Meanwhile....

Your 149 deg C sould like is about steam out temperature so a WNC load case at this temperature is required if your line is not gas line.

From your description, a spring can is not required.

The purpose of the tracing is to keep the line warm so probably you will not have problems with the by-pass line. But the 327 deg C design temperature of the steam line mean that you have to take a look also at this line to see if is flexible enough (visual check).

Read also:

http://www.cheresources.com/steam_tracing.shtml

http://www.steamonline.com/tracing.html

Regards,