Moog 760 Series Owner's manual

1. INTRODUCTION
This manual provides instructions and procedures necessary to install,
operate and troubleshoot the Moog 760 Series Industrial Servovalve.
Troubleshooting instructions are outlined so that only the specific component(s)
suspected of failure may be identified.
2. OPERATION
The Moog 760 Series Industrial Servovalve consists of a polarized electrical
torque motor and two stages of hydraulic power amplification .The motor
armature extends into the air gaps of the magnetic flux circuit and is supported
in this position by a flexure tube member.The flexure tube acts as a seal
between the electromagnetic and hydraulic sections of the valve.The two motor
coils surround the armature, one on each side of the flexure tube.
The flapper of the first stage hydraulic amplifier is rigidly attached to the
midpoint of the armature.The flapper extends through the flexure tube and
passes between two nozzles, creating two variable orifices between the nozzle
tips and the flapper.The pressure controlled by the flapper and nozzle variable
orifice is fed to the end areas of the second stage spool.
The second stage is a conventional 4-way spool design in which output
flow from the valve, at a fixed valve pressure drop, is proportional to spool
displacement from the null position.A cantilever feedback spring is fixed to the
flapper and engages a slot at the center of the spool. Displacement of the spool
deflects the feedback spring which creates a force on the armature/flapper
assembly.
Input signal induces a magnetic charge in the armature and causes a
deflection of the armature and flapper.This assembly pivots about the flexure
tube and increases the size of one nozzle orifice and decreases the size of the
other.
This action creates a differential pressure from one end of the spool to the
other and results in spool displacement.The spool displacement causes a force in
the feedback wire which opposes the original input signal torque. Spool
movement continues until the feedback wire force equals the input signal force.
760 Series Installation and
Operation Instruction
Electrohydraulic Servovalve
ELECTROHYDRAULIC VALVE CUT-AWAY
CAUTION
DISASSEMBLY, MAINTENANCE, OR REPAIR OTHER THAN IN ACCORDANCE WITH THE
INSTRUCTIONS HEREIN OR OTHER SPECIFIC WRITTEN DIRECTIONS FROM MOOG WILL
INVALIDATE MOOG’S OBLIGATIONS UNDER ITS WARRANTY. Figure 1 Moog Series 760
Upper Polepiece
Flexure Tube
Flapper
Lower Polepiece
Feedback Wire
Inlet Orifice
Magnet
Coil
Armature
Nozzle
Spool
Control Port B
Return
Control Port A
Pressure
Filter

3. HYDRAULIC SYSTEM PREPARATION
To prolong servovalve operational life and to reduce hydraulic system
maintenance, it is recommended that the hydraulic fluid be kept at a cleanliness
level of ISO DIS 4406 Code 16/13 maximum, 14/11 recommended.The most
effective filtration scheme incorporates the use of a kidney loop or “off-line”
filtration as one of the major filtration components.The filter for the “off-line”
filtration scheme should be a B3≥75 filter for maximum effectiveness.
Upon system startup, and prior to mounting the servovalve, the entire
hydraulic system should be purged of built-in contaminating particles by an
adequate flushing.The servovalve should be replaced by a flushing manifold and
the hydraulic circuit powered up under conditions of fluid temperature and fluid
velocity reasonably simulating normal operating conditions. New system filters
are installed during the flushing process whenever the pressure drop across the
filter element becomes excessive.The flushing processes should turn over the
fluid in the reservoir between fifty to one hundred times.
To maintain a clean hydraulic system, the filters must be replaced on a
periodic basis. It is best to monitor the pressure drop across the filter assembly
and replace the filter element when the pressure drop becomes excessive. In
addition to other filters that are installed in the hydraulic circuit, it is
recommended that a large capacity, low pressure ß3≥75 filter be installed in the
return line. This filter will increase the interval between filter element
replacement and greatly reduce the system contamination level.
4. INSTALLATION
The Moog 760 Series Industrial Servovalve may be mounted in any
position, provided the servovalve pressure, piston, and return ports match
respective manifold ports.
The mounting pattern and port location of the servovalve is shown on
figure 4.The servo-valve should be mounted with 5/16-18 x 1.75 inch long,
socket head cap screws.Apply a light film of oil to the screw threads and torque
to 96 inch pounds.
Wire mating connector for desired coil configuration and polarity. Thread
connector to valve.
5. MECHANICAL NULL ADJUSTMENT
It is often desirable to adjust the flow null of a servovalve independent of
other system parameters.The “mechanical null adjustment” on the Moog 760
Series servovalve allows at least ±20% adjustment of flow null.
The “mechanical null adjustor” is an eccentric bushing retainer pin, located
above the “return” port designation on the valve body (see Figure 2) which,
when rotated, provides control of the bushing position. Mechanical feedback
elements position the spool relative to the valve body for a given input signal.
Therefore, a movement of the bushing relative to the body changes the flow null.
Adjustment Procedure
Using a 3/8inch offset box wrench, loosen the self-locking fitting until the
null adjustor pin can be rotated. (This should usually be less than 1/2 turn).
DO NOT remove self-locking fitting. Insert a 3/32 inch Allen wrench in null
adjustor pin. Use the 3/32 Allen wrench to rotate the mechanical null adjustor
pin to obtain desired flow null.Torque self-locking fitting to 57 inch lbs.
Note:
Clockwise rotation of null adjustor pin produces open loop flow from port B to port A.
Tools and Equipment
a. Blade screwdriver
b. Allen wrench set (3/32,5/32,1/4inch)
c. No. 2-56 NC by 1-1/2inch screw
d. Torque wrenches (57 and 96 inch-pounds)
e. 3/8inch offset box wrench
f. Tweezers
6.GENERAL SERVICING RECOMMENDATIONS
a. Disconnect the electrical lead to the servovalve.
b. Relieve the hydraulic system of residual pressure.
c. Remove the servovalve.
Table 1. Replacement Parts
Part Description Qty. Part Number
760 Series Filter Replacement Kit 1 B52555RK004K001
Inlet Orifice - Body O-Ring (1) 2 -42082-059
Filter Plug - Body O-Ring (1) 2 -42082-060
End Cap - Bushing O-Ring (1) 2 -42082-042
End Cap - Body O-ring (1) 2 -42082-001
Filter Tube (1) 1 -23020
Base O-Rings 4 -42082-022
(1) Included in Filter Replacement Kit
Figure 2
Mechanical Null Adjustment

Potential Trouble
Servovalve does not follow input command
signal. (Actuator or components are
stationary or creeping slowly).
High threshold. (Jerky, possible oscillatory
or "hunting" motion in closed loop system).
Poor response. (Servovalve output lags
electrical command signal).
High Null Bias, (High input current required
to maintain hydraulic cylinder or motor
stationary).
Probable Cause
1. Plugged inlet filter element.
1. Plugged filter element.
1. Partially plugged filter element.
1. Incorrect null adjustment.
2. Partially plugged filter element.
Remedy
1. Replace filter element.
1. Replace filter element.
1. Replace filter element.
Check for dirty hydraulic fluid in system.
1. Readjust null.
2. Replace filter element and check for dirty
hydraulic fluid in system.
7.TROUBLESHOOTING CHART
The following troubleshooting chart list potential troubles encountered, probable causes, and remedies.
8. FILTER ASSEMBLY REPLACEMENT
a. Remove eight socket head cap screws and lockwashers using a 5/32 inch
Allen wrench. Remove end caps.
b. Remove O-Rings from end caps.
c. Remove filter plug and inlet orifice assembly from both sides of body.
Note: 2-56 screw threads into the filter plug and inlet orifice assembly.
Remove filter.The inlet orifice assemblies are matched to each other and
are therefore interchangeable.
Note: These assemblies seat in body and cannot go through bore during
removal.
d. Remove O-Rings from filter plugs and O-Rings from inlet orifice
assemblies.
e. Visually inspect filter orifice assemblies for damage or foreign matter.
f. Discard O-Rings and filters.
g. Install O-Rings on filter plugs, and O-Rings on inlet orifices.
h. Install filter, inlet orifice assembly, and a filter plug in body. Inlet
orifice assembly pilots into filter. Install the other inlet orifice assembly and
filter plug into other end of filter. Inlet orifice assemblies are
interchangeable.
i. Install O-Rings on end caps.
j. Install end caps on body and install eight socket head cap screws and
lockwashers.Torque the screws to 57 inch-pounds.
9. FUNCTIONAL CHECKOUT AND CENTERING
a. Install servovalve on hydraulic system or test fixture, but do not connect
electrical lead.
b. Apply required system pressure to servovalve and visually examine for
evidence of external leakage. If leakage is present and cannot be rectified
by replacing O-Rings, remove the discrepant component and return for
repair or replacement.
Note: If the system components are drifting or hardover, adjust
the mechanical null of the servovalve.
c. Connect electrical lead to servovalve and check phasing in accordance
with system requirements.
10. AUTHORIZED REPAIR FACILITIES
Moog does not authorize any facilities other than Moog or Moog subsidiaries to
repair its servovalves. It is recommended you contact Moog at [phone]
to locate your closest Moog repair facility. Repair by an independent
(unauthorized) repair house will result in voiding the Moog warranty and could
lead to performance degradation or safety problems.
Figure 3
Inlet Orifice Assemblies
(one each end of body)
End Plate
Filter Tube
Orifice Assembly
End Cap-Body
O-Rings
Filter Plug
Filter Plug
O-Ring Inlet Orifice O-Ring

760 SERIES INSTALLATION AND OPERATION INSTRUCTION NOTES
TYPICAL WIRING SCHEMATIC
The products described herein are subject to change at any time without notice, including, but not limited to, product features, specifications, and designs.
1 Valve Weight:
1.1 lbs (0.5 kg)
2 Polarity:
A&C (+), B&D (-) produces flow out
port B
3 Manifold O-Rings
0.070 (1.78) sect x 0.426 (10.82) I.D.
(Universal dash No. 13)
4 Surface:
Surface to which valve is
mounted requires 32 ( ) finish, flat
within .001 [0.025] TIR
5 Electrical Connector:
Mates with MS3106-14S-2S or equivalent
6 Null Adjust:
Flow out of port B will increase with
clockwise rotations of null adjust pin
7 Compressed OilVolume
for one control port: 0.229 in3
(3.75 cm3)
8 Suggested Mounting Screws:
0.312-18 x 1.750 lg (M8 x 45)
socket head screw (4 req'd)
Dimensions in parenthesis are in millimeters.
2
ABCD
∆∆
Figure 4
RETURN PORT T
PRESSURE PORT P
CONTROL PORT B
3.88
1.94
1.750
.875
.670
.875
.437
CONTROL PORT A
1.500
.500
3.000
1.750 .390
3.500
VALVE MOUNTS ON THIS
MANIFOLD SURFACE
.437
.875
.670
1.281
2.562
1
PORT PER SAE J1926
1.0625-12 UN-2B DASH 12
STR THD O-RING BOSS
(.75 [19.05] TUBE OD REF)
4 PLACES
1.00
4 PL
1.25
32
2.00
2.11
4.22
RET AUX PRESS
760
PORT PER SAE J1926
.4375-20 UNF-2B DASH 4
STR THD O-RING BOSS
(.25 TUBE OD REF)
.001
.156 (3.96) AUXILIARY
PILOT PRESSURE PORT
.008 M
4X .312 [7.92]
.014 M
4X .3125-18 UNC-2B THD
.007 M
.015 M
.136 .20
.014 M
.50 .63
4X .344 [8.74] THRU
[50.8]
[53.6]
[107.19]
[31.75]
[44.45]
[22.23]
[50.8]
[17.02]
[11.1]
[38.1]
[76.2]
[12.7]
[9.91]
[44.45]
[88.9]
[98.55]
[49.28]
[65.07]
[32.54]
[49.28]
[11.1]
[17.02]
[25.4]
P
PIN B
PIN D
PIN C
PIN A
1.125
[28.58]
.09
[2.3]
.09
[2.3]
[44.45]
1.750
[22.23]
.875
[65.07]
2.562
[32.54]
1.281
1.89
[48.0]
3.78 MAX
[96.0]
1.72 MAX
[43.7]
3.44 MAX
[87.4]
3.83 MAX
[97.3]
ELECTRICAL
LOCATING PIN
2.11
[53.6]
2.17
[55.1]
2.85 MAX
[72.4]
EXTERNAL 
NULL 
ADJUST
3/32 IN. 
HEX 
SOCKET
4X .328 [8.33] THRU
TO DEPTH SHOWN (1.125 REF)
.008 M
.531 [13.49]
CONNECTOR
Moog Inc., East Aurora, NY 14052-0018
Telephone: [phone]
Fax: [phone]
Toll Free: +1-800-272-MOOG
www.moog.com/industrial
CDS6541 Rev G 500-315 0408
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