Danfoss LPV Service guide
MAKING MODERN LIVING POSSIBLE
Service Manual
Closed Circuit Axial Piston Pumps
LPV
powersolutions.danfoss.com
Service Manual LPV Closed Circuit Axial Piston Pumps
Revision history Table of revisions
Date Changed Rev
July 2015 Danfoss layout 0100
November 2006 First printing A
2 11004904 • Rev 0100 • July 2015
Service Manual
LPV Closed Circuit Axial Piston Pumps
Contents
Introduction
Overview..............................................................................................................................................................................................4
Warranty.............................................................................................................................................................................................. 4
General instructions........................................................................................................................................................................ 4
Safety Precautions............................................................................................................................................................................5
Symbols used in Danfoss literature............................................................................................................................................6
Design...................................................................................................................................................................................................6
Direct displacement drive system..............................................................................................................................................8
LPV Pump schematic diagram.....................................................................................................................................................8
Operation
HPRV (High pressure relief valve)............................................................................................................................................... 9
Bypass function.................................................................................................................................................................................9
CPRV (Charge pressure relief valve)........................................................................................................................................ 10
Loop flushing valve.......................................................................................................................................................................10
Neutral return mechanism..........................................................................................................................................................11
Technical specifications
Specifications...................................................................................................................................................................................12
Fluid and filter recommendations
Fluid and filter recommendations........................................................................................................................................... 15
Startup procedures
General ..............................................................................................................................................................................................16
Start-up procedure........................................................................................................................................................................16
Pressure measurements
Required tools.................................................................................................................................................................................17
Port locations and gauge installation.....................................................................................................................................17
Troubleshooting
Overview........................................................................................................................................................................................... 18
System operating hot...................................................................................................................................................................18
Transmission operates normally in one direction only....................................................................................................18
System will not operate in either direction.......................................................................................................................... 18
System noise or vibration........................................................................................................................................................... 19
Sluggish system response...........................................................................................................................................................19
Adjustments
Pump adjustment.......................................................................................................................................................................... 20
Standard procedures, inspections, and adjustments....................................................................................................... 20
Charge pressure relief valve adjustments.............................................................................................................................20
System check and HPRV.............................................................................................................................................................. 22
Checking for proper HPRV valve operation.................................................................................................................... 22
Loop flushing valve.......................................................................................................................................................................22
Neutral return mechanism..........................................................................................................................................................23
Leveling swashplate with pump installed on machine....................................................................................................24
Minor repair
Input shaft and seal.......................................................................................................................................................................25
Trunion seal......................................................................................................................................................................................29
High Pressure Relief Valves.........................................................................................................................................................30
Charge pressure relief valve.......................................................................................................................................................31
Loop flushing valve.......................................................................................................................................................................32
Bypass valve.....................................................................................................................................................................................33
Coupling............................................................................................................................................................................................34
Torque chart
Fasteners and plugs...................................................................................................................................................................... 35
Fastener size and torque chart..................................................................................................................................................35
Plug size and torque chart..........................................................................................................................................................35
11004904 • Rev 0100 • July 2015 3
Service Manual
Introduction
Overview
Warranty
LPV Closed Circuit Axial Piston Pumps
This manual includes information for the installation, maintenance, and minor repair of the LPV pump. It
includes a description of the unit and its individual components, troubleshooting information, and minor
repair procedures.
Performing minor repairs requires the unit to be removed 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 Global Service Partners is available for major repairs. Danfoss Global
Service Partners are trained by the factory and certified on a regular basis. You can locate your nearest
Global Service Partner using the distributor locator at www.sauer-danfoss.com. Click on the Sales and
Service link.
Performing installation, maintenance, and minor repairs according to the procedures in this manual will
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 LPV variable displacement closed circuit pumps.
Remove the unit
Prior to performing major 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 by using a clean solvent wash and air drying is usually adequate.
As with any precision equipment, all parts must be kept free of foreign materials 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.
Lubricate moving parts
During assembly, coat all moving parts with a film of clean hydraulic oil. This assures that these parts will
be lubricated during start-up.
Replace all O-rings and gaskets
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Service Manual
Introduction
Safety Precautions
LPV Closed Circuit Axial Piston Pumps
It is recommended that all O-rings be replaced. Lightly lubricate all O-rings with clean petroleum jelly
prior to assembly.
Secure the unit
For major repair, place the unit in a stable position with the shaft pointing downward. It will be necessary
to secure the pump while removing and torquing the endcap bolts.
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.
Unintended Machine Movement
Warning
Unintended movement of the machine or mechanism may cause injury to the technician or bystanders.
To protect against unintended movement, secure the machine or disable/disconnect the mechanism
while servicing.
Flammable Cleaning Solvents
Warning
Some cleaning solvents are flammable. To avoid possible fire, do not use cleaning solvents in an area
where a source of ignition may be present.
Fluid Under Pressure
Warning
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.
Personal Safety
Warning
Protect yourself from injury. Use proper safety equipment, including safety glasses, at all times.
Hazardous Material
Warning
Hydraulic fluid contains hazardous material. Avoid prolonged contact with hydraulic fluid. Always
dispose of used hydraulic fluid according to state, and federal environmental regulations.
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Service Manual
LPV Closed Circuit Axial Piston Pumps
Introduction
Symbols used in Danfoss literature
WARNING may result in injury Tip, helpful suggestion
CAUTION may result in damage to product or
property
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
Lubricate with hydraulic fluid
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.
Design
LPV represents a family of hydrostatic pumps for low to medium power applications with maximum
pressures up to 345 bar [5000 psi]. These pumps can be applied with other products in a system to
transfer and control hydraulic power.
LPV pumps provide an infinitely variable speed range between zero and maximum in both forward and
reverse modes of operation. LPV pumps come in three displacements (25 cm3 [1.53 in3], 30 cm3 [1.83
in3], and 35 cm3 [2.32 in3]).
LPV pumps are compact, high power density units. All models use the parallel axial piston / slipper
concept in conjunction with a tiltable swashplate to vary the pump’s displacement. Reversing the angle
of the swashplate reverses the flow of fluid from the pump, reversing the direction of rotation of the
motor output.
LPV pumps are provided with an internal neutral return mechanism for ease of installation, and are
available with optional loop flushing for circuit flexibility. LPV pumps are designed to receive charge flow
from an auxiliary circuit or from a gear pump mounted on the auxiliary mounting pad. LPV pumps feature
an SAE A auxiliary mounting pad to accept auxiliary hydraulic pumps for use in complementary hydraulic
systems.
LPV pumps include a trunnion style direct displacement control.
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P106 271E
Input shaft
Ball bearing
Needle bearing
Tapered roller bearing
Cylinder block
Valve plate
Cylinder block spring
Piston
Slipper
Swashplate
Trunion
Service Manual LPV Closed Circuit Axial Piston Pumps
Introduction
LPV cross section
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Variable
displacement
pump
Input
shaft
Cylinder
block
assembly
HPRV valves
Loop flushing valves
OMS
orbital
motor
Suction flow
Servo pressure
High pressure
Case flow
Charge pressure
Output
shaft
Filter
Charge
pump
Reservoir
Heat
exchanger
Heat exchanger
bypass
Charge relief
valve
Bypass
valve
P100 586E
L1
L2
Charge pressure
inlet
Port A
Port B
P106 287E
Service Manual
LPV Closed Circuit Axial Piston Pumps
Introduction
Direct displacement drive system
The direct displacement control varies the swashplate angle. Swashplate angle determines pump flow
and motor speed.
Pictorial circuit diagram
The diagram shows an LPV pump driving an OMR motor. The system shown uses an external charge
pump and external filter. Charge pressure relief valves, high pressure relief valves, and loop flushing
valves are shown separated from the pump to provide clarity to the hydraulic system.
LPV Pump schematic diagram
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P106 286E
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Service Manual
LPV Closed Circuit Axial Piston Pumps
Operation
HPRV (High pressure relief valve)
LPV pumps are equipped with a combination high pressure relief and charge check valve. The highpressure relief function is a dissipative (with heat generation) pressure control valve for the purpose of
limiting excessive system pressures. The charge check function acts to replenish the low-pressure side of
the working loop with charge oil. Each side of the transmission loop has a dedicated HPRV valve that is
non-adjustable with a factory set pressure. When system pressure exceeds the factory setting of the
valve, oil is passed from the high pressure system loop, into the charge gallery, and into the low pressure
system loop via the charge check.
HPRV valve
Bypass function
The LPV contains a dedicated bypass valve. The bypass function is activated when the bypass valve is
mechanically backed out 3 full turns (maximum). The bypass function allows a machine or load to be
moved without rotating the pump shaft or prime mover.
Bypass valve
Caution
Excessive speeds and extended load/vehicle movement must be avoided. The load or vehicle should be
moved not more than 20% of maximum speed and for a duration not exceeding 3 minutes. Damage to
drive motor(s) is possible. When the bypass function is no longer needed care should be taken to reseat
the bypass valves to the normal operating position.
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P106 274E
Charge
pressure
Case
pressure
P106 276E
Service Manual
LPV Closed Circuit Axial Piston Pumps
Operation
CPRV (Charge pressure relief valve)
An internal charge relief valve regulates charge pressure. Charge pressure is supplied to maintain a
minimum pressure in the low side of the transmission loop.
CPRV valve
Minimum charge pressure is the lowest pressure allowed to maintain a safe working condition in the low
side of the loop.
Maximum charge pressure is the highest charge pressure allowed by the charge relief adjustment, and
which provides normal component life. The charge pressure setting listed in the order code is the set
pressure of the charge relief valve with the pump in neutral, operating with 5 gpm of charge flow. The
charge pressure setting is referenced to case pressure. Charge pressure is the differential pressure above
case pressure.
Loop flushing valve
LPV pumps incorporate an optional integral loop flushing valve, which removes heat and contaminants
from the main loop at an increased rate.
Loop flushing valve
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Adjusting cam
Lock/seal nut
Shaft
Swashplate
Neutral
return
arm
Adjusting cam
P106 278E
Service Manual LPV Closed Circuit Axial Piston Pumps
Operation
Neutral return mechanism
The neutral return mechanism is designed to mechanically return the pump to zero displacement. A cam
allows precise zero displacement adjustment.
Neutral return adjusting cam
Neutral return mechanism
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