Flowserve Cast Globe Valves - Manual (Page 8)

Globe Valves FCD ADENIM0011-00
8
1.0 VALVE DESCRIPTION
(Continued)
1.3 Design Features (Continued)
1.3.2 Bonnet Seals
Anchor/Darling Globe valves are supplied with two basic types of bodybonnet closures: bolted bonnet or pressure
seal. The bolted bonnet closure (Fig. 3) is a bolted flange tongue and groove joint with spiral-wound stainless
steel gasket and asbestos filler. The seal depends upon the bolt preload to maintain sufficient compressive force
on the gasket.
Pressure seal type closures (Figs. 4 & 5) utilize a tapered soft metal ring gasket for sealing. The gasket is
contained within the body neck bore by a retaining ring. The tapered inner surface of the gasket bears against a
mating annular surface on the valve bonnet. Under internal pressure, the bonnet is forced against the pressure
seal gasket, wedging it against the body neck wall. A slight interference angle produces a line contact and high
sealing pressure. The greater the valve pressure the tighter the metal-ta-metal seal. No bolting is required to
maintain the seal although the bonnet is initially drawn into contact with the pressure seal by cap screws.
FIGURE 3 FIGURE 4
FIGURE 5