KTH Sales, Inc.
Notes regarding the use of pumps for electroless nickel or electroless copper
solutions.
Due to the self plating nature of the above plating solutions care must be
exercised in selection of pumps for these applications. Being self-plating, metal
particles will be deposited on CPVC, polypropylene plastics as well as ceramic materials,
under some conditions:
Horizontal centrifugal pumps that are sealed with double or water-flushed
mechanical seals have been tried without much success for long periods of time. The
mechanical seal faces will be plated with metal and will rapidly wear the seal faces to a
point of failure – the pump will then leak.
Magnetic driven pump will also suffer damage due to the metal deposits on the
ceramic shaft or bearing within the pump. Failure may not cause leaking but will lead to
continued parts failures and high maintenance costs.
Vertical immersion pumps such as Penguin P Series pumps have performed very well
for this application. The open clearances of this seal less and bearing free pump design
will tolerate a level of plateup of material and continue to pump with little problems.
Nitric acid used for stripping however does have an effect on the standard materials
(CPVC) of construction. The use of PVDF (Kynar) thermoplastic as the impeller material
offers advantages of; (1) Higher working temperature. (2) greater resistance to plateup
and (3) greater corrosion resistance to Nitric strip.
PVDF impellers can and are commonly used within a CPVC housing. This offers an
economical advantage verses an all PVDF pump. KTH Sales will modify the standard CPVC
construction pump by changing the impeller to PVDF and using a Viton head O-ring. Penguin
pump model numbers equipped with this option will end with the letters "A-EN".
The temperature of most EN systems of
190oF introduces extra care be
given in piping support and pump housing support. CPVC material is slightly
above to the
maximum operating temperature of 180 oF and
is flexible. Piping stress will distort the housing and if excessive will cause the
housing (or head) to rub against the impeller. Inspection of this type of failure will
show an egg shape enlargement of the housing at the area of contact with the impellers
sleeve and/or wear within the impeller side of the head of the pump. The impeller will
also show the results of rubbing with a failure of the impeller sleeve or impeller drive
insert. (It was not the impellers fault however you still may need a new one.) The housing
will take a new shape (that of bent) and will not return to the old shape of straight
– sorry, it will need replacement as well. The piping stress must be removed or the
pump will fail again.
The use of all PVDF construction of the pump will offer a greater level of
tolerance of piping stress over that of CPVC. The material having greater strength (and
cost) than CPVC is less subject to this failure however is not immune. Bottom Line: The
installation of the pump should be free of piping stress.
Please keep in mind, heating of nitric acid will cause a failure of CPVC in all
cases. The sign of the heating will show a whiting color of the CPVC and may show signs of
melting. This will also effect the piping system as well if CPVC.
Penguin has lowered the maximum temperature
recommendation of CPVC from 200 to 180 oF
KTH Sales, Inc. - revised August,
2000
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