INTRUSIVE MAINTENANCE // LIVE PLANT

Isolation is a managed state, not a closed valve.

Your task: make a compressor safe to open, keep the isolation effective while work proceeds, and return the plant without creating a new hazard.

Training boundary

This demonstrator is based on HSG253. It does not replace site procedures, PTW, risk assessment, competent judgement or authorised isolation personnel.

HSG253 ¶1–9, ¶101–106

The HSG253 lifecycle

Select a stage to inspect its purpose. The work only becomes safe when the chain is complete.

Operating principles

LIVE ENERGY

Identify process, mechanical, electrical and other hazards—not just the fluid.

¶20, ¶87–100

ALARP

Use the lowest-risk reasonably practicable option; engineering controls are preferred.

¶13–16, ¶103–125

PROVE / MONITOR

Security includes hardware, identification, securing, proving and work control.

¶109, ¶165–183

METHOD LAB

Integrity is a decision

All methods can fail. Match the final isolation to the consequence of failure; complexity itself creates opportunities for error.

I / POSITIVE

Complete separation: physical disconnection, or DBB plus spade.

Use: vessel entry, toxic fluids, high consequence situations.

¶97, ¶109–120; Appendix 5

II / PROVED

Valved isolation whose closure is confirmed through a bleed/vent. DBB has greater mechanical security than SBB.

Caution: SBB should not generally be used for hazardous substances unless risk assessment accepts it.

¶118–120, ¶165–183

III / NON-PROVED

Valved isolation with no provision to confirm closure before breaking containment. Where possible, use double rather than single valve.

¶111–120

Energy map

SCENARIO / COMPRESSOR C-201

Open the machine without opening the hazard.

Maintenance requests intrusive work on a centrifugal gas compressor. The plant remains live elsewhere. You are the isolation planner working with operations and maintenance.

Plant state

DECISION ASSESSMENT

Can you see the weak link?

Five judgement items. Your score is not competence by itself: critical misconceptions are surfaced for reinforcement.

OFFLINE FIELD TUTOR

Ask the isolation authority

Choose a question. The tutor is deliberately bounded to the supplied HSG253 content and will challenge unsafe reasoning.