Application examples of the non-stop \"drilling under pressure\" technology

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1 Application example (1) Gas resistance in 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 relief 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 bulge 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 and hydrogen compressors to varying degrees, causing the compressors to operate with excessive current, which in turn results in a continuous rise in the electricity consumption of 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 further lowered it to 0.02 MPa. As a result, the power consumption of the compressor dropped sharply, helping the company save hundreds of thousands of yuan in losses. 2 Tool fabrication and operation methods: (1) Based on the diameter of the pipe for which drilling is required, prepare a set of leak-sealing clamps to secure it in place (make sure to use shims for proper sealing), and drill holes in half of these clamps; then weld a ball valve with a diameter of around Dg20 to them (the valve size should be determined based on the diameter of the drill bit). (2) Construct a packing fixture based on Figure 1, and attach it to the valve body using flanges; the concentricity between the flange and the packing sleeve should not exceed 0.10 mm (machining after welding). The inner diameter of the flange is determined according to the diameter of the drill bit, while the inner diameter of the packing sleeve is determined based on the diameter of the packing used. http://www.nmtech.com.cn/jishuwang/upload/0605081454098110.jpg (3) After processing the clamps, valves, and packing sleeves, assemble them according to the diagram; compress the packing using a gland flange, and drill directly with an extended drill bit. During drilling, the filler is continuously compressed to ensure a tight bond between it and the drill bit, thereby preventing the medium inside the pipe from leaking out along with the drill bit. (4) After the hole is drilled through, slowly pull out the drill bit until it reaches the packing sleeve; then close the valve, ensuring it is fully closed before pulling out the drill bit. After the valve, piping can be arranged arbitrarily for venting or introducing a medium. 3 Renovation plans and scope of implementation: When drilling holes in pipes, sometimes the large diameter of the pipes, inadequate sealing by gaskets, or poor sealing of ball valves can result in all efforts made for drilling under pressure being wasted. If such a situation occurs, the device shown in Figure 2 can be used as a remedy: a taper is created at the front end of the hollow tube according to the diameter of the drilled hole, and it is pressed in with slight force so that it fits tightly against the drilled area; the back end of the hollow tube is then welded directly to a valve for control. http://www.nmtech.com.cn/jishuwang/upload/0605081455307969.jpg In medium and low-pressure pipelines used for transporting non-flammable and non-explosive media, this method can be employed in the event of air blockages or crystallization, without the need to stop the operation; this helps to maintain continuous production and provides a solid foundation for achieving stable high yields.