Danfoss S90 Service guide

Service Manual

Series 90 Pumps

www.danfoss.com

Service Manual

Series 90 Pumps

Revision history	Table of revisions
	Date	Changed	Rev
	February 2020	Added HCEDC information and changed document number from 520L0818	0203
	August 2015	edits to Aux Pad minor repair	0102
	December 2014	Danfoss layout	BA
	June 2012	minor edits	AD
	December 2011	minor edits	AC
	April 2008	page 70 correction to bolt torques	AB
	October 2007	First printing	AA

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Service Manual
Series 90 Pumps
Contents
Introduction
Overview..............................................................................................................................................................................................	5
Warranty..............................................................................................................................................................................................	5
General instructions........................................................................................................................................................................	5
Remove the unit..........................................................................................................................................................................	5
Replace all O-rings and gaskets.............................................................................................................................................	5
Safety Precautions............................................................................................................................................................................	6
Unintended Machine Movement..........................................................................................................................................	6
Flammable Cleaning Solvents................................................................................................................................................	6
Fluid Under Pressure..................................................................................................................................................................	6
Personal Safety.............................................................................................................................................................................	6
Symbols used in Danfoss literature............................................................................................................................................	7
Design...................................................................................................................................................................................................	7
The system circuit.............................................................................................................................................................................	8
The basic closed circuit.............................................................................................................................................................	8
Case drain and heat exchanger..............................................................................................................................................	9
Operation
S90 charge pump operation......................................................................................................................................................	11
S90 charge relief valve operation.............................................................................................................................................	11
S90 multi-function valve operation.........................................................................................................................................	11
S90 pressure limiter/high pressure relief valve operation..............................................................................................	12
S90 system check valve operation...........................................................................................................................................	12
S90 bypass valves operation......................................................................................................................................................	12
S90 speed sensor operation.......................................................................................................................................................	13
S90 filtration options....................................................................................................................................................................	13
S90 pressure override (POR) operation..................................................................................................................................	13
S90 MDC operation.......................................................................................................................................................................	14
S90 non-linear MDC operation.................................................................................................................................................	14
S90 MDC solenoid override valve operation........................................................................................................................	14
Neutral start switch (NSS) for MDC..........................................................................................................................................	14
S90 HDC operation........................................................................................................................................................................	14
S90 EDC operation.........................................................................................................................................................................	15
S90 Automotive control (FBA II B) operation.......................................................................................................................	15
S90 3-Position (FNR) electric control operation..................................................................................................................	15
High Current Electrical Displacement Control (HCEDC)..................................................................................................	15
HCEDC Principle........................................................................................................................................................................	15
HCEDC Operation.....................................................................................................................................................................	16
Manual OverRide (MOR)..............................................................................................................................................................	16
Operating parameters
S90 Input speed..............................................................................................................................................................................	18
S90 system pressure......................................................................................................................................................................	18
S90 charge pressure......................................................................................................................................................................	18
S90 charge inlet pressure............................................................................................................................................................	19
Case pressure...................................................................................................................................................................................	19
Temperature and viscosity.........................................................................................................................................................	19
Fluid and filter recommendations...........................................................................................................................................	19
Technical specifications
Overview...........................................................................................................................................................................................	21
Features and options....................................................................................................................................................................	21
Operating parameters..................................................................................................................................................................	21
Fluid specifications........................................................................................................................................................................	21
Initial start-up procedure
General ..............................................................................................................................................................................................	23
Start-up procedure........................................................................................................................................................................	23
Pressure measurement
Required tools.................................................................................................................................................................................	24

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Series 90 Pumps
Contents
Port locations and gauge installation.....................................................................................................................................		24
Troubleshooting
Overview...........................................................................................................................................................................................		27
Neutral difficult or impossible to find.....................................................................................................................................		27
System operating hot...................................................................................................................................................................		27
Transmission operates normally in one direction only....................................................................................................		27
System will not operate in either direction..........................................................................................................................		28
Low motor output torque...........................................................................................................................................................		28
Improper motor output speed..................................................................................................................................................		28
System noise or vibration...........................................................................................................................................................		29
System response is sluggish......................................................................................................................................................		29
Adjustments
Standard procedures, inspections, and adjustments.......................................................................................................		30
Adjustments.....................................................................................................................................................................................		30
Charge pressure relief valve adjustment...............................................................................................................................		30
Multi-function valve pressure adjustment............................................................................................................................		32
Engaging the bypass function..................................................................................................................................................		33
Pressure override (POR) valve pressure adjustment (option for 180 frame size)....................................................		34
Displacement limiter adjustment............................................................................................................................................		35
Control Neutral Adjustment.......................................................................................................................................................		36
Verify neutral setting...............................................................................................................................................................		37
Servo Adjustment Side M4....................................................................................................................................................		37
Standard manual displacement control (MDC) adjustment..........................................................................................		38
Non-linear manual displacement control (MDC)...............................................................................................................		38
MDC Neutral start switch (NSS) adjustments.......................................................................................................................		39
Checking switch continuity........................................................................................................................................................		42
Hydraulic displacement control (HDC) and electric displacement control (EDC) adjustment..........................		43
Speed sensor adjustment...........................................................................................................................................................		44
Minor repair
Standard procedures....................................................................................................................................................................		46
Shaft seal and shaft replacement.............................................................................................................................................		46
Multi-function valve cartridges.................................................................................................................................................		49
Multi-function valve cartridges - pre 1988............................................................................................................................		51
Pressure override valve (option for 180 frame size)..........................................................................................................		53
Charge pressure relief valve.......................................................................................................................................................		53
Adding an Auxiliary pad to a pump previously without one.........................................................................................		55
Auxiliary pad....................................................................................................................................................................................		56
Charge pump...................................................................................................................................................................................		57
Integral charge pressure filter replacement.........................................................................................................................		61
Pump control cover plate...........................................................................................................................................................		63
Displacement control orifices....................................................................................................................................................		63
Displacement control orifice check valve.............................................................................................................................		64
Displacement control adapter plate (early production 130 pumps only).................................................................		64
Manual displacement control (MDC)......................................................................................................................................		65
Solenoid override valve for MDC..............................................................................................................................................		66
Solenoid override valve for MDC with pressure released brake...................................................................................		67
Hydraulic and electric displacement controls.....................................................................................................................		68
Pressure control pilot (PCP) for electric displacement control (EDC)..........................................................................		70
3-Position (FNR) electric control...............................................................................................................................................		70
Displacement control filter screens.........................................................................................................................................		72
Speed sensor...................................................................................................................................................................................		72
Control Module Repair.................................................................................................................................................................		73
Replace control solenoids/actuator housing.......................................................................................................................		75
Torque chart
Fastener size and torque chart..................................................................................................................................................		76
Plug size and torque chart..........................................................................................................................................................		77
Fasteners and plugs......................................................................................................................................................................		78
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Service Manual

Series 90 Pumps

Introduction

Overview

This manual includes information for the installation, maintenance, and minor repair of Series 90 axial piston closed circuit pumps. It includes a description of the unit and its individual components, troubleshooting information, and minor repair procedures.

Performing minor repairs requires you remove the unit from the vehicle/machine. Thoroughly clean the unit before beginning maintenance or repair activities. Since dirt and contamination are the greatest enemies of any type of hydraulic equipment, follow cleanliness requirements strictly. This is especially important when changing the system filter and when removing hoses or plumbing.

A worldwide network of Danfoss Global Service Partners (GSPs) is available for major repairs. Danfoss trains GSPs and certifies their facilities on a regular basis. You can locate your nearest ASC using the distributor locator at www.DanfossPower Solutions.com. Click on the Sales and Service link.

Warranty

Performing installation, maintenance, and minor repairs according to the procedures in this manual will not affect your warranty. Major repairs requiring the removal of a unit’s rear or side cover voids the warranty unless done by a Danfoss Authorized Service Center.

General instructions

Follow these general procedures when repairing this product.

Remove the unit

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

Keep it clean

Cleanliness is a primary means of assuring satisfactory pump life, on either new or repaired units. Clean the outside of the pump thoroughly before disassembly. Take care to avoid contamination of the system ports. Cleaning parts by using a clean solvent wash and air drying is usually adequate.

As with any precision equipment, 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 pump with a protective layer of plastic.

Replace all O-rings and gaskets

Danfoss recommends that you replace all O-rings, seals and gaskets. 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. It will be necessary to secure the pump while removing and torquing end covers, controls, and valves.

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Series 90 Pumps

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

Unintended movement of the machine or mechanism may cause injury to the technician or bystanders. Secure the machine or disable/disconnect the mechanism while servicing to protect against unintended movement.

Flammable Cleaning Solvents

Some cleaning solvents are flammable.

Do not use cleaning solvents in an area where a source of ignition may be present to avoid possible fire.

Fluid Under Pressure

Escaping hydraulic fluid under pressure can have sufficient force to penetrate your skin causing serious injury and/or infection. This fluid may also be hot enough to cause burns.

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. Use caution when dealing with hydraulic fluid under pressure. Seek medical attention immediately if you are cut by hydraulic fluid.

Personal Safety

Protect yourself from injury whenever servicing a hydraulic system.

Use proper safety equipment, including safety glasses, at all times.

Hazardous Material

Hydraulic fluid contains hazardous material.

Avoid prolonged contact with hydraulic fluid. Always dispose of used hydraulic fluid according to state, and federal environmental regulations.

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Series 90 Pumps

Introduction

Symbols used in Danfoss literature

WARNING may result in injury

CAUTION may result in damage to product or property

Reusable part

Non-reusable part, use a new part

Non-removable item

Option - either part may exist

Superseded - parts are not interchangeable Measurement required

Flatness specification

Parallelism specification

External hex head

Internal hex head

Torx head

O-ring boss port

Tip, helpful suggestion

Lubricate with hydraulic fluid

Apply grease / petroleum jelly

Apply locking compound

Inspect for wear or damage

Clean area or part

Be careful not to scratch or damage Note correct orientation

Mark orientation for reinstallation

Torque specification

Press in - press fit

Pull out with tool – press fit

Cover splines with installation sleeve

Pressure measurement/gauge location or specification

The symbols above appear in the illustrations and text of this manual. They are intended to communicate helpful information at the point where it is most useful to the reader. In most instances, the appearance of the symbol itself denotes its meaning. The legend above defines each symbol and explains its purpose.

Design

Danfoss Series 90 closed circuit piston pumps convert input torque into hydraulic power. The input shaft transmits rotational force to the cylinder block. Bearings support the input shaft at the front and rear of the pump. The shaft is splined into the cylinder block. A lip-seal at the front end of the pump prevents leakage where the shaft exits the pump housing. The spinning cylinder block contains nine reciprocating pistons. A ball joint at one end connects each piston to a brass slipper. Fixed-clearance hold-down brackets keep the slippers in contact with the swashplate. The reciprocating movement of the pistons occurs as the slippers slide against the inclined swashplate during rotation. The valve plate connects one half of the cylinder block to low pressure and the other half to high pressure. As each piston cycles in and out of its bore, fluid is drawn from the inlet and displaced to the outlet thereby imparting hydraulic power into the system. A small amount of fluid flows from the cylinder block/valve plate and slipper/ swashplate interfaces for lubrication and cooling. Case drain ports return this fluid to the reservoir.

The angle of the swashplate controls the volume of fluid displaced into the system. The servo piston forces the swashplate into an inclined position. The pump control, acting on input from the operator, by modulating pressure balance across the servo piston, sets displacement in the system circuit.

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Series 90 Pumps

Introduction

Cross section

	Piston
	Slipper
Slider block	Displacement control
	Servo arm
	Servo piston

			Feedback linkage
			Cradle bearing
Bushing
Cylinder block			Roller bearing
			Shaft
Valve plate			seal
Rear
bushing
			Input shaft
Charge pump	Swashplate	Cradle guide	P106 648E

The system circuit

The basic closed circuit

Hydraulic lines connect the main ports of the pump to the main ports of the motor. Fluid flows in either direction from the pump to the motor then back to the pump in this closed circuit. Either of the hydraulic lines can be under high pressure. In pumping mode the position of the pump swashplate determines which line is high pressure as well as the direction of fluid flow.

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Series 90 Pumps

Introduction

Basic closed circuit diagram

Reservoir

Input

PV

MF

Output

Flow (Bi-directional)

Case drain line

P104 120E

Case drain and heat exchanger

The pump and motor require case drain lines to remove hot fluid from the system. The topmost port drains the motor to ensure the case remains full of fluid. Fluid routes through the lower drain port on the pump and out the topmost port to the reservoir. A heat exchanger, with a bypass valve, cools the case drain fluid before it returns to the reservoir.

System circuit diagram

Control handle	Displacement control valve
		Heat exchanger bypass valve
		Orificed heck	Reservoi
				Vacuum gauge
		valve
					valve	P102 000
Reversiblevariable	Servo control cylinder				Fixed displacement motor
displacement pump
			To
			pump
		Servo	case
		pressure
		relief valves
		Charge pump
Input shaft		Multi-function valve				Output shaft
				Motor swashplate
Pump swashplate	Servo control cylinder			Loop flushing valve
		Pump			Motor
Working loop (high pressure)		Working loop (low pressur e)	Suction line	Control fluid	Case drain fluid

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Series 90 Pumps

Introduction

Pump schematic

		M3
X5
		A
		M1
M5
M4
		M2
		B
L1	S	L2
		P104 126E

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Series 90 Pumps

Operation

S90 charge pump operation

The charge pump is necessary to supply cool fluid to the system, to maintain positive pressure in the main system loop, to provide pressure to operate the control system, and to make up for internal leakage. Charge pressure must be at its specified pressure under all conditions to prevent damage to the transmission.

The charge pump is a fixed-displacement, gerotor type pump driven off the main pump shaft. The charge relief valve limits charge pressure.

Pump charge system

Case
drain		Charge relief valve
line
		System
		check
		valves
Input	PV	PF
		Charge
		pump
	Inlet filter
	Tank	P104 121E

S90 charge relief valve operation

The charge relief valve on the pump maintains charge pressure at a designated level. A direct-acting poppet valve relieves fluid when charge pressure reaches a certain level. This level is nominally set referencing case pressure at 1500 rpm. This nominal setting assumes the pump is in neutral (zero flow). In forward or reverse, charge pressure is lower. The pump model code specifies the charge relief valve setting.

Charge pressure relief valve

Charge pressure

P106 157E

S90 multi-function valve operation

The multi-function valve incorporates the system check valve, the pressure limiter valve, the high pressure relief valve, and the bypass valve in a replaceable cartridge. These functions are described separately. There are two multi-function valve cartridges in each Series 90 pump to handle functions in either direction. See corresponding sections for adjustments and repairs.

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Series 90 Pumps

Operation

Multi-function valve

	Pressure limiter housing		High pressure		Check valve
			relief / check
	Pressure limiter		valve poppet		poppet
	lock nut
	Pressure limiter
	adjustment screw
	Bypass			Bypass
	actuator	Pressure limiter
					P104 122E
		valve poppet

Some multi-function valves do not include a pressure limiter valve

S90 pressure limiter/high pressure relief valve operation

Series 90 pumps have a sequenced pressure limiting system and high pressure relief valves. When the system pressure reaches the preset, the pressure limiter system rapidly de-strokes the pump to limit system pressure. For unusually rapid load application, the high pressure relief valve immediately limits system pressure by cross-porting system flow. The pressure limiter valve acts as the pilot for the high pressure relief valve spool. The high pressure relief valve is sequenced to operate at approximately 35 bar (500 psi) above the level that initiates the pressure limiter valve.

Circuit diagram showing pressure control mechanism

	To control
	Multi-function valve
Servo piston	Bypass
Port "A"	adjustment
	Pres.
	Valve
Port "B"
Servo piston	Charge
	pressure
	relief valve

Multi-function valve

P104 123E

For some applications, such as dual path vehicles, the pressure limiter function may be defeated so that only the high pressure relief valve function remains.

S90 system check valve operation

The system check valves allow pressurized flow from the charge pump to enter the low pressure side of the loop. This is needed as the pump generally loses system pressure due to lubrication/cooling flow and other factors. Since the pump operates in either direction, the system uses two check valves to direct the charge supply into the low pressure lines. The system check valves are part of the multi-function valve assembly.

S90 bypass valves operation

You can operate the bypass valves to move the vehicle or mechanical function when the pump is not running. Manually resetting the valve position opens the valve. The bypass valves are built into the multifunction valves.

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Series 90 Pumps

Operation

S90 speed sensor operation

An optional speed sensor can provide unit speed information. The sensor reads a magnetic ring on the unit’s cylinder block. See the corresponding section to locate, install, and adjust the speed sensor.

S90 filtration options

Series 90 pumps may have either suction or charge pressure filtration to filter the fluid entering the circuit.

The suction filter is in the circuit between the reservoir and the inlet to the charge pump, as shown below. The use of a filter contamination monitor is recommended.

Suction filtration

Hydraulic fluid reservoir	Manometer

Charge pump

Filter

To low	Adjustable
	charge pressure relief valve
loop and	To pump case	P102 003E
control

S90 suction filtration operation

The suction filter is in the circuit between the reservoir and the inlet to the charge pump, as shown above. The use of a filter contamination monitor is recommended.

S90 charge pressure filtration operation

Filtration options R, T, P, and L are pressure filters mounted on the pump or remotely for ease of servicing.

You will typically find a 100-125 µm mesh screen, in the reservoir or the charge inlet. This system requires a filter capable of withstanding charge pressure (reference to atmosphere - add case pressure).

Charge pressure filtration

	Screen
Hydraulic fluid reservoir		Adjustable
		charge pressure
		relief valve
	Charge pump
To low	Filter	To pump case

	pressure
	side and	P102 004E
	control

S90 pressure override (POR) operation

The pressure override valve is only available for the 180cc frame size only.

The Pressure OverRide valve (POR) modulates control pressure to maintain a pump displacement which produces a system pressure level less than or equal to the POR setting. For unusually rapid load application, the high pressure relief valve function of the multi-function valves is available to also limit the pressure level.

The pressure override consists of a three-way normally open valve which operates in series with the pump displacement control. Control supply pressure normally ports through the POR valve to the

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Service Manual

Series 90 Pumps

Operation

displacement control valve. If the system demands a pressure above the override setting, the POR valve overrides the control by reducing the pressure to the displacement control. As the control pressure reduces, the internal forces rotating the swashplate overcome the force of the servo pistons and decreases the pump’s displacement.

POR-Valve (180 frame size only)

	To control
		Multi-function valve
	Pressure	Bypass
	override control valve
		adjustment
	Port "A"
	Shuttle
	valve
	Port "B"

Multi-function valve

Charge pressure relief valve

P104 124E

S90 MDC operation

The manual displacement control converts a mechanical input signal to a hydraulic signal using a spring centered four-way servo valve. This valve ports hydraulic pressure to either side of a dual-acting servo piston. The servo piston rotates the cradle swashplate through an angular rotation of ±17°, varying the pump’s displacement from full in one direction to full in the opposite direction. The angular position of the pump swashplate is proportional to the rotation of the control input shaft.

S90 non-linear MDC operation

The non-linear manual displacement control operates in the same manner except that it is designed so the change in the angular position of the pump swashplate progressively increases as the control input shaft is rotated toward its maximum displacement position.

S90 MDC solenoid override valve operation

A solenoid override valve option is available for the MDC. This safety feature returns the swashplate to zero displacement. It is available in normally open (activate to allow) or normally closed (activate to disallow) options.

Neutral start switch (NSS) for MDC

The neutral start switch is an optional feature available with the MDC. When connected properly with the vehicle’s electrical system, the neutral start switch ensures that the prime mover can start only when the control is in neutral position.

S90 HDC operation

The hydraulic displacement control uses a hydraulic input signal to operate a spring-centered four-way servo valve. This valve ports hydraulic pressure to either side of a dual-acting servo piston. The servo piston rotates the cradle swashplate through an angular rotation of ±17°, thus varying the pump’s displacement from full displacement in one direction to full displacement in the opposite direction. The angular position of the pump swashplate is proportional to input pressure.

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Operation

S90 EDC operation

The electric displacement control uses a Pressure Control Pilot (PCP) valve to modulate pressure balance across the spring-centered four-way servo valve. The PCP valve converts a DC electrical input signal to a hydraulic signal. The servo valve ports hydraulic pressure to either side of a dual-acting servo piston. The servo piston rotates the swashplate through an angular rotation of ±17°, varying the pump’s displacement. The angular position of the swashplate is proportional to the EDC input.

S90 Automotive control (FBA II B) operation

The automotive control allows the operator to drive a vehicle similar to an automobile with an automatic transmission. The automotive control includes a three-position electric control to provide direction control.

S90 3-Position (FNR) electric control operation

This control utilizes a 12 or 24 Vdc electrically operated spool valve to port pressure to either side of the pump servo piston. Energizing one of the solenoids causes the pump to go to its maximum displacement in the corresponding direction. All functions of the three-position (FNR) electric control are preset at the factory

High Current Electrical Displacement Control (HCEDC)

HCEDC Principle

An HCEDC is a displacement (flow) control. Pump swashplate position is proportional to the input command and therefore vehicle or load speed (excluding influence of efficiency), is dependent only on the prime mover speed or motor displacement.

P003 191

The High Current Electrical Displacement Control (HCEDC) consists of a pair of proportional solenoids on each side of a three-position, four-way porting spool. The proportional solenoid applies a force input to the spool, which ports hydraulic pressure to either side of a double acting servo piston. Differential pressure across the servo piston rotates the swashplate, changing the pump‘s displacement from full displacement in one direction to full displacement in the opposite direction. Under some circumstances, such as contamination, the control spool could stick and cause the pump to stay at some displacement.

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Series 90 Pumps

Operation

HCEDC schematic

	M14
C2		C1
F00B	F00A	T	P

Feedback from
Swash plate	P003 478E

A serviceable 125 μm screen is located in the supply line immediately before the control porting spool.

HCEDC Operation

S90 HCEDC’s are current driven controls requiring a Pulse Width Modulated (PWM) signal. Pulse width modulation allows more precise control of current to the solenoids. The PWM signal causes the solenoid pin to push against the porting spool, which pressurizes one end of the servo piston, while draining the other. Pressure differential across the servo piston moves the swashplate.

A swashplate feedback link, opposing control links, and a linear spring provide swashplate position force feedback to the solenoid. The control system reaches equilibrium when the position of the swashplate spring feedback force exactly balances the input command solenoid force from the operator. As hydraulic pressures in the operating loop change with load, the control assembly and servo/swashplate system work constantly to maintain the commanded position of the swashplate.

The HCEDC incorporates a positive neutral deadband as a result of the control spool porting, pre-loads from the servo piston assembly, and the linear control spring. Once the neutral threshold current is reached, the swashplate is positioned directly proportional to the control current. To minimize the effect of the control neutral deadband, we recommend the transmission controller or operator input device incorporate a jump up current to offset a portion of the neutral deadband.

The neutral position of the control spool does provide a positive pre-load pressure to each end of the servo piston assembly.

When the control input signal is either lost or removed, or if there is a loss of charge pressure, the springloaded servo piston will automatically return the pump to the neutral position.

Manual OverRide (MOR)

All high current controls are standard with Manual Over Ride (MOR), used for temporary actuation of the control to aid in diagnostics.

Unintended MOR operation will cause the pump to go into stroke. The vehicle or device must always be in a safe condition (i.e. vehicle lifted off the ground) when using the MOR function. The MOR plunger has a 4 mm diameter and must be manually depressed to be engaged. Depressing the plunger mechanically moves the control spool which allows the pump to go on stroke. The MOR should be engaged anticipating a full stroke response from the pump.

W Warning

An O-ring seal is used to seal the MOR plunger where initial actuation of the function will require a force of 45 N to engage the plunger. Additional actuations typically require less force to engage the MOR plunger. Proportional control of the pump using the MOR should not be expected.

Refer to the control flow table for the relationship of solenoid to direction of flow.

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Series 90 Pumps

Operation

P003 204

MOR Schematic diagram (EDC shown)

C2

C1

P108758

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Series 90 Pumps

Operating parameters

S90 Input speed

There are three acceptable input speeds that the S90 pump should operate in. The input speeds are Minimum speed, Continuous speed and Maximum speed.

Minimum speed is the lowest input speed recommended during engine idle condition. Operating below minimum speed limits the pump’s ability to maintain adequate flow for lubrication and power transmission.

Continuous speed is the highest input speed recommended at full power condition. Operating at or below this speed should yield satisfactory product life.

Maximum speed is the highest operating speed permitted. Exceeding maximum speed reduces product life and can cause loss of hydrostatic power and braking capacity. Never exceed the maximum speed limit under any operating conditions.

When determining speed limits for a particular application see Danfoss publication BLN-9884 Pressure and speed limits.

W Warning

Unintended vehicle or machine movement hazard

Exceeding maximum speed may cause a loss of hydrostatic drive line power and 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.

S90 system pressure

System pressure is the differential pressure between system ports A and B. It is the dominant operating variable affecting hydraulic unit life. High system pressure, which results from high load, reduces expected life.

Continuous pressure is the average, regularly occurring operating pressure. Operating at or below this pressure should yield satisfactory product life.

Maximum pressure is the highest intermittent pressure allowed. Maximum machine load should never exceed this pressure. For all applications, the load should move below this pressure.

All pressure limits are differential pressures referenced to low loop (charge) pressure. Subtract low loop pressure from gauge readings to compute the differential.

System pressure must remain at or below continuous pressure during normal operation to achieve expected life.

S90 charge pressure

An internal charge relief valve regulates charge pressure. The charge pump supplies the control with pressure to operate the swashplate and to maintain a minimum pressure in the low side of the transmission loop.

Minimum charge pressure is the lowest pressure allowed to maintain a safe working condition in the low side of the loop. Minimum control pressure requirements are a function of speed, pressure, and swashplate angle, and may be higher than the minimum charge pressure shown in the operating parameters table.

Maximum charge pressure is the highest charge pressure allowed by the charge relief adjustment, and provides normal component life. You can use elevated charge pressure as a secondary means to reduce the swashplate response time.

The charge pressure setting in the order code is the set pressure of the charge relief valve with the pump in neutral, operating at 1800 min-1 (rpm), and with a fluid viscosity of 32 mm2/sec (150 SUS). The charge pressure setting is referenced to case pressure. Charge pressure is the differential pressure above case pressure.

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Series 90 Pumps

Operating parameters

S90 charge inlet pressure

At normal operating temperature charge inlet pressure must not fall below rated charge inlet pressure.

Minimum charge inlet pressure is only allowed at cold start conditions. In some applications it may be necessary to warm up the fluid by running the engine at limited speed until the system fluid temperature reaches an acceptable level.

Case pressure

Under normal operating conditions, do not exceed the rated case pressure. During cold start, maintain the case pressure below maximum intermittent case pressure.

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.

Temperature and viscosity

Temperature

The high temperature limits apply at the hottest point in the transmission loop, which is normally the motor case drain. Maintain system temperature below the quoted rated temperature.

Never exceed the maximum intermittent temperature.

Cold oil will generally not affect the durability of the transmission components, but it may affect the ability of oil to flow and transmit power; therefore temperatures should remain 16 °C [30 °F] above the pour point of the hydraulic fluid.

The minimum temperature relates to the physical properties of component materials.Size heat exchangers to keep the fluid within these limits. Test heat exchangers to verify that these temperature limits are not exceeded.

Viscosity

For maximum efficiency and bearing life, ensure the fluid viscosity remains in the recommended range.

Minimum viscosity should be encountered only during brief occasions of maximum ambient temperature and severe duty cycle operation.

Maximum viscosity should be encountered only at cold start.

Fluid and filter recommendations

To ensure optimum pump life, perform regular maintenance of the fluid and filter. Contaminated fluid is the main cause of unit failure. Maintain fluid cleanliness when servicing.

Check the reservoir daily for proper fluid level, the presence of water, and rancid fluid odor. Fluid contaminated by water may appear cloudy or milky or free water may settle in the bottom of the reservoir. Rancid odor indicates the fluid has been exposed to excessive heat. Change the fluid immediately if these conditions occur. Correct the problem immediately.

Inspect vehicle for leaks daily.

Change the fluid and filter per the vehicle/machine manufacturer’s recommendations or at the intervals shown in the table. Change fluid after first 500 hours.

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Operating parameters

Fluid and filter change interval

Reservoir type	Max oil change interval
Sealed	2000 hours
Breather	500 hours

C Caution

High temperatures and pressures result in accelerated fluid aging. Change fluid more frequently if operating under extreme conditions.

Change the fluid more frequently if it becomes contaminated with foreign matter (dirt, water, grease, etc.) or if the fluid is subjected to temperature levels greater than the recommended maximum.

Dispose of used hydraulic fluid properly. Never reuse hydraulic fluid.

Change filters whenever the fluid is changed or when the filter indicator indicates a filter change. Replace all fluid lost during filter change.

For detailed filtration information, see Danfoss publication 520L0463 Fluids and Filtration. For information on biodegradable fluids see Danfoss publication 520L0465 Biodegradable Hydraulic Fluids.

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Technical specifications

Overview

	Specifications and operating parameters for pumps appear here for reference.
Features and options
Model		Series 90 Pumps
Mount		SAE B, SAE C and E (SAE J 744)
Pump type		Axial piston type
Rotation		Bidirectional
Installation position		Discretionary: Housing must always be filled with hydraulic fluid. Do not install with control on bottom.
Input shafts		Splined
Control options		MDC (with options), EDC, HDC, FNR

Operating parameters

Parameter		Unit	Pressure
System pressure	Rated	bar	420 [6000]
		[psi]
	Maximum		480 [7000]
	Minimum low loop		10 [150]
Charge pressure	Minimum	bar	10 [150]
		[psi]
	Maximum		35 [508]
Charge inlet pressure	Rated	bar (absolute)	0.7	[9]
		[in Hg vacuum]
	Minimum (cold start)		0.2	[24]
Case pressure	Rated	bar	3.0	[40]
		[psi]
	Maximum		5.0	[75]

Parameter	Unit	Frame size
		042	055	075	100	130	180	250
Displacement	cm³	42	55	75	100	130	180	250
(maximum)	[in³]	[2.56]	[3.35]	[4.57]	[6.10]	[7.93]	[10.98]	[15.25]
Minimum speed	min-1 (rpm)	500	500	500	500	500	500	500
Rated speed	min-1 (rpm)	4200	3900	3600	3300	3100	2600	2300
Maximum speed	min-1 (rpm)	4600	4250	3950	3650	3400	2850	2500
Maximum attainable speed at	min-1 (rpm)	5000	4700	4300	4000	3700	3150	3750
maximum displacement
Theoretical torque at maximum	N•m/bar	0.67	0.88	1.19	1.59	2.07	2.87	3.97
displacement	[lbf•in/1000	[380]	[530]	[730]	[870]	[1260]	[1750]	[2433]
	psi]
Weight (base unit only)	kg	34	40	49	68	88	136	154
	[lb]	[75]	[88]	[108]	[150]	[195]	[300]	[340]

Fluid specifications

Ratings and data are based on operation with premium petroleum-based hydraulic fluids containing oxidation and foam inhibitors.

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Technical specifications

Parameter		Unit	Minimum	Continuous	Maximum
Viscosity		mm2/sec (cSt)	7	12-60	1600
		[SUS]	[47]	[66-278]	[7500]
Temperature		°C [°F]	-40 [-40]	104 [220]	115 [240]
Cleanliness			ISO 4406 Class 22/18/13 or better
Filtration efficiency	suction filtration		β35-44=75 (β10≥2)
	charge filtration		β15-20=75 (β10≥10)

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Initial start-up procedure

General

Follow this procedure when starting-up a new pump installation or when restarting an installation in which the pump was removed.

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.

Prior to installing the pump, inspect for shipping damage.

Start-up procedure

1.Ensure that the hydraulic fluid and system components (reservoir, hoses, valves, fittings, and heat exchanger) are clean and free of contamination.

2.Install new system filter element(s) if necessary. Check that inlet line fittings are properly tightened and there are no air leaks.

3.Install the pump. Install a 50 bar [1000 psi] gauge in the charge pressure gauge port M

4.Fill the housing by adding filtered fluid in the upper case drain port. Open the case plug in the top of the control to assist with air bleed.

5.Fill the reservoir with hydraulic fluid of the recommended type and viscosity. Use a 10-micron filler filter. Fill inlet line from reservoir to pump.

6.Disconnect the pump control input signal.

After start-up the fluid level in the reservoir may drop due to filling of the system components. Check the level in the reservoir to maintain a full fluid level throughout the start-up procedure.

C Caution

Damage to hydraulic components may occur from failure to maintain fluid supply.

7.Use a common method to disable the engine to prevent the engine from starting. Crank the starter for several seconds. Do not to exceed the engine manufacturer’s recommendation. Wait 30 seconds and then crank the engine a second time. This operation helps remove air from the system lines. Refill the reservoir to recommended full fluid level.

8.When charge pressure reaches 3.5 bar [50 psi], enable and start engine. Let the engine run for a minimum of 30 seconds at low idle to allow the air to work itself out of the system. Check for leaks at all line connections and listen for cavitation. Check for proper fluid level in reservoir.

C Caution

Air entrapment in fluid under high pressure may damage hydraulic components.

Do not run at maximum pressure until system is free of air and fluid has been thoroughly filtered.

9.When adequate charge pressure is established (as shown in model code), increase engine speed to normal operating rpm to further purge residual air from the system.

10.Shut off the engine. Connect the pump control signal. Start the engine, checking to be certain the pump remains in neutral. Run the engine at normal operating speed and carefully check for forward and reverse control operation.

11.Continue to cycle between forward and reverse for at least five minutes to bleed all air and flush system contaminants out of loop.

Normal charge pressure fluctuation may occur during forward and reverse operation.

12.Check that the reservoir is full. Remove charge pressure gauge. The pump is now ready for operation.

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Pressure measurement

Required tools

You can perform the service procedures described in this manual using common mechanic’s tools. Special tools, if required are shown. Use calibrated pressure gauges to ensure accuracy. Use snubbers to protect pressure gauges.

Port locations and gauge installation

The following sections list the ports for each type of hydraulic unit. The fitting size and recommended pressure gauge are also specified.

The following table and drawings show the port locations and gauge sizes needed.

Port information

Port identifier	Pressure obtained	Gauge size	Port size
M1, M2	System pressure	1000 bar [10 000 psi]	9/16-18
M3 (M6)	Charge pressure	50 bar [1000 psi]	9/16-18
M4, M5	Servo pressure	50 bar [1000 psi]	9/16-18
L1, L2	Case pressure	10 bar [100 psi]	030-042	7/8-14
			055-100	1-1/16-12
			130	1-5/16-12
			180-250	1-5/8-12
X1, X2	HDC/EDC control pressure	50 bar [1000 psi]	7/16-20 or 9/16-18
X3	External control pressure	50 bar [1000 psi]	9/16-18
S	Charge pump inlet	Vacuum gauge,	030-042	1-1/16-12
		Tee into inlet line
			055-075	1-5/16-12
			100-180	1-5/8-12
			250	1-1/2 SAE-split flange

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