In the process of thermal throttling and expansion of natural gas, due to the Joule-Thomson effect, there is usually a temperature drop. For every 0.2-0.3MPa drop in pressure, the temperature drops by about 1°C. If the natural gas pressure is adjusted from 4MPa to 0.4MPa, the temperature of the natural gas at the outlet of the pressure regulating and metering skid will drop by more than 12℃. In winter, when the temperature is below 10℃, the outlet temperature of the pressure regulating and metering skid will drop below -2℃.
Due to the relatively small diameter of the pilot pipe or valve port of the pressure regulating and metering skid, if the natural gas contains moisture and impurities, ice blockage may be formed at the pipe or valve port of the pilot, thereby causing the pressure regulating and metering skid to adjust the pressure. If the function fails, the high-pressure natural gas directly enters the downstream pipeline of the pressure regulating and metering skid, which has a direct impact on the safety of gas use. In this regard, the normal operation of the equipment can be maintained by locally increasing the natural gas temperature at the inlet of the pressure regulating and metering skid.
The commonly used methods to increase the natural gas temperature at the inlet of the pilot of the pressure regulating and metering skid are: pipeline electric heat tracing method, vortex pilot gas heater method, pilot heater method, heat exchanger method, etc. Each heating method has its own advantages and disadvantages.
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