SANDPIPER MHDF3 - Manual (Page 8)

mhdf3dl7sm-rev1210 Model MHDF3 Page 6
AIR VALVE LUBRICATION
The MARATHON pump’s pilot valve and main air valve assemblies are
designed to operate WITHOUT lubrication. This is the preferred mode of
operation. There may be instances of personal preference, or poor quality air supplies
when lubrication of the compressed air supply is required. The pump air system will
operate with properly lubricated compressed air supplies. Proper lubrication of the
compressed air supply would entail the use of an air line lubricator (available from
Warren Rupp) set to deliver one drop of 10 weight, non-detergent oil for every 20
SCFM of air the pump consumed at its point of operation. Consult the pump’s published
Performance Curve to determine this.
It is important to remember to inspect the sleeve and spool set routinely. It should
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
compressed 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.
Externally Serviceable Air Distribution System
Please refer to the exploded view drawing and parts list in the Service Manual
supplied 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.
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.
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. 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.