Danfoss LPV Manual

Technical Information
Axial Piston Pumps
LPV
powersolutions.danfoss.com

Revision history Table of revisions
Date Changed Rev
September 2017 update model code 0102
July 2015 Danfoss Layout 0100
January 2009 neutral assist return mechanism - changes AF
October 2008 added serial number plate drawing AE
April 2008 changes to auxilliary mounting dimensions AD
August 2007 revised endcap and loop flusing options in model code AC
May 2007 correct displacement errors AB
July 2006 First edition A-0
Technical Information
LPV Axial Piston Pumps
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General description Overview..............................................................................................................................................................................................4
Design...................................................................................................................................................................................................4
Typical applications.........................................................................................................................................................................4
LPV product specifications............................................................................................................................................................4
Design...................................................................................................................................................................................................6
Direct displacement drive system..............................................................................................................................................7
LPV Pump schematic diagram.....................................................................................................................................................7
Operating parameters Overview..............................................................................................................................................................................................8
Input speed.........................................................................................................................................................................................8
System pressure................................................................................................................................................................................8
Pressure Ratings................................................................................................................................................................................8
Viscosity............................................................................................................................................................................................... 8
Temperature.......................................................................................................................................................................................9
Case pressure.....................................................................................................................................................................................9
Independent braking system.......................................................................................................................................................9
Reservoir.............................................................................................................................................................................................. 9
System design parameters Case drain......................................................................................................................................................................................... 10
Charge flow requirements..........................................................................................................................................................10
Loop flushing...................................................................................................................................................................................10
Bearing loads and life................................................................................................................................................................... 10
Applications with external shaft loads..............................................................................................................................10
Hydraulic unit life...........................................................................................................................................................................12
Mounting flange loads.................................................................................................................................................................12
Estimating overhung load moments.................................................................................................................................12
Input shaft torque rating and spline lubrication................................................................................................................13
Understanding and minimizing system noise.....................................................................................................................13
Sizing equations.............................................................................................................................................................................14
Fluids.................................................................................................................................................................................................. 14
Filtration system.............................................................................................................................................................................15
Charge filtration........................................................................................................................................................................16
Suction filtration....................................................................................................................................................................... 16
Operation HPRV (High pressure relief valve).............................................................................................................................................17
Bypass function...............................................................................................................................................................................17
CPRV (Charge pressure relief valve)........................................................................................................................................ 17
Loop flushing valve.......................................................................................................................................................................18
Neutral return mechanism..........................................................................................................................................................18
Technical specifications Specifications...................................................................................................................................................................................20
Product coding LPV Model Code............................................................................................................................................................................. 23
Features and options Controls............................................................................................................................................................................................. 26
Direct displacement control.................................................................................................................................................26
Features and benefits..............................................................................................................................................................26
Control handle requirements...............................................................................................................................................26
Input shafts.......................................................................................................................................................................................27
Auxiliary mounting pads.............................................................................................................................................................28
SAE-A Auxiliary mounting..................................................................................................................................................... 28
Installation drawings LPV Installation drawings............................................................................................................................................................30
LPV Schematic.................................................................................................................................................................................31
Technical Information
LPV Axial Piston Pumps
Contents
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Overview
LPV is a family of variable displacement, axial piston pumps for closed circuit applications. The LPV family
is uniquely designed to optimize performance, size, and cost, matching the work requirements of the
demanding turf care and utility vehicle marketplace. This document gives the detailed specifications and
features for LPV pumps.
Design
High performance
•Displacements 25 cm³/rev [1.53 in3/rev], 30 cm³/rev [1.83 in3/rev], 35 cm³/rev [2.14 in3/rev]
•Speeds up to 3600 rpm
•Pressures up to 210 bar [3045 psi] continuous, and 345 bar [5000 psi] peak
•Direct displacement control
Latest technology
•Customer-driven using quality function deployment (QFD) and design for manufacturability (DFM)
techniques
•Optimized valve plates for quiet operation
•Compact package size minimizing installation space requirements
•Single piece rigid housing to reduce noise and leak paths
•Integrated neutral return mechanism for simplified installation
•Optional loop flushing for circuit flexibility
Reliability
•Designed to rigorous standards
•Proven in both laboratory and field
•Manufactured to rigid quality standards
•Long service life
Typical applications
•Turf care
•Utility vehicles
LPV product specifications
Basic units
The LPV pumps provide an infinitely variable speed range between zero and maximum in both forward
and reverse modes of operation.
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
output motor.
Technical Information
LPV Axial Piston Pumps
General description
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LPV pump
Serial number plate
Made in USA
Place of Manufacture
Part Number
Serial Number
Model
Code
LPVAAADAEACCABDDD
P107852
83002847
A084012345
RAFFBNNN***
Technical Information
LPV Axial Piston Pumps
General description
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Design
LPV is a family of hydrostatic pumps for low to medium power applications with maximum loads of 345
bar [5000 psi]. You can apply these pumps 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[2.14 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 have an internal neutral return mechanism for ease of installation, and are available with
optional loop flushing for circuit flexibility. LPV pumps can 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.
LPV cross section
P106271
Input shaft
Ball bearing
Needle bearing
Tapered roller bearing
Cylinder block
Valve plate
Cylinder block spring
Piston
Slipper
Swashplate
Trunion
Technical Information
LPV Axial Piston Pumps
General description
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Direct displacement drive system
The direct displacement control varies the swashplate angle. Swashplate angle determines pump flow
and motor speed.
Pictorial circuit diagram
Variable
displacement
pump
Input
shaft
Cylinder
block
assembly
HPRV valves Loop flushing valves
OMR
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
P100586
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
Charge pressure
inlet
Port A
Port B
P106287
L2
L1
Technical Information
LPV Axial Piston Pumps
General description
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Overview
This section defines the operating parameters and limitations for LPV pumps with regard to input speeds
and pressures. For actual parameters, refer to Technical specifications on page 20.
Input speed
The table in Technical specifications on page 20, gives rated and maximum speeds for each
displacement. Not all displacements operate under the same speed limits. Definitions of these speed
limits appear below.
Continuous speed is the maximum recommended operating speed at full power condition. Operating at
or below this speed should yield satisfactory product life. Do not exceed maximum pump speed during
unloaded, on-road travel over level ground.
Maximum speed is the highest operating speed permitted. Exceeding maximum speed reduces pump
life and can cause loss of hydrostatic power and braking capacity. Never exceed the maximum speed
limit under any operating conditions.
W
Warning
Unintended vehicle or machine movement hazard.
The loss of hydrostatic drive line power, in any mode of operation (forward, neutral, or reverse) may cause
the system to lose hydrostatic braking capacity. You must provide a braking system, redundant to the
hydrostatic transmission, sufficient to stop and hold the vehicle or machine in the event of hydrostatic
drive power loss.
System pressure
The table in Technical specifications on page 20, gives maximum and maximum working pressure
ratings for each displacement. Not all displacements operate under the same pressure limits. Definitions
of the operating pressure limits appear below.
Pressure Ratings
System pressure is the differential pressure between high pressure system ports. It is the dominant
operating variable affecting hydraulic unit life. High system pressure, which results from high load,
reduces expected life. Hydraulic unit life depends on the speed and normal operating, or weighted
average, pressure that can only be determined from a duty cycle analysis.
Application pressure is the high pressure relief or pressure limiter setting normally defined within the
order code of the pump. This is the applied system pressure at which the driveline generates the
maximum calculated pull or torque in the application.
Maximum Working pressure is the highest recommended application pressure. Maximum working
pressure is not intended to be a continuous pressure. Propel systems with application pressures at, or
below, this pressure should yield satisfactory unit life given proper component sizing.
Maximum pressure is the highest allowable application pressure under any circumstance. Application
pressures above maximum working pressure will only be considered with duty cycle analysis and factory
approval.
Minimum low loop pressure must be maintained under all operating conditions to avoid cavitation.
All pressure limits are differential pressures referenced to low loop (charge) pressure. Subtract low loop
pressure from gauge readings to compute the differential.
Viscosity
Maintain fluid viscosity within the recommended range for maximum efficiency and bearing life.
Minimum viscosity should only occur during brief occasions of maximum ambient temperature and
Technical Information
LPV Axial Piston Pumps
Operating parameters
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severe duty cycle operation. Maximum viscosity should only occur at cold start. Limit speeds until the
system warms up. Refer to Specifications on page 20, for specifications.
Temperature
Maintain fluid temperature within the limits shown in the table. Technical specifications on page 20.
Minimum temperature relates to the physical properties of the component materials. Cold oil will not
affect the durability of the pump components, however, it may affect the ability of the pump to provide
flow and transmit power. Maximum temperature is based on material properties. Don't exceed it.
Measure maximum temperature at the hottest point in the system. This is usually the case drain. Refer to
Specifications on page 20, for specifications.
Ensure fluid temperature and viscosity limits are concurrently satisfied.
Case pressure
Do not allow case pressure to exceed ratings under normal operating conditions. During cold start, keep
case pressure below maximum intermittent case pressure. Size drain plumbing accordingly.
C
Caution
Possible component damage or leakage.
Operation with case pressure in excess of stated limits may damage seals, gaskets, and/or housings,
causing external leakage. Performance may also be affected since charge and system pressure are
additive to case pressure.
Independent braking system
W
Warning
Unintended vehicle or machine movement hazard.
The loss of hydrostatic drive line power, in any mode of operation (forward, neutral, or reverse) may cause
the system to lose hydrostatic braking capacity. You must provide a braking system, redundant to the
hydrostatic transmission, sufficient to stop and hold the vehicle or machine in the event of hydrostatic
drive power loss.
Reservoir
The reservoir provides clean fluid, dissipates heat, and removes trapped air from the hydraulic fluid. It
allows for fluid volume changes associated with fluid expansion and cylinder differential volumes.
Minimum reservoir capacity depends on the volume needed to perform these functions. Typically, a
capacity of 5/8 of the charge pump flow (per minute) is satisfactory for a closed reservoir. Open circuit
systems sharing a common reservoir require greater fluid capacity.
Locate the reservoir outlet (suction line) near the bottom, allowing clearance for settling foreign particles.
Use a 100 - 125 µm screen covering the outlet port.
Place the reservoir inlet (return lines) below the lowest expected fluid level, as far away from the outlet as
possible. Use a baffle (or baffles) between the reservoir inlet and outlet ports to promote de-aeration and
reduce fluid surging.
Technical Information
LPV Axial Piston Pumps
Operating parameters
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Case drain
Connect the case drain line to one of the case outlets to return internal leakage to the system reservoir.
Use the higher of the outlets to promote complete filling of the case. Case drain fluid is typically the
hottest fluid in the system. Return case drain flow through the heat exchanger to the reservoir.
Charge flow requirements
All LPV pumps applied in closed circuit installations require charge flow. The charge pump provides flow
to make up internal leakage, maintain a positive pressure in the main circuit, provide flow for cooling and
filtration, replace any leakage losses from external valving or auxiliary systems, and to provide flow and
pressure for the control system.
Many factors influence the charge flow requirements and charge pump size selection. These factors
include system pressure, pump speed, pump swashplate angle, type of fluid, temperature, size of heat
exchanger, length and size of hydraulic lines, control response characteristics, auxiliary flow
requirements, hydrostatic motor type, etc. When sizing and selecting hydrostatic units for an application,
it is frequently not possible to have all the information necessary to accurately evaluate all aspects of
charge pump size selection.
Maintain charge pressure at the level specified in the table Technical specifications on page 20 under all
operating conditions to prevent damage to the transmission. Danfoss recommends testing under actual
operating conditions to verify this.
Charge pump displacement should be at least 10% of the total displacement of all axial piston
components in the system. However, unusual application conditions may require a more detailed review
of charge pump sizing. Refer to Selection of Drive line Components, BLN-9985, for a more detailed
selection procedure, or contact your Danfoss representative for assistance.
Loop flushing
Closed circuit systems may require loop flushing to meet temperature and cleanliness requirements. A
loop flushing valve removes hot fluid from the low pressure side of the system loop for additional cooling
and filtering. Ensure the charge pump provides adequate flow for loop flushing and the loop flushing
valve does not cause charge pressure to drop below recommended limits.
LPV utilizes a special loop flushing spool design. On dual path systems, take special care to verify
acceptable performance.
Bearing loads and life
Bearing life is a function of speed, system pressure, charge pressure, and swashplate angle, plus any
external side or thrust loads. The influence of swashplate angle includes displacement as well as
direction. External loads are found in applications where the pump is driven with a side/thrust load (belt
or gear) as well as in installations with misalignment and improper concentricity between the pump and
drive coupling. All external side loads will act to reduce the normal bearing life of a pump. Other life
factors include oil type and viscosity.
In vehicle propel drives with no external shaft loads and where the system pressure and swashplate angle
are changing direction and magnitude regularly, the normal L20 bearing life (80 % survival) will exceed
the hydraulic load-life of the unit.
In non propel drives such as vibratory drives, conveyor drives, or fan drives, the operating speed and
pressure are often nearly constant and the swashplate angle is predominantly at maximum. These drives
have a distinctive duty cycle compared to a propulsion drive. In these types of applications a bearing life
review is recommended.
Applications with external shaft loads
LPV pumps have bearings that can accept some external radial and thrust loads. When external loads are
present, the allowable radial shaft loads are a function of the load position relative to the mounting
Technical Information
LPV Axial Piston Pumps
System design parameters
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flange, the load orientation relative to the internal loads, and the operating pressures of the hydraulic
unit. In applications with external shaft loads, you can minimize the impact on bearing life with proper
orientation of the load.
Optimum pump orientation is a consideration of the net loading on the shaft from the external load, the
pump rotating group and the charge pump load.
•In applications where the pump is operated such that nearly equal amounts of forward vs reverse
swashplate operation is experienced; bearing life can be optimized by orientating the external side
load at 0° or 180° such that the external side load acts 90° to the rotating group load.
•In applications where the pump is operated such that the swashplate is predominantly (> 75 %) on
one side of neutral (ie vibratory, conveyor, typical propel); bearing life can be optimized by
orientating the external side load generally opposite (90° or 270°) the internal rotating group load.
The direction of internal loading is a function of rotation and which system port has flow out. Contact
Danfoss for a bearing life review if external side loads are present.
You can calculate the maximum allowable radial load (Re), using the formula below, the maximum
external moment (Me) from the table on the next page, and the distance (L) from the mounting flange to
the load.
Re= Me/ L
Avoid thrust loads in either direction.
If continuously applied external radial loads are 25% of the maximum allowable or more, or thrust loads
are known to occur, contact your Danfoss representative for an evaluation of unit bearing life.
Tapered output shafts or clamp-type couplings are recommended for applications where radial shaft side
loads are present.
Direction of external shaft load
0° Re
180° Re
90° Re 270° Re
Axis of
swashplate
rotation
End view
of shaft
P100595
Orient radial shaft
load to 90° or 270°
(opposite of
block load)
Shaft loading parameters
ReMaximum radial load
MeMaximum external moment
L Distance from mounting flange to point of load
FbForce of block
TeThrust load
Maximum external shaft moments
LPV
Me/N•m [in•lbf] 101 [890]
Technical Information
LPV Axial Piston Pumps
System design parameters
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Diagram of external radial shaft loads
R
T
P106280
L
e
F
e
b
0
180
90 270
ReRe
Re
Re
Hydraulic unit life
Hydraulic unit life is the life expectancy of the hydraulic components. It is a function of speed and
system pressure. System pressure is the dominant operating variable. High pressure, which results from
high load, reduces expected life.
Design the hydraulic system to a projected machine duty cycle. Know the expected percentages of time
at various loads and speeds. Ask your Danfoss representative to calculate an appropriate pressure based
your hydraulic system design. If duty cycle data is not available, input power and pump displacement are
used to calculate system pressure.
All pressure limits are differential pressures (referenced to charge pressure) and assume normal charge
pressure.
LPV pumps will meet satisfactory life expectancy if applied within the parameters specified in this
bulletin. For more detailed information on hydraulic unit life see Pressure and Speed Limits, BLN-9884.
Mounting flange loads
Estimating overhung load moments
Adding auxiliary pumps and/or subjecting pumps to high shock loads may result in excessive loading of
the mounting flange. Applications which experience extreme resonant vibrations or shock may require
additional pump support. You can estimate the overhung load moment for multiple pump mounting
using the formula below.
MS= GS(W1L1+ W2L2+ ... +WnLn)
MC= GC(W1L1+ W2L2+ ... +WnLn)
Where:
MC= Rated load moment N•m [lbf•in]
MS= Shock load moment N•m [lbf•in]
GC= Rated (vibratory) acceleration (G’s)* m/s2 [ft/s2]
GS= Maximum (shock) acceleration (G’s)* m/s2 [ft/s2]
Wn= Weight of nth pump
Ln= Distance from mounting flange to CG (center of gravity) of nth pump
(Refer to Installation drawings on page 30 to locate CG of pump.)
* Carry out calculations by multiplying gravity (g = 9.81 m/s2[32 ft/s2]) with a given factor. This factor depends
on the application.
Refer to Specifications on page 20, for allowable overhung load moment values.
Technical Information
LPV Axial Piston Pumps
System design parameters
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Shaft loading parameters
P106285
Center of gravity - pump 1
Center of gravity - pump 2
L 1
L 2
Mounting flange
Input shaft torque rating and spline lubrication
A spline running in oil-flooded environment provides superior oxygen restriction in addition to
contaminant flushing. An oil-flooded spline is found in a pump to pump drive (mounted on the auxiliary
pad of another pump). An oil-flooded spline connection can withstand a continuously applied torque up
to the published maximum rating. Maximum torque ratings are based on torsional fatigue strength of
the shaft and assume a maximum of 200,000 load reversals.
Coupling arrangements that are not oil-flooded require a reduced torque rating due to spline tooth wear.
Contact your Danfoss representative for torque ratings if your application involves non oil-flooded
couplings.
Danfoss recommends mating splines adhere to ANSI B92.1-Class 5. Danfoss external splines are modified
class 5 fillet root side fit. The external major diameter and circular tooth thickness dimensions are reduced
to ensure a good clearance fit with the mating spline. See Input shafts on page 27 for full spline
dimensions and data.
Maintain a spline engagement at least equal to the pitch diameter to maximize spline life. Spline
engagement of less than ¾ pitch diameter is subject to high contact stress and spline fretting.
Alignment between the mating spline's pitch diameters is another critical factor in determining the
operating life of a splined drive connection. Plug-in, or rigid spline drive installations can impose severe
radial loads on the shaft. The radial load is a function of the transmitted torque and shaft eccentricity.
Increased spline clearance will not totally alleviate this condition; but, increased spline clearance will
prevent mechanical interference due to misalignment or radial eccentricity between the pitch diameters
of the mating splines. Maximize spline life by adding an intermediate coupling between the bearing
supported splined shafts.
Torques are additive for multiple pump installations. Ensure total through torque for the main pump and
auxiliary pump does not exceed published maximum shaft torque. See Input shafts on page 27 for shaft
torque ratings.
Understanding and minimizing system noise
A table in the Specifications on page 20, gives sound levels for each displacement. Sound level data are
collected at various operating speeds and pressures in a semi-anechoic chamber. Many factors contribute
to the overall noise level of any application. Here is some information to help understand the nature of
noise in fluid power systems, and some suggestions to help minimize it.
Noise is transmitted in fluid power systems in two ways: as fluid borne noise, and structure borne noise.
Fluid-borne noise (pressure ripple or pulsation) is created as pumping elements discharge oil into the
pump outlet. It is affected by the compressibility of the oil, and the pump's ability to transition pumping
Technical Information
LPV Axial Piston Pumps
System design parameters
©Danfoss | September 2017 520L0954 | BC00000044en-US0102 | 13

elements from high to low pressure. Pulsations travel through the hydraulic lines at the speed of sound
(about 1400 m/s [4600 ft/sec] in oil) until there is a change (such as an elbow) in the line. Amplitude varies
with overall line length and position.
Structure-borne noise is transmitted wherever the pump casing connects to the rest of the system. The
way system components respond to excitation depends on their size, form, material, and mounting.
System lines and pump mounting can amplify pump noise. Follow these suggestions to help minimize
noise in your application:
•Use flexible hoses.
•Limit system line length.
•If possible, optimize system line position to minimize noise.
•If you must use steel plumbing, clamp the lines.
•If you add additional support, use rubber mounts.
•Test for resonants in the operating range, if possible avoid them.
Sizing equations
Use these equations to help choose the right pump size and displacement for your application. An
evaluation of the machine system to determine the required motor speed and torque to perform the
necessary work function initiates the design process. Refer to Selection of drive line components,
BLN-9985, for a more complete description of hydrostatic drive line sizing. First select motor size to
transmit the maximum required torque. Then select pump as a flow source to achieve the maximum
motor speed.
Fluids
Ratings and performance data are based on operating with hydraulic fluids containing oxidation, rust
and foam inhibitors. These fluids must possess good thermal and hydrolytic stability to prevent wear,
erosion, and corrosion of pump components. Never mix hydraulic fluids of different types.
Technical Information
LPV Axial Piston Pumps
System design parameters
14 | ©Danfoss | September 2017 520L0954 | BC00000044en-US0102

Fire resistant fluids are also suitable at modified operating conditions. Please see Hydraulic Fluids and
Lubricants Technical Information, 520L0463, for more information. Refer to Experience with Biodegradable
Hydraulic Fluids Technical Information, 520L0465, for information relating to biodegradable fluids.
The following hydraulic fluids are suitable:
•Hydraulic Oil ISO 11 158 - HM (Seal compatibility and vane pump wear resistance per DIN 51 524-2
must be met)
•Hydraulic Oil ISO 11 158 - HV (Seal compatibility and vane pump wear resistance per DIN 51 524-3
must be met)
•Hydraulic Oil DIN 51 524-2 - HLP• Hydraulic Oil DIN 51 524-3 - HVLP
•Automatic Transmission Fluid (ATF) A Suffix A (GM)
•Automatic transmission fluid Dexron II (GM), which meets Allison C-3 and Caterpillar TO-2 test
•Automatic transmission fluid M2C33F and G (Ford)
•Engine oils API classification SL, SJ (for gasoline engines) and CI-4, CH-4, CG-4, CF-4 and CF (for diesel
engines)
•Super Tractor Oil Universal (STOU) special agricultural tractor fluid
Filtration system
To prevent premature wear, ensure only clean fluid enters the hydrostatic transmission circuit. Danfoss
reccommends a filter capable of controlling the fluid cleanliness to ISO 4406 class 22/18/13 (SAE J1165) or
better, under normal operating conditions.
Filtration strategies include suction or pressure filtration. The selection of a filter depends on a number of
factors including the contaminant ingression rate, the generation of contaminants in the system, the
required fluid cleanliness, and the desired maintenance interval. Select filters to meet the above
requirements using rating parameters of efficiency and capacity.
You can express measured filter efficiency with a Beta ratio1(βX). For simple suction-filtered closed circuit
transmissions and open circuit transmissions with return line filtration, a filter with a β-ratio within the
range of β35-45 = 75 (β10 ≥ 2) or better should be satisfactory. For some open circuit systems, and closed
circuits with cylinders being supplied from the same reservoir, we recommend a considerably higher
filter efficiency. This also applies to systems with gears or clutches using a common reservoir. These
systems typically require a charge pressure or return filtration system with a filter β-ratio in the range of
β15-20 = 75 (β10 ≥ 10) or better.
Because each system is unique, only a thorough testing and evaluation program can fully validate the
filtration system. Please see Design Guidelines for Hydraulic Fluid Cleanliness Technical Information,
520L0467 for more information.
Ensure fluid entering pump is free of contaminants to prevent damage (including premature wear) to the
system. LPV pumps require system filtration capable of maintaining fluid cleanliness at ISO 4406-1999
class 22/18/13 or better.
Consider these factors when selecting a system filter:
•Cleanliness specifications
•Contaminant ingression rates
•Flow capacity
•Desired maintenance interval
Locate filter either on the inlet (suction filtration) or discharge (charge pressure filtration) side of the
charge pump. Either strategy is applicable for LPV pumps.
1Filter βx-ratio is a measure of filter efficiency defined by ISO 4572. It is defined as the ratio of the number of particles greater than a
given diameter (“x” in microns) upstream of the filter to the number of these particles downstream of the filter.
Technical Information
LPV Axial Piston Pumps
System design parameters
©Danfoss | September 2017 520L0954 | BC00000044en-US0102 | 15

Charge filtration
The pressure filter is remotely mounted in the circuit after the charge pump, as shown in the
accompanying illustration.
Filters used in charge pressure filtration circuits must be rated to at least 34.5 bar [500 psi] pressure.
Danfoss recommends locating a 100 - 125 µm screen in the reservoir or in the charge inlet line when
using charge pressure filtration.
A filter bypass valve is necessary to prevent damage to the system. In the event of high pressure drop
associated with a blocked filter or cold start-up conditions, fluid will bypass the filter. Avoid working with
an open bypass for an extended period. We recommend a visual or electrical bypass indicator. Proper
filter maintenance is mandatory.
Charge filtration
Reservoir
Filter
with bypass
Charge
pump
Charge relief
valve
To pump case
To Low Pressure
side of loop
and servo control
Strainer
P106279
Suction filtration
The suction filter is placed in the circuit between the reservoir and the inlet to the charge pump as shown
in the accompanying illustration.
Suction filtration
Reservoir
Filter
Charge
pump
Charge relief
valve
To pump case
To low pressure
side of loop
and servo control
Strainer
P106352
Technical Information
LPV Axial Piston Pumps
System design parameters
16 | ©Danfoss | September 2017 520L0954 | BC00000044en-US0102

HPRV (High pressure relief valve)
LPV pumps are equipped with a combination high pressure relief and charge check valve. The high-
pressure 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. The high pressure relief valve used on LPV is designed to remove
pressure spikes for short periods of time. Operating over the high pressure relief valve for extended
periods may damage the pump.
HPRV valve
P106273
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
P106286
C
Caution
Excessive speed or extended movement will damage the pump and motor(s)
Avoid excessive speeds and extended load/vehicle movement. Do not move the load or vehicle more
than 20 % of maximum speed or for longer than 3 minutes. When the bypass function is no longer
needed, reseat the bypass valve to the normal operating position.
CPRV (Charge pressure relief valve)
An internal charge relief valve regulates charge pressure. The charge pump supplies pressure to maintain
a minimum pressure in the low side of the transmission loop.
Technical Information
LPV Axial Piston Pumps
Operation
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CPRV valve
P106274
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 which provides normal component
life. Elevated charge pressure can be used as a secondary means to reduce the swashplate response time.
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.
LPV is designed for a maximum charge flow of 57 L/min [15 US gal/min].
Loop flushing valve
LPV pumps incorporate an optional integral loop flushing valve, which removes heat and contaminants
from the main loop.
LPV utilizes a special loop flushing spool design. On dual path systems, take special care to verify
acceptable performance.
Loop flushing valve
P106276
Neutral return mechanism
The neutral return mechanism mechanically returns the pump to zero displacement. A cam allows
precise zero displacement adjustment.
Maximum return force of the neutral return mechanism is 5.65 N•m [50 lbf•in]
W
Warning
Failure of the pump to return to neutral in the absence of control input will cause unintended
vehicle movement. Some control systems may require an additional neutral return mechanism to
overcome friction in the control linkage. Verify pump returns to neutral under all operating conditions
when the control is released.
Technical Information
LPV Axial Piston Pumps
Operation
18 | ©Danfoss | September 2017 520L0954 | BC00000044en-US0102

Neutral return adjustment screw
P106277
Adjusting screw
Lock/seal nut
Neutral return mechanism
Shaft
Swashplate
Neutral
return
arm
Adjusting cam P106278
Technical Information
LPV Axial Piston Pumps
Operation
©Danfoss | September 2017 520L0954 | BC00000044en-US0102 | 19

Specifications
General specifications
Design Axial piston pump of trunion swashplate design with variable displacement
Direction of rotation Clockwise, counter-clockwise
Port connections Main pressure ports: SAE straight thread O-ring boss
Recommended installation
position
Pump installation recommended with control position on the bottom or side.
Consult Danfoss for non conformance to these guidelines. The housing must always
be filled with hydraulic fluid.
Physical properties
Displacement
Feature Unit 25 30 35
Maximum displacement cm³ [in³] 25 [1.53] 30 [1.83] 35 [2.14]
Flow at rated speed (theoretical) l/min
[US gal/min]
85.2
[22.5]
104.9
[27.7]
137.0
[36.2]
Input torque at maximum displacement
(theoretical)
N•m/ bar
[lbf•in/1000 psi]
0.4
[244]
0.5
[291]
0.6
[340]
Mass moment of inertia of internal rotating
components
kg•m²
[slug•ft²]
0.001670
[0.0012]
0.001580
[0.00120]
0.001530
[0.0011]
Weight kg [lb] 23 [51]
Rotation Clockwise, counter-clockwise
Mounting SAE B 2 bolt
Auxiliary mounting SAE J744 A 9T, SPCL 11T
System ports (type) 1 1/16-12 UNF-2B ORB
System ports (location) Twin radial
Control types Direct displacement control
Shafts Splined SAE 13 tooth, 15 tooth
Case drain ports 1 1/16-12 SAE ORB
Operating parameters
Displacement
Rating Units 25 30 35
Input speed2minimum min-1 (rpm) 500 500 500
continuous 3400 3500 3600
maximum 3950 4150 4300
Pressure maximum working bar [psi] 400 [5800] 350 [5075] 300 [4350]
maximum 415 [6020] 400 [5800] 350 [5075]
External shaft loads External moment (Me) N•m [lbf•in] 7.7 [68]
Thrust in (Tin), out (Tout) N [lbf] 750 [169]
Bearing life (max.
swashplate angle
and max.
continuous speed)
at 210 bar [3045 psi] B10 hours 120,000 63,000 37,000
Charge pressure minimum bar [psi] 6 [87]
maximum 30 [435]
Technical Information
LPV Axial Piston Pumps
Technical specifications
20 | ©Danfoss | September 2017 520L0954 | BC00000044en-US0102