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
