22
If the spool does not move freely, the spool is sticking inside the
body bore. Remove the spool and recheck the spool and body
bore for scratches and/or burrs. remove any minor scratches
or burrs with India stone or crocus cloth. Repeat steps A and B.
Note
An alternate test is to turn the body on end and allow
gravity to pull the spool from the body into your hand. if
the spool does not move under the influence of gravity,
the spool is sticking inside the body bore.
If the spool binding persists, replace the valve.
Check the feel of the spool. If side movement of the spool
can be felt within the body bore, the body/spool clearances
are excessive. A new spool and body have a select fit of
approximately 0.0002-0.0003 inch. Body/spool clearances in
excess of this value may still work satisfactorily in your
system; however, limitations are dependant on how much
leakage your valve system can tolerate. Normally, excessive
body/spool clearances dictate replacing the entire valve.
Note
If a new spool is installed into a new or used body, break
the feathered edges of the spool balancing grooves with
a three or four cornered India stone. See Figure 20.
Lightly polish the spool with #500 grit paper. Wash the
spool in clean solvent. Repeat steps A and B.
Step 6 pertains to detented ‘‘N’’ pilot valves only.
6. Check the detent by moving the push pin through the
detent. A steady frictional force should be observed. If
the detent force is weak (less than 1 lb.), replace the
detent subassembly. The detent should be assembled on
the polished end of the spool.
7. Perform a continuity test on each solenoid coil S/A.
Resistance values will vary with the voltage rating of the
coil. Refer to Table 8. This test is superficial, but a more
rigorous test requires special equipment. If the coil
seems to be burned or extreme heat is encountered
during operation, the coil may be shorted. make sure the
correct voltage is being applied to the coil.
Figure 20. Spool Balancing Grooves
Land Balancing Grooves
Voltage
Coil Resistance
6 DC
1.5 Ohms
12 DC
5 Ohms
24 DC
24 Ohms
48 DC
80 Ohms
115 DC
480 Ohms
230 DC
1800 Ohms
115 AC (60 Hz)
13 Ohms
230 AC (60 Hz)
50 Ohms
460 AC (60 Hz)
204 Ohms
Table 8. Coil Resistance
J. Assembly
Before assembly, obtain the correct seal kit as noted in the
parts drawing. Lubricate all ‘‘O’’ rings and internal parts with
clean system fluid to provide initial lubrication and facilitate
assembly.
Check the model code to determine correct assembly of
units. If a L.H. suffix appears in the model code, the pilot
valve solenoid is assembled left hand. In such cases, all pilot
valve parts are reversed except the body and spool,
Assembly will be in reverse of the disassembly sequence
shown in Figures 15 and 17 unless otherwise specified.
K. General Main Stage Assembly
(Refer to Figure 15)
1. Install ‘‘O’’ rings (22) on plugs (23). Lubricate plug
threads and install plugs into body (5). Torque plugs to
value noted in parts drawing. Refer to Table 1.
2. Tap new rest pin(s) (26) into place if removed during
disassembly.
Note
The following step pertains to integral check valve models.
3. Place spring (19) into poppet (18) and then install poppet
into pressure port (P) cavity as shown. Obtain a suitable
push rod and press seat (17) into pressure port (P)
cavity. (See assembly drawing for seat orientation.) Use
an arbor press for this operation. Install ‘‘O’’ ring (16) into
pressure port mounting groove.
4. Install ‘‘O’’ rings (24) into ‘X’ and ‘Y’ port mounting
grooves.
5. Install ‘‘O’’ rings (25) into port mounting grooves ‘A’, ‘B’,
‘P’ and ‘T’.
