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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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