A, an overview of the high pressure liquid ammonia pump P101A/B is the key of the urea plant equipment, in the 1980 s SUNDSTRAND company introduces HMP - from the United States 5112 type high speed centrifugal pump, the working status to open a case, export design pressure for the 27 mpa, high-speed spindle speed of 20445 r/min; The outlet check valve as single swing since high pressure seal check valve, structure and basic parameters such as shown in table 1, the main role for the P101A/B closed automatically when the pump, to prevent the reverse pressure medium back to pump impeller, protecting P101 pump function. After years of operation, two valves in serious leakage, and P101A pump discharge check valve leakage, the above two kinds of failure if not timely solve, will seriously affect the safety of urea production, thus to overhaul the, because of the pump discharge check Industrial Valves exist at the same time, both inside and outside leakage, as an example to introduce the following on this valve. Second, the high pressure liquid ammonia pump discharge check valve maintenance problems ( 1) High pressure liquid ammonia pump discharge check valve by valve core is in a state of work for a long time, the valve core to wear grinding shaft hole into ellipse, lead to valve heart sinking, often open the valve seat sealing surface below the seriously damaged, resulting in serious leakage. ( 2) High pressure liquid ammonia pump discharge check valve, due to manufacturing defect and medium corrosion of cracked body outer seal part, led to the liquid ammonia leakage. Three, repair plan because of the high pressure liquid ammonia pump discharge valve check valve as welding, the maintenance time constraints, not offline repair. Decided to use the method to repair at the site. Repair the leakage and the leakage on two aspects: 1. Leakage repair plan, 1) With a small electric grinder manual polishing outside the valve sealing surface crack, penetrant inspection on the surface at the same time, until the crack defect is eliminated. ( 2) Choose A402 electrode ( Chromium and nickel stainless steel electrode 21) Repair welding by heating spot welding process, the body outside the sealing surface grinding. ( 3) With a small electric grinder manual grinding welds, make its basic level height and the body surface. ( 4) Making the inner ring type grinding ring. ( 5) Grinding ring made of manual for the sealing surface grinding, grinding inside diameter: after 160. 7mm。 ( 6) According to the diameter distribution of sealing ring after grinding. 2. Leakage repair plan, 1) With portable grinding machine grinding seat sealing surface. Ensure its in the presence of carbide recovery is circular. ( 2) Positioning on the lathe with four card find the original valve core shaft hole center, simultaneously reaming. ( 3) Two ring (car system 1Gr18Ni9Ti) Set in the reaming. Ensure that under the condition of invariable in the center, to cooperate with reasonable wear axis, and spot welding. ( 4) Car system wear axis ( 1Gr13) 。 ( 5) With carbide D547 molybdenum electrode repair welding Industrial Valves head, according to the ground after the seat hole with repairing the valve sealing surface. ( 6) Try to match with red lead after the test, to ensure its tightness. Four, the conclusion according to the above scheme for high pressure liquid ammonia pump check valve of the export of P101 after repair, to solve the problem of the valve leakage, after more than a year of operation, the use effect is good, the maintenance of the same type high pressure check valves and other self sealing valve has the certain model function.
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