Technology for installing thermocouple protection tubes under pressure

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Yu Guoqing explained in detail how to install thermocouple protection tubes without shutting down the equipment, and this approach can also be applied to installing primary pressure tapping valves for instruments without interrupting operations. Keywords: under pressure; centrifuge; special valves; sealing packing chamber; drilling under pressure 1 Analysis of the process operation parameters of the unit The process pipeline has a diameter of Φ159 ×4.5; the operating pressure is 1–1.2 MPa, the operating temperature is 230°C–240°C, and the medium used is steam. Due to the fact that the medium is non-flammable and not susceptible to sparks generated during operation, pressurized drilling technology can be employed. 2 　Manufacturing of special valves 　Select a gate valve based on the thickness of the thermocouple protection tube to be installed. The thermocouple protection tube we selected is a Φ12 ×2 1cr18Ni9Ti stainless steel tube (L = 450, 1 piece). The valve selected is Z11H - 40 -15, and the flange used is PG40, Dg20, in one piece; a seamless steel pipe with dimensions Φ32X ×2.5 is cut into two sections of 100 mm each. The specific welding method is shown in Figure 1. Once welded, a special valve is obtained, which is then welded onto the process pipeline. ? 3 　Construction of the sealing packing chambers 　Two sealing packing chambers are specially manufactured according to the flange dimensions specified in Figure 1, as shown in Figures 2 and 3. 4 　Drilling under pressure 　A special valve is connected to the sealing gasket in the drilling chamber designed for working under pressure; a longer drill bit with a diameter of Φ14 is used to carry out drilling under pressure. Once the Φ159 pipeline has been drilled through, the drill bit is slowly pulled out past the valve. At this point the valve is closed, and the drill bit is removed from the sealing chamber – thus completing the drilling under pressure process. Then, remove this stuffing chamber. ? 5 　Installing a thermocouple protection tube under pressure 　Connect the thermocouple’s sealing packing chamber to the special valve flange using gaskets. Insert the thermocouple protection tube into the valve, then tighten the packing cover slightly; use a lever to apply additional force. Next, open the gate valve and insert the protection tube into the process pipeline so that it aligns with the center line. Tighten the packing again, and thus the installation of the thermocouple protection tube under pressure is complete.