SANDPIPER MHP2M - Manual (Page 3)

mhp2mdl4sm-rev0513 Model MHP2M Page 3
move back and forth freely. This is most important when the air supply is lubricated. If
a lubricator is used, oil accumulation will, over time, collect any debris from the com-
pressed air. This can prevent the pump from operating properly.
Water in the compressed air supply can create problems such as icing or
freezing of the exhaust air causing the pump to cycle erratically, or stop operating. This
can be addressed by using a point of use air dryer (available from Warren Rupp) to
supplement a plant’s air drying equipment. This device will remove excess water from
the compressed air supply and alleviate the icing or freezing problem.
ESADS: Externally Serviceable Air Distribution System
Please refer to the exploded view drawing and parts list in the Service Manual sup-
plied with your pump. If you need replacement or additional copies, contact your local
Warren Rupp Distributor, or the Warren Rupp factory Literature Department at the
number shown below. To receive the correct manual, you must specify the MODEL and
TYPE information found on the name plate of the pump.
Main Air Valve
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 sup-
ply, 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 pres-
sure 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. Reinstall 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, reinstall the valve body on the pump using new
gaskets. Tighten the four hex head capscrews evenly and in an alternating cross
pattern.
PILOT VALVE ACTUATOR SERVICING
The bushings for the pilot valve actuators are threaded into the intermedi-
ate bracket from the outside. The plunger may be removed for inspection or
replacement from the inside by removing the air distribution valve body and the pilot valve
body from the pump. The plungers should be visible as you look into the intermediate
from the top. Depending on their position, you may find it necessary to use a fine piece
of wire to pull them out.
Under rare circumstances, it may become necessary to replace the o-ring seal. The
bushing can be pushed through the inner chamber by removing the outer chamber the
assembly to reach the bushing.