As stated in Part 3 of this series, there are three types of steam tracing:
In this installation, we look at the Internal Method and Jacketing.
Internal steam tracing is considerably more difficult. It requires some complicated fittings where the steam line enters and leaves the product pipe. This often requires packing glands or stuffing boxes, and makes repairs more challenging.
There is also the danger of cross contamination between the steam and the product. A much faster heat- up is obtained, however, and a much better heat transfer is obtained than with the external method, especially if the tracer line is coiled within the product line.
The jacketed method more closely resembles a typical double pipe heat exchanger.
Here, the steam heating is provided from outside the product line, and there is much more heating surface available than with either of the other two methods. There is a lower temperature drop possible between the tracer medium and the product with this system due to the greater amount of transfer surface. The heat transfer rate is more predictable, and the heat-up from cold is faster. However, the cost is higher than either of the other two methods, it is difficult to repair, and there is still danger of cross-contamination.
Excerpts from: Basics of Industrial Steam Utilization
Harry Woebkenberg, VP Marketing / Jordan Valve Product Manager