Articles
Shear Valves Following a recent site visit by John Wigfull & Co Ltd, Richard Wigfull uncovered incorrect use of a Risbridger vapour recovery shear valve for LPG service and wrote to Risbridger to make them aware. Risbridger have never advised customers to use the vapour valve for LPG installations, and have always differentiated them on literature and packaging. They were at a loss to know why the vapour valve would be used as there is no cost advantage in doing so. Risbridger sent this letter to Richard following his site visit results: Dear Richard Thank you for your letter of the above reference, and for your visit to our stand at the IFFE Show. I can confirm that we have investigated the use of our Vapour Line Shear valve, and Trevor has advised his customer that the use of our Stage 2 Vapour Line return valve is not suitable. I understand that the installer has already received valves to replace ones incorrectly installed. We will be writing separately to this installer and have amended our literature to make clear the correct usage of both valves. Please see copy enclosed. Graham has confirmed that the RISSHEAR-G2 Stage 2 Petroleum vapour return line shear valve has a maximum operating pressure of 35 mbar. This valve must not be used with LPG. The seals in this valve are also incompatible with LPG as they are viton, not nitrile. Each LPG installation should have two RIS-SHEAR-LPG valve one each in the delivery and return lines. I would be happy for you to let the LPGA of this problem and will give you any assistance in this as required, just let me know if I can help. We appreciate your quick action and involvement in this incident, thank you very much for your help.
STAGE 2 VAPOUR LINE SHEAR VALVE •
Normally open, full-flow design with low pressure drop
•
Dual opposed piston design avoids partial break interference and leakage condition
•
Seals upstream & downstream upon impact
•
Cylindrical body fits through and allows sealing with standard membrane seals
•
Shuts fully irrespective of direction of impact
•
400kg break force
•
Variety of end adaptors available
•
Non-spark brass construction
•
The installation tool allows correct alignment and prevents pre-stressing the shear valve
•
Pressure rated for maximum of 35 mbar,
seals viton,
to be used on petroleum stage 2 vapour return lines only
LPG SHEAR VALVE •
Full flow design with low pressure drop
•
1" nominal size for 80 l/min flow rating
•
Displaced ball design prevents ‘partial break interference’ leaks
•
Seals upstream and downstream upon impact
•
Shuts fully irrespective of direction of impact
•
Consistent 420 Nm bending moment break
•
25 bar pressure rating with 12:1 safety factor
•
Non-spark brass body construction, nitrile seals
•
Optional mounting kits available
•
Optional end fittings available
•
Installation tool allows correct alignment & prevents pre-stressing the shear valve
With best regards, Yours sincerely Annie Risbridger Sales & Marketing Director
Risbridger Ltd, Stychens Lane, Bletchingley, Redhill, Surrey. RH1 4LN Tel: +44 (0) 1883 743107 Fax: +44 (0) 1883 744342 email: info@risbridger.com www.risbridger.com
59
