Procedure: Multiple Energy Source Isolation for Permit to Work

Purpose. This procedure describes how an isolator plans, applies, proves, locks and records an isolation involving more than one energy source before a permit to work is issued.

1.Scope

This procedure applies to any task on plant that carries two or more energy sources, for example a boiler feed pump with electrical supply, suction and discharge pressure, lubrication oil and stored rotational energy. It must be read with the Permit to Work and Isolation Policy.

2.Step 1: Identify every energy source

The isolator must review the piping and instrumentation drawing and the electrical single line diagram and must list every energy source connected to the plant item, including sources that can back feed from other plant. The list must be checked by a second authorised person.

• Electrical supply and control power
• Pressure on suction, discharge, seal and cooling lines
• Hot fluids and steam
• Lubrication and hydraulic oil
• Stored mechanical and gravitational energy

3.Step 2: Plan the isolation

The isolator must prepare the isolation list with the isolation point identifier, the method (open, close, rack out, blank, chain), the proving method and the restoration sequence. The control room must confirm that the isolation will not affect running plant beyond the planned scope.

4.Step 3: Apply and prove

Isolations must be applied in the listed order, each locked and tagged. Electrical isolations must be proven dead with a tested instrument. Pressure isolations must be proven by venting and draining at the work face with a gauge reading zero. Rotating plant must be restrained where it can turn.

5.Step 4: Record and issue

The isolator must record each isolation point, lock number and proving result in the Permit and Isolation Register and must attach the isolation list to the permit. The permit issuer must walk the isolation with the permit recipient before the permit is accepted.

6.Step 5: Restore

Restoration must follow the sequence on the list in reverse unless the list states otherwise. The control room must be told before and after each restoration step that affects operating plant. The register must be updated to Restored when complete.