Australian Pipeline Valve - Installation, Operation and Maintenance Manual
21
SIDE ENTRY 3P TRUNNION BALL VALVES API6D STANDARD - BVF100 SERIES
pressure should not exceed in 1.33 times the valve pressure rating at the specified maximum operating
temperature; however, pop-off action usually happens long before, with just a few bars of differential
pressure. For standard API6D ball valves, both seats are self relieving. However, on request valves can be
ordered with just upstream or just downstream seat as self relieving. Also “double piston effect” (DPE)
seats can be specified. DPE seated valves must have an external relief safety valve fitted to the body
which vents to atmosphere. Due to environmental requirements this must now be plumbed back into the
upstream side of the valve or recycled elsewhere. Refer Section 10.0 for more information.
Both seats are self relieving hence over-pressure can be relieved up or/and
downstream. Custom ‘single piston’ seats can be specified on one side, and ‘double
piston’ seats on the other side to allow pressure to only automatically relieve just
upstream or just downstream.
