tank dike area. Carbon steel valves are permitted, provided
they are internally plated with chromium. Electroless nickel
plating is also acceptable.
b) Valves for quick or frequent opening may be one
of the following:
seating material is burned out in a fire exposure, a metal-to-
metal seat will remain to affect closure and comply with
API Std 607. Require synthetic seals or seating material to
be of Teflon or viton. Where line pigging is required or if
within ten pipe diameters upstream and/or five pipe diameters
sensing device such as a venturi, use full port ball valves.
Valves should comply with API Std 608.
(2) High-performance wafer trunion (butterfly)
valves. Use Teflon or viton synthetic seals or seating
material. Design the valve so that if the synthetic seating
material is burned out in a fire, a metal-to-metal seat will
remain to affect closure. Use valves of high-performance type
with eccentric disc shaft and clamping action for bubble-tight
shutoff. Do not use these valves on Air Force projects. On
other service projects, use only as operating valves and not
where isolation or absolute closure is required, such as on
tanks. Their use is discouraged outside of fillstands and
aircraft direct fueling stations.
Provide Teflon-sleeved nonlubricated plug
c) Use check valves to prevent backflow through
pumps, branch lines, meters, or other locations where runback
or reverse flow must be avoided. Check valves may be of the
swing disk, spring-loaded poppet, ball, or diaphragm-actuated
types. Use swing checks of soft-seated non-slamming type with
renewable seats and disks. Use diaphragm non-surge check