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Interpretation Double bloc and bleed

Interpretation Double bloc and bleed

Interpretation Double bloc and bleed

(OP)
We interpret double block and bleed function as DBB valve or manifolds used in instrumentations systems (Swagelok / Parker Style)

But for Bigger size pipe line valves (around 12")  the same terminology is used (Kuka/Kace catalogues)
Can somebody add more on the mechanism of this type sealing
Thanks

RE: Interpretation Double bloc and bleed

Double block and bleed is a technique that is mentioned in the OSHA rules as a valid method to isolate energy away from hot work (some of the others are insert-blinds and mis-aligning piping).  They don't define it, but it is taken by most companies to be two sealing surfaces (the "double block") separated by a section of evacuated pipe (the "bleed").

Some companies require that the double block be two independent valves separated by some distance (from inches to miles), others consider a trunion ball valve with a functioning body bleed to be adequate.  Some companies have restrictions on what can be done downstream of DBB (one company that I work with does not allow hot work in a confined space to be done downstream of DBB).

David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
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RE: Interpretation Double bloc and bleed

Some comapanies now require a second element in addition to a valve for a "block" upstream of hot work where there is potential for explosive conditions.

It is common for valves to leak. If relying on a double block and bleed in hot work, a flange or equivalent may also be used downstream of the block valve.

RE: Interpretation Double bloc and bleed

Actually, OHSA does define a double block and bleed. See thread408-94849. Of course, companies often go beyond OSHA minimums, and individual states may have tighter restrictions also. California is one which allows DBB's for entry but with restrictions.

jt

RE: Interpretation Double bloc and bleed

for work with hazardous products we used the DBB with spectacle blinds.

the sequence is as follows:
block valve
double flanged spool piece with bleed
spectacle blind
double flanged spool piece with bleed
block valve

saludos.
a.

RE: Interpretation Double bloc and bleed

(OP)
Can somebody share the sizes they have used and also advise some technically sound equipment provider?

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