4 inch DBB valve 4

[Rovshan]

Dear Valve specialists

Could you please advise which type of valve can be used as DBB function for 4"? But not monoblock DBB valve.
Other word: 1 ball, 2 seats

Regards

 

[shvet]

https://files.engineering.com/getfi...-89546e08b1da&file=Double_block_and_bleed.PDF

 

[LittleInch]

Ball valve?

Your question is very vague.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Rovshan]

What type of valve can be used instead of a Monoblock DBB(one body, 2 balls)valve.
In other words is there any option to use Ball, Gate, Plug valves with function of DBB?

 

[shvet]

What type of valve can be used instead of a Monoblock DBB(one body, 2 balls)valve.

Any one having vented area between 2 seats: ball, gate, plug etc.

 

[Rovshan]

What about seat type (SPE or DPE)

 

[LittleInch]

Yes.

Gate and plug often need to have positive pressure / split seats to be really good, but most will seal from either direction which is the definition of Double block.

If you want bleed in the cavity then you need to have split seats or double expanding as they call them sometimes.

In theory a DPE seat makes a ball valve a true DBB with venting the cavity or DIB as it should really be called, but these are not widely accepted as being an effective Double Block and Bleed valve.

There are loads of explanations out there if you look.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Rovshan]

Thanks to all for assisstance !

 

[GBTorpenhow]

A small caveat to consider: An API 6D trunnion ball valve with SPE seats and a body vent may or may not be technically equivalent to a monoblock DB&B valve, depending on where the DB&B requirement is coming from and how it is defined.

For example, OSHA defines double block and bleed in the context of energy isolation for confined entry as "the closure of a line, duct, or pipe by closing and locking or tagging two in-line valves and by opening and locking or tagging a drain or vent valve in the line between the two closed valves." A single ball valve would not meet that definition regardless of the seat configuration.

 

[LittleInch]

Interesting. How do they consider an expanding gate? That is much more positive, but isn't two separate valves.?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[GBTorpenhow]

Interesting. How do they consider an expanding gate? That is much more positive, but isn't two separate valves.?

OSHA seems to be of the opinion that a single line valve of any description is not permitted for isolation of hazards during entry into a permit required confined space. (

https://www.osha.gov/laws-regs/standardinterpretations/2021-11-12)

When I last looked into this I don't believe I found OSHA references to double block in bleed in other contexts but it's admittedly been a while.

 

[bcd]

The definition of double block and bleed varies by standard.

API 6D has pressure coming from both ends of the valve simultaneously and there is a vent in the center body cavity to verify both seats are sealing.

API 608 definition has the pressure direction from only one port, and both seats are sealing. In other words, two seats provide double protection from a leak going downstream. This in more in-line with what OSHA and other safety organizations are thinking. Redundant sealing in one direction with a way to prove the first seal is working with a bleed between. However, it does not align with API 6D definition which often causes confusion.