Eaton Vickers SF4-140-20-002-10 User manual

Two-Stage Flapper Type Servo Valve
SF4-140-20-002-10
SF4-100-30-002-10
Overhaul Manual
I-3063-S
Revised 02/01/74
Vickers®
Valves

2
Table of Contents
Section Page
I. Introduction 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A. Reference Material 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B. Kits 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
II. Overhaul 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A. Unit Removal 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B. Special Tools 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C. Improvised Tools 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
D. Disassembly 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
E. Cleaning 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
F. Inspection, Repair, and Replacement 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
G. Assembly 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
H. Unit Installation 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
III. Test Procedure 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A. Test 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3
Section I – Introduction
A. Reference Material
Installation dimensions and operating specifications are not
contained in this manual. Refer to installation drawing
501170 for that information.
B. Kits
A gasket kit is available for this servo valve. It is recom-
mended that new O-Rings and gaskets be used during
overhaul. The part number of the kit is 919529.
x 100 Equals Supply Pressure in psi
3 5
1
34 512
2
Table 1. Model Code Breakdown
Servo Valve, series, 4-way
x 0.1 Equals Flow Rate in gpm
Model Series Design No. & Modification
4Coil Designation - number x 10
Equals Coil Resistance in Ohms
Figure 1. Exploded View of Servo Valve
30 6
7
5
8
9
36
29 25 24 23 19 18 21 13 12
31 32 33
34
37
1
2
3
4
17
22 16 20 15
14
27 35 28 26 11 10
Pilot
Stage

4
Legend for Figures 1 thru 4
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
199811
207892
376706
323926
174638
–
286122
353860
353859
42590
68904
344966
323931
351042
102671
346773
154006
352641
233106
351437
343410
112201
323933
233106
200345
351436
343414
157515
154139
154004
11012
323923
154140
942070
942320
64765
16794
7074
323921
O-Ring
Screw
Cover
Gasket
Screw
Nameplate
Gasket
Screw
Clamp
Screw
Washer
Screw and Lock Washer S/A
Armature Flapper
Spring
Retaining Ring
Coil and Seal
O-Ring
Lock Nut
Washer
Nozzle (SF4-100-30-002-10)
Nozzle (SF4-140-20-002-10)
Screw
Frame
Washer
Nut
Adjusting Screw
Adapter Plate S/A
O-Ring
O-Ring
O-Ring
Screw
Cover
O-Ring
Spool S/A (SF4-140-20-002-10)
Spool S/A (SF4-100-30-002-10)
Plug
Orifice Plug
Plug
Body
5
4
1
1
4
1
1
1
1
2
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
4
1
1
1
1
1
1
1
1
Y
Y
Y
Y
Y
Y
Y
Y
Index
Number
Part
Number Name Qty.
Y919529 Gasket Kit

5
Section II –Overhaul
A. Unit Removal
WARNING
Turn off all electrical power and relieve hydraulic
pressure. Block any load that could generate
pressure.
1. Remove the unit from the system.
2. Cap all system openings to prevent entry of dirt.
B. Special Tools
The following special tools are needed:
1. Torque wrench rated in lb.in.
2. Flushing plate. Refer to figure 6 for dimensions.
3. 0-500 milliammeter.
C. Improvised Tools
No improvised tools are required for overhaul.
D. Disassembly
Periodic maintenance of the valve will generally not require
disassembly to the extent described here. However, the
sequence can also be used as a guide for partial disassem-
bly. In general, disassembly is accomplished in the item
number sequence shown on Figure 1. Special procedures
are included in the following steps:
1. Thoroughly clean the exterior of the valve.
2. The valve is full of fluid, so hold it over a container
when the cover (3, Figure 1) is removed.
3. Remove parts (1) thru (11) according to sequence.
4. Remove the pilot stage parts (12) thru (26) as a unit
by pulling the adapter (26) from the main stage body (37); at
the same time, push the coil connector from the body. See
Figure 4. Disassemble the pilot stage according to numerical
sequence in Figure 1.
5. Remove parts (27) thru (37).
E. Cleaning
All parts must be thoroughly cleaned and kept clean during
inspection and assembly. The close tolerance of servo
valves makes this requirement more stringent than usual.
Use a commercial solvent which is compatible with the sys-
tem fluid to clean the parts. Compressed air may be used in
cleaning the valve but it must be filtered to remove water and
contamination. Clean compressed air is particularly useful in
cleaning the spool orifices and body passages.
Figure 2. Locating of Adjustment Screw Nuts and Washers
19
18
22
24
23
25
Washer
Lock
Nut
Frame
Nut
Adjusting
Screw
Washer
F. Inspection, Repair, and
Replacement
Check that all internal passages are clean and unob-
structed. Examine all mating surfaces for nicks and burrs.
Check the condition of threaded parts and threaded holes.
Check the retaining ring (15). Minor burrs can be removed
with an India stone.
CAUTION
The spool (33) must not have the land edges broken
with the stone. They are held to a very close
tolerance.
1. Make sure that the 0.020 hole in the side of the spool
(33) and the 0.030 hole in the orifice plug which is screwed
in the end of the spool are completely open. (See Figure 5.)
The orifice plug in the end of the spool may have to be
removed to clean out contaminants that have gathered
inside the spool.
Figure 3. Pilot Stage Servo Valve Adjustment Locations
25
13
26
12
20
Adjusting Screw
Holding Screws
and Lockwashers
0.010 Clearance
Nozzle
Flapper Armature
Adapter S/A
Extrusion

6
2. Check the 0.060 hole in the nozzle (20).
3. Check frame (22) for cracks or distortion.
4. Check the feedback spring (14) for distortion.
5. Make a continuity check of the coil and seal
subassembly (16). Resistance values should range from 18
to 22 ohms. This test is superficial but a more rigorous test
requires special equipment.
6. Check the adapter (26) and spool mating surfaces.
Insert the spool into the adapter and rotate the spool. The
spool must not bind in any position.
G. Assembly
Replace the gaskets and O-Rings with those supplied in the
gasket kit. Apply a light film of clean system fluid to the parts
prior to installing them. This will make assembly easier and
provide initial lubrication. Special procedures are included in
the following steps:
1. Assemble parts (37) thru (35). See Figure 1.
2. Assemble the pilot stage portion of the valve as
follows:
a. Assemble parts (26), (22) , (21) and (20).
b. Install adjusting screw (25) thru the adapter (26),
attach standard nut (24) and washer (23) and turn the nut on
until it bottoms against the shoulder of the adjusting screw.
See Figures 2 and 3.
c. Turn the adjusting screw (25) thru the hole on the
frame (22) far enough to attach the other washer (19) and
lock nut (18).
d. Turn one of the nuts until it contacts the frame,
then tighten the other nut. See Figure 2.
NOTE
After tightening the nuts (18) and (24) against their
respective washers, the adjusting screw (25) should
turn free and have no end play between the screw
and the frame (22).
e. Assemble parts (17) thru (15). See Figure 1.
CAUTION
Be careful when installing flapper armature (13). The
securing screws (12) extend thru the frame (22) and
could break the insultation on the coil. See Figure 3.
Figure 4. Sectional View
Wires
8 9
14
10
11
26
37
33 Spool S/A
Body
& Clamp and Screw
Note: Push coil connector out of
body at same time pilot
stage is being removed.
Feedback Spring
Screw
Washer
Adapter S/A
”A”

7
Figure 5. Spool Subassembly
Orifice Plug
See Note:
Holes must be clean
Note: Grip here if orifice plug must be
removed to clean inside of spool.
f. Place a 0.010 shim between the flapper armature (13)
and the nozzle (20) while tightening the two holding screws
and lockwashers (12). See Figure 3.
NOTE
The flapper armature must be square with the
nozzle when the operation is completed and have a
0.010 clearance. A change in the setting of the
adjustment screw (25) may be required during this
procedure to keep the flapper armature square with
the nozzle.
3. Install O-Ring parts (29) thru (27) into valve body
(37).
4. Insert spool subassembly (33) into body (37). The
small end of the spool must extend from the valve
approximately one inch. Assemble the pilot stage (adapter
subassembly (26)) over the spool for alignment purposes.
Guide coil wires thru body hole and align the coil connector
with body hole while installing. See Figure 4. Tighten the
adapter holding screws (10) and washers (11) alternately
until the pilot stage is flush against the valve.
5. Check spool to see that it doesn’t bind in the adapter
(26) then torque the screws to 16-18 lb. in. Recheck for
binding.
6. Assemble the feedback spring (14) to the flapper
armature by twisting the spring over the extrusion until the
spring is tight against the flapper armature. Use a twisting
motion only, lateral force against the flapper armature may
bend it. See Figure 4.
7. Assemble parts (34) and (32) thru (30).
8. Turn adjusting screw (25) until light can just be seen
between the flapper and orifice, point ”A”, Figure 4. This is a
preliminary null adjustment.
9. Assemble clamp (9) and screw (8) over the wire.
Route the wire ends thru the hole to the outside of the valve.
See Figure 4.
NOTE
The name plate, gasket, and screws, parts (7) thru
(5), should not be installed at this time since a final
null adjustment must be made before normal
operation can begin.
10. Install parts (4) thru (1). Torque screws (2) to
16-18 lb. in.

8
Figure 6. Flushing Plate
3.00
1.438
2.130
2.120
1.067
1.057
2.44
0.943
0.933 0.943
0.933
0.312
0.536
0.526
1.567
1.557
1.817
1.807
0.2812 Drill thru
4 holes
0.4219 Drill - 2.72 deep
1/4 NPT thread
1.000
Stock
0.844
0.610
0.615 Dia.
3 Places 0.015 R
Max.
0.045
0.050
63
0.500
0.4219 Drill - 0.53 deep
counterbore as shown -
3 holes
1.438
0.500 0.4219 Drill - 2.12 deep
1/4 NPT thread
Material:
Free machining
low carbon steel
Surface finish:
125 except where specified.
H. Unit Installation
Flush the system through 10 micron full flow filters prior to
installing the servo valve. A flushing plate can be manufac-
tured. (See Figure 6.) The plate passes the fluid directly to
the tank port. Continue flushing until new filters show no sign
of contamination. It may be necessary to change the system
fluid. If so, filter the new fluid as it is poured into the reservoir
and then flush the system as described above. After the
system is flushed, remove the flushing plate and install the
servo valve. Torque the mounting screws to a maximum of
112 lb.in.

9
Section III –Test Procedure
A. Test
1. Utilize your present control system to test the servo
valve as follows:
CAUTION
Check polarity of 0-500 milliammeter with system
polarity prior to installation to prevent meter damage.
a. Connect meter in system according to Figure 7.
b. Adjust appropriate system command control until a
reading of 190 milliamps is observed on meter.
c. Energize the hydraulic system and adjust for hydrau-
lic null (no movement of hydraulic motor or cylinder) with
adjustment screw (25). See Figure 1.
d. Slowly vary the system command controls so that
current shown on the milliameter varies from 0-400
milliamps. A smooth transition from zero to maximum flow
should occur both sides of center (null) position. Erratic
movement may indicate that the servo valve spool is sticking.
Figure 7. Servo Test Wiring Circuit
Command
System
Servo
Coil
0-500
MA
–
–
+
–+
+