Cleaning,
Inspection
and Repair
5
Table 1
AISI Type
Tempered at
HRc
D2 950° F
(510° C)
58-60
M2
1,050° F (566° C)
61-64
M4 1,050° F
(566° C)
61-64
REMEMBER:
Zenith metering pumps are
made for exacting duty. In order to devel-
op the high pressure demanded, the
clearance between the metering gears
and their housing must be as small as
possible, yet large enough to allow ade-
quate lubrication.
All parts are machined to extreme accura-
cy; critical dimensions are held between
one and two ten-thousandths of an inch
(.0001"/.0002"). Because of these close
running clearances, Zenith pumps require
careful maintenance and handling, espe-
cially of component parts. The slightest
burr, nick or particle of foreign matter can
cause scoring or even seizure. Zenith
pumps are precision instruments; you
can't keep them too clean. Please treat
them with care, and if it’s at all possible,
set aside a separate clean area for pump
maintenance.
To clean H-Series metering pumps,
place them in a suitable furnace and
gradually heat in an inert atmosphere for
the initial hour to prevent flashing of the
polymer. Time at temperature will be relat-
ed to the pump size and the degree of
polymer contamination and should be
determined by trial.
NOTE:
Careful control of the furnace
temperature and atmosphere is critical.
Should the temperature exceed the origi-
nal tempering temperature, the
steel hardness will draw back and the
dimensional stability of the pump may
be upset. Consult Table 1 for proper tem-
pering temperature.
Another acceptable cleaning method
is to immerse the pump in a fluidized bed
cleaning bath. The bath should be heated
to a temperature that is sufficient to car-
burize the polymer. The carburization
process usually takes between 3 to 12
hours, depending on the polymer type,
temperature, pump size, and furnace load.
CAUTION:
Avoid exposing the pump to
thermal shock when using this method of
cleaning.
After gradually cooling to room tem-
perature, the pump should be thoroughly
flushed in a clean solvent. It may be
necessary to disassemble the seal
arrangement to remove polymer ash.
Always replace the carbon seal plate
(if equipped) and fasteners after pump
burnout. If the pump was performing
satisfactorily when removed from service
and still turns freely after burnout, pres-
sure test it and add a high-temperature
lubricant to prepare it for return to service.
To store for future use, simply add a rust
preventative oil.
It is recommended that pump
users institute a program of dimensional
inspection of critical parts in order to keep
maintenance and operating costs at a
minimum. By noting the performance of a
pump immediately before removing it from
service and correlating the performance
to measured component wear, the user
can establish the maximum wear limits for
the pump’s critical components. Further,
he can predict the service life of the
pump, and schedule his down-time
accordingly.
As with any other Zenith pump, H-
Series pumps may be returned to Zenith
for complete rehabilitation as necessary.
This procedure may be desirable if only a
few pumps are involved. If a large number
of pumps are to be maintained at the
user’s plant, it may be worthwhile to have
key personnel attend a maintenance
seminar at the Zenith factory to view the
manufacturing, gaging, and assembly
techniques involved in producing the
H-Series pump. In addition, Zenith also
offers a contract service program. Please
contact Zenith for further information on
these items.
