Pipelines & Pipeline Safety - LINE BREAK - SHAFER VALVE CLOSESE 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: 9 -LINE BREAK - SHAFER VALVE CLOSES

This diagram shows the action of the Shafer valve when a 'Line-break' (rupture) occurs in the 'X' section of the pipeline.

The rapid and sustained pressure drop in the pipeline is sensed by the orifice 'RO' by the difference between the pressure in tank G.2 (original pipeline pressure), and the falling pressure of the burst pipeline.

This pressure drop causes diaphragm 'D' to rise. The diaphragm stem contacts the control arm 'L' and pushes it upwards. This action operates poppet valve 'P2' which closes tank H.1. atmospheric vent and opens the power gas line from tank G.1. into tank H.1.

The increased pressure in H.1. forces the hydraulic oil to pass to the top of the operating piston to close the valve. At the same time, the high pressure oil also opens valve V.1. which allows the oil from BENEATH the piston to transfer to tank H.2. through valve V.1. The top of tank H.2. is vented to atmosphere through Poppet valve P.1. to allow for the displacement caused by the rising oil level.

With the Shafer valve now closed, the 'X' section of pipe will continue to depressure due to the line break.

The 'Y' section will contain a good pressure which will move the shuttle valves V.3. and V.4. across due to the D.P. between 'X' & 'Y', closing the impulse line from the damaged 'X' section by valve


Figure. 9



Last Updated on Thursday, 29 April 2010 19:56