Danfoss LPV User guide

Technical Information

Axial Piston Pumps

LPV

www.danfoss.com

Technical Information

LPV Axial Piston Pumps

Revision history	Table of revisions
	Date		Changed	Rev
	April 2021		Changed document number from 'BC00000044' and '520L0954' to 'BC152886483590' and	0301
			removed obsolete end cap options
	May 2018		add straight keyed shaft	0103
	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

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Technical Information
LPV Axial Piston Pumps
Contents
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........................................................................................................................................................................	15
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.......................................................................................................................................................................................	26
Auxiliary mounting pads.............................................................................................................................................................	27
SAE-A Auxiliary mounting.....................................................................................................................................................	27
Installation drawings
LPV Installation drawings............................................................................................................................................................	29
LPV Schematic.................................................................................................................................................................................	30

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Technical Information

LPV Axial Piston Pumps

General description

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.

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Technical Information

LPV Axial Piston Pumps

General description

LPV pump

Serial number plate

Model		LPVAAADAEACCABDDD
Code		RAFFBNNN***					Part Number
	83002847
							Serial Number
			A084012345
		Made in USA
				Place of Manufac tur e
							P107852

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Technical Information

LPV Axial Piston Pumps

General description

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

Cylinder block

Valve plate

Trunion

Tapered roller bearing

Ball bearing

Input shaft

Needle bearing	Piston		Swashplate
Cylinder block spring		Slipper	P106271

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Technical Information

LPV Axial Piston Pumps

General description

Direct displacement drive system

The direct displacement control varies the swashplate angle. Swashplate angle determines pump flow and motor speed.

Pictorial circuit diagram

Cylinder
block					OMR
assembl y
					orbital
					motor
					Output
					shaft
Input				Suction flow
shaft	Variable	HPRV valves	Loop flushing valves	Charge pressur e
	displacement			Servo pressur e
	pump
				High pressur e
				Case flow	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

L2

Port A

Port B

L1

P106287

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Technical Information

LPV Axial Piston Pumps

Operating parameters

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

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Technical Information

LPV Axial Piston Pumps

Operating parameters

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.

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Technical Information

LPV Axial Piston Pumps

System design parameters

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

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