Pressure Seal Gate Valve

Fig-1: The pressure-seal cross view of high pressure gate valve:segmented thrust ring, seal ring, and metallic gasket.

As illustrated in Fig-1, the pressure sealed bonnet-body joint of a high pressure gate valve is constructed by proper arrangement of body, bonnet, metallic gasket, seal ring, segmental thrust ring, retainer, body cover and a couple of bolts & nuts. The lower end of the bonnet is outwardly sloped to form a sealing contact with the inverted frusto-conical surface of the metallic gasket. The metallic gasket, usually made of soft steel material, is held down by a segmented thrust ring which is inserted into the annular groove of the valve body. The words “segmented” or “segmental” refer to the thrust ring consisting of a plurality of segments all of which may be cut from a single ring. A seal ring made of hard metal is placed between the thrust ring and the gasket and serves to distribute pressure on the thrust ring the gasket preventing deformation of the top surface of the relatively soft gasket. Both the metallic gasket and the seal ring shall be furnished with spaced threaded holes for ease of removing and maintenance. Besides, A – There shall be a 1° angle between mating surfaces of the bonnet slope and the gasket slope. This wedged design ensures a tight seal at either low or high line pressure. B – The interior sealing surface at the body neck shall be welded with a stainless steel inlay to provide finer grain and smooth finish as well as better corrosion resistance. C – Radial bores are furnished in the valve body through which a knock-out pin may be inserted for driving the segmental rings out of the groove. D – A small end bevel on the gasket to prevent it from scraping or catching in the groove.