Page 125 - Valve Selection Handbook

112 Valve Selection Handbook

gate valves accommodate both reduced-bore and full-bore ball valves
throughout.
The master standard for face-to-face dimensions is ISO 5752. This
standard includes all the recognized dimensions worldwide that are used
in the piping industry. However, ISO 5752 does not try to define
reduced-bore or full-bore except for sizes DN 200 (NFS 8) through DN
300 (NFS 12) of class 300.
Standards Pertaining to Ball Valves

Appendix C provides a list of U.S. and British standards pertaining to
ball valves.

Applications

Duty:
Stopping and starting flow
Moderate throttling
Flow diversion
Service:
Gases
Liquids
Non-abrasive slurries
Vacuum
Cryogenic

BUTTERFLY VALVES

Butterfly valves are rotary valves in which a disc-shaped closure mem-
ber is rotated through 90°, or approximately, to open or close the flow
passage. The butterfly valves shown in Figure 3-69 through Figure 3-83
represent a cross section of the many variations available.
The original butterfly valve is the simple pipeline damper that is not
intended for tight shut-off. This valve is still an important member of the
butterfly valve family.
The advent of elastomers has initiated the rapid development of tight
shut-off butterfly valves in which the elastomer serves as the sealing ele-
ment between the rim of the disc and the valve body. The original use of
these valves was for water.