Pipelines & Pipeline Safety - RE-OPEN THE SHAFER VALVE PDF Print E-mail
Written by Norrie   
Thursday, 29 April 2010 19:53
Article Index
Pipelines & Pipeline Safety
TRANSMISSION OF FLUIDS
JOINING OF PIPELINES
PIPELINE SUPPORTS
PIPELINE ANCHOR POINTS
EXPANSION LOOPS (or BENDS)
PIPELINE SAFETY
'SHAFER' AUTOMATIC LINE-BREAK VALVE
LINE BREAK - SHAFER VALVE CLOSES
AUTOMATIC RESET
RE-OPEN THE SHAFER VALVE
PIPELINE SPHERING
All Pages

FIGURE: 11 – RE-OPEN THE SHAFER VALVE

The Shafer valve will NOT OPEN automatically.

With the line break repaired and the pipeline pressurized, it is now time to re-open the Shafer valve.

(It should NOT be opened before the line pressure is equalized each side of the Shafer. If the Shafer is to be opened with the complete line de-pressured, and no pressure is available in the power gas tank, then the manual pump (M) is used).

The line pressure will replenish the power gas in tank G.1., through the check valve V.5.

Tank G.2. will also come to line pressure. To open the valve, the control arm lever is manually depressed (pushed down) and HELD DOWN until the Shafer is fully open.

Manually pushing and holding down the control arm, operates Poppet valve 'P.1.' which moves down against its spring. This action closes the vent to atmosphere from tank H.2. and opens the power gas from tank G.1. into the top of tank H.2. The oil enters the Shafer operator cylinder 'CP' and pushes the piston up to open the Shafer valve. The oil ABOVE the piston operator is transferred back to tank H.1. through valve V.2. which has been opened by the HP oil.

H.1. is vented to atmosphere through poppet valve P.2. When the Shafer is fully open, the control arm is released and returns to the horizontal position. Poppet valve P.1. moves up to close the power gas supply and open tank H.2. to atmosphere. All pressures will stabilize, valves V.1 and V.2 will close and valves V.3 & V.4 will become centralized. The Shafer valve is returned to the original condition as in Diagram 1. and is ready for the next emergency.


Figure. 11



Last Updated on Thursday, 29 April 2010 19:56