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LO/TO wrt PSVs

LO/TO wrt PSVs

LO/TO wrt PSVs

(OP)
Hi all!
On a P&ID I've found a note referring to a PSV located on a separator which read "LO/TO required": can, please, anybody clarify the meaning of such acronym?
Thank you.
4Advice

RE: LO/TO wrt PSVs

LO/TO is actually used as an acronym in much of the OSHA post-reg literature. They mean it to be "Lock Out/Tag Out". I'd say that the guy who put the note on the P&ID was an idiot. LO/TO is intended for short duration maintenance activities. For something that is permanently locked open (EXCEPT during maintenance) the note is usually "LO" for "locked open".

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

RE: LO/TO wrt PSVs

I love acronyms, especially when they are ill defined.

RE: LO/TO wrt PSVs

Quote:

They mean it to be "Lock Out/Tag Out". I'd say that the guy who put the note on the P&ID was an idiot. LO/TO is intended for short duration maintenance activities. For something that is permanently locked open (EXCEPT during maintenance) the note is usually "LO" for "locked open".

Or it might mean that the valves are required to have features to accept the lock.

Isn't ambiguity great?

RE: LO/TO wrt PSVs

Ot it might mean that it will require "lock open" under normal conditions, and LOTO closed for safety testing. I've seen that several times.

RE: LO/TO wrt PSVs

Yeah, "great". I've seen a designation on valves under PSV that said "LO, must have fittings for lock". LO/TO is so specific to energy isolation for maintenance that it really shouldn't be used for something normally locked open.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

RE: LO/TO wrt PSVs


I love the acronyms. I guess WTF means "water treatment facility".

RE: LO/TO wrt PSVs

I use WTF more often than LO.

RE: LO/TO wrt PSVs

P&IDs are not for procedural stuff. Lock out/Tag out should be documented elsewhere.

Pamela K. Quillin, P.E.
Quillin Engineering, LLC

RE: LO/TO wrt PSVs

I had a partner once who did a startup in the PRC back in the Nixon "ping pong diplomacy" era. As he inspected incoming components he marked all failures with NFG and tossed them in a pile for disposal. The Chinese workers, not accustom to throwing ANYTHING away, would retrieve them and put them back into the supply chain. He eventually noticed things coming through a second time, but the NFG tags were removed. He confronted the Chinese workers, who explained to him that they had no idea what NFG meant, that it was not listed in any translation guides they had. He told them, "No F###ing Good" and left it at that. 3 days later they approached him and said, "We understand "No" and "Good", but what means "F###ing"? That apparently was not in their translation guides either. He made a circle with his thumb and forefinger, then thrust his other forefinger in and out of it. He said the laughter went on for 20 minutes! Then the Chinese said they used the exact same terminology!

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)

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