Moog 641 Installation And Operation Instruction Manual
1.INTRODUCTION
This manual provides instructions and procedures necessary to install,
operate and troubleshoot the Moog 641 Series Proportional Control Valve.
Troubleshooting instructions are outlined so that the specific component(s)
suspected of failure can be identified.
2. OPERATION
The Moog 641 Series proportional control valves are suitable for open
and closed loop position and velocity control systems where accelerations need
to be regulated.The 641 can be used like a directional solenoid valve or a
proportional valve while controlling ram or motor acceleration,deceleration
and velocity.
The 641 Series valves are two-stage devices consisting of a double nozzleflapper pilot stage and a sliding spool main stage.The position of the main stage
spool is measured by a non-contacting position transducer. On-board integrated
electronics provide closed-loop position control of the main stage spool.
The operation of the 641 Series valve is controlled by an electrical
command signal (VQS) provided to the integrated control electronics which
drives the pilot stage coils.The current sent from the electronics causes the
flapper to move toward one nozzle,diverting the pilot stage flow to one end of
the spool.The position transducer measures the position of the spool (VLI) and
produces a feedback voltage which is directed back to the control amplifier and
compared to the command voltage.The control amplifier then drives the pilot
stage until the command voltage and feedback voltage are equal,centering the
flapper between the nozzles which holds the spool at a position proportional to
the command signal.
m
641 Series Installation and
Operation Instruction
Proportional Control Valve
ELECTROHYDRA ULIC VAL VE CUT -A WA Y
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 641
SINGLE STAGE
PILOT VALVE
SPOOL
PATB
INLET ORIFICE
NOZZLE
MAIN STAGE
FLAPPER
OSCILLATORDEMODULATOR
POSITION
CONTROL
AMPLIFIER
V
QS
V
LI
SPOOL POSITION
TRANSDUCER
(LVDT)
3.HYDRAULIC SYSTEM PREPARATION
To prolong proportional control valve operational life and to reduce
hydraulic system maintenance,it is recommended that the hydraulic fluid be
kept at a cleanliness level of ISO Code 14/11 (NAS Class 5) or better.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 ß3≥75 filter for maximum effectiveness.
Upon system start-up,and prior to mounting the valve, the entire
hydraulic system should be purged of built-in contaminating particles by an
adequate flushing.The valve should be replaced by a flushing plate and the
hydraulic circuit powered up under conditions of fluid temperature and fluid
velocity reasonably simulating the normal operating conditions.Best possible
flushing is achieved if a 4 way/3 position directional control valve is fitted in
place of the proportional valve since,when the directional control valve is
actuated alternately,the downstream actuators are also flushed.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 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 system contamination.
4.INSTALLATION
The Moog 641 Series Proportional Control Valves may be mounted in any
position,provided the valve pressure,control,and return ports match respective
manifold ports.The mounting pattern and port location of the valve are shown
on Installation Drawing No.G2785. Apply a light film of oil to the mounting
screw threads and torque the screws to 90 inch-pounds.
Wire mating connector for desired coil configuration and polarity. Thread
connector to valve.
5.ELECTRICAL NULL ADJUSTMENT
It may be desirable to adjust the proportional valve for flow null
independent of other system parameters.The electrical null adjustment permits
convenient control set-ups.The electrical null adjust is a 4-turn potentiometer
located behind the pan head screw in the electronics housing.When turned,it
provides control of the spool position to obtain the desired flow null.
Adjustment Procedure
1. Verify that ±15 vdc power is supplied to the valve,and that the input signal
(pin D or E) is zero or grounded.
2. Using a flat blade screwdriver, remove the pan head screw (see Figure 2)
to permit adjustment of the potentiometer.
3. Using a flat blade screwdriver, adjust the potentiometer to obtain the
desired flow null. Note: Clockwise rotation of the potentiometer p
reduces flow out of control port A.
4. Replace the pan head screw.
5. Restore the input signal wiring for system operation.
Tools and Equipment:
a. Flat blade screwdriver
b. Allen wrench set (21/2,3,4,5 mm;3/16,7/32inch )
c. Volt-ohm-milliammeter
d. Torque wrenches,various,to meet reassembly requirements
6.GENERAL SERVICING RECOMMENDATIONS
a. Disconnect the electrical lead to the control valve.
b. Relieve the hydraulic system of residual pressure.
c. Remove the valve.
Table 1. Replacement Parts
Part Description Qty. Part Number
641 Series Filter Replacement Kit 1 B52555RK90K1
Base O-Rings 5 42082-4
Base O-Rings 2 42082-11
Filter O-Ring (1) 1 G2140-13-15
Filter Retainer Plate O-Ring (1) 1 G2140-17-20
Filter (1) 1 G2196-100
(1) Included in Filter Replacement Kit
Figure 2
Electrical Null Adjustment
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