Moog 631 Series Owner's manual

1.INTRODUCTION
This manual provides instructions and procedures necessary to install,
operate and troubleshoot the Moog 631 Series Industrial Servovalve.
Troubleshooting instructions are outlined so that only the specific component(s)
suspected of failure may be identified.
2. OPERATION
The Moog 631 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 hole 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. This 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.
m
631 Series Installation and
Operation Instruction
Electrohydraulic Servovalve
ELECTROHYDRAULICVALVE CUT-AWAY
CAUTION
DISASSEMBLY, MAINTENANCE,OR REPAIR OTHERTHAN INACCORDANCEWITHTHE
INSTRUCTIONS HEREIN OR OTHER SPECIFICWRITTEN DIRECTIONS FROM MOOGWILL
INVALIDATE MOOG’S OBLIGATIONS UNDER ITSWARRANTY.
NullAccess
Screw
NullAdjust
Upper Polepiece
Torque Motor Coil
Armature FlexureTube
Flapper
Nozzle
FeedbackWire
Spool
Inlet Orifice
Filter Plate
Filter
External Pilot
Supply
Figure 1 Moog Series 631
ATBPX

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 uses a kidney loop or “off-line” filtration.The filter for
the“off-line” filtration should be a ß3≥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
replacements and greatly reduce the system contamination level.
4.INSTALLATION
The Moog 631 Series Servovalves may be mounted in any position,provided the
servovalve pressure,control,and return ports match respective manifold ports.
The mounting pattern and port location of servovalve are shown on Figure 4.
Apply a light film of oil to the mounting screw threads and torque the screws to
96 inch-pounds.
Wiring mating connector for desired coil configuration and polarity.
Thread connector to valve.
5.MECHANICAL NULLADJUSTMENT
It may be desirable to adjust the servovalve for flow null independent of other
system parameters. The mechanical null adjustment permits convenient control
function set-ups.
The mechanical null adjustor is a hex socket setscrew located behind the
pan head screw in the motor cap (see Figure 2) which,when adjusted,provides
control of the spool position to obtain the desired flow null.
NORMALADJUSTMENT SHOULD REQUIRE LESSTHAN ± ONETURN.
LIMIT NULL SCREWADJUSTMENTTO LESSTHAN ±TWOTURNS.
Adjustment Procedure
a. Using a blade screwdriver,remove the null access screw to permit
adjustment of the hex socket setscrew.
b. Using a 2-1/2inch long,1/8inchAllenWrench,adjust the set screw to obtain
the desired flow null.
Note: Clockwise rotation of the set screw produces flow out portA.
c. After the desired flow null has been obtained, replace the null access screw.
Tools and Equipment
a. Blade screwdriver
b. Allen wrench set (3mm,1/8inch)
c. 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
631 Series Filter Replacement Kit 1 B52555RK69K1
Base O-Ring 5 G2141-12-20
Base O-Ring 1 G2141-8-20
Filter O-Ring (1) 1 G2141-13-15
Filter O-Ring (1) 1 G2141-17-20
Filter (1) 1 G2916-100
(1) Included in Filter Replacement Kit
Figure 2
Mechanical NullAdjustment NullAccess Screw

PotentialTrouble
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
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.FILTERASSEMBLY REPLACEMENT
a. Remove the four socket head capscrews and lockwashers with 3mmAllen
wrench.
b. Remove the filter retainer.
c. Remove and discard the filter disk.
d. Remove and replace the O-Ring on the filter retainer and the O-Ring in
the filter bore.
e. Reinstall in reverse order,torque screws to 35-40 in-lbs.
9.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
O-Ring (Filter Disk) O-Ring Retainer
Socket Head Screw (4)
Filter Disk
Filter Retainer
Lockwasher (4)

2.126
2.95
[74.9]
[54.00]
1.812
[46.00]
4.20
[106.7]
2.60
[66.0]
1.57
[40.0]
1.39
[35.3]
3.72
[94.5]
3.84
[97.5]
REPLACEABLE FILTER
ELECTRICAL CONNECTOR
PIN B
PIN A
PIN C
PIN D
NULL ADJUST
COVER SCREW
INSTALL SEAL WASHER
AND SCREW FOR
INTERNAL PILOT SUPPLY
SEAL WASHER AND SCREW SHOWN
INSTALLED FOR EXTERNAL PILOT SUPPLY
4.67 MAX
[118.6]
2.76
[70.0]
3.23 MAX
[82.0]
1.063
[27.00]
5.43 MAX
[137.9]
4 X .256 [6.5] THRU
.433 [11.0]
TO DEPTH SHOWN (2.29 REF)
.011 M
2.29
[58.2]
1.38
[35.0] 1.72 [43.7]
.906
[23.00]
5.07 MAX
[128.8]
OPTIONAL MANUAL
OVERRIDE HANDLE 5
O Ø .001 M
4 HOLES
.063
[1.60]
.374
[9.50]
.658
[16.70]
1.417
[36.00]
B
P
T
AX
.937
[23.80] .937
[23.80]
.406
[10.30]
.406
[10.30]
631 SERIES INSTALLATIONAND OPERATION INSTRUCTION
CDS6196 Rev B 500-316 298
Industrial Controls Division
Moog Inc.,EastAurora,NY 14052-0018
Telephone:[phone]
Fax:[phone]
Toll Free: 1-800-272-MOOG
NOTES
TYPICALWIRING 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 Fluid:
Industrial type petroleum base
hydraulic fluid,maintained to ISO DIS
4406 Code 14/11 recommended.
2 OperatingTemperature Range:
0°F [-18°C]TO +200°F [+93°C].
3 Valve Phasing:
Flow out port B results when:
Series coils:B & C connected, A+,D-;
Parallel coils:A & C connected,B & D
connected,A+,D-.
4 Surface:
Surface to which valve is mounted
requires 64 ( ) finish,flat within .002
[0.05]TIR.
5 NullAdjust:
Flow out Port A results with clockwise
rotation of null adjust set screw (1/8hex
key).
3
ABCD
∆∆