Page 108 - Valve Selection Handbook

Manual Valves 95

development of the eccentric plug valve shown in Figure 3-53 in which
an eccentric plug matches a raised face in the valve body. By this method
of seating, the valve is easy to operate and capable of handling sticky
substances that are difficult to handle with other types of valves. The
seating faces may be in metallic contact or lined with an elastomer or
plastic in conjunction with the lining of the valve body.

Taper Plug Valves

Taper plug valves permit the leakage gap between the seatings to be
adjusted by forcing the plug deeper into the seat. The plug may also be
rotated while in intimate contact with the valve body, or lifted out of the
valve body prior to rotation and seated again after being rotated through
90°, depending on design.
Figure 3-54 shows a taper plug valve with unlubricated metal seatings.
Because the friction between the seatings is high in this case, the permis-
sible seating load is limited to keep the plug freely movable. The leakage

Figure 3-54. Taper Plug Valve with
Unlubricated Metal Seatings. (Courtesy
ofPegler Hattersley Limited.)

Figure 3-55. Lubricated Taper Plug Valve.
(Courtesy ofSerck Audco Pty. Ltd.)