Nace CP 1, Course Manual

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Installing C.P. Components 8:7
CP 1 – Cathodic Protection Tester Course Manual
©
NACE International, 2000
07/01/04
Test Box
1
3
2
Terminal
Board
5
4
Test Box
1
3
2
Terminal
Board
5
4
Figure 8.5 Foreign Line Crossing Test Station
A
foreign line refers to any line other than the one with which you are
concerned. It may be another line from your own company or it may belong
to another company. When the foreign line belongs to another company,
the wires attached to that line must be installed by representatives of that
company.
Isolating Joint
All local and national codes should be followed in installing electrical
isolators. Under no circumstances should an isolating device be installed
where an explosive or combustible environment is present. Select locations
where an electrical spark or discharge across the dielectric materials of the
isolation device cannot produce ignition.
If an isolating joint must be installed in a area where the atmosphere or
leakage of product could cause ignition if a spark occurred, a grounding cell
or surge protector must be installed across the joint.
It is important to locate isolators so they will not be bypassed or short
circuited by other connections or piping. Wherever possible locate isolating
devices in an accessible place where repairs can be made.
Electrical isolators for piping systems come in a variety of types. These
include flanges, couplings, and unions. Flanges may be double insulated or
single insulated. Figures 8.6
to 8.8 show the construction of a number of
different types of pipe isolation joints.