Flowserve Swing Check Valves 2.5-24 - Manual (Page 7)

Swing Check Valves FCD ADENIM0013-00
6
1.0 VALVE DESCRIPTION
(Continued)
1.3
Design Features
1.3.1 Bonnet Seals
Anchor/Darling swing check valves are supplied with two basic types of body/bonnet closures; bolted
bonnet or pressure seal. The bolted bonnet closure (Fig. 2) is a bolted flange tongue and groove joint
with a gasket generally comprised of spiral-wound stainless steel and asbestos filler. The seal
depends upon the bolt preload to maintain sufficient compressive force on the gasket.
Pressure seal type closures (Fig. 3) 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 angular 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-to-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 2 Figure 3