×
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

Two valve Isolation rule

Two valve Isolation rule

Two valve Isolation rule

(OP)
I'm looking for which spec or code states that when work is carried out on equipment on an operational plant that the piece of equipment is isolated by two valves. Any one remember where this is written down.

thanks

RE: Two valve Isolation rule

I have seen and heard this question asked many times in other forums. The code and most standards only provide minimum requirements, and are not intended to specify or regulate company safety programs. Safety programs require common sense and must be controlled by the organization that owns/operates or repairs hazardous equipment.

With that said, in certain applications - for example separate boilers (not twin furnace boilers) that feed into a common steam outlet header the ASME B&PV code requires a stop and check valve as a form of double isolation to assure that steam from one boiler does not back feed into the other boiler. This is part safety, and to protect isolated equipment from damage.

Regarding non-boiler applications, double isolation is a good thing, regardless. Safety is most important, and if you need to provide a zone of isolation using two valves to assure personal safety so be it. You might want to check OSHA requirements for more information.

RE: Two valve Isolation rule

jaxon-

Presuming you are governed by US OSHA (not a more stringent State version or some other country), you need to read up on 29 CFR 1910. Make sure you read 1910.146 and 1910.147 available at http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&;p_id=9797 and http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&;p_id=9804

What you seem to be referring to is a double block and bleed (DBB) setup (but that is most often three valves or one specialty valve and a bleeder valve). A DBB is one means of energy isolation which is acceptable to OSHA. Many will argue that it is not the best means of isolation, and I'll tend to agree that blinding or disaligning pipe spools is preferrable.

See also:
thread408-94849
thread408-122807

jt

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