Volume-II of IV - GAIL

MECON LIMITED
Delhi
PROCESS & PIPING
DESIGN SECTION
TECHNICAL SPECIFICATION FOR
TEMPORARY CATHODIC
PROTECTION SYSTEM
TECHNICAL SPECIFICATION NO. : MEC/TS/05/62/016A REV-1 Page 16 of 19
11.2 Commissioning
(vii) Spark Gap Arrester
- Location/ identification No
- Ratings
- Check for healthiness
11.2.1 Natural pipe to soil potential shall be measured at each test station location prior to
connecting anodes to pipeline. The pipe to soil potential observation shall be repeated
after connecting the anodes and allowing sufficient time for polarisation. The current
output of the anode installation shall also be measured to ensure that it does not
exceed the output current capacity of the anodes. In case the anode output current
exceeds the rated capacity it shall be controlled by insertion of resistance element in
the anode circuit inside test station and the pipe to soil potential shall be rechecked for
adequacy of protection. Additional anodes shall be provided where required to achieve
desired level of protection.
Each anode installation shall become individually operational as above.
11.2.2 After connecting all the anode ground beds to pipeline, measurement of pipe to soil
potentials shall be taken at each test station to ensure conformity to protection
criteria.
11.2.3 In case of insufficient protection as per the CP design criteria on any portion of the
pipeline, CONTRACTOR shall carry out necessary additions modification to the
provided protection in consultation with the ENGINEER.
11.3 Interference Mitigation
Investigation shall be made for stray current electrolysis of the pipeline, AC induction
on pipeline due to overhead high voltage line, interference due to high voltage DC
lines, electric traction, etc.
Measurements including pipe to soil potential and pipeline current etc., on the
pipeline/structure being CP protected shall be made to investigate the current
discharge and collection locations.
In case of fluctuating stray currents investigation shall be made continuously over a
period of time and if required simultaneously at different locations to find out the stray
current source. For long time measurements, recorders shall preferably be used.
Where foreign pipeline (unprotected or protected by independent CP system) runs in
parallel to the pipeline in same trench or very near to the pipeline, and is not bonded
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