29
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 breakdowns.
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. Packing that
appears to be worn, or no longer regulates leakage
properly should be replaced. Mechanical seals should
be cleaned and thoroughly flushed.
Couplings should be dismantled and thoroughly
cleaned. Lubricate the coupling with one of the
coupling manufacturer's recommended lubricants
where required.
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 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 1oz. 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.
NOTE: Excess grease is the most common cause
of overheating.
The bearing frame should be kept clean, since any
contamination of foreign matter which gets into the
housing will destroy bearings in a short time. When
cleaning bearings, use a bearing cleaning solvent, or
an industrial cleaning solvent. Do not use gasoline.
Use lint free cloths. Do not use waste rags.
A regular ball bearing grease should be used, but a
standard commercial vaseline can be substituted if
necessary.
Do not use graphite. A NGLI No. 1 or 2 grease is
generally satisfactory for operation at ordinary
temperatures, the lighter grease for operation at high
speed or low room temperature.
Mineral greases with a soda soap base are
recommended. Grease made from animal or
vegetable oils are not recommended due to the
danger of deterioration and forming of acid. Most
of the leading oil companies have special bearing
greases which are satisfactory. For specific
recommendations, consult the factory.
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.
Grease lubricated bearings should not be used
where temperature of the pumped liquid exceeds
350°F.
