Safety Critical Equipment Definition

[sys1]

What is the most acceptable and worked upon definition of a safety critical equipment in an oil & gas industry?
And tell me if every PSV gets qualified to be a safety critical device?

[octane]

In simple words, any equipment which contributes to avoid a major accident hazard in an industry is classified as a safety critical equipment.
So it depends what has been classified as major accident hazard and which equipment act as barriers.

[arcpro]

Yeah, that's that.
I got one from UK's offshore safety regulations and is reflected throughout the industry:
Safety Critical Equipment is any equipment, system, or component whose failure could cause or contribute substantially to a major accident, or whose purpose is to prevent, detect, control, or mitigate the consequences of a major accident.

[opo21]

You can identify them from the bow-ties, all preventive ones before the top threat, and the mitigative ones after the threat occurs.
The swiss cheese model is the one encompassing all of the safety critical equipment related to MAH.

[sys1]

Thanks.

[ivani1]

Sys1
Just to provide you the reply with the second part of your question, no not all PSVs are considered as safety critical - not those on flammable /hazardous /toxic services where barrier breakdown would lead to a major accident hazard.