scope:

This standard sets performance requirements for temperature limit and supervisory switches used as safety devices in industrial heating control systems. They are intended to operate electrical switching devices in order to initiate a safety shutdown or initiate an alarm under abnormal conditions. Process temperature controllers and/or recorders can also be certified if they are provided with limit and/or supervisory functions.

The requirements of this standard shall be used to measure and describe the performance of thermal switches in response to exposure from heat, cold, abnormalities, etc., under controlled laboratory conditions. The results of these controlled exposures shall not be used to describe or appraise actual exposure conditions since such conditions vary widely. Dielectric strength and proper operation with variations in supply voltage are also assessed.

Purpose

This standard states testing and certification requirements for temperature limit and supervisory switches. These switches use inputs from thermocouples or resistance temperature devices (RTDs). They may be stand-alone devices or incorporated into a temperature controller.

Testing and certification criteria shall include, but are not limited to, performance requirements, marking requirements, examination of manufacturing facility(ies), audit of quality assurance procedures, and a surveillance program.