TIPS ON CONDENSER ERECTION AND START BOILER FEED PUMP ERECTION --PART -I

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condenser.

-The joining plates between the water chambers should be welded and checked before lowering of condenser intervals.

-The corners of the neck joint with LP turbine should be checked to ensure completeness.

-The welding of the stiffeners with the main tube plate should be done only after welding  of all support plates with the shell and stiffness has been completed.

-Welding sequence should be reversed for every layers of welding.

-During pre-assembly of bottom plates / side walls & dome walls it is advisable to put a packer below the joint so that during welding the plates straighten out.

-Not more than four welders should be deployed during the welding of the internals. Adequate supervision should be exercised to ensure proper welding sequence.

-It is desirable that after 50% of the welding of internals has been completed the alignment of the tube plates is rechecked. Subsequent welding sequence should be decided based on the observation made.

-During tubing in case the tube is not going freely the holes of the tubes support plates may be reamed suitably.

HYDRAULIC TEST OF WATER BOXES

The condensers are subjected to a hydraulic pressure test on the cw side. For this purpose, the cw inlet and outlet pipes must be blanked using suitable hydro-test flanges and the manholes using the original covers. The water box covers must be mounted ready for operation and a protective coating must have been applied to the water boxes.

The hydro-test can also be done by closing the butterfly valves in the inlet and outlet of condensers. This apart from also ensuring the tightness of B.F. valves and expansion joints, reduce the time cycle as the temporary test flanges need not be erected.

After the hydro test, drain the cw.

BOILER FEED PUMP

There are  3x50% Boiler feed pumps in a major power station  i.e. 500MW and above  with 02 number  Turbine Driven and one number motor driven. Motor driven pump is located in between operating floor and zero meter floor (8.5m) . Turbine driven pumps are located on operating floor ( near B row column). Motor (10 MW  approx) squirrel cage  constant speed  with Hydraulic coupling for variable speed is coupled in between main pump and booster pump. Around 10 MW capacity single cylinder variable speed turbine  is used turbo driven BFP.

Details of specification will be available with OEM’s O&M manual and erection manual. I will give a very short description of these pumps which may get overlooked during erection and commissioning.

- Main pump will have butt weld discharge connection. Suction connection can be butt weld or  flanged connection.

- Booster pump will have flanged connection both in suction and discharge.

-One pump can handle approx 65% of  unit rated  load flow and head  .

-Trip speed of steam turbine will be 10% above the design speed of boiler feed pump.

-Minimum recirculation of booster pump and main pump is around 25% of design flow.

- All pumps and accessories of MDBFP and TDBFPs are interchangeable.

- Fabricated base plates are used for booster pump , gear box ,main pump, hydraulic coupling  etc

- During parallel operation of MDBFP and TDBFP the difference of flow in any one pump should be less than 5%.

continued to part -ii
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