WILDEN PUMPS , AIR OPERATED DIAPHRAGM PUMPS ON CHEMICAL TANKERS- CAPT AJIT VADAKAYIL
Wilden or Versa-matic
diaphragm pumps need no special introduction. These are air operated diaphragm
pumps.
This piece is meant to
highlight the safety and chemical resistance aspects. In any case every crew
member must be familiar in rigging up a wilden pump as they are used for
chemical spill contingency.
Wilden pump is not a
submersible pump. You have to keep the pump just above the level of the liquid
to be pumped.
There must be an
awareness of the diaphragm material or the pump is spoilt and worse people
could get injured very badly or there could be an explosion. It may develop
fluid dischg pressure equal to the air supply pressure. Always wear eye
protection when working with the pump.
See video below to understand how the pump works.
On chemical tankers we
do not use neoprene or Buna rubber diaphragm wilden pumps. Rather only Teflon
or Viton pumps are used . SS shell is preferred as many chemicals react with
aluminium and alloys shells.
Usual models supplied on board are M1, M2 and M4
models. An M4 SS model with Teflon
diaphragm will weigh about 19 kgs.
Teflon elastomeric
diaphragms are not as efficient as rubber as the discharge capacity is reduced
by 20% and the suction lift is also reduced. The wilden pump in the ballast
pumproom can have a neoprene diaphragm.
If the chemical is
viscous a larger non collapsible and reinforced inlet pipe is required to avoid
cavitation. It is critical that on the suction side there must not be any leaks
. The suction flexible mouth must be sliced off at an angle to mate on to the
tank bottom.
M2 pumps are used to mop the couple of litres of condensed water at the Framo deepwell pump suction mouths of all cargo tanks after final steaming.
M2 pumps are used to mop the couple of litres of condensed water at the Framo deepwell pump suction mouths of all cargo tanks after final steaming.
Drain the compressed
air line before you use it to power the wilden pump. This is most important if
you are using it to pump a water reactive chemical. Imagine heat and exothermic
sputtering of Sulphuric acid inside the pump because of a leaky diaphragm.
If
there are air bubbles in the discharge of the pump it means the diaphragm is
torn or the diaphragm plated to pump shaft is not tight. Do not put your face
next to the air exhaust which may be contaminated .
The bottom orifice is
always the suction and the top one is always the discharge.
Always keep sufficient
wilden pump spares.
If you have to use it
inside the tanks use an air exhaust muffler—or you may land up wearing ear
protection which is not desired. Always
shut off the air supply and disconnect it from the pump before doing any maintenance
or inspection.
When pumping flammable
and static accumulator liquids the wilden pump must be earthed. Sparks can
ignite and cause an explosion. Many of you must have experienced wilden pump
shock.
Never exceed the max
temp limit of the diaphragm, balls and seats of your pump.
Viton/ -40C to 176 C
Teflon/ 4C to 105 C
Neoprene / -18C to 93C
CAPT AJIT VADAKAYIL
( 30 Years in command.)
Sir,
ReplyDeleteAre the strokes in these kind of pumps fast enough to give a steady flow of fluid or the flow keeps pulsing ? Also how many strokes per minute a Wilden pump is capable of, depending upon the type of diaphragm used.
Thanks.
hi matt,
DeleteM2 will give 2 cubic metres discharge per hour, if you run the pump optimum.
air flow can be controlled to decrease output.
M4 will give 4 cum/ hour and so on.
the flow is NOT steady like that of a gear pump or screw pump.
capt ajit vadakayil
..
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