The first activity commissioning engineer will associate is
Hydraulic Test of the Boiler.
Though the Hydraulic Test is erection activity and
to be conducted by them only.
I will discuss the procedure of Hydraulic test of a
Supercritical/subcritical unit .
Calculate the water
volume of different section :-
a) Economiser b) Furnace
c) Super heater d) Separator and collector
d) Re heater
e) Start up system.
In 660MW unit the
volume worked out is around 710 cu. metre. This is required to
calculate the chemical requirement for the test.( Ammonia and Hydrazine Hydrate)
The
Unit shall be hydraulically tested for conformation to IBR code requirements.
It
is preferable to do the hydraulic test of the complete Boiler (except Re-heater
section)
in one stroke at the stipulated Hydraulic test pressure. If it is not
possible to accomplish this,
the hydraulic test may be conducted in two sub
stages.
Stage IA - Hydraulic Test of the drainable
portion only may be conducted at a pressure
1.5 times the design pressure. Suitable
dummies shall be provided at SH platen inlet link
pipes. After completing the
hydrostatic test for drainable portion, the system will be
drained and vented
for drying and released for subsequent work.
Stage IB – Later Hydraulic test for the entire system comprising both drainable and
non-drainable portions up to Boiler Stop valves is conducted at a pressure 1.5
times
the design pressure.
Stage II
- This
covers the total Reheat circuit comprising CRH lines starting from
CRH NRV, tap
off lines emanating from CRH lines up to first isolation valve, HPBP
valve
downstream line, Re heater hot reheat lines up to IV, LPBP lines up to LPBP
valves .
Air
tightness test shall be performed before filling water in the Boiler (for
carrying
out the hydrostatic test ). This is done to detect leakages due to
valves left in open
position, forgotten gamma plugs, any cuts not observed by
visual inspection etc.
For doing this station compressor should be ready to
deliver air .
During
testing at least two properly calibrated standard test pressure gauges of
suitable range calibrated from a NABL accredited laboratory are to be used. One
of
the gauges is mounted at drum floor/near and the other near pressure raising
pump.
The least count of the gauge should preferably be 1Kg/cm2.
DM water of quality specified below containing 200 PPM of
hydrazine and
having pH between 9.5 and 10.0 by addition of adequate quantity
of ammonia
shall be used for Hydraulic test.
pH at 25 0C : 7
+ 0.2
Conductivity : < 0.2 m mho/cm
Total hardness : Nil
Total Silica : <
0.02 ppm
Chloride : Nil
Sodium : 0.003
ppm
During testing the temperature of water should
be above 210C but should not exceed 49 0C.
Availability of reciprocating type pressurizing pump (H and Q of the pumps):
(a) 600 Kg/cm2,
30 LPM and (b) 600 Kg/cm2, 50 LPM.
Availability
of reciprocating type chemical injecting pump of 600 Kg/cm2
& 12 LPM.
Alternatively, hydro test pump can be utilized as chemical dozing
pump.
Availability
of Boiler fill pump.
Availability of power supply to the motors of these pumps.
Availability
of Temporary tanks, Temporary fill pumps and dosing pumps.
Availability
of flood lights and 24V hand lamps.
Availability of reliable communications system such as
walkie-talkie sets, telephones etc.
Availability
of Fire Tender and Ambulance near the test area.
Readiness of stair-cases, platforms, hand rails,
approaches etc.,
Delivery line of pressurizing pump should be high pressure seamless pipe to
withstand
the required test pressure.
While raising the pressure for the first time no individual
should be allowed to enter
the Boiler house when the pressure in the Boiler is
above 25 Kg/cm2.
Medical assistance should be readily available.
Erection of the Boiler pressure parts is complete as per
drawing. All necessary
welding jobs are complete, stress relieved and x-rayed.
All gamma plugs are seal
welded. All Quality checks as per approved Erection
FQP are also complete.
No welding including attachment welding or welding on tube will be allowed
subsequently.
Filled & signed copies of FQPs and
Erection Protocols with exceptions highlighted
are handed over to the
commissioning group.
Effective communication facility is available
between Drum floor, pressurizing pump
area and other operating areas.
Sky
climbers / Scaffolding arrangements are provided inside the Boiler.
A cross functional team to be formed to identify leaks at different portion of the boiler.
Boiler drain is suitably connected to
storm water drain / DM plant neutralizing pit.
All debris shall be removed manually from all
pressure parts, buckstays etc.
All manhole closure
plates and header handhole caps are
closed and bolted
or welded tight.
Check that hydrostatic test plugs are
installed where necessary and gags are fitted correctly.
Verify that locking arrangements for
spring supports are provided when required for stress compensation.
Before
filling the boiler with water, an air tightness test is to be performed to
detect
leakages due to valve left in open condition, X-ray plug forgotten, any
cuts etc. not
observed by visual inspection. This will reduce the DM water
consumption and time as well.
The air should be filtered
and free from oil and dust prior to entering the unit.
Boiler is
to be pressurized with air up to
2 Kg/cm2 (G).
Before admitting air, close manholes, isolating valves in drain
lines, branching lines
and vent lines including the vent valves in SH link,
economizer link and separator link,
drain and test valves in official pressure
gauge etc.
Boiler is inspected. The pressure is raised up to 25
Kg/cm2 and a thorough inspection of the
Boiler is done. For Stages
IA & IB the pressure is raised in steps and held for 10 minutes at
100
& 200 Kg/cm2. The rate of rise of pressure should not
be more than 10 Kg/cm2 per minute
up to approximately 80% of the
test pressure and should be 1 to 2 Kg/cm2 per minute beyond
that
value. The required test pressure shall never be exceeded by more than 6%.
Hand tighten safety valve gags at 80%
of pressure of lowest safety valve set pressure.
After reaching the test pressure the pressurizing pump is stopped
immediately and power
supply to the pump is cut off.
Pr gauge showing the Hydro test Pressure 106 kg/cm2 ( Re heater)
LINK 1 - PLEASE CLICK HERE
LINK 2 - PLEASE CLICK HERE
