SANDPIPER MP05D - Manual (Page 14)

Models MP05D, MP08D, MP12D and MP14D Design Level 1 Page 2 520-168 thru 171-000 3/03
CAUTION
If a diaphragm fails the pumped product
or fumes can enter the air side of the
pump. This side is exhausted through
the exhaust port (muffler).
When the product is a hazardous or
toxic material, the exhaust should be
piped to an appropriate area for safe
disposition.
When the product source is at a higher
level than the pump (flooded suction),
the exhaust should be piped to a higher
level than the product to prevent spills
caused by siphoning. (Both pumping
diaphragms and driver diaphragms
must fail for this to occur.)
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 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 MARATHON Distributor, or the MARATHON 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 abra-
sions. 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 equiva-
lent, 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, gasket and bumper 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. 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, 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.
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
CAUTION
Before maintenance or repair, shut off
the compressed air line, bleed the
pressure, and disconnect the air line
from the pump. The discharge line may
be pressurized and must be bled of its
pressure. When the pump is used for
toxic or aggressive fluids, it should be
flushed clean prior to disassembly.