Eaton Vickers DG3V-8 Series Overhaul Manual page 20

6. Remove pilot spool (22) from body (10).
7. Secure the body and remove plug (24) and ''O'' Ring (25)
from body (10). Discard ''O'' Ring (25).
8 If necessary, remove rest pins (26) with vise grip pliers.
H. Cleaning
All parts must be thoroughly cleaned and kept clean during
inspection and assembly. Close tolerance of valve bodies
and spools make this requirement critical. Clean all parts
with a commercial solvent that is compatible with system
fluid. Compressed air may be used to clean valve, but it
must be filtered to remove water and contamination. Clean
compressed air is particularly useful for cleaning spool
orifices, body passages and drying parts.
I. Inspection, Repair and Replacement
1. Check that all internal passages are clean and free from
obstruction. Examine all mating surfaces for nicks and
burrs. Minor nicks and burrs can be removed with crocus
cloth or an India stone.
CAUTION
DO NOT stone the edges of spool sealing
lands. Remove minor burrs with #500 grit
paper. Use the paper very lightly on the
outer diameter of each spool.
2. Inspect all screws for evidence of damaged threads. If
threads are damaged, replace the screws.
3. Inspect all springs for distortion or wear. The ends of the
springs shall be square and parallel to each other.
Replace springs that are damaged or distorted.
4. Check push pins, pole faces, washers, and manual
plungers for burrs, cracks or mushrooming. Replace all
parts that show evidence of wear.
5. Visually inspect the internal coring (bore) of each body for
large scratches or erosion across the spool land sealing
areas. If such evidence is found, replace valve. If the body
bore passes inspection, check bore to spool clearance
as follows:
A. Lubricate spools and body bores with clean system
fluid. make sure the parts are clean.
B. Insert the spool into its body bore. Rotate the spool
360_ while moving it back and forth. Observe the following:
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.
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.
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 spool 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
both ends 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.
Land Balancing Grooves
Figure 16. Spool Balancing Grooves
Note
Note
20