Special oilfield wellhead valve door improvement

Oil extraction wellhead ( Christmas tree) With gate valve door is one of the largest dedicated gate door, dosage of oil field in the process of gate door manufacturing, valve body intensity of hydrostatic pressure test and sealing test qualified rate is too low, 30% ~ 70%) And long plagued factory. Just above the crux of the problem are analyzed, and puts forward the solution. 1, gate valve, gate valve door blank casting process improvement wellhead door USES the sand mold cast steel blank, in the process of gate valve gate valve door a body, in cooperation with the valve seat in thread often appear in the casting defects such as blow hole, shrinkage, the macro analysis of the gate door profile, found that hot section area have different degrees of shrinkage phenomenon, in order to solve the above problems, the gate door casting process improved test many times. 1) To improve the water the riser system. Will be installed in the valve body on both sides of the cylinder is poured riser system instead of the valve at the bottom of the door set with runner system; 2) Change of sand casting for the investment casting; 3) Change side pouring method for top pouring method, and make the flange down. Because the investment casting sand casting is better than the permeability, faster, more even cooling conditions, so the organization is more dense. Because of liquid steel poured in from the top, but also from the riser directly pouring in, pouring the location of the riser section near the hot area. Gate door create the extremely good order for the casting solidification conditions, hot get timely feeding section area, so the production of casting organization density after process improvement, to eliminate the casting defects such as shrinkage, shrinkage, product qualification rate reached more than 99%. 2 and gate valve door measures to improve the precision of machining manufacturing sealing effect is made key elements of the valve gate. Gate valve door seal mechanical processing industry has always been difficult to solve problems, to improve the manufacturing precision of the valve door, ensure the valve door sealing effect, through theoretical research and production practice, summed up the following improvement measures. The valve body is the most critical gate protege during processing parts, due to the requirement of the structure, the valve seat sealing surface and center symmetry plane tilted 30 ~ 60. For small and medium-sized gate valve gate valve body, the use of auxiliary bending plates with horizontal lathe tooling to complete the valve seat of the inclined plane processing. But must make the pledge that we shall make the plate Angle ( 30 ~ 60) In accordance with technological requirements of valve body. At the same time, should be more strictly to ensure machine tool center high and bending tooling center high coincidence. Permissible error control in 0. 02mm～0. 4 mm between. In addition, the gate valve gate valve body should be considered in the process of machining a clamping, positioning accuracy and reliability. By heavy face of lathe spindle's line should be as a reference, using vertical wedge grooves on the surface of the plate and the sliding the valve body end of the wedge block flange face looking for positive pressure tight, in two sides respectively. In addition, the gate valve gate valve body in the process of machining, must on the lathe tooling by rotate it back 1800 finish on both ends of the valve body cavity machining. The rotation accuracy is to rely on distribution in rotary flange two symmetrical distribution of conical repositioning to ensure that the positioning pin hole. Gate valve gate inversion error is 0. 1毫米~ 0。 02mm。 In addition, to choose appropriate gate door with counterweight and bent plates. It is well known that curved plate on lathe tooling static balance directly affect the machining precision of lathe and the production efficiency, so in the plate shape and layout of balancing the up and down a lot of work, one is the radius of gyration minimize gate door counterweight, the second is on the gate door layout using the cylindrical inner structure, improve the performance of dynamic balance on the circumferential direction, the machine speed and workpiece machining accuracy to improve as soon as possible. Finally, to ensure the parts in the gate door seal coordination processing.