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 6 of 19
As far as possible equipment including test stations, anode lead junction boxes, etc.,
shall be located in safe area. All equipment located in hazardous areas shall be of
flame proof type as per IS:2148 for gas groups IIA & IIB and temp. class T3.
6.1 Anode Ground Beds
6.1.1 The pipeline shall be protected by prepacked zinc/ magnesium anodes.
6.1.2 Anodes shall be installed along the pipeline at suitable intervals as per pipeline protection
voltage attenuation calculations and ground bed resistance/ current output of anode
installations. Minimum one anode installation shall be provided for every one km. of the
pipeline. In congested area, minimum one anode installation shall be provided for every
250 meter of pipeline length.
6.1.3 Each electrically continuous section of pipeline shall preferably be protected totally by one
type (material) of anodes to avoid inter-anode circulation currents.
6.1.4 The anodes shall be installed at sufficient depth to reach moist soil and shall be
separated from the pipe line by at least 5m and 2m for magnesium and zinc anodes
respectively. The anode connections to pipeline shall be routed through test stations.
6.1.5 At the temporary cathodic protection anode ground bed, the leads of all the anodes shall
be joined together in a junction box filled with epoxy and buried. A single cable shall be
routed from the junction box to the test station. At permanent CP anode ground bed (i.e.
at cased crossing), the leads of all the anodes shall be brought up to the test station and
shall be terminated individually.
6.1.6 For sacrificial anode ground bed which shall be integrated with permanent CP System the
leads of all the anodes shall be brought up to the test station and shall be terminated
individually.
6.1.7 The number of anodes at each ground bed shall be sufficient for providing the specified
pipe protection current density taking into consideration the ground bed resistance, pipe
coating resistance, cable resistance, etc. Contractor shall prepare a table for number of
anodes required at different soil resistivities to produce the specified protection current.
6.2.1 Magnesium anode
The anode shall be of high manganese, magnesium alloy packed with special back fill.
The metallurgical composition, potential and consumption rate of anode shall be as
below:
D:\old data\FATEH\MP Region\Kailaras\Tender RFQ\TCP&PCP\Temporary Cathodic Protection - 016A-R1.doc