Positive Isolation: Isolation of process piping, equipment or vessels from hazardous materials (vapors, liquids, or solids) such that it is impossible for hazardous materials to enter the work area. Single Valve Isolation: Most common valves provide only one sealing surface to isolate upstream pressure and fluids.

Is double block and bleed positive isolation?

A double block and bleed is often used for a more positive isolation of a process fluid from other equipment. It normally consists of two block valves (Valves 1 and 2 in the pictures) and a bleed valve (Valve 3) to a safe location, consistent with local environmental regulations.

What is proved isolation?

Proved Isolation: is a valved isolation where effectiveness of the isolation can be confirmed via vent/bleed points before breaking into the system, and for the duration of the isolation.