18
MAINTENANCE
GENERAL MAINTENANCE
Operating conditions vary so widely that to
recommend one schedule of preventative
maintenance for all centrifugal pumps is not
possible. Yet some sort of regular inspection must
be planned and followed. We suggest a
permanent record be kept of the periodic
inspections and maintenance performed on your
pump. This recognition of maintenance procedure
will keep your pump in good working condition,
and prevent costly breakdown.
One of the best rules to follow in the proper
maintenance of your centrifugal pump is to keep a
record of actual operating hours. Then, after a
predetermined period of operation has elapsed,
the pump should be given a thorough inspection.
The length of this operating period will vary with
different applications, and can only be determined
from experience. New equipment, however,
should be examined after a relatively short period
of operation. The next inspection period can be
lengthened somewhat. This system can be
followed until a maximum period of operation is
reached which should be considered the operating
schedule between inspections.
MAINTENANCE OF PUMP DUE TO FLOOD
DAMAGE
The servicing of centrifugal pumps after a flooded
condition is a comparatively simple matter under
normal conditions.
Bearings are a primary concern on pumping units.
First, dismantle the bearings; clean and inspect
them for any rusted or badly worn surfaces. If
bearings are free from rust and wear, reassemble
and relubricate them with one of the
recommended pump lubricants. Depending on the
length of time the pump has remained in the
flooded area, it is unlikely that bearing
replacement is necessary; however, in the event
that rust or worn surfaces appear, it may be
necessary to replace the bearings.
Next, inspect the stuffing box, and clean out any
foreign matter that might clog the box. Mechanical
seals should be cleaned and thoroughly flushed.
Couplings should be dismantled and thoroughly
cleaned.
Any pump that is properly sealed at all joints and
connected to both the suction and discharge
should exclude outside liquid. Therefore, it should
not be necessary to go beyond the bearings,
stuffing box, and coupling when servicing the
pump.
BEARING LUBRICATION – GREASE
Grease lubricated ball bearings are packed with
grease at the factory and ordinarily will require no
attention before starting, provided the pump has
been stored in a clean, dry place prior to its first
operation. The bearings should be watched the
first hour or so after the pump has been started to
see that they are operating properly.
The importance of proper lubrication cannot be
over emphasized. It is difficult to say how often a
bearing should be greased, since that depends on
the conditions of operation. It is well advised to
add one ounce of grease at regular intervals, but it
is equally important to avoid adding too much
grease. For average operating conditions, it is
recommended that 1 oz. of grease be added at
intervals of three to six months, and only clean
grease be used. It is always best if unit can be
stopped while grease is added to avoid
overloading.
The grease relief plug should be removed from the
outboard bearing housing before adding new
grease to the bearing. The plug should then be left
out until the pump is run for a minimum of 2 hours
and the system has reached its normal operating
temperature.
NOTE:
Excess grease is the most common cause
of overheating.
A lithium-based NLGI-2 grade grease should be
used for lubricating bearings where the ambient
temperature is above -20°F. Grease lubricated
bearings are packed at the factory with Shell
Alvania No. 2. Other recommended greases are
Texaco Multifak No. 2 and Mobilux No. 2 grease.
Greases made from animal or vegetable oils are
not recommended due to the danger of
deterioration and forming of acid. Do not use
graphite. Use of an ISO VG 100 mineral base oil
with rust and oxidation inhibitors is recommended.
The maximum desirable operating temperature for
ball bearings is 180°F. Should the temperature of
the bearing frame rise above 180°F, the pump
should be shut down to determine the cause.
MECHANICAL SEALS
a. Mechanical seals are precision products and
should be treated with care. Use special care