Pressure Seal bonnet Globe valve는 body와 bonnet 사이에 gasket를 넣어 body의 내압에 의해 bonnet를 밀어 올려서 누설을 방지하는 고온고압 발전소에 가장 많이 사용되고 있다. Bolt로 체결하지 않는 구조로 Top Flange가 없고 Bolted bonnet 밸브보다 면간거리가 짧아 중량이 가볍고 주로 맞대기 용접으로 배관에 부착한다.
유량 및 압력 조절이 가능하나 Gate valve에 비해 많은 작동 힘이 필요하다.
■ YOKE SLEEVE
The standard material of the Yoke Sleeve is Nodular Ni-resist D2 with over a 1150℃(2100℉) dissolution point in conformity with API Std. Specifications.
The bonnet is of a steel forging identical to the body to insure high reliability. The bonnet has a perfect body-bonnet seal and both ease of dismantling and reassembly are ensured. The body and bonnet of our valves are carefully machined to achieve perfect coaxiality and eliminate any misalignment which may cause damaged stems.
The stem, of one-piece construction, is heat treated to secure the adequate mechanical properties and surface, hardness. Accurate machining and grinding insure that there is minimized friction during valve opening/shutting. the round head of the stem gives a point contact with the inside of the disc housing and thus prevents galling.
■ BACK SEAT
All of our valves are equipped with a backseat to allow packing replacement with the valve fully opened. The conical shape contact seat in the bonnet assembly in integrally stellite faced.
The disc of our globes is a loose disc which freely revolves around the stem, thereby preventing freiction and galling with the seating surface when the valve is shut. The outside diameter of the disc is accurately finished and cylindrical in shape to travel along the body guides. A stellite 6 layer is applied to the conical seating surface of the disc. This deposit undergoes a special heat treatment to secure the required hardness and soundness. In addition, the lapped finish insures a perfect mating with the seats.
The Stellite 6 seating surface is integrally applied to the body by means of welding in all valve sizes. Perfect mating of the disc surfaces is achieved by lapping applied to the seating surface.
The cylindrically shaped valve body prevents distortion or undue stress under extreme working conditions. In addition, adequate padding ensures a sound cast structure in the critical area. The wall thickness is greater than, or in accordance with API, ANSI and ASME requirements. The area contacting the pressure seal gasket has a stainless steel 18/8 inlay to eliminate corrosion or wire drawing. The close tolerances of the inside diameter of this area are attained by accurate machining and honing finish.