A manual body bleed valve is included on the APV as standard. This bleed valve
installed in the relief system is opened after the APV valve is closed. Seal
effectiveness can be immediately evaluated, after allowing a few seconds for
stabilisation of cavity volume due to entrained air or gas. The bleed valve must be
closed before the APV valve is opened.
An isolation valve installed in the upstream throat tap is also included. It must be left
open to permit relief system to relieve pressure upstream. The isolation valve will be
used only for maintenance and troubleshooting which will be explained later. Valve
is to be CLOSED ON FOR REPAIR. If closed during normal operation the automatic
portion of the relief system (relief/check valve) will be defeated. (The outlet of the
relief valve would close when closing the isolation valve).
Valve Operation
In the fully open position, the resilient seals are positioned out of the flow
path and protected within the body of the valve itself.
As the valve is cycled from the fully open to closed position, the plug
begins a 90 degree rotation. During the entire rotation of the plug the
resilient seals located on both slips are retracted away from the body.
This ensures that there is no rubbing or scraping action on these resilient
seals during rotation of the plug from the open to the closed position.
Australian Pipeline Valve - Installation, Operation and Maintenance Manual
15
EXPANDING SEAL PLUG VALVE DOUBLE BLOCK & BLEED API6D - TWIN SERIES
