Riser ESDV

[MortenA]

The Lord Cullen report following the Piper Alpha disaster recommends that Riser ESDV's shall not be flanged towards the riser side but welded on.

Does anybody here then have an opinion on if a valve thats made from 3 pieces (bolted together) instead of a top entry valve meets this recommendation? The valves is equipped with a pup-piece and welded to the riser.

Best regards

Morten

 

[Elvie]

Consider that any valve may need maintenance so your "side entry " type if welded to the riser cannot be maintained without huge operating losses (sealine depressurization, inerting ,valve cutting from line ,etc).If you insist for an ESDV to be upstream welded to the riser then you have to select a ball valve "top entry " type for in situ maintenance.But a "top entry" valve is not going to perform as well as a "side entry".So my recommendations :
1) use rather a thru conduit gate valve,API 6D designed, bolted bonnet,M/M seated,expandable gate if dia and size may be accomodated on your platform;as such this valve ,welded to the sealine may be maintained in situ;
2) if this cannot work (high valve rating and dia) go for "side entry" ball valve flanged or rather hubbed to the riser.Make sure the riser is anchored upstream the ESDV so the valve is not submitted to riser movements and stresses.
3) last solution ball valve "top entry" butt welded to the riser.Riser still need to be anchored upstream ESDV.
Finally make sur ball valve is also M/M seated ,have a robust valve designed and fabricated by a reliable manufacturer.