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Wushihua II fertilizer is a large-scale ammonia plant with natural gas as its raw material. Due to the balance of the steam system of the plant, superheated steam generated by the first-stage reformer (pressure 12.5MPa, temperature 515 ℃) is used for steam-driven steam turbine. In normal operation, extra steam is used in subsequent sections and other medium-pressure devices, which requires temperature reduction and decompression, and the temperature is reduced to 355 ° C by superheated steam and the pressure is reduced to 3.8 MPa. HV-112 and PV-172A (same type, same parameters) must be shut off and not allowed to leak when steam is not enough or driving. If the leak will directly affect the steam-driven turbine work efficiency. The design of the two valves used in Italy ABB manufacturers production of temperature and pressure control valve, since April 7, 1997 since the vote, since the original design of the valve there are many problems, the original system of temperature and pressure relief valve (one) can not reuse. The end of 1998, the choice of Swedish BTG production temperature and pressure regulator, overhaul in September 1999 when installed on-line, smooth operation so far (more than 400 days). Reached no accident, no leakage, energy saving purposes, for the safe production of fertilizer plants, equipment and lay a solid foundation for the normal operation. 1 temperature and pressure regulator valve application PV-172A, HIV-112 temperature and pressure regulator valve parameters: normal flow 100000kg / h: inlet pressure 12.5NPa, outlet pressure 3.9MPa, pressure drop 8.7MPa; inlet temperature 515 ℃ , Outlet temperature 350 ℃, import and export saturation temperature 328.21,248.83 ℃; inlet size DN = 150mm, outlet size DN = 100mm. Characteristics of linear, spray water inlet 290 ℃, pressure 15.1MPa, diameter DN = 50mm. The HV-112, PV-172A is a single-seat, balanced sleeve valve with sprinkler system. The one-seat sleeve valve must have a guide seal ring made of flexible graphite. This single-seat sleeve balanced spool, the internal leakage is only two: one is the seat and the spool sealing surface is destroyed; the second is the spool on the guide ring is damaged. In August 1997, serious internal leakage occurred in PV-172A. The spool-mounted sealing ring was replaced by the Italian representative for free and the internal leakage started in less than a month. Replace the spool sealing guide ring again when parking, the result of less than a month to start the internal leakage. In early 1998, PV-172A packing leakage occurred again, to take pressure and plugging measures. Due to the long-term stuffing box in the gel state, affected by temperature and curing, valve stem failure, the control valve completely out of control. Overhaul in 1998 when the use of double-cylinder floor support, instrumentation interlock control, the use of September 1999. In order to ensure the smooth operation of two chemical fertilizers, overhaul to replace the control valve BTG company, this serious problem was solved. Cause of internal leakage: ①control valve in the selection of material has a larger defect, the matching valve is not reasonable, the sealing surface is not resistant to corrosion, impatience flushing, which is the main reason for leakage. ② stem design is too thin, bending strength is low, resulting in spool jam, stem bending and many other failures. ③ regulating valve stuffing box design is not reasonable, especially high temperature and pressure control valve stuffing box is extremely unreasonable. The depth of the general stuffing box design for more than 100mm, but ABB manufacturers only 50 ~ 80mm, simply can not meet the special environmental conditions, so high temperature regulating valve stuffing box is easy to leak. ④ regulating valve actuator in the design there are many problems. Currently, the world's leading design standards for control valves are: light weight, small size, large flow coefficient, multi-spring diaphragm or cylinder-type actuators, high-quality regulation. However, PV-172A control valve actuator height of up to 2.2m, we can see the design height is too high, prone to shaking. If there is slight vibration, the actuator will first damage the valve stem and stuffing box. ⑤ PV-172A valve stem and putt joint Department is very weak, the coupling strength is not enough, compared with other manufacturers from the design structure is not very satisfactory, the joint block heat treatment hardness is not enough, often sliding wire, tripping, resulting in regulating valve out of control. 2 Sweden BTG company temperature and pressure relief valve application features Optional BTG's temperature and pressure regulator valve model VST-SE, which is characterized by: high reliability, wide load adjustment range, the flow can be adjusted from 2% Adjust to 100%, accurate temperature and pressure regulation, long service life, maintenance-free and minimal spare parts, low noise, less vibration. From the design point of view, the overall use of forged steel body material, both inside and outside by smooth curve machining molding to ensure that the valve temperature and cooling when the minimum thermal stress, bonnet and bonnet with pressurized self-sealing, to ensure non-leakage and removal convenience . Multi-step decompression by cage-style spools and multi-layer cage overflow vessels ensures that steam is always controlled within a reasonable range of pressure during decompression to reduce vibration and noise. Stem and valve stem with interference fit installation, does not loosen does not fall off, the design of flexible seat to ensure long-term operation of the valve does not leak, the temperature reduction of water points in the valve steam flow rate of the largest parts of the flow regulating range of products Patented technology using steam forced atomization. In addition, the biggest feature of BTG's temperature and pressure relief valve is the long valve seat, the valve spool has a reliable guiding role. The concentricity of the valve core and the valve seat sealing surface is high. The valve seat is designed as an elastic piece. Decreased by rapid changes in temperature, it compensates with rapid changes in temperature, which has a great effect on the valve plug and seat seal. The material is made of Hagnes 25 hard alloy steel. The valve rod has strong stability when it moves. The cage valve makes the valve linearly adjusted. The valve core is made of stainless steel. The surface is nitrided. The valve stem and stem are made of expanded graphite. Reliable, easy to disassemble. Due to the hollow steel structure of the connecting bracket of BTG's implementing agency, the sand filling in order to reduce vibration and heat, thus overcoming unnecessary maintenance caused by on-site vibration; good stability, less vibration and less bending of the stem , Stuffing box is not easy to damage. On the valve cover and the general control valve design is very different, BTG design on the valve cover is inlaid, the outer wall and the valve for the gap with the wall, the inner wall and the spool guide part match. From this point on the spool of coaxiality, stability has a very important role. Therefore, the valve than the average valve high coaxiality, good stability, small vibration. The above points are the maximum design advantages of the control valve produced by BTG, reducing vibration, reducing noise, improving concentricity and improving sealing performance from many directions, and finally prolonging the service life of the control valve. 3 HV-112 on-site operation of the valve due to the selection of more advanced production technology, since September 1999 on-line installation, operation so far (400 days) did not affect the normal production of the device due to the valve, reducing the amount of normal maintenance to ensure that the two Smooth operation. According to the Daqing fertilizer plant usage, BTG production of the temperature and pressure control valve can be used at least 8 to 12 years overhaul, due to prolonged maintenance, may cause the joint bolt rust, to prevent the bolt rust, run 3 ~ 5 years one by one remove the bolt bolt coated with molybdenum disulfide, in order to facilitate the next normal maintenance.