Moog 72K Series Owner's manual

1. INTRODUCTION
This manual provides instructions and procedures necessary to install,
operate and troubleshoot the Moog Inc. Series 72K or G72K intrinsic safety
protected industrial serovalve. The (G)72K series valves are electrical equip-
ment for hazardous areas with intrinsic safety or non-incendive protection.
The approved hazardous location markings include:
II 1 G Ex ia IIB/IIC T4 Ga KEMA 02ATEX 1015 X
II 3 G Ex ec IIC T4 Gc KEMA 02ATEX 1016 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 G72K 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 Inc. Series (G)72K Electrohydraulic 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 four-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 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.
�
(G)72K Series Installation
and Operation Instruction
Electrohydraulic Servovalve
Intrinsic Safety Protected
ELECTROHYDRAULIC VALVE CUT-AWAY
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.
Coil
Armature
Magnet
Flexure Tube
Inlet
Orifice
Polepiece
Connector
Filter
Feedback Wire
Spool
Figure 1 Moog Series 72K and (G)72K
Supply Pressure
B
Tank
A
Nozzle
t

3. ELECTRICAL INFORMATION AND INTRINSICALLY
SAFE CIRCUIT SAFETY PARAMETERS
a. A wide choice of coils is available for a variety of rated current
requirements. The torque motor coil leads are attached to the connector
so external connections can provide series, parallel or single coil
operation. The valves are equipped either with an MS type connector or
with pigtail leads for electrical wiring. Refer to installation drawings of the
specific model for details. Servovalve coils should be driven with current
to provide consistency throughout the temperature range.
b. The (G)72K valves are approved for intrinsically safe protection per EN
IEC 60079-0 : 2018, EN 60079-7 : 2015, and EN 60079-11 : 2012 for
ATEX, and IEC 60079-0 : 2017, IEC 60079-7 : 2017, and IEC 60079-11 :
2011 for IECEx. The approved safety parameters are listed in the following
table for all the coils used by (G)72K series. Coil number is marked on
the valve nameplate.
Coil Configuration Marking Ui(MAX) Ii(MAX)
G4220-031 (single, series, parallel) Ex ia IIB T4 12 V 120 mA
G4220-051/098 (single, series, parallel) Ex ia IIB T4 12 V 240 mA
G4221-001 G4220-042 (single) Ex ia IIC T4 16 V 160 mA
G4221-001 G4220-042 (single) Ex ia IIC T4 24.4 V 85 mA
G4220-031 (single, parallel) Ex ia IIC T4 30 V 26 mA
G4220-031 (series) Ex ia IIC T4 30 V 18 mA
G4220-051/098 (single, parallel) Ex ia IIC T4 30 V 19 mA
G4220-051/098 (series) Ex ia IIC T4 30 V 12.7 mA
G4220-042 (single) Ex ia IIC T4 30 V 37 mA
G4220-042 (parallel) Ex ia IIC T4 30 V 20 mA
G4220-042 (series) Ex ia IIC T4 30 V 10 mA
G4221-001 (single) Ex ia IIC T4 30 V 28 mA
c. The (G)72K valves are approved for non-incendive operation for supply
current not to exceed 50 mA dc.
d. When making electric connections to the valve, appropriate measures must
be taken to ensure that locally different earth potential do not result in
excessive ground currents. When barriers are required for the hazardous
location, hazardous area (field) wiring must meet the requirements of
the barrier manufacturer. All barriers must be mounted and installed in
compliance with the barrier manufacturer’s requirements. Twisted pairs of
18-20 gage wire are recommended. If shielded wire is used, connect shield
wire to earth ground only at the barrier strip.
4. SPECIAL CONDITIONS FOR SAFE USE
Because the enclosure of the apparatus is made of aluminum, if it is
mounted in an area where the use of category 1 G apparatus is required, it
must be installed such that even in the event of rare incidents, ignition sources
due to impact and friction sparks are excluded.
When the electrohydraulic servovalve is used in an application for type of
explosion protection intrinsic safety “i”, the appropriate box on the data label
must be scored. When the electrohydraulic servovalve is used in an application
for type of explosion protection “n”, the appropriate box on the data label
must be scored.
After use in an application for type of explosion protection “n”, the
servovalve cannot abe safely used in a intrinsically safe application.
The screwed cable connector may only be disconnected when the circuit
is de-energized or when the location is known to be non-hazardous.
When used at an ambient temperature ≥70°C, heat resistant cable must
be used with a continuous operating temperature in accordance with the
application.
When the electrohydraulic servovalve is used in type of protection “n”
or “ec”, the equipment shall only be used in an area of not more than Pollution
Degree 2, as defined in IEC 60664-1.
The cable gland shall be installed such that impact is not possible.
When the electrohydraulic servovalve is used in type of protection “n”
or “ec”, the user shall provide additional clamping of the cable to ensure that
pulling is not transmitted to the terminations.
5. 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.
6. INSTALLATION
The Moog (G)72K series industrial servovalve may be mounted in any
position, provided the servovalve pressure, control, and tank ports match
respective manifold ports. The mounting pattern and port location of the
servovalve is shown on Figure 4. The servovalve should be mounted with 3/8-16
x 2.00 inch long, socket head cap screws. Apply a light film of oil to the screw
threads and torque to 175 inch-pounds. Wire mating connector for desired coil
configuration and polarity. Thread connector to valve.
7. MECHANICAL NULL ADJUSTMENT
It is often desirable to adjust the flow null of a servovalve independent of
other system parameters. The “mechanical null adjustment” on the Moog (G)72K
Series servovalve allows at least ±20% adjustment of flow null. The “mechanical
null adjustor” is an eccentric bushing retainer pin, located above the tank port
designation on the valve body (see Figure 2) which, when rotated, provides
control of the bushing position. Mechanical feedback elements position the
spool relative to the valve body for a given input signal. Therefore, a movement
of the bushing relative to the body changes the flow null.
Mechanical Adjustment Procedure
Using a 3/8inch offset box wrench, loosen the self-locking fitting until the
null adjustor pin can be rotated. (This should usually be less than 1/2 turn).
DO NOT remove self-locking fitting. Insert a 3/32 inch Allen wrench in null
adjustor pin. Use the 3/32 Allen wrench to rotate the mechanical null adjustor
pin to obtain desired flow null. Torque self-locking fitting to 57 inch lbs.
Note:
Clockwise rotation of null adjustor pin produces flow from port P to port B.
Tools and Equipment
a. Blade screwdriver
b. Allen wrench set (3/32, 7/64, 3/8, 3/16)
c. No. 2-56 NC by 11/2inch screw
d. Torque wrenches
e.
3/8 inch offset box wrench
f. Tweezers
Figure 2
Mechanical Null Adjustment

Potential Trouble
Servovalve does not follow input command
signal. (Actuator or components are
stationary or creeping slowly.)
Poor response. (Servovalve output lags
electrical command signal).
Output flow obtained from one control
port only. (Actuator is hardover, or
hydraulic motor is rapidly rotating. No
response to electrical command signal.)
Low flow gain. (Failure to meet high rate
or rapid traverse speeds.)
High threshold. (Jerky, possible oscillatory
or “hunting” motion in closed loop system.)
High Null Bias. (High input current
required to maintain hydraulic cylinder or
motor stationary.)
Probable Cause
1. Open coil assembly or open coil leads.
2. Plugged inlet filter element.
Partially plugged filter element.
1. Plugged inlet orifices.
2. Plugged inlet filter element.
3. Plugged hydraulic amplifier assembly.
4. Jammed spool.
Shorted coil assembly.
“Sticky” spool
1. Incorrect null adjustment
2. Partially plugged inlet orifice assembly.
3. Partially plugged filter element.
4. Partially plugged nozzle.
Remedy
1. Return to factory.
2. Replace filter element.
Replace filter element and check for dirty
hydraulic fluid in system.
1. Return to factory.
2. Replace filter element.
3. Return to factory.
4. Return to factory.
Return to factory.
Return to factory.
1. Readjust null
2. Return to factory.
3. Replace filter element and check for
dirty hydraulic fluid in system.
4. Return to factory.
9. TROUBLESHOOTING CHART The following troubleshooting chart list potential troubles encountered, probable causes, and remedies.
10. FIELD REPLACEABLE FILTER ASSEMBLY REPLACEMENT
a. Remove four socket head cap screws and lockwashers on filter cover
using a 3/16 inch Allen wrench. Remove filter cover plate. Use 1/4-28 screw
to pull filter plug out.
b. Remove o-rings and old filter from filter plug.
c. Inspect filter for foreign material and discard.
d. Install o-rings on filter plug and inside new filter.
e. Install filter, filter plug and cover plate. Torque screws to 85 inch-pounds.
11. FUNCTIONAL CHECKOUT AND CENTERING
a. Install servovalve on hydraulic system or test fixture, but do not connect
electrical lead.
b. Apply required system pressure to servovalve and visually examine for
evidence of external leakage. If leakage is present and cannot be rectified
by replacing o-rings, remove the discrepant component and return for
repair or replacement.
Note: If the system components are drifting or hardover, adjust
the mechanical null of the servovalve.
c. Connect electrical lead to servovalve and check phasing in accordance
with system requirements.
12. AUTHORIZED REPAIR FACILITIES
If servovalve continues to malfunction after all recommended corrective
action procedures are performed, defective valve should be returned to
Moog for repair. 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.
13. DECLARATION OF MANUFACTURER
An EU Declaration of Conformity according to Council Directive
2014/34/EU is supplied with each servovalve.
Figure 3
Filter Tube
Inlet Orifice
Assembly
Filter Plug
Field
Replaceable
Filter
Filter Housing
O-Rings
Table 1. Replacement Parts
Part Description Qty. Part Number
(G)72K Series Filter Replacement Kit 1 B52555RK099K001
Base O-Rings 4 -42082-040
Base O-Ring (X-Port) 1 -42082-013
Filter Housing O-Rings (I) 2 -42082-039
Field Replaceable
Filter Internal O-Ring (I) 1 -42082-013
Filter Plug O-Rings (I) 2 -42082-060
Inlet Orifice O-Rings (I) 2 -42082-059
Pilot Stage Filter Tube (I) 1 -23020
Field Replaceable Filter (I) 1 -22050
Motor Cap Gasket (I) 1 -24509
(I) Included in Filter Replacement Kit.
8. GENERAL SERVICING RECOMMENDATIONS
a. Disconnect electrical lead to servovalve.
b. Relieve hydraulic system of residual pressure.
c. Remove servovalve.

3.05
[77.5]
4.06
[103.1]
3.28
[83.3]
.28
[7.1]
2.75
[69.9] 3.69
[93.7]
6.70
[170.2]
5.15
[130.8]
4.48
[113.8]
MAX
2.38 [60.5]
DIA TYP
1.37
[34.8]
PIN D
PIN C
PIN A
PIN B
1.50
[38.1]
FIELD REPLACEABLE
FIRST STAGE FILTER .86
[22.0] 1.73
[43.9]
2.26
[57.4]
2.03
[51.6]
1.81
[46.0]
2.24
[56.9]
OPTIONAL
MAGNETIC
NULL ADJUST
4 MOUNTING HOLES
.406 [10.31] THRU
LOCATING PIN
1.437
[36.50]
2.875
[73.03]
3.375
[85.73]
1.687
[42.85]
.25 [6.4]
PRESS
MECHANICAL
NULL ADJUST
3.62 MAX
[92.0]
(G)72K SERIES INSTALLATION AND OPERATION INSTRUCTION
Moog Inc., East Aurora, NY 14052-0018
Telephone: [phone]
Fax: [phone]
Toll Free: 1-800-272-MOOG
www.moog.com
TJW/PDF RevF, January 2023, Id. CDS6754
TYPICAL WIRING 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 Operating Temperature Range:
-40˚F to 275˚F [-40˚C to 135˚C] unless
otherwise specified on nameplate.
3 Valve Phasing:
Flow out port B results when Series coils:
B & C connected, A+, D-;
Parallel coils: A & C connected, B & D
connected; Single coil: A+, B-, or C+, D-.
4 Surface:
Surface to which valve is mounted
requires 63 [ ] finish, flat within .002
[0.05] TIR.
5 Null Adjust:
Flow out port B results with clockwise
rotation of null adjust screw (3/32 hex key).
6 Ports:
P, T, A & B: 0.625 [18.88] Diam. port
O-Rings: 0.070 [1.78] section x 0.801
[20.34] I.D. (universal size -019).
Valves are supplied for either internal
or external pressurization of pilot stage
through Auxiliary Port: Aux. Port Diam;
0.213 [5.41]. Aux. Port O-Ring: 0.070
[1.78] section x 0.364 [9.25] I.D. (universal
size -012).
M
M
M
M
4X .397 THRU
VALVE MOUNTS
ON THIS MANIFOLD
SURFACE
PRESSURE PORT
TANK PORT
CONTROL PORT B
5.00
2.50
CONTROL PORT A
4X .375-16 UNC-2B THD
.013
4.250
2.125
2.000
1.000
1.000
2.000
4.250
2.125
2.875
1.437
.750
PRESSURE PORT
1.687
.750
1.500
3.375
1.60
1.500
2
PORT PER SAE J1926
.4375-20 UNF-2B
DASH 4 STR THD O-RING
BOSS (.25 TUBE OD REF)
63
2.50
5.00
2.50
P
4X PORT PER SAE J1926
1.625-12 UN-2B
DASH 20 STR THD O-RING
BOSS (1.25 TUBE OD REF)
.0015
1.25
4 PL
.39 .30
.014
.593 .60
.250 AUXILIARY PILOT
.014 M
.014
4X .688
.014
3
A B C D
DD
Figure 4
4
5
CERTIFICATION CONTROLLED RELATED DOCUMENT
THIS INSTALLATION INSTRUCTION IS CERTIFICATION CONTROLLED.
REVISION SHALL BE APPROVED BY THE MOOG ICD Ex/ATEX
AUTHORIZED PERSON AND MAY REQUIRE APPROVAL BY THE ATEX
NOTIFIED BODY.
APPLICABLE CERTIFICATE(S):
KEMA 02ATEX1015 X
KEMA 02ATEX1016 X