×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Isolation procedures question

Isolation procedures question

Isolation procedures question

(OP)
I am trying to find some isolation procedures for using double block and bleed valves, when/where to use them and procedures for PSV isolation, when/where.  I really would just like to be pointed in the right direction for some reading material.  I have already tryed to go through ASME and CSA code, but it is not of to much help.  If there are any good write ups on double block and bleed procedures and PSV isolation procedures I would really appreciate it.

Thanks!

RE: Isolation procedures question

The best source is the actual manufacturer of DBB valves, who are suppose to comply with specific requirements ( corrosive, explosive environments, lethal service, etc..).
Cheers,
gr2vessels

RE: Isolation procedures question

I dont think there is a specfic stander or code will give you a sufcient material for DBB, each company has its own isolation procedures for using double block and bleed valves.

RE: Isolation procedures question

The legal requirement is positive isolation from energy source.  With energy source being pressure, chemicals, or other hazards. How you decide to accomplish that is a company decision.

RE: Isolation procedures question

Some systems with standards that require automated double block and bleed valves include fuel gas to fired heaters and oxygen systems.

RE: Isolation procedures question

ash9144,
Correct the DBB is to provide positive isolation. The full intent is for positive and verifiable isolation. First block valve provides isolation, bleed is the point where isolation is verified (first valve is holding), second isolation is braces for the belt, if the first valve fails the energy source (pressure, chemical, electrical etc) is bled off through the bleed while the second valve holds.
For references try OHS authorities or pressure vessel inspection procedures.

Mark Hutton


 

RE: Isolation procedures question

May I take the slight liberty on HEC words;The bleed valve is also a check of energy inflow from either side and thus care taking for safety's sake.

Definitely operationally Positive Isolation is the main duty of Double Block& Bleed system.
At times it's supplemented with sealing Or Chain-Lock system

Hope this helps

Best Regards
Qalander(Chem)

RE: Isolation procedures question

As far as I know, DBB isolations schemes and guidelines are extensively discussed in the following fundamental

"The safe isolation of plant and equipment"
Oil Industry Advisory Committee, HSE Books 1997

For PSV, if there are 2 PSV's and one is 100% spare, the spare one shall be locked closed in order to avoid error in leaving the spare operating (this would result in chattering of PSV's).

RE: Isolation procedures question

There is no standard for positive isolation. It is the responsibility of a company to prove it has it's own standards. However most North Sea oil companies have pretty similar procedures as they all work together.
These use a matrix that shows pressure, flammability, temperature etc and reads out a standard based on the criteria. For example a 6" oil line may require a higher level of isolation than a 48" water line

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources