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 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 79-100 Series Industrial Servovalve may be mounted in any
position,provided the servovalve pressure,control and return ports match
respective manifold ports.
Caution: If the servovalve is mounted vertically,the third stage spool may drift
to one side when hydraulics are shut off.This may result in sudden movement of
equipment when starting up.
The mounting pattern and port location of the servovalve is shown on
Figure 2.The servovalve should be mounted with 3/8-16 x 2.5 inch long high
strength socket head capscrews.Apply a light film of oil to the screw threads
and torque to foot pounds.
On selected models,the pilot valve supply and return may be supplied
through external lines attached to the valve body or an intermediate manifold.
Wire mating connector for desired coil configuration and polarity.Thread
connector to valve.Wire transducer according to the installation drawing,
Figure 2.
5.MECHANICAL NULLADJUSTMENT
There is no mechanical null adjust.Typically, a bias potentiometer is
provided on the electronics to null the valve.If adjustment of the transducer is
required,refer to the proper steps below.
a. Remove the two socket head screws holding the transducer cover to the
end cap.Carefully remove cover to prevent damage to the transducer
wiring.
b. Loosen the jam nut using a 15/8open end wrench.
c. Adjust transducer case to achieve required transducer null voltage.
Caution: Limit adjustment to ±2 turns.Excess loosening of transducer
case will result in the release of hydraulic fluid.
d. Tighten jam nut.Replace transducer cover, being careful not to damage the
transducer wires,using two socket head capscrews with lockwashers.
Torque to 10 inch pounds.
Tools and Equipment
a. MetricAllen wrench set
b. StandardAllen wrench set
c. Open end wrench
6.GENERAL SERVICING RECOMMENDATIONS
a. Disconnect electrical lead to servovalve.
b. Relieve hydraulic system of residual pressure.
c. Remove servovalve.
Table 1.Replacement Parts
Part Description Qty. Part Number
Base O-Rings 4 42082-40
PilotValve Base O-Rings 4 42082-22
Base X-Y O-Rings 2 42082-12
Adapter Plate Base 3 42082-22
O-Rings 1 42082-8
