IEEE 515:2017 pdf free download – IEEE Standard for the Testing, Design,lnstallation, and Maintenance of Electrical Resistance Trace Heating for Industrial Applications
4.1.5 Thermal stability of electrical insulating material
A sample of the trace heater shall be placed in a forced-circulation air oven.The oven shall be heated to, andmaintained for a period of four weeks at a temperature of 20 °C above the maximum withstand temperaturedeclared by the manufacturer.
The sample shall be removed from the air oven and cooled to room temperature. Trace heater samples shallbe wound six close turns around a mandrel having a radius equal to six times the diameter or six times thethickness of the trace heater. Integral components and trace heater panels shall not be wound around themandrel. Trace heater pads shall be wrapped on a mandrel with a radius equivalent to the manufacturer’sminimum recommended bending radius. While still on the mandrel, the sample, except at terminations or endswhere the conductor is exposed, shall be submerged in tap water for 5 min. While still in the tap water, thedielectric test 4.1.1 and the insulation resistance test 4.1.2 shall be conducted. Upon completion of the test, thesample shall have no visible cracks when examined with normal vision.
Terminations that improve the vapor tightness ofMl trace heaters with electrical insulation that is a hygroscopicmaterial (for example, the cold end seals) are subjected to a temperature of 80± 2°C for 4 weeks at not lessthan 90% relative humidity(R.H.). Compliance of the sample or prototype shall be verified by testing theelectrical insulation in accordance with 4.1.1 and 4.1.2.
4.1.6 Thermal performance test
lt is critical that the maximum sheath temperature of a trace heater is lower than the maximum ratings of thetrace heater materials. This test demonstrates the thermal safety by verifying the power output stability for allparallel trace heater products with respect to time.
The test apparatus shall consist of a heated metal platen maintained at the specified high test temperature anda cooled metal platen maintained at the specified low test temperature with the test samples being alternatedbetween the platens, or the test shall consist of a metal platen with built in heating and cooling capabilityto change the temperature within the specified levels. The apparatus is intended to be located in a roomtemperature environment. The platen(s) shall be sized to expose all parts of the trace heater samples, whichwould be exposed under normal installation conditions, to the temperature levels required by this procedure.The test apparatus shall verify that the trace heater samples are in intimate contact with the platen. The testapparatus may be supplied with a sample mounting fixture. Offsets may be built into the fixture or platen(s) toaccommodate end termination/power transition fittings/boots, if provided, where their size profile exceeds thetrace heater profile.The apparatus shall allow energizing of the trace heater samples as required during the testprocedure.
The samples shall be thermally insulated on the side not facing the platen so as to improve effective heattransfer from the platen to the trace heater samples.
The temperature of the platen(s) shall be uniformly controlled to a maximum tolerance of土5 °C for platentemperatures less than 100 °C or 5% of the maximum continuous operating temperature if above 100 °C.
The platen described above may be a flat metal plate, a metal pipe, or a metal surface typical of the majority ofapplications for the trace heater being tested.
The trace heater samples shall be within the upper half of the manufacturer’s declared thermal output tolerance,as determined by 4.1.11 b).For trace heaters that are irregular in shape, and for surface heaters.