LOT/Specific/TBT-LOT-005

Hydraulic and Pneumatic Isolation

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Hydraulic and Pneumatic Isolation

Toolbox Talk Record

Ref: TBT-LOT-005  |  Issue: 1  |  Date: March 2026
PresenterProject
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What?

  • Hydraulic and pneumatic systems store energy under pressure even when machines are switched off.
  • Trapped pressure in hoses, rams, and accumulators can cause sudden violent movement on release.
  • Hydraulic fluid under pressure can penetrate skin through pinhole leaks, causing tissue damage.
  • Pneumatic systems use compressed air which can cause injection injuries and hearing damage.
  • Isolation must include depressurising the system, not just shutting off the power source.
  • Accumulators store pressurised fluid and must be bled down separately during isolation.
  • PUWER 1998 requires that equipment is isolated from all energy sources before maintenance.
  • Visual checks are not enough — verify zero pressure on a gauge before opening a system.
  • Many construction plant items including excavators and cranes have hydraulic systems.
  • Only competent persons should carry out hydraulic or pneumatic isolation procedures.

Why?

Prevent injection injuriesHigh-pressure hydraulic fluid penetrating skin causes tissue death and amputation risk.
Avoid crushingUnexpected movement from trapped pressure can crush workers nearby.
Legal compliancePUWER requires all stored energy to be dissipated before maintenance begins.
Equipment protectionUncontrolled pressure release damages components and creates further hazards.
Do Don't
  • Shut off the power source and isolate all hydraulic or pneumatic supply lines.
  • Depressurise the system fully using the correct bleed-down procedure.
  • Bleed accumulators separately — they hold pressure independently of the main system.
  • Verify zero pressure on the system gauge before opening any connections.
  • Apply lock out tag out devices to all isolation points after depressurising.
  • Wear face and hand protection when working near pressurised fittings.
  • Use the manufacturer's manual for system-specific isolation steps.
  • Block or prop hydraulic rams to prevent gravity-induced movement after isolation.
  • Inspect hoses and fittings for damage or leaks before re-pressurising.
  • Record the isolation on the permit and inform all affected personnel.
  • DON'T assume a hydraulic system is safe because the engine is off.
  • DON'T run your hand over hydraulic hoses to check for leaks.
  • DON'T open fittings or connections without confirming zero pressure first.
  • DON'T stand under hydraulic rams without mechanical props in place.
  • DON'T use compressed air to clean clothing, skin, or the work area.
  • DON'T forget to bleed accumulators — they hold pressure after shut-down.
  • DON'T attempt hydraulic isolation without proper training and competence.
  • DON'T re-pressurise a system without removing all locks and tags first.
  • DON'T ignore small leaks — pinhole jets can penetrate skin unseen.
  • DON'T bypass pressure relief valves or safety devices for any reason.

See also: Lock Out Tag Out Awareness | Mechanical Isolation
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