A Guide to the different types of O' Brien Sample Bundle Electric Heat Tracers
The weakest link in the sample transport system is often the selection and installation of the heat trace medium and temperature control scheme.
Use the 2003 O’Brien Corporation • QLT-OBA-TRACER • 25 APR 03 guideline to see cut to length limitations table and selection for the different Electric Tracer Types
There are three primary tracing mediums:
Electric, Steam and Re-circulated fluids .
Consistent temperature maintenance is a critical aspect of the sample transport system, yet its design and installation is often treated without the same care. Heat tracing is required for process and stack gas analyzers to maintain a specific process temperature as well as freeze protection.
Electric heat trace products come in a wide range of heater types, accessories and temperature control schemes. There are a host of safety issues related to electrical code
compliance and approvals. Electric heat tracers can be categorized by several factors: output characteristics, the ability to cut-to-length, and temperature limits. Each heater will have its own performance and application limitations.
The output of the heater will be either fixed or variable. Fixed output heaters are referred to as ‘constant wattage,’ the output does not vary with temperature. Variable output heaters are referred to as ‘self-limiting,’ ‘self-regulating,’ ‘variable resistance’ or ‘power-limiting.’ In all cases the output varies with the temperature of the heater; as the temperature increases the output decreases.
The Ability to Cut-to-Length:
This refers to the ability to cut a heater to a desired length in the field without specialized training or tools. If a heater cannot be cut in the field it is referred to as ‘fixed’ length. In order to shorten a fixed length heater it requires specialized training and / or the addition of a transformer or a controller with power limiting capabilities.
Cut-to-length heaters are divided into two subgroups: those that can be cut anywhere and those that must be cut at specific locations or nodes. The second subgroup is called zone heaters.
Each heater will have a maximum maintain temperature as well as a maximum exposure temperature. Exposure temperatures can be rated as power on or power off and a heater may have a higher ‘intermittent’ exposure temperature rating.