Considering process temperatures when designing electrical heat tracing for hazardous areas

Hazardous areas in many industrial process facilities often represent design challenges for high temperature electrical heat tracing (EHT) applications. When there is a relatively close proximity of the maintenance temperatures and Auto-ignition Temperature (AIT) or T-Rating, Controlled Designs per IEEE-515-2004 are utilized to achieve the desired maintain temperatures. Other common techniques of reducing heat tracing sheath temperatures include improving tracer contact with the process pipe, decreasing tracer output and / or increasing the number of heat tracing passes. This paper will present design methods to establish maximum heat tracing sheath temperatures in Class I Division 2 gaseous environments. Design tradeoffs and resolution approaches when the process temperature exceeds the AIT or T-rating are also presented.