|Good maintenance practices
begin when parts are first received. Inspecting parts when they
first arrive should be mandatory. Too often, parts are received
and accepted with the stroke of a pen and are later found to be
defective when they are needed most. The maintenance department
should be informed when spares and replacement parts are being received,
particularly where major components are concerned. They should then
test the equipment to ensure that it meets the client?s design specifications
before acceptance while it is still under the manufacturer?s warranty.
the contract negotiations for the equipment, the buyer should
insist that the manufacturer?s warranty does not start until the
equipment is operating to the client?s satisfaction.
Often, during new
plant construction, equipment will lie in the storeroom without
any maintenance for many months, which negates the warranty even
before installation and operation.
When a major component
or complete piece of equipment is tested at the manufacturer?s
site, it is virtually guaranteed to pass the acceptance inspection
because it is set up under ideal conditions. However, when the
equipment is being delivered, it is often subjected to abuse during
transportation. This abuse is usually not intentional; but in
the course of being transported, the equipment can be subjected
to vibration, false Brinnelling of bearings (false Brinelling
is a fretting-type phenomenon normally caused by vibration while
the bearing is not rotating or by oscillating motion of very small
amplitude), or improperly placed lifting slings, which allows
bending of the frame or bedplate to take place. This can take
place two or three times before the equipment is finally lifted
into position. The only guarantee that is left is for the client
and the manufacturer?s representative to perform a quality control
audit at each step of the receipt and installation process. If
this type of control is not practiced, you can expect the equipment
to experience problems that will place it in a reactive-maintenance
mode over its operational lifetime.
When spare parts and
components are to be stored for a lengthy period, the storeroom
should have a maintenance program in place and a maintenance schedule
set to perform periodic tasks to ensure that those components
and parts will always be ready to use.
The following guidelines
are based on manufacturers? storage instructions and my past experience.
Motors should be rotated
at least 4½ turns every two weeks to prevent false Brinnelling
of the bearings. This is to ensure the bearing?s rolling elements
are lubricated during rotation. The extra ½ turn takes
the rotor shaft off of its last standing position, thus preventing
further loading at the previous rotor location.
To ensure that grease
is suitable for use in certain bearings, all recommended greases
should be color-coded and the grease guns suitably colored to
match that particular grade of grease. The amount of grease that
is delivered from one stroke of the grease gun should be weighed
and inscribed permanently on the barrel of the gun for future
Before greasing bearings,
ensure the correct grade of grease will be used and determine
how much is to be applied. Bearing grease should be checked at
least twice a year to ensure there are no signs of separation
contamination. Also check that the grease nipples are clean. As
an added precaution, installation of plastic caps over the nipples
should be used to color-code to match the grease guns, to protect
the grease nipple ports, and to prevent ingress of dirt into the
bearings during greasing operations. Add make-up
grease to each bearing cavity with its vent drain plug removed
to permit excess grease to vent. During greasing operations, turn
the shaft by hand to ensure even distribution of grease within
the cavity. When the excess grease stops venting, replace the
drain plug and wipe the area clean with a lint free rag.
The lower half of
a bearing should be 1/3 to ½ full when the bearing cavity
is correctly greased.
Motors heaters (if
fitted) should be checked on a monthly schedule to ensure that
the heaters are energized and that there is no sign of condensation
forming on the windings. Insulation tests should be performed
at least every six months.
Motors should be stored
in a controlled environment and kept off concrete floors to avoid
dust collecting in the vents and windings. Avoid areas of dampness
and direct exposure to fans or vents.
must always be considered as precision products and, as such,
they must be stored in a clean, temperature-controlled environment.
Users often stock
bearings in fairly large quantities. However, even though the
manufacturer takes precautions to deliver quality products that
are properly packaged to withstand long periods of time, damage
often occurs in the storeroom. New bearings can be damaged if
they get too hot, are stored in damp or extremely dirty locations,
if packing boxes are opened and then improperly resealed, or someone
drops them. Once these protective properties are lost, the bearing
can rust from having lost its protection against dampness.
New bearings are shipped
in plastic sealed bags or wrapped in moisture resistant paper.
Do not use
newspaper or ordinary untreated paper. These products have a blotting
effect and will soak up oil or grease; they also have an affinity
for moisture and should never be used to protect new or used bearings
in long-term storage.
The following precautions
must be observed to prevent bearings from getting dirty and rusty:
All bearings should be
stored flat on the shelves and clearly labeled with their respective
identifiers such as:
- Never store bearings
next to steam lines, a furnace, or in unusually warm areas within
- Never store bearings
where direct sunlight hits them as this will melt factory-protective
- Never let bearing
boxes or wrappings become excessively dirty or wet.
- Never handle bearings
with bare hands if boxes or wrappings are opened and improperly
resealed. The natural pH balance of the human body is very acidic
and can cause corrosion in bearings that have been touched by
- Never use untreated
paper to wrap bearings that are being returned to stock.
- Never return bearings
to stock that have not been properly lubricated with grease.
Grease should be worked in between the balls or rollers to coat
every surface, including the inside and outside of the races
to prevent rust formation on uncoated surfaces of the metal.
- Never use compressed
air to blow-dry bearings after cleaning. This is a dangerous
practice that can cause the rolling elements to spin at high
speeds, which can shatter the more-brittle outer race and severely
maim or kill someone.
- Never use cotton
waste or dirty clothes to wipe or handle bearings.
- Lint and other
foreign matter may cause serious damage.
- Never polish out
nicks and abrasions with emery cloths.
- Never bump or
drop bearings, even on soft wooden surfaces, as this will jolt
the rolling elements against the cages causing minute indentations.
This is usually referred to as false Brinnelling.
The bearings should be
grouped together by manufacturer, type and size in isolated cubicles
with the above information clearly posted in front of the cubicle
- Job identifier
(pump, motor, fan etc.)
- Bearing manufacturer
(SKF, Fafnir, Timken etc.)
- Bearing type (SKF
series SDAF 230 KA) Spherical Roller Bearing Pillow Blocks etc.
- Number and type
of rolling elements (ball, roller, needle etc.)
cylindrical sleeve bearings should be placed flat on wooden bases.
Ensure the protection covers are in place over the openings to
protect the Babbitt faces and edges from damage.
A max/min set of numbers
should also be established and posted to inform people of stock
levels so that those levels will be maintained. This should take
into account what the manufacturer?s lead times are for deliveries
of that part.
of new pumps is critically important to the general overall health
of the machine. When new pump units complete with motor and/or
gearbox arrive on site, an immediate on-site inspection should
be carried out. Often, a pump unit may have three different manufacturers?
equipment on a skid (bedplate), a motor, and a gearbox and pump
that a fourth member then assembles. Each of the three principle
suppliers may have different ideas about how their components
should be installed and then, in many cases, the fourth member
installs the equipment on the skid to their standards. Their standard
practices may not be in compliance with the original manufacturer?s
standards. This scenario may cause problems for the receiving
client when it comes to warranty repairs.
Sometimes, the main
parties will not honor any warranty agreements because they did
not sell their equipment direct to the user. The assembler is
then responsible but may not have the skills or carry appropriate
spares toresolve any problems. The assembler may even have their
own parts identifiers, which may be totally different from those
of the original equipment manufacturer. Therefore, the user should
initiate a receipt inspection program for all equipment by looking
at the following key points:
In conclusion, avoid
substituting spare parts, as they are often the unwitting source
of major problems. In most troubleshooting cases, a substituted
part is overlooked because it has been newly installed and, being
new, is viewed as perfect. For example, if a cast iron motor is
being replaced, it is often replaced with a lighter weight motor
because of the materials used in its construction. This factor may
be the cause of resonance, which can be destructive. The natural
frequency of the unit is now changed due to the lighter weight and
may cause a machine to destruct because its natural frequency is
within plus or minus 500 cycles per minute. Ball and roller bearings
are also a major source of resonance when the substitute bearing
meets the physical dimensions but has a different number of rolling
elements, which can put it outside the design specifications for
- Ensure the bedplate
is level and is not twisted.
- Inspect the entire
unit for dings and scratches that might indicatedamage in transit.
- Remove the protective
covers from the suction and discharge nozzles, and check single-stage
pumps for signs of internal damage or contaminants. Replace
and secure the protective covers after the inspection is completed.
Note: Heavy duty and multi-stage pumps will require a more
in-depth inspection program involving removal of casing covers
etc., but will use the same inspection techniques described
in this section.
- Check the shafts
for total indicated run-out (TIR) to ensure the shafts are straight.
TIR should not exceed +/- 0.002" (Verify the TIRspecification
from the manufacturer).
- Examine the shafts
for surface damage that may indicate the unit was improperly
slung when handled in transportation.
- Check the rotation
of the shaft by hand or a strap wrench. Never use a pipe wrench
to turn the shaft as this will damage the shaft surface and
probably negate the manufacturer?s warranty too.
- Because of transportation
hazard laws, there is no oil in the equipment?s bearing wells.
The bearings are lightly oiled or greased to prevent damage
from dirt and any slight movements that would be experienced
in transit. Therefore, the oilwells should be filled to the
appropriate working level with the recommended grade of oil.
At this point, rotate the shafts three or four turns to ensure
the lubricant gets on to the working surfaces of the bearings.
- Inspect the gland/mechanical
seal area to ensure there are no problems. Standard packing
type glands should have the gland follower inserted into the
stuffing box to a depth of 13 the thickness of a packing ring.
Note: It is often a good practice to remove the pump manufacturer?s
packing from the glands (and valves) and repack the gland with
packing that has proven to be satisfactory in service for that
pump and the system it will be used in. Depending on the reputation
of the manufacturer, it has been found that the cheapest grade
of compatible packing has been installed and will not perform
very well for any appreciable period of time.
- Keep vertical
pumps stored in the upright position. If they are stored in
the horizontal position, the shaft may bend during lifting operations.
As the lifting tackle is usually placed on the motor, the weight
of the pump acts on its own swivel point, namely the casing
of the pump where it is resting on the floor, and tends to bow
the center of the pump during the lifting process. The shaft
that is the weakest component will also bend and may not return
to its original straightness. Note: Always check the shaft
TIR (+/- 0.002") after moving a vertical pump into the upright
position, especially on pumps over 4-feet in length.
- Include each new
piece of rotating equipment in the storeroom maintenance schedule.
Never let the purchasing
department decide which parts are to be bought for replacement when
their purchasing power is limited to the lowest of three bids. Your
equipment must be maintained to the specifications that were calculated
for the machine in question. If it is not, the substituted parts
will eventually destroy the machine with resonance.