SANDPIPER ST25A - Manual (Page 4)

520-005-000 1/04 Models ST1-A, ST25A Type 4 Page 4
MoDelS WiTH 1" SUcTion/DiScHArGe or lArGer, AnD
MeTAl cenTer SecTionS
The main air valve sleeve and spool set is located in the valve body mounted on the
pump with four hex head capscrews. The valve body assembly is removed from the
pump by removing these four hex head capscrews.
With the valve body assembly off the pump, access to the sleeve and spool set is
made by removing four hex head capscrews (each end) on the end caps of the valve
body assembly. With the end caps removed, slide the spool back and forth in the sleeve.
The spool is closely sized to the sleeve and must move freely to allow for proper pump
operation. An accumulation of oil, dirt or other contaminants from the pump’s air supply,
or from a failed diaphragm, may prevent the spool from moving freely. 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. Dam-
age 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 prop-
erly. 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, keeping the counter-bored end toward you, and install the spring
and 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.
MoDelS WiTH 1" SUcTion/DiScHArGe or lArGer, AnD
non-MeTAl cenTer SecTionS
The main air valve sleeve and spool set is located in the valve body mounted on the
pump with four hex head capscrews. The valve body assembly is removed from the pump
by removing these four hex head capscrews.
With the valve body assembly off the pump, access to the sleeve and spool set is
made by removing a retaining ring (each end) securing the end cap on the valve body
assembly. With the end caps removed, slide the spool back and forth in the sleeve.
The spool is closely sized to the sleeve and must move freely to allow for proper pump
operation. An accumulation of oil, dirt or other contaminants from the pump’s air supply,
or from a failed diaphragm, may prevent the spool from moving freely. 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.