The Demand for Valves in Petrochemical Industry (2)
Valves Specialized in Petrochemical Industry
Among the valves specialized in petrochemical industry, the most typical valves are single-acting slide valves and double-acting slide valves of the catalytic cracking unit. The single-acting valve sends the catalyst with the carbon deposition after the reaction to the regenerator to burn it or bring the regenerated catalyst from the regenerator to the riser. The design pressure is from 0.2 to 2.3MPa, and the design temperature is from 500 to 900℃. The double-acting slide valve is the valve that controls the pressure of the regenerator, and the operating medium is the high-temperature flue gas with a tiny quantity of catalyst. The design pressure is 0.3MPa, and the design temperature is 870℃. The slide valves are driven by wind or motors, and in the transmission system of the pneumatic motor, the locator can accept pneumatic signal from 0.2 to 1.0kgf/cm2. The control system composed of check valves, air evacuation valves and quick-opening valves can have the sensitivity of 1/400 and the accuracy of 1/100.
The specifications of ethylene cracking facilities’ cracking and sliding valves are from 3 to 42 inches, and the operating temperature is from 415 to 593℃. These valves adopt the welding structure, the sealing surface made of hard alloy by overlaying welding. the double parallel gate and the sealing auxiliary without selection. Dish springs and wedge-type structures can ensure that the valves are flexible and reliable. The expansion joint inside the valve can stop the cracked gas from leaking to the valve cavity. The valve body are made of 15CrMo, and the internals are 15CrMo, 35CrMo and 2Cr13.
For the high-temperature and high-pressure angle globe valves and throttle valves of synthesis ammonia equipment, the operating temperature is 560℃; the nominal pressure is less than or equal to 42Mpa; the nominal dimension is from DN10 to 110mm; the media are methyl alcohol, hydrogen sulfide, nitrogen, etc. The nominal dimension of oxygen globe valves and ball valves of air separation plants is less than or equal to 900mm; the minimum allowable temperature is -196℃; the nominal temperature is 0.2 to 16Mpa. There are some special valves of wellhead equipment often used in oil exploitation. The valves include the oil inlet valve whose nominal pressure is from API2000 to 20000Psi, the Ap16A flat gate valves for the natural gas wellhead, angle throttle valves, pilot relief valves AP16D fully welded ball valves and the metal sealed ball valves with the changed pressure.
These special valves for petrochemical industry are difficult to be manufactured with complex technology and high requirements on quality and reliability. The materials these valves are made of should be properly chosen and the manufacturing process should be rigorous. Because the media for petrochemical production are almost the media of high temperature, high pressure, flammability, explosiveness, corrosion and poison, and it will result in such major personal and property accidents as leakage, ignition and poisoning. Therefore, the requirements on the quality of the special valves for petrochemical industry are usually very high.
Source: China Valves Manufacturer – Yaang Pipe Industry (www.ugsteelmill.com)