Heat Tracing

 

Heat tracing, which is also known as steam tracing or tube tracing, features small diameter tubing (typically 3/8" or 1/2") that is secured to the pipe being heated.  A heating medium such as steam or hot oil flows inside the tubing and transfers heat to the pipe.  Since steam is most often used as the medium, heat tracing is often referred to as steam tracing.  Tube tracing is a more technically accurate name, but it is less commonly used.  Often, steam tracing is enhanced by surrounding the tube with heat transfer compound to improve the heat transfer from the tube to the pipe.  Other heat transfer enhancements may be employed to help transfer heat from the tubing to the piping.

Thermal Capability
Steam tracing is capable of only a fraction of the heat transfer rates attainable with jacketed piping.  This is due to its significantly less surface area (the tubing contacts the pipe at a single point) and installation reliability.  Since tubing is most commonly available in rolls, during installation it must be straightened and bent to follow the pipe.  This often results in air gaps between the tubing and pipe which reduces the heat transfer of the system.  More tracers can be used to increase the total heat transfer rate of the system.  Wall temperature maintenance is difficult with steam tracing since the uncertainty in tube/pipe contact makes it difficult to model the actual wall temperature distribution.  Heat transfer modeling is critical for wall temperature applications, and many tubing vendors do not possess the modeling capability to provide an engineered system.  Steam tracing is most commonly used in freeze protection applications where there is a high temperature difference (typically 200°F) between the heating medium and the process freezing point.  Even with heat transfer enhancements, steam tracing is more suited for high temperature difference applications.

Safety and Reliability
Unlike jacketed piping, steam tracing is not susceptible to cross contamination, and it does not present any major safety concerns.  Steam tracing does suffer from poor reliability due to its sensitivity to installation quality.  Steam tracing circuit design usually is set by plant specifications that govern such things as circuit length and trapping procedures.  Since the system is not engineered, the specifications are conservative, and the resulting circuit design is not optimized.  This can result in a large utilities infrastructure required to support the system.  This infrastructure must be maintained for the life of the plant, and any components that are not functioning properly can compromise the entire system.


Cost
Total system costs of steam tracing tend to be at parity with bolt-on jacketing when the costs of utilities infrastructure are included.  Utilities infrastructure is a much bigger component of a steam tracing system compared to a bolt-on jacketing system (60% of total system cost versus 20%), so an economic analysis may be required to fully evaluate the two technologies for a given project.