Moog G761K Series Assembly, Installation And Operation Instructions

1. INTRODUCTION
This manual provides instructions and procedures necessary to install,
operate and troubleshoot the Moog Inc. Series G761K or 761K intrinsic
safety protected industrial serovalve. The (G)761K series valves are electrical
equipment for hazardous areas requiring intrinsic safety or non-incendive
protection. The approved hazardous location markings include:
II 1G Ex ia IIB/IIC T4 Ga KEMA 02 ATEX1015 X
II 3G Ex ec II T3 Gc KEMA 02ATEX1016 X
0344 per ATEX directive 2014/34/EU
Ex ia IIB/IIC T4 Ga IECEx KEM 10.0041X
Ex ec IIC T4 Gc IECEx KEM 10.0041X
per IECEx certification scheme.
The G761K servovalves are also approved by FM, CSA, and TIIS for
hazardous locations. They are intended for directional, position, velocity,
pressure and force control in hydraulic control systems that operate with
mineral oil based fluids. Others on request.
2. OPERATION
The Moog (G)761K 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 transmits 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.
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 AND YIELD THE INTRINSICALLY
SAFE PROTECTION PERMIT NULL AND VOID.
(G)761K Series Installation
and Operation Instruction
Electrohydraulic Servovalve
Intrinsic Safety Protected
ELECTROHYDRAULIC VALVE CUT-AWAY
Coil
Armature
Nozzle
Feedback Wire
Spool
Filter
P A
Figure 1 Moog Series G761K
Upper Polepiece
Flexure Tube
Lower Polepiece
Flapper
Inlet Orifice
T B P x