Boiler Feed Pump

Lack of, or poor, lubrication.

You should be talking to the boiler maker. They will actually have seen the boiler in question and might be able to answer your question with some intelligence, instead of blindly speculating, like I just did.

sir maker is sulzer

capacity is 55cumtr 300kw motor,2980rpm

no change in oil level in oil cup and when pump start after some time bearing temp. goes to 210deg c also mechanical seal damage

You should be talking to the boiler maker. They will actually have seen the boiler in question and might be able to answer your question with some intelligence, instead of blindly speculating, like I just did.

sir balancing leak off line pressure is high what effect on pump?

if balancing leak off line is isolate what effect on pump or what is the importance of this line

"There is none so deaf as the one that will not listen." You have the advice, Taffy, so if I were you I would be getting on the telephone and doing just what has been said above.

Is the boiler feed pump under warranty?

How is the motor coupled to the pump?

Was the drive alignment of pump & motor precise?

Where are you located?

Is the lubricant of bearing as recommended?

This is for starter.

pump under warreanty priod

motor directly coupled with pump

Was the drive alignment of pump & motor precise?- yes

location west bengal- durgapur

Is the lubricant of bearing as recommended?- yes

I would advise you, to immediately report failure of feed pump bearing, to your vendor/supplier & claim warranty without further delay.

Defective bearing

1 - water strainer before pump is blocked

2 - damaged isolating valves (not fully opened )

both will lead to water trapping ( no or weak discharge ) so pump temperature will rise up and damaging mechanical seal

No! It can't be those! If it is then he can't claim a warranty replacement from the supplier!!

warranty for pump , not for fittings

what if we guess that a new pump has installed with old defective fittings

More than likely this was caused by unfamiliarity with the operational constraints of this type of pump. From OP's post #4

"...sir balancing leak off line pressure is high what effect on pump?

if balancing leak off line is isolate what effect on pump or what is the importance of this line..."

These questions indicate that the fluid was forced under the seal, on to the bearing surface, and subsequently washing out the lubrication thereby destroying the bearing.

Boiler Feedwater Pumps are extremely high pressure pumps requiring complex seal mechanisms to keep this from happening. Part of this includes balancing the pressure on both sides of the bearings by introducing pump internal pressure on the outer seal so that there will be minimal delta p across the bearing, that is one of the purposes of the "leak off line", similarly for minimizing the load on the thrust bearings.

If that line is inadvertently closed or not wide open then there will be a large delta p across the bearing that will ultimately let feedwater to flow from the high side of the pump, through the seal, and into the lubricating system, or the shaft will not stay centered in the housing due to unequal pressures on the thrust bearings.

Another consideration is thermal distortion of the rotor and/or casing due to inadequate thermal soaking during startup and shutdown conditions. If the manufacturer's recommendations are not followed rigorously then during these periods the shaft will bow and/or the casing will distort sufficiently to cause seal/bearing misalignments that will lead to early life failures of either or both due to out of spec operation.

Your pump probably needs a complete disassembly to determine the true extent of the damage. As others have said, call someone who has experience with this pump.

You/ Boiler supplier did not align the Pump Motor with the pump Coupling. The coupling to be first balanced on a lathe. The shaft inside has ceased the bearing due unbalanced rotation.