Use of ESDV as DBB valve

[MortenA]

Would anybody like to comment on this: Is it OK to use an ESDV as one of the valves in a DBB arrangement?

Best regards

Morten

 

[EGT01]

Morten,

If the double block and bleed is a function of the emergency shutdown, then I would see no problems but I don't think that is what you are asking.

If you are wanting to use the ESDV for something other than the emergency event for which it is intended, then it would seem that you would have to defeat or bypass the control logic provided to control the valve. This opens the door for potential problems. Such safety logic would typically have a high level of supervisory control so that not just anyone could do that without proper authority. This would seem to make using it as a DBB for more "routine" operations quite burdensome and rightly so.

Are your safety systems following the newer Safety Integrity Level (SIL) guidelines? I'm only vaguely familiar with these guidelines but I wonder if what you propose would have an impact on the SIL determination for the ESD system. Maybe that could answer your question.

In some cases, I've seen that the desired SIL can be achieved by activating a normal process control valve along with an independent, designated ESDV. I mention this only because I've seen normal process control valves used as part of an ESD system but can't recall knowing an ESDV being used for "routine" operations.

Of course this is only opinion and I'm not an instrument engineer but I've had to review quite a few safety systems during HAZOPs. Also, I don't know the details of your particular system, but unless there was good argument otherwise, I think I would avoid it.

 

[jsummerfield]

Burner fuel shutoff valves are commonly installed in a double block and bleed arrangement. Depending upon your application and your definition the burner shutdown valves could be regarded as double block and bleed. Also, a line may have a process block valve in series with a shutdown valve.

In the gas industry, most shutdown valves are quarter turn line-class ball valves. The process application dictates the requirements. The valve does not define the application as emergency shutdown. Perhaps the valve is defined as a process shutdown valve applicable to a simple single-vessel/single pump system. High level stops inflow. Low level stops outflow. The same valve may also close in the event of a unit fire. In this case the process shutdown valve is the emergency shutdown valve.

Clarify your situation. Perhaps we can address your question if better understood.

John

 

[SooCS]

DBB is provided for positive isolation of an equipment from high pressure system for maintenance. I believe it is recommended in API 14E or 14J(cant remember exactly which) for process system higher than ANSI 600#. DBB is normally provided around and to by-passed equipment like control valve, filter, hx, etc while process is still on-line. ESDV is definately a better isolation valve than a manual valve and should be allowed as one of the DBB. However, if ESDV is used as a DBB, the whole process system will need to be shutdown which defects the purpose of DBB.

This is not to be confused with automatic DBB, which is basically two SDV and a BDV in between. Automatic DBB is normally used in fuel gas supply to combustion equipment like fire heaters. This is to be 99.999 % sure, fuel supply is positively isolated in the event of an upset in the combustion equipment. This is for observes reason of not to continue supply fuel to fire. In this case a ESDV can be used as one of the SDV. However, your vendor may prefer that the whole automatic DBB system to be intergreted to his control system as a whole. I prefered to provided a SDV at the source fuel supply and the other close to the fired equipment.

Hope this will help.

 

[reliablesam]

Any tight on/off shutoff valve like an ESD valve can be used in a DBB arrangment. The ESD valve can be used if you are going to isolate any segment of your process from neigboring segments without affecting the production.