Process, Hydraulic, and Pneumatic Energy Isolation Methods

If you happen to work on a design or operations of a process plant then the knowledge of isolation methods of lines and equipment becomes must and unavoidable.

A quick review of basic methods of isolation follows…….

There are four primary methods for isolating process lines and equipment to prevent the release of energy or materials. The isolation methods are arranged below in general order of protection provided from lowest to highest, but the specific isolation method is determined by the tasks to be performed and the associated material/stored energy.

Single block valve

Use of a single block valve is the minimum isolation procedure for certain routine maintenance operations where no open flame work or toxic material is involved. This isolation method must not be used when piping or equipment containing hazardous materials is to be opened, for confined space entry, or hot work activities.

Double block and bleed

Double block and bleed (DB&B) is a method of isolating process piping where two block valves in series are closed, locked (chained), and tagged with a bleed or vent valve in the line between the two closed valves that is locked and tagged open (see Figure A). Companies have detailed standards for applying DB&B as an isolation method. This isolation method must not be used when piping or equipment containing hazardous materials is to be opened for confined space entry or hot work activities.

Blinding

Blinding is the installation of a solid metal plate between two pipe flanges or at the end of a disconnected pipe to prevent any materials from being released. It involves inserting a slip

blind or blind flange at a flanged joint or swinging (rolling) a spectacle blind if provided by design. The blind point(s) must have a completed hold tag.

Disconnection of piping

Disconnection of piping is the physical disconnection of the piping where allowed by flanges. Steps must be taken to ensure no hazardous materials can leak or be discharged from the open ends of piping (e.g., blinding). The disconnection point(s) must have a completed hold tag.

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