Problems with instrument heat traces
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During equipment maintenance, heat tracing is installed. I noticed that for the instrument-related heat tracing, thin stainless steel tubes are used, while for general piping heat tracing, DN25 steel tubes are employed. I’m not sure why the materials used for heat tracing differ, nor why the thickness of the heat tracing tubes varies. If anyone knows the reason, please let me know; thanks, points will be given
For general instrument heating tubes and pressure guiding tubes, 14*2 or 18*3 diameter pipes are used. The advantage of using stainless steel for heating tubes is their corrosion resistance; as a result, they have a longer service life compared to ordinary carbon steel heating tubes. Depending on the properties of the medium being heated, heat tracing is further divided into heavy heat tracing and light heat tracing. Compared to ordinary pipelines, those pipelines for which instruments require heating are thinner; using thicker pipelines would be wasteful.
For our instruments, we generally use 6 or 8 copper tubes; for pressure tapping pipelines, stainless steel tubes are used as instrument heating lines, and the heating lines can also be selected based on the process medium
For heat-traced pipelines, sizes of 14, 18, and 22 are commonly used; I’ve never seen steel pipes with a DN25 diameter as you mentioned. As for the material, if the factory has the means, stainless steel 304 is usually used, while for those with limited resources, carbon steel pipes will suffice
There are two types of instrument heating: steam heating and electric heating, and the choice can be made based on the specific conditions on site. It is important to note that the steam supply or power source must be stable and reliable, in order to prevent the instruments from being damaged by freezing or the steam heating tubes themselves from being damaged as a result of a disruption in the heat supply. Secondly, it is to prevent overheating from affecting the proper operation of the instruments. In the past, heating was applied to the pressure tapping tubes used for measuring flow rate by differential pressure using steam; this caused the water inside those tubes to vaporize, resulting in severe fluctuations in flow rate and preventing normal operation. Later, electric heating was used instead. Third, low-pressure saturated steam should be used, as this prevents overheating and ensures safety. Fourth is regular inspections to check whether the power supply, steam, or steam traps are functioning properly.
HG/T 20514-2000 Code for Design of Heat Tracing and Insulation of Instruments and Pipelines
If you follow the methods of those people upstairs to provide heat tracing, you’ll have a lot to do in winter.