STORED ENERGY
Case study 1 – Flanged weld testers and expanding plugs
Sudden Pressure Release
When
August 2010 (Synergi 19843)
Impact
Sudden release of pressure and ejection of Flange Weld Tester
(FWT) plug
Air out and pressure monitoring
Hydrotest space
Positive confirmation
of zero pressure
before dismantling
Monitoring pressure
behind plug and
bleed port
Water in and pressurization
Individual suffered serious head injuries but fortunately
recovered over time
• Check for pressure behind plug and bleed down as required (leave bleed open)
• Undo seal engagement nut
• Loosen large nuts and confirm assembly free to move
• Loosen flange bolts gradually ensuring centre shaft is free at all times
Key messages
When using FWT to hydro test a weld ensure safe system of
work and pressure isolation to avoid the device becoming a
projectile:
• Permit to Work
• Safe Isolation Procedure
• Risk Awareness and competency for the job
What happened?
Injured Party (IP) was involved in the hydro-test of a newly welded
flange on the produced water line (PWL). The IP was dismantling
the FWT and removed the flange itself leaving just the plug
in the PWL. The IP found the FWT difficult to remove and was
attempting to free the unit when the plug was ejected under
pressure that had built up in the line and the IP was directly in the
line of fire.
!
Flange Weld Tester (FWT)
The IP was medivaced to the local hospital and after surgery
was placed in a medically induced coma. Fortunately the IP later
recovered and was able to return to work.
The pressure build up behind the FWT could be due to:
• Hydraulic pressure caused by leakage of water beyond the plug
on the FWT due to the seal not being properly engaged
• Pneumatic pressure released into the line through an
ineffective isolation
LIFE SAVERS
STORED ENERGY
Case study 1 – Flanged weld testers and expanding plugs
Sudden Pressure Release
Problems
The following issues were identified as root causes of the
incident:
As a result of this incident the following items were highlighted:
• No Permit to Work
• Use competent people familiar with the risk
• Lack of awareness that pressure could build up behind the plug
• Risk assessment with toolbox talk
• No means to monitor the pressure behind the plug seal
• Follow operating procedures
• Risk Assessment and Standard Operating procedures not
followed
• A means to monitor the pressure behind the FWT is required
• Permit to Work must be adhered to with procedures for Safe
Isolation and Reinstatement
Learning points
Flanged weld testers and expanding plugs are used for hydrotesting of new welds or for creating temporary isolation while
welding takes place. These devices can become a projectile and
cause serious injury with only limited pressure due to:
• Pressure from the test area passing the seal
• Passing isolations upstream of the tester
• Change in isolation status during the use of the flange tester
• Head of liquid from hydro-test fluid, passing isolations on
liquid systems or gradual draining of liquids within the line
• Thermal expansion, especially when liquids are in the line
For more information on Stored Energy safety:
• Group Subject Matter Expert on Stored Energy – Paul Dows (Paul.dows@bg-group.com)
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• BG Life Savers Portal pages and Step Forward website
• BG Group Standard BGA-OPS-OS-0019 Application of Process Isolations
• BG Group Standard BG-ST-OPS-OPS-022 Permit to Work System Requirements
• BG Group Standard BG-ST-ENG-PROC-002 Safe Plant and Equipment Isolation
• Safety Moments on Jive
LIFE SAVERS