Danfoss 51 Series User manual

MAKING MODERN LIVING POSSIBLE
Service Manual
Electrohydraulic Controls Series 51
A7, D7, D8, DA, DC, EE, EP, EQ,
ER, ES, L1, L2, L7
powersolutions.danfoss.com

Revision history Table of revisions
Date Changed Rev
July 2014 Danfoss layout BA
July 2009 First edition AA
Service Manual Series 51 Electrohydraulic Proportional Controls Service Manual
211009448 • Rev BA • July 2014

Introduction
Safety Precautions............................................................................................................................................................................5
Unintended Machine Movement..........................................................................................................................................5
Flammable Cleaning Solvents................................................................................................................................................5
Fluid Under Pressure..................................................................................................................................................................5
Personal Safety.............................................................................................................................................................................5
Hazardous Material.....................................................................................................................................................................5
Symbols used in Danfoss literature............................................................................................................................................6
Overview..............................................................................................................................................................................................6
General Instructions........................................................................................................................................................................ 7
Keep it Clean................................................................................................................................................................................. 7
Inspect for System Contamination....................................................................................................................................... 7
Replace the O-rings and Gaskets...........................................................................................................................................7
Lubricate all Moving Parts........................................................................................................................................................7
Torque Procedure....................................................................................................................................................................... 7
General Description.........................................................................................................................................................................7
Overview........................................................................................................................................................................................ 7
Multifunction Block.................................................................................................................................................................... 7
Pressure Compensating OverRide (PCOR) Option..........................................................................................................8
Brake Pressure Defeat (BPD) option..................................................................................................................................... 8
Threshold and Ramp Springs............................................................................................................................................... 10
Pressure measurements
Port Locations and Gauge Installation................................................................................................................................... 11
Adjustments
Threshold Setting...........................................................................................................................................................................12
Checking Threshold Setting................................................................................................................................................. 12
Adjusting Threshold Setting.................................................................................................................................................12
Pressure compensator Override (PCOR) setting.................................................................................................................13
PCOR Adjustment.....................................................................................................................................................................13
Checking PCOR Setting on a Test Stand.......................................................................................................................... 14
Adjusting the PCOR Setting..................................................................................................................................................14
PCOR
Optional PCOR Housing Repair.................................................................................................................................................15
Disassembly................................................................................................................................................................................15
Inspection....................................................................................................................................................................................15
Assembly......................................................................................................................................................................................15
Multifunction block
Optional Multifunction Block Repair.......................................................................................................................................17
Disassembly................................................................................................................................................................................17
Inspection....................................................................................................................................................................................18
Assembly......................................................................................................................................................................................18
A7, L1, L2, L7 Controls
Operation .........................................................................................................................................................................................19
General Description.................................................................................................................................................................19
Proportional Solenoid.............................................................................................................................................................19
Check Valve.................................................................................................................................................................................19
Schematic......................................................................................................................................................................................... 21
Repair..................................................................................................................................................................................................21
Removing Solenoid..................................................................................................................................................................21
Disassembly................................................................................................................................................................................21
Inspection....................................................................................................................................................................................23
Assembly......................................................................................................................................................................................23
Solenoid Assembly...................................................................................................................................................................23
D7, D8, DA, DC Controls
Operation..........................................................................................................................................................................................24
General Description.................................................................................................................................................................24
Service Manual Series 51 Electrohydraulic Proportional Controls Service Manual
Contents
11009448 • Rev BA • July 2014 3

Pressure-Reducing Valve....................................................................................................................................................... 24
Schematic......................................................................................................................................................................................... 25
Repair..................................................................................................................................................................................................26
Disassembly................................................................................................................................................................................26
Inspection....................................................................................................................................................................................27
Assembly......................................................................................................................................................................................27
EE Control
Operation..........................................................................................................................................................................................29
General Description.................................................................................................................................................................29
Repair..................................................................................................................................................................................................30
Disassembly................................................................................................................................................................................30
Inspection....................................................................................................................................................................................31
Assembly......................................................................................................................................................................................31
EP, EQ, ER, ES Controls
Operation..........................................................................................................................................................................................33
General Description.................................................................................................................................................................33
Schematics........................................................................................................................................................................................34
Definitions...................................................................................................................................................................................35
Repair..................................................................................................................................................................................................35
Control Housing Disassembly..............................................................................................................................................35
PCOR Disassembly....................................................................................................................................................................36
Multifunction Block Disassembly........................................................................................................................................37
Control Orifices..........................................................................................................................................................................38
Inspection....................................................................................................................................................................................39
Multifunction Block Assembly............................................................................................................................................. 39
Inspection....................................................................................................................................................................................40
PCOR Assembly......................................................................................................................................................................... 40
Control Housing Assembly....................................................................................................................................................41
Service Manual Series 51 Electrohydraulic Proportional Controls Service Manual
Contents
411009448 • Rev BA • July 2014

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.
Service Manual Series 51 Electrohydraulic Proportional Controls Service Manual
Introduction
11009448 • Rev BA • July 2014 5

Symbols used in Danfoss literature
WARNING may result in injury Tip, helpful suggestion
CAUTION may result in damage to product or
property
Lubricate with hydraulic fluid
Reusable part Apply grease / petroleum jelly
Non-reusable part, use a new part Apply locking compound
Non-removable item Inspect for wear or damage
Option - either part may exist Clean area or part
Superseded - parts are not interchangeable Be careful not to scratch or damage
Measurement required Note correct orientation
Flatness specification Mark orientation for reinstallation
Parallelism specification Torque specification
External hex head Press in - press fit
Internal hex head Pull out with tool – press fit
Torx head Cover splines with installation sleeve
O-ring boss port Pressure measurement/gauge location or
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.
Overview
This manual includes information for the installation, maintenance, and minor repair of Series 51
electrohydraulic proportional controls. It includes a description of the unit and its individual components,
and minor repair procedures.
Performing minor repairs may require removal of 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, strictly follow cleanliness requirements. This is especially
important when changing the system filter and when removing hoses or plumbing.
A worldwide network of Danfoss Global Service Partners is available for major repairs. Danfoss Global
Service Partners are trained by the factory and certified on a regular basis. You can locate your nearest
Global Service Partner using the distributor locator at www.powersolutionsdanfoss.com. Click on the
Sales and Service link.
Service Manual Series 51 Electrohydraulic Proportional Controls Service Manual
Introduction
611009448 • Rev BA • July 2014

General Instructions
Keep it Clean
You can complete many repairs or adjustments without removing the unit from the machine, if the unit is
accessible and you can thoroughly clean it before beginning any procedures.
Cleanliness is a primary means of assuring satisfactory motor life on either new or repaired units. Clean
the outside of the motor thoroughly before disassembly. Take care to avoid contamination of the system
ports. Cleaning parts with 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. Cap all hoses after
removal, and plug all open ports. Cover any unattended parts with a protective layer of plastic.
Inspect for System Contamination
Inspect the motor for signs of system contamination. If you find contamination, fully disassemble, clean
and inspect all components of the motor.
Replace the O-rings and Gaskets
Replace all O-rings and gaskets. Discard them only after you make certain that you have the correct
replacement parts. Lightly lubricate all O-rings with clean petroleum jelly before assembly.
Lubricate all Moving Parts
During reassembly, coat all moving parts with a film of clean hydraulic oil. This helps lubricate the
surfaces during start-up.
For fluid quality requirements, refer to Hydraulic Fluids and Lubricants, Technical Information 520L0463.
Torque Procedure
During reassembly, cross torque all retaining screws to the given value. Do not overtorque.
General Description
Overview
Electrohydraulic proportional controls infinitely vary motor displacement between maximum and
minimum. They do this by shifting the 4-way valve. The spool position shifts with an
•electric pressure-reducing valve. It varies signal pressure on the end of the 4-way valve (D7, D8
controls), or
•electrically varied differential pressure on the ends of a piston connected to the 4‑way valve (EP, EQ,
ER, ES, ED, EE controls), or
•electric proportional solenoid acting directly on the 4-way valve (A7, L1, L2, L7 controls).
Multifunction Block
Some of the electrohydraulic proportional controls are used in conjunction with the multifunction block.
The multifunction block is a manifold with a shuttle valve that routes high loop (system pressure) from
port A or B to the 4-way valve while routing the low loop (stystem pressure) to the PCOR valve. The 4-way
valve directs this pressure to the ends of the servo piston to change displacement. The multifunction
block may also provides the pressure compensating override (PCOR) option that regulates system
pressure.
Service Manual Series 51 Electrohydraulic Proportional Controls Service Manual
Introduction
11009448 • Rev BA • July 2014 7

Pressure Compensating OverRide (PCOR) Option
The PCOR function allows the motor to match its displacement to the system load. The PCOR overrides
the control command allowing the motor to increase displacement when system pressure reaches a set
level due to load. This permits the motor to regulate system pressure by modulating the displacement of
the rotating group. As displacement increases, so does available torque while output speed decreases
and system pressure remains nearly constant at the PCOR setting.
The PCOR setting pressure is adjustable from 110 to 370 bar [1595 to 5365 psi]. Optional orifices at
locations T4, T5, T6, U6, and U7 regulate the speed of the PCOR operation.
PCOR
N20 N16
N27
N23
N27
N18
N14
N29
N23
P101 906
Brake Pressure Defeat (BPD) option
The PCOR function can be equipped with a brake pressure defeat (BPD) option that defeats the PCOR
operation during dynamic braking. A shuttle spool in the multifunction block in front of the PCOR valve
directs only acceleration system pressure to the PCOR. During deceleration, the high dynamic braking
pressure is blocked from the PCOR. This limits rapid and uncontrolled pressures or engine over-speeding
while the vehicle/machine is slowing down. External hydraulic signal pressures fed to ports XA or XB are
essential to operate the BPD spool. PCOR operation on one-system pressure side is also an option.
EP, EQ Electrohydraulic Proportional Control with Pressure Compensator and Hydraulic Brake Pressure Defeat.
Service Manual Series 51 Electrohydraulic Proportional Controls Service Manual
Introduction
811009448 • Rev BA • July 2014

BPD
M4 M3
M1
L1
L2
M5
M2
M8M7
X1
B
XB XA A
Max.
displ.
P101 907
PCOR
Multifunction Block
Control
BPD
BPD option
Shuttle valve
Brake defeat spool
P106 431E
PCOR spool
PCOR adjuster
Service Manual Series 51 Electrohydraulic Proportional Controls Service Manual
Introduction
11009448 • Rev BA • July 2014 9

Threshold and Ramp Springs
A threshold spring and ramp spring(s) act on the opposite end of the 4-way valve. The threshold
adjustment screw (S100) varies the threshold spring force. This changes the signal current required to
move the 4-way valve and start the change in displacement. The S10* ramp spring(s)—two used in 160 cc
and 250 cc motors and one used in 80 cc and 110 cc motors—increase the force on the 4-way valve as
the servo piston moves toward minimum displacement. This provides a motor displacement
proportional to the variable input signal current.
The control-operating threshold (the signal current or force when the motor starts to shift) is adjustable.
Adjust it using the S100 adjusting screw in the motor’s end cap.
Changing ramp spring force requires replacing the springs. There are several spring rates available.
Optional orifices may be installed at several locations to regulate shift speed. Refer to the Model Code for
your motor for details.
Ramp Springs
J50
S100
(includes J30)
P101 909
J20
S10
S10*
J10*
S10*
S20
J30
160cc and 250cc
80cc and 110cc
Service Manual Series 51 Electrohydraulic Proportional Controls Service Manual
Introduction
10 11009448 • Rev BA • July 2014

Port Locations and Gauge Installation
Series 51 Motors
M2
Y
side port
M4
M1
Main ports A+B
M5
M7
L2
M3
L1
M1 M5
W
W
M3
Y
P101 204E
System pressure A+B
Guage port M1+M2
Axial port
Main
port B
Main
port A
M5
M3
M4
Y
W
Y
Axial port
P101 204E
M5
Legend
Abbreviation Definition
L1 Case drain; (1-5/16-12UNF)
L2 Alternate case drain: (1-5/16-12UNF)
M1 Gauge port: system pressure A (9/16-18UNF)
M2 Gauge port: system pressure B (9/16-18UNF)
M3 Gauge port: servo pressure min. angle (9/16-18UNF)
M4, Gauge port: servo pressure max. angle (9/16-18UNF)
M5 Gauge port: servo supply pressure (9/16-18UNF)
M7 Control pressure port (9/16-18UNF)
Service Manual Series 51 Electrohydraulic Proportional Controls Service Manual
Pressure measurements
11009448 • Rev BA • July 2014 11

Threshold Setting
Checking Threshold Setting
1. Install a 50 bar [600 psi] gauge at port M3 to read minimum servo pressure.
2. Install a 50 bar [600 psi] gauge at port M4 to read maximum servo pressure.
3. Install meter to read signal current.
4. Increase the signal current to the proper setting.
The pressure at port M3 should rise to about 100 psi [6.89 bar] higher than the pressure at port M4.
This causes the servo piston to start to move toward minimum position. Signal current at this point is
the threshold setting.
On a test stand, increase signal current until the flow from the motor begins to decrease. The signal
current at this point is the threshold setting.
Adjusting Threshold Setting
1. Using a 10 mm wrench, loosen the locknut on the adjusting screw.
2. Using a 3 mm internal hex wrench turn the adjusting screw:
•Clockwise (cw) to increase the setting
•Counterclockwise (ccw) to decrease the setting.
3. While holding the position of the adjustment screw:
•tighten the locknut
•using a 10 mm wrench torque the locknut to 9 N•m [6.6 lbf•ft].
Service Manual Series 51 Electrohydraulic Proportional Controls Service Manual
Adjustments
12 11009448 • Rev BA • July 2014

Locknut and Threshold
Spring seat
P101 911
Locknut
10 mm
9 Nm [6.6 lbf•ft]
Pressure compensator Override (PCOR) setting
PCOR Adjustment
In order to measure and adjust the start pressure setting for the PCOR function:
1. Install a 600 bar [10000 psi] gauge at port M1 or M2 or M5 to read high system pressure.
2. Install a 600 bar [10000 psi] gauge at port M3 to read minimum servo pressure.
3. Lock the motor shaft from moving by:
•Applying the park brake, apply an extreme load, or
•Position the machine against an immovable object, or
•Other means to hold the machine.
4. Start the prime mover. Operate at medium RPM.
5. Stroke the pump very slowly to gradually increase the system pressure.
Service Manual Series 51 Electrohydraulic Proportional Controls Service Manual
Adjustments
11009448 • Rev BA • July 2014 13

An alternate method to slowly increase the system pressure is to use the pump’s pressure limiter (PL)
valve. Lower the PL setting below the PCOR setting. Stroke the pump to about one-fourth
displacement. Raise the PL setting slowly to increase system pressure until pressure at the M3 port
drops down. System pressure at this point is the PCOR setting. Adjust the PL back to its proper setting
after checking the PCOR setting.
6. Increase system pressure until pressure at port M3 drops down, system pressure at this point is the
PCOR setting.
Checking PCOR Setting on a Test Stand
Increase system pressure until the system flow begins to increase. System pressure at this point is the
PCOR setting.
W
Warning
System pressure may increase rapidly when flow increases.
Adjusting the PCOR Setting
For PCOR valves mounted on a Multiblock; use a 1-1/16 in. wrench to loosen the lock nut on the
adjusting screw. Using a large screw driver or a 13 mm wrench turn the adjusting screw clockwise to
increase pressure setting or counter clockwise to lower pressure setting. One turn of the adjusting
screw changes the setting approximately 69 bar [1000 psi].
Service Manual Series 51 Electrohydraulic Proportional Controls Service Manual
Adjustments
14 11009448 • Rev BA • July 2014

Optional PCOR Housing Repair
Disassembly
1. Remove plugs (N27). Remove and discard O-rings (N27A).
2. Using a 1 inch hex wrench, remove plug (N23). Remove and discard O-ring (N23A).
3. Remove locknut (N14).
4. Remove adjustment plug (Z00). Remove and discard O-ring (N16J).
5. Remove spring (N18).
6. Remove spool and spring guide assembly (N20).
7. Remove screws (N29).
8. Remove and discard O-rings (N24P, N82).
9. If present, remove orifices (U6, U7).
PCOR
N82
N29
N20 N14
N18
Z00
N87
U6 U7
N24P
P106 384E
N23
N27
N27
N16J
Legend
Item Wrench size Torque
N27 1/8 inch internal hex 7 Nm [4 lbf•ft]
N23 1 inch 40 Nm [30 lbf•ft]
U6, U7 3 mm internal hex 6 Nm [4 lbf•ft]
N29 5 mm internal hex 16 Nm [12 lbf•ft]
N14 1-5/16 inch N/A
Inspection
Clean and inspect components for damage or foreign material. Replace damaged parts.
Assembly
1. If previously removed, Use a 3mm internal hex wrench to install orifices (U6, U7). Torque to 6 N•m [4
lbf•ft].
2. Using petroleum jelly to retain them, install new interface O-rings (N24P, N82).
Service Manual Series 51 Electrohydraulic Proportional Controls Service Manual
PCOR
11009448 • Rev BA • July 2014 15

3. Position PCOR on multiblock. Install screws (N29). Torque using a 5 mm internal hex wrench to 16
N•m [12 lbf•ft].
4. Lubricate and install spool and spring guide assembly (N20).
5. Install spring (N18) to cavity.
6. Lubricate and install new O-ring (N16J). Install adjustment plug (Z00).
7. Using a 1-1/16 inch hex wrench, install locknut (N14). Do not torque until after PCOR adjustment.
Refer to PCOR Adjustment on page 13 for instructions.
8. Lubricate and install a new O-ring (N23A). Using a 1 inch hex wrench, install plug (N23). Torque to 40
N•m [30 lbf•ft].
9. Lubricate and install new O-rings (N27A). Using a 1/8 inch internal hex wrench, install and torque
plugs (N27) to 7 N•m [4 lbf•ft].
Service Manual Series 51 Electrohydraulic Proportional Controls Service Manual
PCOR
16 11009448 • Rev BA • July 2014

Optional Multifunction Block Repair
Disassembly
1. Using a ¼ inch internal hex wrench, remove plugs (N26). Remove and discard O-rings (N26A).
2. Remove the spool (N30).
3. Using a 1/8 inch internal hex wrench, remove plugs (N27). Remove and discard O-rings (N27A).
4. Remove screws (N58).
5. Remove the multifunction block (N1A1).
6. Remove and discard the O-rings (G36, G38, G42) or gasket (N240).
7. If present, remove and discard screens (N52).
E*, F* Control
G42
G42
G38
G38
G38
G36
N52
N30
N1A1
N58 P101210
N27
N27
N27
N27
N26
N26
N240
Legend
Item Wrench size Torque
N27 1/8 inch internal hex 7 Nm [4 lbf•ft]
N26 1/4 inch internal hex 37 Nm [28 lbf•ft]
Service Manual Series 51 Electrohydraulic Proportional Controls Service Manual
Multifunction block
11009448 • Rev BA • July 2014 17

Legend (continued)
Item Wrench size Torque
N58
80cc, 110cc
8 mm internal hex 78 Nm [58 lbf•ft]
N58
160cc, 250cc
10 mm internal hex 110 Nm [81 lbf•ft]
Inspection
Clean and inspect components for damage or foreign material. Replace damaged parts.
Assembly
1. Lubricate and install new O-rings (N27A). Install plugs (N27) using a 1/8 inch internal hex wrench.
Torque to 7 N•m [4 lbf•ft].
2. Using petroleum jelly to retain them, install new interface O-rings (G36, G38, G42) or gasket (N240).
3. Position the multifunction block on the endcap. Install screws (N58). Torque screws as shown in the
table.
4. Lubricate and install the double-resolver spool (N30). Spool is symetrical, either end first.
5. Lubricate and install new O-rings (N26A). Using a 1/4 inch internal hex wrench, install plugs (N26).
Torque to 37 N•m [28 lbf•ft].
Service Manual Series 51 Electrohydraulic Proportional Controls Service Manual
Multifunction block
18 11009448 • Rev BA • July 2014

Operation
General Description
The A7, L1, L2, L7 controls consist of a ported housing mounted directly on the end cap. It contains a
check valve. A direct acting proportional solenoid, with a pushpin, is mounted onto the housing. This
solenoid is high-current. It has an input range of 440 to 1290 mA (12V) or 220 to 645 mA (24v). These
controls are not available with pressure compensator override.
Proportional Solenoid
The proportional solenoid, through the pushpin, presses directly against the 4‑way valve. With signal
current below the threshold setting, the motor defaults to maximum displacement. An increase in signal
current above the threshold setting, shifts motor displacement steplessly from maximum to minimum.
Connector Oder Code
Order code Volts Connector
A7 12v AMP Junior Timer
L1 12v DIN
L2 24v DIN
L7 12v AMP Junior Timer
Check Valve
The check valve resolves which system port (A or B) is higher pressure. It routes this higher pressure to
the 4-way valve, as servo supply pressure, to power the servo piston.
Service Manual Series 51 Electrohydraulic Proportional Controls Service Manual
A7, L1, L2, L7 Controls
11009448 • Rev BA • July 2014 19

A7, L1, L2, L7 controls
F32
F324
M1
M18
M18A
M10
M16
M16A
M22
G38
G42 G38
G42
G36
M18
M12
P101 908
Service Manual Series 51 Electrohydraulic Proportional Controls Service Manual
A7, L1, L2, L7 Controls
20 11009448 • Rev BA • July 2014