Pressure Seal bonnet Gate valve는 body와 bonnet사이에 gasket를 넣어 body의 내압에 의해 bonnet를 밀어 올려서누설을 방지하는 고온고압 발전소에 가장 많이 사용되고 있다. Bolt로 체결하지 않는구조로 Top Flange가 없고 bolted bonnet valve보다 면간거리가 짧아 중량이 가볍고 주로 맞대기 용접으로 배관에 부착한다.
■ YOKE SLEEVE
The upper portion of the Yoke Sleeve is hexagonally tapered to fix the handwheel. The standard material of the Yoke Sleeve is Nodular Ni-resist D2 with over 1150℃(2100℉) dissolutiion point in accordance 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 bodies and bonnets of the valve are machined by special purpose machines to achieve perfect coaxiality and eliminate any misalignment which may damage th stems.
The machined forged stem comes with a T-shape head, which connects the slot of the wedge. The contacting surface of the head spherically shaped, thereby giving it greater strength and durability. It is heat treated to give it adequate mechanical properties and surface hardness. Accurate machining and lapping insure minimized friction during opening and shutting.
■ BACK SEAT
All of our valves are provided with positive backseat, and packing replacement can be done with the valve fully open. the conical seat and the guide are integrally stellite faced.
■ SEAT RING
The stellite 6 surface of the seat ring is integrally applied to the body by means of welding in all valve sizes. Lapping applied to the seating surface ensures perfect mating with the wedge surfaces.
■ FLEXIBLE WEDGE
The flexible wedge designed to absorb thermally-induced body distortion, thereby making it ideal for high temperature steam or water supply piping. A Stellite 6 layer is applied to the seating surface, and this deposit is subjected to a special heat treatment to secure required hardness and soundness. The lapped finish then insures perfect mating with the seats.
The valve body is cylindrically shaped to prevent distortion or undue stress during extreme working conditions. In addition, adequate padding helps to achieve a sound cast structure in critical area. The wall thickness is greater than, or in accordance with API, ANSI and ASME requirements. the contact surfaces ensure that a minimum specific pressure is achieved. The area contacting the pressure seal gasket has a stainless steel 18/8 inlay to eliminate corrosion or wire drawing and to insure easy dismantling at all times. The close tolerances of the inside diameter of this area are attained by accurate machining and honing finish.