Page 467 - Handbook of Energy Engineering Calculations

1. Choose the type of steam tracing to use for the pipeline

As this fuel-oil unloading pipeline will be used only intermittently (as when a
tanker or tank truck delivers a load of fuel oil), use internal steam tracing and
an unlagged (no insulation) pipeline.
When internal-trace pipes are installed, all the available heat-transfer
surface is utilized. The disadvantages are: (a) reduction in the equivalent

internal diameter of the pipeline, (b) loss of ability to clean the pipeline by
pigging or by using rotary brushes, (c) difficulty in cleaning fouled heat-
transfer surfaces.

The trace pipe can only be installed in straight lengths of pipeline that are
free of valves. Trace-pipe lengths have to be short, to prevent problems in
supporting the trace pipe. It must enter and leave the pipeline frequently,
increasing the possibility of leaks. Stresses arising due to differential
expansion of the trace and the pipeline should be considered.

One possible application of the internal type of trace is for a fuel-oil
unloading line, where the operating temperature is such that it is
uneconomical to insulate the line, and where the line is used only

intermittently. (Insulation is essential for externally traced lines.) Internal
tracing is acceptable only if leakage of steam into the product conveyed by
the pipeline can be tolerated.

2. Determine the Reynolds number for the pipeline
Using the nomenclature given, apply the Reynolds number equation. Or:

Heat loss—Neglecting the effect of the internal tracer at this point: