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5. Maintenance and Inspection
5.1 General
• During operation, the temperature will rise corresponding to the compression ratio due to compression heat. However, if
localised temperature hot spots occur or the paintwork is scorched, this is abnormal. It may be because of the interference
of rotor with casing, or the pump has sucked in some foreign material. Therefore, stop the pump immediately to check the
condition. In some case, the rotors and the casings might have corroded after a long service life, which will make the
clearance between these parts larger and result in high rates of pumped gas re-cycling, with the result that the temperature
rise becomes higher than it was initially. In such cases, the pumping speed will be reduced. Stop the pump and take
measurements of the clearances for consideration of corrective action.
• Abnormalities can be noted by making routine checks on bearing temperature, vibration or noise. Therefore, daily inspec-
tion is advised.
• Interference between rotors or between rotor and casing can be noted by listening to sound through a stethoscope applied
against the casing.
• In winter, in cold regions, whenever the pump is stopped, cooling water should be drained. Freezing of water could damage
the jacket.
5.2 Periodical Inspection
a.) Daily
• Oil-Level Gauge: Excess or lack of lubricant can damage gears and bearings.
• Check that the amount of cooling water is adequate.
• Check the temperatures of Grease cover and Front end Cover. Use of a suitable thermometer or a surface thermometer may
be convenient.
• Check the suction and discharge pressures. To check these pressures, make sure that the operation of the pump is within
planned specifications.
• Check the load on the motor. Note that an increase in the motor load indicates some kind of abnormality.
b.) Monthly
• Check tension of V-belt.
• Check lubricant colour (If, Oil colour is discoloured, replace lubricant).
• Check oil level. If oil consumption is high with no apparent leaks, check mech. seal.
c.) Every 6 month
• Check pipe connections.
• Check oil & grease and change them when need.
d.) Yearly
• Check mech. seals, lip seals & oil seal.
• Check inner surface of rotors and casings. Disassemble the piping on suction side to check the inner surface of rotors and
casings.
• Check the gear. - Remove the front end cover to check the gear.
• Replace lubricant in the front end cover.
Screw vacuum pump maintenance and check list
No.
Item
Check point
a.) b.) c.) d.)
1
Ampere of motor
Any change? Ampere as specified?
•
2
Rotation
Is rotation smooth and correct
•
3
Suction and discharge pressure
Are those pressure as specified
•
4
Noise and Vibration
Any abnormal sound or vibration
•
5
Temperature
Any excessive oil temperature rise on bearing and other parts
•
6
Oil amount of front end cover
Is oil at proper level?
•
7
Water contamination of front end cover Clean or not?
•
8
Oil leak
Oil not leaked?
•
9
Lubricant replacement
All oil & grease in front end cover & grease cover to be replaced
•
10
Amount and pressure of cooling water
for pump casing & silencer (separator)
Is the amount as specified?
•
11
Suction and discharge pipe
Is there any scale?
•
12
Cleaning and dry run at stop
Close the main V/V on suction side, and run for 20 ~ 30 min.
while purging N
2
or air
13
Check inside of casing and rotor
Any rust or flaw found?
•
14
Mech. seal, lip seal, bearing, o-ring,
packing V-belt / coupling
Replace when need
•
