2000 Hook-up Book

Steam Tracing

Tracer Steam Distribution It is important that the steam sup ply should always be taken from a source which is continuously available, even during a normal shut down period. Tracer lines and jacketed pipe may have to work at any steam pressure (usually in the range between 10 and 250 psi, but always choose the lowest pres sure to give the required product temperature. Excessively high pressures cause much waste and should only be used where a high product temperature is essential). To suit product temperature requirements, it may be necessary to use steam at different pres sures. It should be distributed at the highest pressure and reduced down to meet the lower pressure requirements. A Reducing Valve can be used for this purpose, Fig. 24. Note: it may be necessary to steam trace the valve body to pre vent damage due to freezing.. A number of tracers can be supplied from one local distribu tion header. This header should be adequately sized to meet the maximum load and drained at its low point by a steam trap as Fig. 25. All branches should be taken off the top of this header, one branch to each tracer line. These branches should be fitted with isolating valves. Don’t undersize these branch connections (1/2" supply to even a 3/8" tracer will avoid undue pres sure drop) and serve only tracers Table 8 Recommended header size for supplying steam tracer lines Header Size Number of 1/2" Tracers 3/4" 2 1" 3-5 1 1 / 2 " 6-15 2" 16-30 Recommended header size for condensate lines Header Size Number of 1/2" Tracers 1" Up to 5 1 1 / 2 " 6-10 2" 11-25

local to the header, otherwise high pressure drop may result. The size of the header will, of course, depend upon the steam pressure and the total load on the tracers but as a general guide, see Table 8: Tracer Trap Sizing Subcooled discharge traps are usually a good choice for tracer service. Tracing loads are approximately 10 to 50 lb./hr., and each tracer requires its own low capacity trap. No two tracers can have exactly the same duty, so group trapping two or more tracers to one trap can considerably impair the efficiency of heat transfer, see Fig. 26 and Fig. 27. Even with multiple tracers on a single product line, each tracer

should be separately trapped— Fig. 28. When branched tracers are taken to serve valves, then each should be separately trapped, Figs. 29, 30, 31 and 32.

SYSTEM DESIGN

Figure 24 Spirax Sarco Reducing Valve

Tracers

Header

Steam Trap

Figure 25

Steam

Steam Trap

Steam Trap

Steam

Figure 29

3/8" (10mm) OD, 1/4" (6mm) Bore

Figure 26 Incorrect Arrangement

Steam Trap

Steam

Steam

Figure 30

Steam Trap

Steam Trap

3/8" (10mm) OD 1/4" (6mm) Bore

Figure 27 Correct Arrangement

Steam Trap

Steam

Steam

Steam Trap

Figure 31 Tracer Lines Around Pump Casing

Figure 28

Steam Trap

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