steam tracing

First of all let's look at the broader subject of supplemental heat application for process plant piping systems.
There are a number of reasons for doing it and a number of methods used to do it.

Methods:
a. Jacketing - This is where you have a pipe inside another pipe. This also called "double pipe systems." With this method the process fluid is carried through the inner pipe and the temperature control fluid is routed through the outer pipe.
b. Commodity Tracing - This is where you have a fairly standard piping system (pipe, fittings, flanges, valves, etc.) to which tubing is applied and the temperature control fluid is routed through the tubing.
c. Electric Tracing - - This is where you have a fairly standard piping system (pipe, fittings, flanges, valves, etc.) to which an electric cable is applied. The electric current generates the heat required to control the temperature.

Reasons for supplemental heat application:
There are two primary of reasons for using supplemental heat application for process plant piping.
First there might be a process reason. The process fluid must be carried with-in a specific temperature range or the process fails. Keep in mind supplemental heat application can also mean controlling the temperature to below ambient. This mean that you might be running a chilled fluid through the "tracer" system.
The second reason for using supplemental heat application is winterizing. In the arctic or other cold climate locations you may need to prevent the freezing of a commodity or even control the temperature of non-process fluids such as safety shower/eye wash water so it is ready for use.

Where the system requires an elevated temperature you can use jacketing, commodity tracing or electric tracing. Where the process commodity is required to be held at a lower that ambient temperature then you can only use the jacketing or the commodity tracing option.

There are a number of variations available for supplemental heat applications and a number of companies that specialize in this field.
For more information see - www.csiheat.com/products.html