersolutions.danfoss.com
Revision history Table of revisions
Date Changed Rev
July 2015 Danfoss layout 0300
Nov 2010 new back page CB
Dec 2009 Major update CA
Jul 2007 Major update BA
Service Manual Series 42 Axial Piston Closed Circuit Pumps
2 520L0638 • Rev 0300 • July 2015
Introduction
Overview..............................................................................................................................................................................................5
Warranty.............................................................................................................................................................................................. 5
General instructions........................................................................................................................................................................ 5
Safety precautions............................................................................................................................................................................6
Symbols used in Danfoss literature............................................................................................................................................7
1998 Model Release
Overview..............................................................................................................................................................................................8
Description of change.....................................................................................................................................................................8
Functional Description
Overview..............................................................................................................................................................................................9
General description and cross-sectional view....................................................................................................................... 9
The system circuit.......................................................................................................................................................................... 10
Pump features.................................................................................................................................................................................10
Filtration options............................................................................................................................................................................12
Displacement limiters...................................................................................................................................................................14
Charge check / high pressure relief valves........................................................................................................................... 14
Bypass valves...................................................................................................................................................................................15
Auxiliary mounting pads.............................................................................................................................................................15
Control Options
Manual displacement control (MDC)......................................................................................................................................17
Electrical displacement control (EDC).................................................................................................................................... 17
High current electrical displacement control (HC-EDC).................................................................................................. 18
Non-feedback proportional hydraulic (NFPH) control.....................................................................................................18
Non-feedback proportional electric (NFPE) control..........................................................................................................19
Forward-Neutral-Reverse (FNR) three-position electric control................................................................................... 20
Technical Specifications
Specifications...................................................................................................................................................................................22
Pressure Measurement
Required tools.................................................................................................................................................................................23
Port locations and pressure gauge installation.................................................................................................................. 23
Ports and pressure gauges......................................................................................................................................................... 23
Initial Start-Up Procedure
General...............................................................................................................................................................................................25
Start-up procedure........................................................................................................................................................................25
Fluid and Filter Maintenance
Recommendations........................................................................................................................................................................ 26
Troubleshooting
Overview........................................................................................................................................................................................... 27
System operating hot...................................................................................................................................................................27
System response is sluggish...................................................................................................................................................... 27
System will not operate in either direction.......................................................................................................................... 28
System will not operate in one direction.............................................................................................................................. 29
Neutral difficult or impossible to find.....................................................................................................................................29
Adjustments
Overview........................................................................................................................................................................................... 30
Displacement limiter adjustment............................................................................................................................................ 30
Pump neutral adjustment...........................................................................................................................................................32
Control neutral adjustment for MDC and EDC/HC-EDC.................................................................................................. 33
Minor Repair
Standard procedures....................................................................................................................................................................35
Size and torque for plugs and fittings....................................................................................................................................35
Charge relief valve......................................................................................................................................................................... 37
Optional speed sensor................................................................................................................................................................. 39
Service Manual
Series 42 Axial Piston Closed Circuit Pumps
Contents
520L0638 • Rev 0300 • July 2015 3
MDC Module....................................................................................................................................................................................40
HC-EDC and EDC Module............................................................................................................................................................43
MDC/EDC Spool, linkage, and neutral adjustment screw...............................................................................................44
MDC Neutral start / backup alarm switch............................................................................................................................. 46
MDC Solenoid override valve.................................................................................................................................................... 49
FNR, NFPE, and NFPH Controls (bolt-on valves)................................................................................................................. 51
FNR, NFPE, and NFPH Controls (integral valves).................................................................................................................52
System Check Relief (SCR) valves (high pressure relief, charge check, and bypass valves)................................53
Auxiliary pad/charge pump cover........................................................................................................................................... 55
Charge pump...................................................................................................................................................................................57
Servo piston covers and NFPH control orifice.....................................................................................................................60
Loop flushing and loop flushing relief valve........................................................................................................................62
Shaft seal, roller bearing, and shaft replacement...............................................................................................................64
Appendix A - Torques
Torque table.....................................................................................................................................................................................68
Appendix B - Specification Tags
Pre-block point change................................................................................................................................................................70
Post-block point change............................................................................................................................................................. 71
Appendix C - Nomenclature
Pre-block point change nomenclature..................................................................................................................................72
Post-block point change nomenclature................................................................................................................................73
Service Manual Series 42 Axial Piston Closed Circuit Pumps
Contents
4 520L0638 • Rev 0300 • July 2015
Overview
This manual includes information for the installation, maintenance, and minor repair of Series 42 axial
piston closed circuit pumps. It includes a description of the unit and its individual components,
troubleshooting information, and minor repair procedures.
Performing minor repairs requires you to remove the unit from the vehicle/machine. Thoroughly clean
the unit before beginning maintenance, or repair activities. Since dirt and contamination are the greatest
enemies of any type of hydraulic equipment, follow cleanliness requirements strictly. This is especially
important when changing the system filter and when removing hoses or plumbing.
A worldwide network of Danfoss Authorized Service Centers (ASCs) is available for major repairs. Danfoss
trains and certifies ASCs on a regular basis. You can locate your nearest ASC using the distributor locator
at www.sauer-danfoss.com. Click on the Sales and Service link.
Warranty
Performing installation, maintenance, and minor repairs according to the procedures in this manual does
not affect your warranty. Major repairs requiring the removal of a unit’s rear cover or front flange voids
the warranty unless done by a Danfoss global service partner.
General instructions
Follow these general procedures when repairing Series 42 variable displacement closed circuit pumps.
Remove the unit
Prior to performing minor repairs, remove the unit from the vehicle/machine. Chock the wheels on the
vehicle or lock the mechanism to inhibit movement. Be aware that hydraulic fluid may be under high
pressure and/or hot. Inspect the outside of the pump and fittings for damage. Cap hoses after removal to
prevent contamination.
Keep it clean
Cleanliness is a primary means of assuring satisfactory pump life, on either new or repaired units. Clean
the outside of the pump thoroughly before disassembly. Take care to avoid contamination of the system
ports. Cleaning parts with a clean solvent wash and air drying is usually adequate.
As with any precision equipment, you must keep all parts free of foreign material and chemicals. Protect
all exposed sealing surfaces and open cavities from damage and foreign material. If left unattended,
cover the pump with a protective layer of plastic.
Replace all O-rings and gaskets
Danfoss recommends replacing all O-rings, gaskets, and seals when servicing. Lightly lubricate all O-rings
with clean petroleum jelly prior to assembly.
Service Manual
Series 42 Axial Piston Closed Circuit Pumps
Introduction
520L0638 • Rev 0300 • July 2015 5
Secure the unit
For repair, place the unit in a stable position with the shaft pointing downward. It is necessary to secure
the pump while removing and torquing end covers, controls, and valves.
Safety precautions
Always consider safety precautions before beginning a service procedure. Protect yourself and others
from injury. Take the following general precautions whenever servicing a hydraulic system.
W
Warning
Unintended vehicle or machine movement hazard
When using the RDM in combination with S45 open circuit pumps with LS or EPC be aware that there will
likely be motor movement as long as the engine is turning. Due to the LS-setting of the pump, a standby
pressure will remain in the system even if the normally closed control is fully energized. Lowest standby
pressures to the motor, 15-18bar or above, may be enough to turn the RDM and has the potential to
cause injury or damage.
W
Warning
Flammable cleaning solvents
Some cleaning solvents are flammable. To eliminate the risk of fire, do not use cleaning solvents in an
area where a source of ignition may be present.
W
Warning
Fluid under pressure
Escaping hydraulic fluid under pressure can have sufficient force to penetrate your skin causing serious
injury and/or infection. This fluid may also be hot enough to cause burns. Use caution when dealing with
hydraulic fluid under pressure. Relieve pressure in the system before removing hoses, fittings, gauges, or
components. Never use your hand or any other body part to check for leaks in a pressurized line. Seek
medical attention immediately if you are cut by hydraulic fluid.
W
Warning
Personal safety
Protect yourself from injury. Use proper safety equipment, including safety glasses, at all times.
Service Manual
Series 42 Axial Piston Closed Circuit Pumps
Introduction
6 520L0638 • Rev 0300 • July 2015
Symbols used in Danfoss literature
WARNING may result in injury Tip, helpful suggestion
CAUTION may result in damage to product or
property
Lubricate with hydraulic fluid
Reusable part Apply grease / petroleum jelly
Non-reusable part, use a new part Apply locking compound
Non-removable item Inspect for wear or damage
Option - either part may exist Clean area or part
Superseded - parts are not interchangeable Be careful not to scratch or damage
Measurement required Note correct orientation
Flatness specification Mark orientation for reinstallation
Parallelism specification Torque specification
External hex head Press in - press fit
Internal hex head Pull out with tool – press fit
Torx head Cover splines with installation sleeve
O-ring boss port Pressure measurement/gauge location or
specification
The symbols above appear in the illustrations and text of this manual. They are intended to communicate
helpful information at the point where it is most useful to the reader. In most instances, the appearance
of the symbol itself denotes its meaning. The legend above defines each symbol and explains its purpose.
Service Manual
Series 42 Axial Piston Closed Circuit Pumps
Introduction
520L0638 • Rev 0300 • July 2015 7
Overview
Parts may or may not be interchangeable between pre-1998 and post-1998 model year pumps. Many
parts, including the housing assembly, are unique to the model year change.
Description of change
Housing
The port cover for the control spool (FOB option - 28 cm3 only) changed from a flat plate with two screws
to an SAE O-ring boss plug. The screw holes for the servo covers and four of the six screw holes for the
side cover are deeper to accept a 10 mm longer screw. The two holes next to the charge pump cover
stayed the same length.
Charge pump
The gerotor drive pin changed to a parallel key. A retaining ring was added to the charge pump shaft to
locate the gerotor. The outer step on the gerotor cover was eliminated and the locating pin slot depth
increased.
Auxiliary flange shipping cover
The cover changed to a flat cover plate with a special seal ring (not to be used to seal an auxiliary pump)
under the cover (A pad only).
Charge relief valve
The relief valve changed from a non-adjustable to an adjustable relief valve. This change requires a 1998
upgrade housing.
Spool - loop flushing
The spool changed to become common between the 28 and 41/51 cm3 pumps. This change requires a
1998 upgrade housing.
Service Manual
Series 42 Axial Piston Closed Circuit Pumps
1998 Model Release
8 520L0638 • Rev 0300 • July 2015
Overview
This section describes the operation of pumps and their serviceable features. It is a useful reference for
readers unfamiliar with the function of this specific pump.
General description and cross-sectional view
The Series 42 pumps are servo controlled, axial piston pumps designed for closed circuit applications. The
input shaft turns the pump cylinder block containing nine reciprocating pistons that are held to the
swashplate with a block spring. Each piston has a brass slipper connected to one end by a ball joint. The
reciprocating movement occurs as the slippers slide along the inclined swashplate during rotation. As
each piston cycles in and out of its bore, fluid is drawn from the inlet and displaced to the outlet thereby
imparting hydraulic power to the system. Via the valve plate, one half of the cylinder block is connected
to low pressure and the other to high pressure. Clearances allow a small amount of fluid to flow from the
cylinder block/valve plate and slipper/swashplate interfaces for lubrication and cooling. Case drain ports
return this fluid to the reservoir.
The angle of the swashplate controls the volume of fluid displaced into the system. The servo piston
forces the swashplate into an inclined position (into stroke). Internal moments and centering springs
within the servo piston return the swashplate to the neutral position (out of stroke).
Cross section
Roller bearing
Swashplate
Piston
Valve plate
Charge pump
Slipper
Cylinder block
Cylinder block
Service Manual Series 42 Axial Piston Closed Circuit Pumps
Functional Description
520L0638 • Rev 0300 • July 2015 9
The system circuit
System circuit diagram
Input
shaft
Suction flow
Servo pressure
High pressure
Case flow
Charge pressure
Output
shaft
Cylinder
block
assembly
Filter
Charge
pump
Reservoir
Fixed
displacement
motor
Cylinder
block
assembly
Heat
exchanger
Check valves
with high pressure
relief valves
Variable
displacement
pump
Heat exchanger
bypass
Charge relief
valve
Displacement control valve
Servo control cylinder
Control
handle
Closed circuit operation
Hydraulic lines connect the main ports of the pump to the main ports of the motor. Fluid flows in either
direction from the pump to the motor and back. Either of the hydraulic lines can be under high pressure.
The position of pump swashplate determines which line is high pressure as well as the direction of flow.
Case drain and heat exchanger
Both the pump and motor must drain fluid. A case drain line achieves this. The line connects to the pump
or motor at the top-most drain port in order to maintain an adequate fluid level in the components. Fluid
cooling demands may require a heat exchanger with a bypass valve to cool the case drain fluid before it
returns to the reservoir.
Pump features
Charge pump
The charge pump is necessary to supply fluid to maintain positive pressure in the system loop, to provide
pressure to operate the control system, and to make up for internal leakage and loop flushing flow. To
prevent damage to the transmission, the pump must maintain the specified charge pressure under all
conditions of operation.
Service Manual
Series 42 Axial Piston Closed Circuit Pumps
Functional Description
10 520L0638 • Rev 0300 • July 2015
Charge pump
Square key
Retainer
ring
Gerotor set
Coupling
O-ring
Gerotor cover
Orientation
pin
P108 065E
Seal
The charge pump is a fixed-displacement, gerotor type pump. The main pump drives the charge pump
off the main shaft. A spring and poppet style relief valve limits charge pressure.
The standard charge pump is satisfactory for most applications; however, other displacements are
available. A gear pump, mounted to the auxiliary pad, may augment charge flow if additional volume is
required.
Charge relief valve
The charge relief valve maintains charge pressure at a designated level. The charge relief valve is a direct
acting poppet valve which opens and discharges fluid to the pump case when pressure reaches that
level. It is nominally set with the pump running at 1800 rpm. In forward or reverse, charge pressure is
slightly lower than when in neutral position. The model code of the pump specifies the charge relief valve
setting.
Loop flushing valve
A loop flushing valve dumps flow from the low side of the main loop, removing heat and contaminants.
Pumps equipped with an integral loop flushing valve also include a loop flushing relief valve. The loop
flushing relief valve poppet includes an orifice that controls flushing flow under most conditions. A
combination of orifice size and charge pressure relief setting produces a specific flushing flow.
Service Manual
Series 42 Axial Piston Closed Circuit Pumps
Functional Description
520L0638 • Rev 0300 • July 2015 11
Charge relief, loop flushing relief, and loop flushing valve
Loop flushing
spoo
l
Loop flushing
relief valve
Charge relief
valve
Loop flushing
defeat spool
P108 095E
Filtration options
Series 42 pumps may be equipped with provisions for either suction or charge pressure filtration to filter
the fluid entering the circuit.
Suction filtration
The suction filter is in the circuit between the reservoir and the inlet to the charge pump.
Suction filtration
Reservoir
Filter
Charge
pump
Charge
relief
valve
To pump case
To low pressure
side of loop and
servo control
Strainer
P001603E
Service Manual
Series 42 Axial Piston Closed Circuit Pumps
Functional Description
12 520L0638 • Rev 0300 • July 2015
Charge pressure filtration
The pressure filter is remotely mounted in the circuit after the charge pump.
You may use partial or full flow pressure filtration circuits with Series 42 pumps. Without a filter adapter,
suction filtration is the only option.
Partial flow pressure filtration
Reservoir
Filter
Charge pump
Charge
relief valve
To pump case
Strainer
To low pressure
side of loop and
servo control
Full flow pressure filtration
Reservoir
Filter
with bypas s
Charge
pump
Charge
relief
pump
To pump case
To low pressure
side of loop and
se rvo contro l
Strainer
P001605E
Service Manual Series 42 Axial Piston Closed Circuit Pumps
Functional Description
520L0638 • Rev 0300 • July 2015 13
Filtration adapters
Full flow
pressure
filtration
Full flow
suction
filtration
Partial flow
pressure
filtration
P108 066E
Displacement limiters
Series 42 pumps are available with mechanical displacement limiters in the servo covers. The
displacement limiters can limit displacement of the pump to any value from maximum to zero in either
direction.
Displacement limiters
Displacement limiter
(factory set for maximum displacement)
Displacement limiter
(set for reduced maximum displacement)
Servo control
cylinder
Charge check / high pressure relief valves
All series 42 pumps have a combination charge check/high pressure relief valve. The charge check
function allows pressurized flow from the charge pump to enter the low pressure side of the loop. This
flow is necessary to replenish fluid discharged to the pump/motor case for lubrication and cooling
requirements. Since the pump can operate in either direction, it uses two charge check valves to direct
the charge supply into the low pressure side.
Service Manual
Series 42 Axial Piston Closed Circuit Pumps
Functional Description
14 520L0638 • Rev 0300 • July 2015
High pressure relief valves are available in a range of settings as shown in the model code. The model
code may specify individual pressure settings. The high pressure relief valve settings are referenced to
charge pressure and are set at 3.8 l/min [1 US gal/min] of flow.
High pressure relief valve
High pressure
side of working loop
Charge check and
high pressure
relief valve
Bypass valves
Optional bypass plungers are available for use when it is necessary to move the vehicle or mechanical
function and the prime mover is not running.
Together, these valves connect both sides of the main hydraulic circuit, allowing fluid to circulate without
rotating the pump and prime mover.
The bypass function is integral to the charge check/high pressure relief valve assembly. Depressing the
plunger in the plug of the valve assembly opens the valve. The valve remains open until the prime mover
restarts or pressure builds in the system and causes the valve the close. You must depress the plungers in
both of the check/relief valve assemblies for proper bypass operation.
C
Caution
Bypass valves are for moving a machine or vehicle for very short distances at very slow speeds. They are
not tow valves. If pressure builds within the system, the valves may close causing damage to the pump
and motor or prime mover. Move the vehicle/machine at no more than 20% of top speed for no more
than three minutes.
Charge check and high pressure relief valves with bypass
To/from other
bypass valve
To/from
working loop
Charge check and
high pressure
relief valve
Bypass
plunger
P100394E
Auxiliary mounting pads
SAE A and SAE B auxiliary mounting flanges are available on all Series 42 pumps and are integral to the
charge pump cover. This flange allows mounting of auxiliary hydraulic pumps and mounting of
additional Series 42 pumps to make tandem pumps. The pads allow full through-torque capability.
Service Manual
Series 42 Axial Piston Closed Circuit Pumps
Functional Description
520L0638 • Rev 0300 • July 2015 15
Auxiliary mounting pads
Pad seal
Cover plate
O-ring
Charge pump cover
P108 096E
U085
U035 (x8)
Service Manual Series 42 Axial Piston Closed Circuit Pumps
Functional Description
16 520L0638 • Rev 0300 • July 2015
Manual displacement control (MDC)
The Manual Displacement Control (MDC) uses a mechanical input to operate the control spool in the
pump. A cam connects the input handle to the control spool allowing manipulation of the operating
curve using different cam profiles. The control spool modulates the pressure balance across the pump’s
servo piston. The angle of the swashplate is proportional to the angular position of the control input. A
mechanical feedback linkage moves the control spool toward neutral as the swashplate angle reaches
the commanded position. Mechanical feedback allows the pump to hold very accurately at the
commanded displacement. Centering springs and internal moments return the swashplate to neutral
position in the absence of control input.
MDC on series 42 pump
Solenoid override valve
A solenoid override valve is available for the manual displacement control. This safety feature shunts the
servo piston allowing the pump to return to neutral when activated. Normally open or normally closed
options are available.
Neutral start switch (NSS)
The Neutral Start Switch (NSS) is an optional cam-operated ball-type microswitch. When connected
properly to the vehicle’s electrical system, the NSS ensures that the prime mover will start only when the
control input shaft is in the neutral position.
Back-up alarm switch (BAS)
The Back-up Alarm Switch (BAS) is available for the MDC and works in association with the NSS. When
connected properly to the vehicle’s electrical system, the BAS can sound an alarm when the control
commands the vehicle into reverse. One cam and switch assembly controls both functions. Repositioning
the cam accommodates both clockwise and counterclockwise control handle rotation to reverse
direction.
Electrical displacement control (EDC)
The Electrical Displacement Control (EDC) is a two-stage control using a DC input current to control
pump displacement. Stage one, the Pressure Control Pilot (PCP) valve, uses the DC input to operate a
torque motor which drives a flapper valve. The flap in the PCP blocks a portion of flow from one or the
other of two nozzles. The two nozzles modulate pressure balance across a sensing piston in the control.
The control piston is connected to the control spool in the pump by a pin and linkage. The control spool
modulates the differential pressure across the pump’s servo piston, this is stage two. The angle of the
swashplate is proportional to the input current. A mechanical feedback linkage moves the control spool
toward neutral as the swashplate angle reaches the commanded position. Mechanical feedback allows
Service Manual
Series 42 Axial Piston Closed Circuit Pumps
Control Options
520L0638 • Rev 0300 • July 2015 17
the pump to hold very accurately at the commanded displacement. Centering springs and internal
moments return the swashplate to neutral position in the absence of control input.
EDC on series 42 pump
High current electrical displacement control (HC-EDC)
The High Current Electrical Displacement Control (HC-EDC) is a two-stage control using a DC input
current with Pulse With Modulation (PWM) to control pump displacement. Stage one uses two
Proportional Pressure Reducing Valves (PPRV), to provide reducing pressure proportional to the input
current. The pressure from each PPRV is provided to each end of the sensing piston in the control: this is
stage one. The sensing piston is connected to the control spool in the pump by a pin and linkage. The
control spool modulates the differential pressure across the pump’s servo piston, this is stage two. The
angle of the swashplate is proportional to the input current.
A mechanical feedback linkage moves the control spool toward neutral as the swashplate angle reaches
the commanded position. Mechanical feedback allows the pump to hold very accurately at the
commanded displacement. Centering springs and internal moments return the swashplate to neutral
position in the absence of control input.
HC-EDC on series 42 pump
Non-feedback proportional hydraulic (NFPH) control
The Non-Feedback Proportional Hydraulic (NFPH) control is a hydraulic displacement control. External
valving supplies an input pressure directly to the pump servo piston via control ports X1 and X2 to
control pump displacement.
Pump displacement is proportional to the pressure difference across the servo piston. However, because
this control does not use mechanical feedback, displacement also depends upon input speed and system
Service Manual
Series 42 Axial Piston Closed Circuit Pumps
Control Options
18 520L0638 • Rev 0300 • July 2015
pressure. This characteristic provides a power limiting function by reducing displacement as system
pressure increases.
NFPH control on series 42 pump
Non-feedback proportional electric (NFPE) control
The Non-Feedback Proportional Electric (NFPE) control is an electric control. A PWM input signal to one of
two solenoids on the control valve ports charge pressure to one side of the servo piston.
Pump displacement is proportional to the signal current. However, because this control does not use
mechanical feedback, displacement also depends on input speed and system pressure. This characteristic
provides a power limiting function by reducing displacement as system pressure increases.
NFPE control on series 42 pump (28/32cc)
Service Manual
Series 42 Axial Piston Closed Circuit Pumps
Control Options
520L0638 • Rev 0300 • July 2015 19
NFPE control on series 42 pump (41/51cc)
P100 415
Forward-Neutral-Reverse (FNR) three-position electric control
The Forward-Neutral-Reverse (FNR) is a three-position control. It uses a 12 or 24 Vdc electrically operated
spool valve to port pressure to either side of the servo piston. Energizing one of the two solenoids will
cause the pump to go to its maximum displacement in the corresponding direction. The FNR control
does not use mechanical feedback.
All functions of the three position (FNR) electric control are preset at the factory.
FNR control on series 42 pump (28/32cc)
Service Manual
Series 42 Axial Piston Closed Circuit Pumps
Control Options
20 520L0638 • Rev 0300 • July 2015
FNR control on series 42 pump (41/51cc)
Service Manual Series 42 Axial Piston Closed Circuit Pumps
Control Options
520L0638 • Rev 0300 • July 2015 21
Specifications
General specifications
Product line Series 42 pumps
Pump type In-line, axial piston, positive displacement variable pumps including cradle
swashplate and servo control
Direction of input rotation Clockwise or counterclockwise available
Installation position Pump installation recommended with the control at the top or side. Consult Danfoss
for non-conformance guidelines. Housing must always be filled with hydraulic fluid.
Filtration configuration Suction or charge pressure filtration
Other system requirements Independent braking system, suitable reservoir and heat exchanger.
Hardware specifications
Model 28 32 41 51
Pump configuration Single pump Single pump Single pump Single pump
Displacement
cm3/rev [in3/rev]
28 [1.71] 31.8 [1.94] 41 [2.50] 51 [3.11]
Mass kg [lbm] 34.5 [76] 34.5 [76] 42 [92] 42 [92]
Case pressure
Rated pressure bar [psi] 3.4 [50]
Maximum pressure (cold start) bar [psi] 10.5 [150]
Speed limits
Frame size cm
3
28 32 41 51
Minimum speed min¯¹ (rpm) 500 500 500 500
Rated speed at maximum displacement min¯¹ (rpm) 3400 3000 3200 2900
Maximum speed at maximum displacement min¯¹ (rpm) 3750 3400 3600 3400
System pressure
Frame size cm
3
28 32 41 51
Rated pressure bar [psi] 385 [5584] 385 [5584] 385 [5584] 350 [5076]
Maximum pressure bar [psi] 415 [6019] 415 [6019] 415 [6019] 385 [5584]
Theoretical flow
Frame size cm
3
28 32 41 51
Theoretical flow at rated speed l/min [US gal/min] 95.2 [25.1] 95.4 [25.2] 131 [34.6] 148 [39.1]
Inlet pressure
Rated pressure (absolute) bar [in Hg vacuum] 0.8 [6]
Minimum pressure (absolute) (cold start) bar [in Hg vacuum] 0.2 [24]
Service Manual Series 42 Axial Piston Closed Circuit Pumps
Technical Specifications
22 520L0638 • Rev 0300 • July 2015
Required tools
You can perform the service procedures in this manual using common mechanic’s hand-tools. Calibrate
gauges frequently to ensure accuracy. Use snubbers to protect pressure gauges.
Port locations and pressure gauge installation
A pump with a manual displacement control (MDC) and no filtration adapter is shown. With nonfeedback controls, the positions of the case drains may vary. With a filtration adapter, the porting in the
filtration options area varies.
Ports and pressure gauges
Proper service and diagnosis may require pressure measurement at various points in the hydraulic circuit.
The Series 42 pump has several locations at which to take these measurements. The following illustration
shows the locations of the various gauge ports. The table shows the recommended gauge size and the
fitting size for each port. Refer to this information when installing pressure gauges.
Gauge ports
Gauge
port
Pressure measured Recommended gauge
size
O-ring boss
28/32 cc 41 / 51 cc
M1 & M2 System pressure for ports A and B 600 bar [8700 psi] 9/16/-18 9/16/-18
M3 Charge pressure 60 bar [870 psi] 3/4-16 * 3/4-16 *
M4 & M5 Servo pressure 60 bar [870 psi] 9/16-18 9/16-18
L1 & L2 Case pressure 35 bar [510 psi] 1-1/16-12 1-5/16-12
S Charge pump inlet pressure 1 bar [30 in Hg vacuum] 1-1/16-12 1-5/16-12
* Some older models may use a 9/16-18 O-ring fitting.
28/32 cm3 base unit with MDC and no filtration adapter
Servo pressure
gauge port M5
Case Drain
Port L2
Charge pressure
gauge port M3
(charge pressure
supply for no
charge pump
option)
Charge pump
inlet port S
Servo pressure
gauge port M4
Case drain
port L1
System pressure
gauge port M2
System
pressure
port B
System
pressure
port A
System pressure
gauge port M1
RIGHT SIDE VIEW
LEFT SIDE VIEW
P108 067E
Service Manual
Series 42 Axial Piston Closed Circuit Pumps
Pressure Measurement
520L0638 • Rev 0300 • July 2015 23
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