Page 270 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

HEAT TRANSFER, INSULATION, AND FREEZE PROTECTION

5.54 CHAPTER FIVE

TABLE 5.18 Recommended Number of Tracer Lines Based on Pipe Size

Number of Nominal pipe
Pipe size, in DN tracer lines size, tracer, in DN
1–3 25–80 1 3/8 12
4–6 100–150 1 1/2 15
8–20 200–500 2 1/2 15
24–30 600–750 3 1/2 15

The tracer pipe is commonly attached to the main line with thin galvanized or stainless
steel bands about 1/2-in (15 mm) wide, between 18 to 20 gauge. The spacing between
bands depends on the size main line, with 3/8-in (DN 12) tracers secured 12 to 18 in apart,
1/2-in (15 mm) tracers secured 18 to 24 in apart, and 3/4-in tracers secured 24 to 36 in
apart. Fittings should have three bands to assure close contact between the tracer and the
pipe. Where it is not desirable to use bands, such as at valve bodies, soft annealed 18-gauge
stainless steel wire is an acceptable alternative.

Application of Insulation
Insulation must cover both the pipe being protected and the tracer line. It is important that
the air space is kept clear. This can be achieved in several ways.
The first method is to wrap both the pipe and tracer with aluminum foil or a thin gal-
vanized steel sheet attached by wire. The insulation is applied over this wrapping. Small
mesh galvanized netting can also be used instead of the foil. The second method is to use
insulation one or two sizes larger than the pipe being protected. This method is the least
costly but the insulation can be easily crushed. The third method is to use special preformed
insulation designed to cover both the pipe and tracer.
The insulation must be covered or finished in a manner that will protect it from mechani-
cal damage and the elements, if installed outdoors.

Steam Pressure
The choice of steam pressure used for tracing must be consistent with the temperature to be
maintained in the pipe to be protected. Low pressure steam of less than 100 psi (680 kPa) is
used unless the temperature must be kept very high. Normally, saturated steam is used for
tracing. Table 5.19 gives the temperature of saturated steam as a function of steam pressure.

TABLE 5.19 Relationship of Steam Pressure to Temperature

Pressure, psig kPa Steam temperature, °F °C
15 105 250 120
30 210 274 133
50 350 298 146
75 525 320 160
100 700 338 168
150 1,050 366 183
200 1,400 388 196

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