Application examples of pressure drilling without stopping the pipeline (2 cases)

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(1) Gas resistance in the copper melt. During the night shift at the refining position in the synthesis workshop, the 27 m3 copper melt pump failed suddenly, causing the inlet pressure to drop to 0.03 MPa. Upon inspection, it was found that a large amount of gas was being generated between the copper melt regenerator and the heater. To completely resolve the issue, a vent valve must be added to the pipeline between the two devices. The production department, in accordance with the allowable oxygen content levels in the copper melt, and the equipment team, in line with the relevant regulations for pressure vessels, successfully carried out drilling under pressure (with the copper melt inside the pipe at 0.1 MPa and a temperature of 70–80°C). Without stopping the operation, a Dg20 ball valve is installed at a high position on the protruding part of the copper melt pipe for venting, thereby ensuring an adequate flow rate from the copper melt pump and keeping all parameters of the refining system within normal ranges, thus avoiding losses resulting from a shutdown of the entire ammonia synthesis system. (2) Replace the drain water heater. In the purification workshop, the pressure difference between the inlet and outlet of the water heater used for changing positions is 0.09 MPa (there should be no pressure difference under normal conditions). An increase in the system’s pressure difference leads to overpressure at various stages of the nitrogen-hydrogen compressors, causing the compressors to operate with excessive current, which in turn results in a continuous rise in electricity consumption in the ammonia synthesis system. Upon analysis, it is estimated that there is a leak in the tubes inside the water heater; the water that seeps out forms numerous crystals when heated by the high-temperature shift gas, which blocks the tubes, reduces the heat exchange area, and causes a pressure difference between the inlet and outlet. Pressure drilling was carried out again (with a gas pressure of 0.8 MPa and a temperature of 200°C), and water was successfully injected into the pipe to dissolve the crystals. That afternoon, the pressure difference was reduced to 0.05 MPa; on the following day, water injection brought it down to 0.02 MPa. The power consumption of the compressor dropped sharply, resulting in savings of hundreds of thousands of yuan.