Table 2: Typical allowances (in mm) per run of cable
NPS
inch
DN
mm
Light
valve
(flanged)
Light
valve
(threaded
or welded)
Heavy
valve
(flanged)
Heavy
valve
(threaded
or welded)
Typical
pipe
shoe
Flange
pair
Field
variance
0.5
15
300
300
300
300
910
300
2%
0.75 20
460
300
460
300
910
300
2%
1
25
610
300
610
300
910
460
2%
1.5
40
760
460
910
460
910
460
2%
2
50
760
610
1060
610
910
460
2%
3
80
910
760
1220
760
910
610
3%
4
100
1220
910
1520
910
910
610
3%
6
150
1520
1060
1830
1060
910
610
3%
8
200
2140
1220
2440
1220
910
610
3%
10 250
2440
1520
3050
1520
910
910
3%
12 300
2750
1830
3660
1830
910
1060
3%
14 350
3050
2140
4270
2140
1370
1220
3%
16 400
3350
2440
4880
2440
1370
1370
3%
18 450
3660
2750
5500
2750
1370
1680
3%
20 500
3970
3050
6100
3050
1370
1830
3%
24 600
4580
3660
7320
3660
1370
2140
3%
1. Allowances above are based on typically available fittings and
supports, with an insulation thickness equivalent to the pipe
insulation. Please refer to the engineering documentation for project
specific allowances.
2. For pipes requiring more than one run of heating cable, apply the
full allowance for each run of cable on each fitting or support as
long as space allows. However, MI heating cables must not touch or
overlap and the minimum spacing between the heating cables must
be respected.
3. For some applications, it may be physically impossible to install all
of the recommended heating cable directly on the fitting or support.
In this case, install the excess heating cable on the pipe, on either
side of the fitting or support, or distribute the additional heater
length along the entire circuit length if a lower local temperature
is acceptable. This constraint may be difficult for small pipes
and/or multiple cable runs. If required, contact Pentair Thermal
Management for assistance.
4. The field variance is important to accomodate expansion and
contraction of the heated equipment. Also refer to figures 12-14 for
more detailed information.
12
12