5 replies to this topic

[omid64]

Considering a system which should be positively isolated  from a live plant.prior to man entry to a vessel inside the system,it shall be positively isolated by means of blind insertion in all feed and products streams. assuming feed stream is a live one which is in operation at a high pressure or in a lethal service which needs double block and bleed isolation, is it possible to consider only a single block valve to permit beak the flange and blind insertion? I

[VeryProfessionalEngineer]

I've seen it done, but that's really dependent on your service. If you are isolating a firewater system and have proven a valve holds, and can mitigate your potential consequences to just somebody getting wet, that's one thing...If you're talking about high pressure or lethal gas on the other side, you'll have to use some judgement and take into account the potential consequences and scope of the blind insertion. You still have to prove the isolation holds in any event.

[Zauberberg]

Imagine yourself or one of your siblings doing the blind insertion under single valve isolation. Would you do it?

[VeryProfessionalEngineer]

Imagine yourself or one of your siblings doing the blind insertion under single valve isolation. Would you do it?

 

This is probably a good philosophy to have, although some people have a pretty high personal tolerance (or ignorance) of risk. High pressure gas, high temperature or otherwise "lethal" or dangerous fluids on the other side=I'm not doing it. 

 

Also, don't assume just because you have a valve that it holds. Many won't. 

[Napo]

Omid64,

You need an approved procedure (in your company) for to this, this document needs the steps review for operations personnel and considerations of safety aspect. After that, you have assume the risk in the work, and the personnel (operation and maintenance) have to respect the document for this work.

Napo.

[MariahAnjelika]

I would think that you'd want to make gurantees, and DBB would provide them, mostly when it is not a matter of contamination in the system, but personnel safety when entering a confined space.