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 12 of 19
6.6 Painting
6.7 Cables
casing. The anode installation shall be sized based on permanent C.P. design
parameters specified for the main pipeline.
The carrier pipe inside the casing shall be protected by zinc ribbon anodes well
connected to the outer surface of bottom of carrier pipe extending upto hour hand
positions of 4 and 8 o'clock. The anodes shall be placed at close intervals as per
design parameters calculations and sized based on the permanent CP design
parameters.
The sheet steel used for fabrication shall be thoroughly cleaned and degreased to
remove mill scale, rust, grease and dirt. Fabricated structures shall be pickled and then
rinsed to remove any trace of acid. The under surfaces shall be prepared by applying a
coat of phosphate paint and a coat of yellow zinc chromate primer. The under surfaces
shall be free from all imperfections before undertaking the finished coat. After
preparation of the under surface, spray painting with two coats of final paint shall be
done. The finished panel shall be dried in oven in dust free atmosphere. Panel finish
shall be free from imperfections like pin holes, orange peels, run off paint, etc.
All unpainted steel parts shall be cadmium plated to prevent rust information.
Cables shall be annealed high conductivity, tinned, stranded copper conductor, XLPE
insulated 650/1100 V grade, armoured, PVC sheathed. The size of the copper
conductor shall be 6 sq mm for anode cable from anode to buried junction box, 10 sq
mm from junction box to test station, 10mm² from test station to pipeline. The size of
the conductor shall be 6 sq mm for potential measurement, 10 sq.mm for current
measurement and 25mm² for bonding, polarisation cell/grounding cell and surge
diverter connection purpose. The anode cable from anode to junction box (buried)
shall be unarmoured. The length of anode tail cable shall be sufficient enough to reach
junction box (buried) in case of temporary CP anodes and up to test station in case of
permanent CP sacrificial anodes. PE Sleeves shall be provided for unarmoured cables.
7.0 INSTALLATION
7.1 Cable Laying
7.1.1 Cables shall be laid in accordance with approved layout drawings to be prepared by
the contractor. No straight through joint shall be permitted in a single run of cable.
Cable route shall be carefully measured and cables cut to required length.
7.1.2 All cables inside station/plant area shall be laid at a depth of 0.75 M. Cables outside
station/plant area shall be laid at a depth of 1.5m. Cables shall be laid in sand under
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