Rules & procedures for applying double block and bleed during maintenance

Are there any procedures or rules available for when to use a double block and bleed? From what pressure, what temperature, what material, the time for the exposure to the dangerous products;
I am a maintenance guy and there is always issues on this subject.
Thanks for sharing any procedure.

It's often a company-specific procedure. But in general, DBBs should be used when breaking containment on any hazardous material or any non-hazardous material (line size greater than 4") greater than 15 barg. Some formal guidelines are given in the HSE document which you can download here:

[url]http://www.hse.gov.uk/pubns/books/hsg253.htm[/url]

thx thumps up

Thanks a lot. Problem solved!

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Regards

[QUOTE=Marty Thompson;266125]Please post a direct link here, that site requires registration and login[/QUOTE]