SANDPIPER HDB2 - Manual (Page 10)

hdb2smdl3sm-rev0614 Model HDB2 Page 8
This can cause the spool to stick in a position that prevents the pump from operating.
If this is the case, the sleeve and spool set should be removed from the valve body
for cleaning and further inspection.
Remove the spool from the sleeve. Using an arbor press or bench vise (with an
improvised mandrel), press the sleeve from the valve body. Take care not to damage
the sleeve. At this point, inspect the o-rings on the sleeve for nicks, tears or abrasions.
Damage of this sort could happen during assembly or servicing. A sheared or cut
o-ring can allow the pump’s compressed air supply to leak or bypass within the air
valve assembly, causing the pump to leak compressed air from the pump air exhaust
or not cycle properly. This is most noticeable at pump dead head or high discharge
pressure conditions. Replace any of these o-rings as required or set up a routine,
preventive maintenance schedule to do so on a regular basis. This practice should
include cleaning the spool and sleeve components with a safety solvent or equivalent,
inspecting for signs of wear or damage, and replacing worn components.
To re-install the sleeve and spool set, lightly lubricate the o-rings on the sleeve
with an o-ring assembly lubricant or lightweight oil (such as 10 wt. air line lubricant).
Press the set into the valve body easily, without shearing the o-rings. Re-install one
end cap, gasket and bumper on the valve body. Using the arbor press or bench vise
that was used in disassembly, press the sleeve back into the valve body. You may
have to clean the surfaces of the valve body where the end caps mount. Material
may remain from the old gasket. Old material not cleaned from this area may cause
air leakage after reassembly. Take care that the bumper stays in place allowing the
sleeve to press in all the way. Re-install the spool, the opposite end cap, gasket and
bumper on the valve body. After inspecting and cleaning the gasket surfaces on the
valve body and intermediate, re-install the valve body on the pump using new gaskets.
Tighten the four hex head capscrews evenly and in an alternating cross pattern.
PILOT VALVE
The pilot valve assembly is accessed by removing the main air distribution valve
body from the pump and lifting the pilot valve body out of the intermediate housing.
Most problems with the pilot valve can be corrected by replacing the o-rings.
Always grease the spool prior to inserting it into the sleeve. If the sleeve is removed
from the body, reinsertion must be at the chamfered side. Grease the o-rings to slide
the sleeve into the valve body. Securely insert the retaining ring around the sleeve.
When reinserting the pilot valve, push both plungers (located inside the intermediate
bracket) out of the path of the pilot valve spool ends to avoid damage.
PILOT VALVE ACTUATOR
Bushings for the pilot valve actuators are threaded into the intermediate bracket
from the outside. The plunger may be removed for inspection or replacement. First
remove the air distribution valve body and the pilot valve body from the pump. The
plungers can be located by looking into the intermediate. It may be necessary to
use a fine piece of wire to pull them out. The bushing can be turned out through the
inner chamber by removing the outer chamber assembly. Replace the bushings if
pins have bent.