4 General Technical Specification of Bhilai Steel Plant, SAIL ...

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General Technical Specification
b) During pneumatic test, pressure shall be gradually reduced to 1.1 times the operating
pressure to check the leakage by soap solution. Test duration shall be minimum 2 hours.
c) Soap solution shall be applied to the weld surfaces / flanges to check for any leakage.
d) Any defect found shall be rectified after releasing the test pressure and after rectification
of defects the test shall be repeated.
During pneumatic tests of all gas pipelines pressure and temperature readings shall be
taken at the beginning and end of the test. The percentage pressure drop (P) shall be
calculated as follows :
P = 100 (1 - P2 / P1 X T1/ T2)
Where P1 and P2 are absolute pressure in the pipe at the beginning and end of test and
T1 and T2 are absolute temperature at the beginning and end of the test.
e) The maximum allowable pressure drop in all gas pipelines shall not exceed 1.0 % per
hour for outdoor pipelines during pneumatic test. For pipeline subjected to hydro test, no
leakage is permissible
1) High pressure pipelines shall be tested as follows :
a) Pipe sections shall be disconnected from the equipment using blank flanges.
b) Vents shall be provided at high points for air release during pipe filling. The vents shall
be plugged with threaded nipples after the tests.
c) Tests shall be carried out before painting of the pipelines and before application of
insulation.
d) Pipe upto 300 mm diameter shall be tested hydraulically for strength by applying test
pressure equivalent to 1.25 times the operating pressure. Test pressure shall be
maintained for 30 minutes and then gradually reduced to the operating pressure. For
steam pipelines test pressure shall be 1.5 times the working pressure and duration 2 hrs.
e) Leakage from welded joints shall be checked by tapping with light hammer. No sweating
should occur on the weld surface. Test shall be considered satisfactory if no visible
leakage is found and pressure in pipeline remains steady.
f) In case hydraulic testing is not feasible, test shall be carried out by compressed air.
Leakage from joints shall be checked by soap solution.
g) Test for tightness shall be carried out using compressed air at the operating pressure,
the test pressure shall be held for 12 hours. The percentage pressure drop calculated as
per formula given in para ( g ) of previous clause shall not exceed.
Commissioning of BF gas, Cold Blast, Nitrogen, Instrument Air, Steam and LPG
pipelines
Pipelines shall be commissioned only after successful completion of preliminary
acceptance test, strength tests and leakage tests.
All valves and regulating devices shall be checked for smooth & proper operation.
All safety relief valves shall be checked and set at required pressure setting.
All instruments, interlocks, etc., shall be checked.
Charging of BF Gas & LPG
Pipelines shall be commissioned only after successful completion of acceptance tests,
strength tests and leakage tests.
Gases & Liquid Fluids
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GS-02