7.3 Powered Hoists: Electric & Pneumatic

Powered Hoists: Electric and Pneumatic

A powered hoist combines a motor, transmission, lifting medium, brake, controls, suspension and supporting structure. Safe selection is a system decision: a suitable motor cannot compensate for an undersized runway, incompatible trolley, wrong duty class, corrosive atmosphere or inadequate electrical or air supply.

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Electric Hoists

Electric hoists commonly use calibrated load chain or wire rope. Chain units are compact and suited to many shorter lifts; wire-rope units can provide longer travel, higher speed or capacity, and different reeving arrangements. Selection data should include:

• marked WLL and load spectrum;
• range of lift, headroom and hook approach;
• starts per hour and duty classification;
• hoisting and travel speeds;
• supply voltage, phases and frequency;
• pendant, radio or fixed controls;
• indoor, outdoor, corrosive, hot or hazardous environment;
• trolley, suspension and runway compatibility; and
• overload protection, brakes and travel limits.

Controls and Isolation

A pendant lets the operator control motion from a safer position. Many designs use a separated low-voltage control circuit to reduce shock risk, but 24 V and 48 V are examples, not one universal statutory pair. The hoist maker's circuit, applicable standard, earthing, enclosure, cable condition and isolating arrangement all matter.

Before maintenance, the equipment needs suitable isolation from every relevant energy source. A pendant stop button is a control, not necessarily an isolator. Follow the site lock-off system and prove the equipment cannot move or re-energize.

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Limits: Working Stops and Final Protection

A working or positional limit stops routine motion at the intended operating position. A separate final or safety limit may protect against overtravel if the working device fails. Designs vary: some interrupt a directional circuit, some remove power through a safety chain, and reset arrangements differ.

The operating principle is consistent:

1. do not use a final safety limit as a routine stop;
2. test limits as required by the manufacturer and maintenance plan;
3. investigate a final-limit trip before returning to service; and
4. ensure reverse motion or recovery follows the designed procedure.

The same discipline applies to travel end stops and anti-collision devices: they are protective layers, not targets for normal operation.

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Pneumatic Hoists

A pneumatic hoist uses compressed air to drive the motor. It can be useful where an electric motor is undesirable, where fine control is needed, or where the environment and certification support its use. Typical controls include pull cords, pendants and pilot-air valves.

Air-Supply Matching

Performance depends on dynamic pressure at the hoist while flowing, not merely receiver pressure. Hose bore, length, fittings, filters and simultaneous air demand create pressure loss. Some hoists require lubricated air; others are designed for oil-free operation. The manual controls:

• permitted pressure range;
• minimum hose bore and maximum practical length;
• filtration and moisture removal;
• whether a lubricator is required or prohibited;
• exhaust routing and icing precautions; and
• brake and control checks after connection.

Before disconnecting a hose, close the supply, operate the controls to release residual pressure, secure the load and verify the system is depressurized.

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Hazardous Atmospheres

An air motor has no electrical commutator, but mechanical impacts, hot surfaces, static electricity, controls and trolleys can still ignite gas or dust. Suitability therefore belongs to the complete certified assembly, not to the power source alone.

Check the hoist's ATEX or UKEX marking against:

Bronze coatings, stainless components or conductive buffers may appear on a certified design, but no particular material set is universally mandated for every Zone 1 hoist. Substituting a hook, chain, wheel or pendant can invalidate the certified configuration.

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Safe-Use Sequence

1. Confirm WLL, duty, environment, support and power supply.
2. Inspect hook, latch, chain or rope, controls, limits, brake, trolley and power feed.
3. Ensure the load is directly below the hoist; do not side-pull or use the load chain or rope as a sling.
4. Raise the load just clear and stop to check brake holding, balance and slinging.
5. Avoid shock loading, rapid reversing and unnecessary inching.
6. Keep people clear of the suspended load and travel path.
7. Park safely with the hook and slack chain controlled.

A failure to lift may be an overload device doing its job. Do not repeatedly reset it; establish the load and cause first.