LOT/Specific/TBT-LOT-016

Gravity and Suspended Load Isolation

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Gravity and suspended load energy is present in equipment with raised components such as rams, arms, and gates.
This stored energy can release unexpectedly, causing crushing injuries if not properly isolated and secured.
Common examples include hydraulic ram cylinders, counterweights, raised platforms, and spring-loaded mechanisms.
Mechanical blocking, pinning, or propping is required to prevent gravity-driven movement during maintenance.
Hydraulic systems can lose pressure over time, causing raised arms or platforms to drop without warning.
PUWER 1998 requires that all forms of stored energy are isolated before maintenance work begins.
Simply switching off a machine does not isolate gravity energy — physical restraint of moving parts is essential.
Gravity energy isolation is often overlooked because the hazard is not as visible as electrical or hydraulic energy.
Chocks, props, safety pins, and rated mechanical supports are used to restrain gravity-loaded components.
Each gravity isolation must be specific to the equipment, verified, and included in the LOTO permit.

Prevent crushing deaths	Gravity-loaded components falling unexpectedly crush and kill maintenance workers beneath them.
Stored energy risk	Hydraulic pressure loss, spring release, and counterweight drop are unpredictable without mechanical isolation.
Legal compliance	PUWER 1998 requires all forms of stored energy including gravity to be controlled before maintenance work.

Don't

Identify all gravity and suspended load hazards during the pre-task risk assessment
Lower raised components to a safe position before starting maintenance wherever possible
Install rated mechanical supports, props, or pins to prevent movement of raised parts
Include gravity isolation as a specific item on every LOTO permit for affected equipment
Verify the mechanical restraint is secure and load-bearing before working beneath any component
Use manufacturer-specified support devices and follow the equipment maintenance manual
Brief all workers on the gravity hazards and the isolation measures in place before starting
Never rely on hydraulic pressure alone to hold a raised component during maintenance
Inspect mechanical supports for damage and correct rating before each use
Remove mechanical supports only after all workers are clear and re-energisation is authorised

DON'T work beneath raised components without rated mechanical supports in place
DON'T rely on hydraulic or pneumatic pressure to hold loads — use mechanical blocking
DON'T forget gravity energy when completing LOTO assessments for equipment maintenance
DON'T use improvised props such as timber or bricks to support heavy equipment parts
DON'T remove safety pins or mechanical supports while anyone is beneath the component
DON'T assume a component will stay in position because it has not moved for a while
DON'T skip the physical verification that mechanical supports are correctly installed
DON'T begin maintenance until the permit confirms gravity energy has been isolated
DON'T use supports rated below the weight of the component they are restraining
DON'T overlook spring-loaded mechanisms which store energy even when equipment is off

See also: LOTO Awareness | Stored Energy Isolation

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