Stand by pump not developed pressure when taken into service

Hi everyone,
I am working in thermal power plant and look after the Maintenance of Boiler and it's auxiliaries.
PROBLEM: for lubrication of fan bearing separate lube oil system is used, which has 2 pump, one as working and other standby.. During pump changeover, standby pump often do not develop pressure due to air ingress. So whenever this problem occur, we loose pump discharge NRV bolts and remove air locks from their, and after removing air locks pump starts to develop pressure.
Every possible measure was done to arrest air locking but still right solution is far from reach.
Pump specs : SCREW PUMP
Flow: 40 LPM
Please put some relevant light on this subject.
Original Post
Please help with more answers:
1. Type of fluid being handled by pump
2. operating temperature of the fluid being pumped
3. RPM of pump
4. Is the prime mover - an electric motor? is it same as the other one where the pump builds pressure?
5. does this happen with the other pump?
6. Normal discharge pressure of the pump
7. Normal suction pressure of the pump
8. Does the suction side has an expansion tank or a tank at positive head?
9. Does the suction of both these pumps have common piping?
10. can you send image of line diagram of this piping alone? you can draw it by hand in a paper and send it.

Thanks
Sriram

Add Reply

Likes (0)
×
×
×
×