Nace CP 1, Course Manual

Page: 226 / 535

Installing C.P. Components 8:27
CP 1 – Cathodic Protection Tester Course Manual
©
NACE International, 2000
07/01/04
Anodes may be attached to a support pipe or in the case of light weight
materials (e.g. MMO), may be lowered down the hole by the anode leads.
Anodes usually have a centering device on them to keep them centered in
the hole. These should not be made of nonmetallic material.
A slotted PVC vent tube is installed down to the bottom of the hole to vent
off any gasses than may be generated by the electrolytic action of the
anodes. This is important since accumulation of gas can increase the
resistance of the anodes to ground.
The length of the hole containing the anodes is then filled with a fine coke
breeze backfill. The backfill and anodes constitute what is known as the
active column or anode area. The hole above the coke breeze may be filled
with native soil, gravel, or simply left open.
The installation is completed by a length of surface casing (which may have
been installed at the beginning of the drilling) with a cap on it. The vent
pipe terminates in a screened cap.
The anode lead wires are led to a junction box and each lead is secured to a
separate terminal. Each terminal is connected to the positive bus bar
through a shunt so the individual anode outputs can be read. Be certain to
mark each anode lead from bottom to top so that each can be identified in
the junction box. A cable is then run from the positive bus bar to the
positive terminal in the rectifier.
All deep anode groundbeds must be permitted, installed and completed in
accordance with state and local codes.