Page 274 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

HEAT TRANSFER, INSULATION, AND FREEZE PROTECTION

5.58 CHAPTER FIVE

FIGURE 5.28 Detail of condensate return manifold.

temperature control valves can reduce shocks to the system by opening and closing slowly,
thus reducing thermal shock, water hammer, and abrupt temperature changes. An additional
advantage is that the automatic feature relieves operating personnel from having to manu-
ally turn on and off steam supply lines at various points throughout the facility.
Other methods used less often include electric, pneumatic, and electric-pneumatic control-
ling devices that also require positioners, set point controllers, temperature sensors, and power
supplies. These methods of controlling the steam supply to the tracer line are more costly, but
generally more accurate, and their use depends on the specifics of the application.
Freeze protection requirements for piping within a facility should be controlled by a
temperature-sensing device attached directly to the pipe being protected. When the pipe
temperature falls below a set point, the steam is turned on, and when it rises above a set point, the
steam is turned off. This sensor should be located as far away from the tracing line as possible.

System Design Procedure
1. Determine the number and size(s) of the pipe(s) to be protected. Use Table 5.18 or 5.20
as a guide to select the number and pipe size of the tracer lines. Freeze protection is
considered type A, noncritical, in Table 5.20. Establish the total number of tracer lines
required, the steam supply location and pressure, and the method of condensate removal
or return. The steam supply must be taken from a source that is continuously available.

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