Danfoss PVG 32 Service guide

Service Manual

PVG 32

powersolutions.danfoss.com

Service Manual

PVG 32 Proportional Valve Group

Revision history	Table of revisions

	Date	Changed	Rev

	February 2017	Updated with PVE Series 7	0301

	May 2014	Converted to Danfoss layout – DITA CMS	BA

	Feb 2006 - Aug 2013	Various changes	AB - BA

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Service Manual
PVG 32 Proportional Valve Group
Contents
Introduction
	Overview..............................................................................................................................................................................................	5
	General instructions........................................................................................................................................................................	5
	Remove the unit..........................................................................................................................................................................	5
	Keep it clean..................................................................................................................................................................................	5
	Replace all O-rings and gaskets.............................................................................................................................................	5
	Secure the unit.............................................................................................................................................................................	5
	Safety precautions............................................................................................................................................................................	6
	Unintended machine movement..........................................................................................................................................	6
	Flammable cleaning solvents.................................................................................................................................................	6
	Fluid under pressure..................................................................................................................................................................	6
	Personal safety.............................................................................................................................................................................	6
	Hazardous material....................................................................................................................................................................	6
	Acronyms.............................................................................................................................................................................................	6
Operation
	PVG 32 group with open center PVP (PVB with flow control spool)..............................................................................	8
	PVG 32 group with closed center PVP (PVB with flow control spool)...........................................................................	8
	PVG 32 sectional drawing..............................................................................................................................................................	9
	PVPC plug for external pilot oil supply.....................................................................................................................................	9
	Friction detent.................................................................................................................................................................................	11
	PVBS, main spools for flow control (standard)....................................................................................................................	12
	PVBS, main spools for flow control (with linear characteristics)...................................................................................	12
	PVBS, main spools for pressure control.................................................................................................................................	12
	PVPX Electrical LS unloading valve..........................................................................................................................................	13
System Troubleshooting
	Overview...........................................................................................................................................................................................	14
	Troubleshooting a PVG valve....................................................................................................................................................	14
	No cylinder/motor response in either direction when remote controller is actuated.........................................	15
	Cylinder/motor responds in one direction only.................................................................................................................	16
	Main valve spool moves without oil passing to cylinder/motor..................................................................................	16
	Cylinder/motor operates without remote controller being operated.......................................................................	17
	Cylinder/motor responds slowly to remote electrical or hydraulic controller actuation....................................	17
	Erratic cylinder/motor response to electrical or hydraulic controller operation....................................................	17
	Hydraulic oil supply.......................................................................................................................................................................	18
	Electrical supply..............................................................................................................................................................................	18
	Hydraulic (remote) pilot control pressure.............................................................................................................................	19
PVG 32 Component Troubleshooting
	Pressure relief valve.......................................................................................................................................................................	20
	Pressure reducing pilot valve....................................................................................................................................................	20
	Pressure gauge connection........................................................................................................................................................	21
	Open center plug...........................................................................................................................................................................	22
	Closed center plug and orifice..................................................................................................................................................	23
	Pressure adjustment spool.........................................................................................................................................................	24
	LS connection..................................................................................................................................................................................	25
	LS signal.............................................................................................................................................................................................	25
	Shuttle valve....................................................................................................................................................................................	26
	LS pressure limiting valve...........................................................................................................................................................	27
	LS A, B shuttle..................................................................................................................................................................................	27
	Main spool........................................................................................................................................................................................	28
	Shock and anti-cavitation valve PVLP.....................................................................................................................................	29
	Pressure compensator..................................................................................................................................................................	30
	Load drop check valve ................................................................................................................................................................	31
	Maximum oil flow adjustment screws for ports A and B.................................................................................................	32
	PVM module.....................................................................................................................................................................................	33
	PVS module......................................................................................................................................................................................	34
	PVPVM module...............................................................................................................................................................................	35
	PVAS module...................................................................................................................................................................................	36
	PVPX LS unloading valve.............................................................................................................................................................	37
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Service Manual

PVG 32 Proportional Valve Group

Contents

PVEM, PVEA, PVEH, PVES electrical actuators......................................................................................................................	38
Troubleshooting Considerations..............................................................................................................................................	38
PVEO ON/OFF electrical actuator.............................................................................................................................................	39
PVPC plug for external pilot control........................................................................................................................................	42
PVMR Friction Module..................................................................................................................................................................	42

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Service Manual

PVG 32 Proportional Valve Group

Introduction

Overview

This manual includes information for servicing PVG 32 valves. It includes a description of the units and their individual components, troubleshooting information, and minor repair procedures.

Performing minor repairs may require removal 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 trains and certifies Global Service Partners on a regular basis. You can locate your nearest Global Service Partner using the distributor locator at www.Danfoss.com.

For specifications and operating parameters on PVG 32 valves, refer to PVG 32 Technical Information Manual 520L0344.

Do not attempt to service PVG valves without build sheet specifications for reference.

General instructions

Follow these general procedures when repairing PVG 32 valves.

Remove the unit

Chock the wheels on the vehicle or lock the mechanism to inhibit movement. Prior to performing repairs, remove the unit from the vehicle/machine. Be aware that hydraulic fluid may be under high pressure and/or hot. Inspect the outside of the valve stack and fittings for damage. Cap hoses after removal to prevent contamination.

Keep it clean

Cleanliness is a primary means of assuring satisfactory motor life, on either new or repaired units. Clean the outside of the valve thoroughly before disassembly. Take care to avoid contamination of the port connections on the valve stack. Clean parts using a clean solvent wash and air dry.

As with any precision equipment, keep all parts free of foreign materials and chemicals. Protect all exposed sealing surfaces and open cavities from damage and foreign material. If left unattended, cover the valve with a protective layer of plastic.

Replace all O-rings and gaskets

Danfoss recommends you replace all O-rings. Lightly lubricate all O-rings with clean petroleum jelly prior to assembly.

Secure the unit

For repair, place the unit in a stable position with the shaft pointing downward. Secure the motor while removing and torquing controls, and valves.

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Introduction

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.

Unintended machine movement

W 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

W 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

W 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

W Warning

Protect yourself from injury. Use proper safety equipment, including safety glasses, at all times.

Hazardous material

W 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.

Acronyms

This table provides a definition of commonly used terms.

P = Proportional V = Valve

	PVP	Pump side module

	PVPV/M	Pump side module

	PVB	Basic module

	PVLA	Anti-cavitation valve

	PVLP	Shock and anti-cavitation valve

	PVS/PVSI	End plate

	PVAS (PVP, PVPV/M)	Assembly kit for PVP, PVPV/M

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PVG 32 Proportional Valve Group

Introduction

PVPX, LS	LS Unloading valve

PVPC	Plug for external pilot oil supply

PVBS	Main spool

PVM	Mechanical activation

PVMD	Cover for mechanical activation

PVH	Cover for hydraulic activation

PVMF	Cover for mechanical float

PVMR	Cover for friction detent PVMR or float position

PVEH, PVES, PVEA	Electrical activation

PVEM	Electrical activation

PVEO	Electrical activation

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Operation

PVG 32 group with open center PVP (PVB with flow control spool)

When the pump starts, and the main spools in the individual basic modules (11) are in the neutral position, oil flows from the pump, through connection P, across the pressure adjustment spool (6) to tank. The oil flow led across the pressure adjustment spool determines the pump pressure (stand-by pressure).

When one or more of the main spools actuate, the highest load pressure is fed through the shuttle valve circuit (10) to the spring chamber behind the pressure adjustment spool (6), and completely or partially closes the connection to tank.

Pump applies pressure to the right-hand side of the pressure adjustment spool (6). The pressure relief valve (1) opens if the load pressure exceeds the set value, diverting pump flow back to tank.

In a pressure-compensated basic module the compensator (14) maintains a constant

Pressure drop across the main spool—both when the load changes and when a module with a higher load pressure is actuated.

With a non pressure-compensated basic module incorporating a load drop check valve (18) in channel P, the check valve prevents return oil flow. The basic module can have the load drop check valve in channel P for functions with over-center valves.

The shock valves PVLP (13) with fixed setting and the suction valves PVLA (17) on ports A and B are used for the protection of the individual working function against overload and/or cavitation.

An adjustable Load Sensing (LS) pressure limiting valve (12) can be built into the A and B ports of pressure-compensated basic modules to limit the pressure from the individual working functions.

The LS pressure limiting valves save energy compared to the shock valves PVLP. With PVLP all the oil flow to the working function flows across the combined shock and suction valves to tank if the pressure exceeds the fixed setting. With LS pressure limiting valves, an oil flow of about 2 l/min [0.5 US gal/min] flows across the LS pressure limiting valve to tank if the pressure exceeds the valve setting.

PVG 32 group with closed center PVP (PVB with flow control spool)

In the closed center version, an orifice (5) and a plug (7) are fitted instead of the plug (4). This means that the pressure adjustment spool (6) only opens to tank when the pressure in channel P exceeds the set value of the pressure relief valve (1).

In LS systems, the load pressure flows to the pump regulator via the LS connection (8).

In the neutral position the pump control sets the displacement so that leakage in the system is compensated to maintain the set stand-by pressure. When a main spool is actuated, the pump regulator adjusts the displacement to maintain the set differential pressure between P and LS.

The pressure relief valve (1) in PVP should be set at a pressure of approximately 30 bar [435 psi] above maximum system pressure (set on the pump or external pressure relief valve).

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PVG 32 Proportional Valve Group

Operation

PVG 32 sectional drawing

PVP

PVB

1.	Pressure relief valve	11.	Main spool
2.	Pressure reduction valve for pilot oil supply	12.	LS pressure limiting valve
3.	Pressure gauge connection	13.	Shock and suction valve, PVLP
4.	Plug, open centre	14.	Pressure compensator
5.	Oriﬁce, closed centre	15.	LS connection, port A
6.	Pressure adjustment spool	16.	LS connection, port B
7.	Plug, closed centre	17.	Suction valve, PVLA
8.	LS connection	18.	Load drop check valve
9.	LS signal	19.	Pilot oil supply for PVE
10.	Shuttle valve	20.	Max. oil flow adjustment screws for
			ports A and B

PVPC plug for external pilot oil supply

PVPC with check valve for open center PVP

PVPC, with check valve, is used in systems where it is necessary to operate the PVG 32 valve by means of the electrical remote control without pump flow. When the external solenoid valve is opened, oil from

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PVG 32 Proportional Valve Group

Operation

the pressure side of the cylinder is fed via the PVPC through the pressure reducing valve to act as the pilot supply for the electrical actuators.

This means that a load can be lowered by means of the remote control lever without starting the pump. The built-in check valve prevents the oil from flowing via the pressure adjustment spool to tank.

With the pump functioning normally, the external solenoid valve is closed to ensure that the load is not lowered due to the pilot supply oil flow requirement of approximately

1 l/min [0.26 US gal/min].

With closed center PVP, the external pilot oil supply can be connected to the pressure gauge connection without the use of a PVPC plug.

Oil

Flow

Direction

PVPC without check valve for open center PVP

PVPC, without check valve, is used in systems where it is necessary to supply the PVG 32 valve with oil from a manually operated emergency pump without directing oil flow to the pilot oil supply (oil consumption about 1 l/min) [0.25 US gal/min].

When the main pump is working normally, the oil is directed through the PVPC plug through the pressure reduction valve to the electrical actuators.

When the main pump flow fails, the external shuttle valve ensures that the oil flow from the manually operated emergency pump is used to pilot open the over center valve and lower the load. The load can only be lowered using the mechanical operating lever of the PVG 32 valve.

With closed center PVP, the external pilot oil supply can be connected to the pressure gauge connection without the use of a PVPC plug.

Oil

Flow

Direction

For specifications on PVG 32 valves, refer to PVG 32 Technical Information Manual 520L0344.

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PVG 32 Proportional Valve Group

Operation

Friction detent

PVMR Friction detent

The friction detent PVMR allows the directional spool to be held in any position, resulting in infinitely variable, pressure compensated flow. The spool position will be held indefinitely without the necessity of holding the mechanical lever.

PVMR should only be used together with PVB basic modules with pressure compensator.

PVMF Mechanical float position lock

This allows the float spool to be held in the float position after release of the mechanical handle.

PVMF

P A F (Standard assembly)

P B F (Optional assembly)

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Operation

PVMF

P B F (Standard assembly)

P A F (Optional assembly)

PVBS, main spools for flow control (standard)

When using standard flow control spools, the pump pressure is determined by the highest load pressure. This is done either via the pressure adjustment spool in open center PVP (fixed displacement pumps) or via the pump regulator (variable displacement pumps).

In this way the pump pressure will always correspond to the load pressure plus the stand-by pressure of the pressure adjustment spool or the pump regulator.

This will normally give optimum and stable adjustment of the oil flow.

PVBS, main spools for flow control (with linear characteristics)

PVBS main spools with linear characteristic have less dead band than standard spools and a completely proportional ratio between control signal and oil flow in the range beyond the dead band.

W Warning

PVBS with linear characteristic must never be used together with PVEM electrical actuators.

The interaction between the small dead band of the spools and the hysteresis of the PVEM actuator of 20% involves a risk of building up a LS pressure in neutral position.

PVBS, main spools for pressure control

In a few systems load sensing pump pressure may result in unstable adjustment of the oil flow and a tendency towards system hunting. This may be the case with working functions that have a large moment of inertia or over-center valves. In such systems main spools for pressure control can be advantageous. The spools are designed in such a way that the pump pressure is controlled by the spool travel. The main spool must be displaced until the pump pressure just exceeds the load pressure before the working function is applied.

If the main spool is held in this position, the pump pressure will remain constant – even if the load pressure changes – giving a stable system.

The use of pressure control spools, however, also means that:

•the oil flow is load dependent

•the dead band is load dependent

•the pump pressure can exceed the load pressure by more than is usual.

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PVG 32 Proportional Valve Group

Operation

Due to these factors use pressure control spools only when you know for certain that problems with stability will arise – or already have arisen.

Use LSA/B when pressure stability is an issue.

PVPX Electrical LS unloading valve

PVPX is a solenoid LS unloading valve. PVPX is fitted into the pump side module enabling a connection to be made between the LS and the tank lines. Thus the LS signal can be relieved to tank by means of an electric signal.

For a PVP pump side module in open center version the relief to tank of the LS signal means that the pressure in the system is reduced to the sum of the tank port pressure plus the neutral flow pressure for the pump side module.

For a PVP pump side module in closed center version, relief to tank of the LS signal occurs when the pressure is reduced by the sum of the tank port pressure for the pump side module plus the stand-by pressure of the pump.

C Caution

Protect yourself from injury. Use proper safety equipment, including safety glasses, at all times.

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PVG 32 Proportional Valve Group

System Troubleshooting

Overview

W Warning

This troubleshooting guide for the PVG valve assemblies does not cover valves that have been altered from original valve build specifications

This section provides general steps to follow if undesirable system conditions are observed. Follow the steps listed until the problem is solved. Some of the items will be system specific. Always observe the safety precautions listed in the Introduction section, and related to your specific equipment.

Confirm that valve is built properly according to the specification sheet.

If necessary, install a lever to the valve to verify proper mechanical function.

Refer to PVG 32 Technical Information Manual 520L0344 for valve configuration information. Refer to PVG 32 Parts Manual 11006794 for part numbers.

Troubleshooting a PVG valve

THINK - before troubleshooting a problem.

Every fault location process should follow a logical and systematic order. It is wisest to start at the beginning:

•Is the oil level correct when the pump is operating?

•Is the condition of oil and filters acceptable?

•Are pressure, flow, and flow direction as specified?

•Is the oil temperature too high or too low (oil viscosity)?

•Are there any unusual vibrations or noise (cavitation)?

If the driver of the vehicle is available, ask him:

•What type of fault it is and how it affects the system?

•How long he has he felt that something has been wrong?

•If he has “fiddled” with the components?

•If he has any hydraulic and electrical diagrams available?

Diagrams are often found in the instructions included with vehicles/machines.

Unfortunately they are often so technical that they are not of much use in a fault location situation. However; the diagram usually shows the order of, and the connections between, the individual components.

When a defective component is identified, clean the component and its surroundings before removal. Remove loose paint from pipes and fittings.

Cover all holes, hoses and pipe ends with plugs or seal with, for example, plastic bags after removal to avoid the entry of dirt during repairs.

Never disassemble hydraulic components outside.

Perform repairs in a workshop on a clean workbench (covered with clean cloth or newspaper). Make sure that a Danfoss service manual for with the product is handy.

Follow the instructions word for word during disassembly and assembly.

If these instructions are not followed closely the system may not operate correctly after repairs are completed.

Note that in some cases special tools are necessary for assembling the product. Our service manuals give full guidance on use of special tools.

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