Page 128 - Valve Selection Handbook

Manual Valves 115

Figure 3-70. Butterfly Valve with
Resilient Replaceable Liner and
Interference-Seated Disc. (Courtesy
of Keystone International, Inc.)

Figure 3-71. Butterfly Valve with
Resilient Liner and Interference-
Seated Double Disc for Double
Block and Bleed Used for Isolating
Food Stuffs from Cleaning-in-
Place Cleaning Fluids. (Courtesy
ofAmri SA.)

There are a number of rubber liner constructions in common use. Typi-
cal constructions are:

1. Rubber liner consisting of a U-shaped ring that is slipped over the
body without bonding, as in the valve shown in Figure 3-70. Such
seats are readily replaceable. If the liner is made of a relatively rigid
material such as PTFE, the valve body is split along the centerline
as shown in Figure 3-72 to permit the liner to be inserted without
manipulation.
2. Rubber liner that is bonded to the valve body. This construction
minimizes the wearing effects of rubber bunching from disc rotation
that may occur if the liner is loose. On the debit side, the rubber
liner cannot be replaced.