33
9
Test Procedures
Raychem-IM-H57548-HWATsystem-EN 16/08
The approximate location of the fault, expressed as a
percentage of the heating cable length from the front
end, is:
Fault location: D = 1/ A x 100
(1/A + 1/B)
Example:
A = 100 ohms
B = 25 ohms
Fault location: D = (1/100) / (1/100 + 1/25) x 100
= 20%
The fault is located 20% from the front end of the
circuit.
3. Capacitance method
This method uses capacitance measurement (nF) as
described in "3. Circuit length verification (capaci-
tance test)" on page 28, to approximate the loca-
tion of a fault where the heating cable has been sev-
ered, or a connection kit has not been connected.
Record the capacitance reading from one end of the
heating cable. The capacitance reading should be
measured between both bus wires twisted together
(positive lead) and the braid (negative lead). Multiply
the measured capacitance with the heating cable’s
capacitance factor as listed in the following example:
Example:
HWAT-R2 = 16.2 nF
Capacitance factor = 5.8 ft/nF
Fault location =
42.2 nF x 5.8 ft/nF = 245 ft (75 m)
from reading location
As an alternative, capacitance values from each
end. The ratio of one capacitance value taken from
one end (A) divided by the sum of both A and B (A
+ B) and then multiplied by 100 yields the distance
from the first end, expressed as a percentage of the
total heating cable circuit length. See Table 4 on
page 29, for capacitance factors.
Fault location: C = A
x 100
(A + B)
