Common Faults and Preventive Measures of Gate valves
Nov 05, 2012
Gate valves are the main components of the oil (gas) wellhead, several kinds of the common faults in the use of the common faults as follows. 1. Leakage between gate valve and gate valve junction First, check whether valve and gate valve connecting bolts are tight or not, if not tighten, its seal ring and the flange seal groove surface if not sufficiently connected, often lead to leakage. Check bolt and nut orderly, tighten all bolts, until the compress seal ring. Second, check the size and accuracy of the surface of the seal ring and the flange seal groove, if the sealing contact surface has wrong size or too rough, to repair or update it. Also check whether the contact surface of seal ring and the flange seal groove exist a little bit erosion, sand hole, sand holes, or impurities, or other defects, if any, should carry on the corresponding welding, repair, or cleaning up. 2. Leakage from bonnet Bonnet leakage, this failure phenomenon often occurs in the leakage of packing seal. First, check seal if fitting is correct, whether it is suitable for seal groove, if there is such a problem, replace the sealing ring or repair the seal groove. Second, check if seals have burrs, fracturing, and twist off, if any, replace the seals. Then, check if the surface of sealing groove seal is rough or have other defects, if there is a defect, eliminate the defects or update the damaged parts. Bonnet or scaffolds by compression seal packing, should check the installation of the packing case, if find packing installed upside down, should remove, carry out in accordance with the correct way to install. Pay special attention to the surface of packing seal joint. Finally, check if the precision of the contact surface of seal fittings meet the requirements. 3. Leakage from valve body cavity In the process of casting, sometimes valve body may appear casting defects, such as sand holes, sand hole. Although it is difficult to find in the process of machining, once the pressure put on the valve body, hidden casting defects will be exposed. If there is this kind of situation, welding, repairing or updating it. 4. Leakage from valve seat and valve plate Leakage occurs in valve seat and plate, which is the most common phenomenon among the installation or maintenance of gate valves. Generally this can be divided into two kinds: one is leaking in seal surface; the other is leaking in seal root. Above all, check the seat and the precision of the sealing contact surface of valve plate. The sealing surface needs grinding, if there is rough surface, remove and grind it again. Second, check whether there are pitting, indentation, sand holes, cracks and other defects the sealing surface, if in this case, replace valve seat and valve plate. For the valve seat with compression spring, should check whether the pressure spring elasticity is conform to the requirements, if less resilient, update the compression spring. Besides, check if T-shape coupling place of valve plate and valve ste...
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