SANDPIPER MHDF25 - Manual (Page 9)

mhdf1dl1sm-rev0711 Models MHDF1 & MHDF25 Page 7
AIR VALVE LUBRICATION
The SANDPlPER 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
MARATHON) 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 Per-
formance 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 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 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+PLUS ® : 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
MARATHON Distributor, or the MARATHON factory Literature Department. To receive
the correct manual, you must specify the MODEL and TYPE information found on the
name plate of the pump.
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 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
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). Re-install one end cap, and retaining ring (see safety warning), on the
valve body. Using the arbor press or bench vise that was used in disassembly,
carefully press the sleeve back into the valve body, without shearing the o-rings.
Re-install the spool, opposite end cap and retaining ring (see safety warning), 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, at 150 in./lbs. (16.94
Newton meters).
SAFETY WARNING
To assure proper pump func-
tion and safe installation of the
retaining ring, check the gap “G”
dimension for full installation
into the valve body grooves.
RECOMMENDED MARATHON
ACCESSORIES TO MAXIMIZE
PUMP PERFORMANCE:
• Surge Suppressor.
For nearly pulse-free flow.
• MARATHON Filter/Regulator.
For modular installation and
service convenience.
• MARATHON Speed Control.
For manual or programmable
process control. Manual adjustment
or 4-20mA reception.
For more detailed information on
these accessories, contact your local
MARATHON Factory-Authorized
Distributor, or Warren Rupp corporate
headquarters or visit:
www.warrenrupp.com
> .232 "G"
Dimensions between lugs