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HOT NEWSAn electric hoist is a simple machine in principle and a surprisingly unforgiving one in service. A motor turns a gearbox, the gearbox turns a drum or rotor, and a brake holds the load. Every one of those four elements can fail, and each fails in a way the operator may experience as a symptom rather than as a cause. A hoist that will not lift may have a dead pendant, a tripped overload protection device, a brake that has not released, or a phase error in the supply. A hoist that lifts but will not hold may have a brake slip issue, a stretched brake spring, or a load above the stated limit. Working through electric hoists methodically, in the order from supply to output, resolves most problems faster than parts replacement does.
The mechanical chain is short and worth understanding before any fault diagnosis begins. The electrical supply feeds a motor, usually a single-phase or three-phase unit selected to match the site supply and the duty. The motor drives a reduction gearbox through a friction wheel or a keyed connection. The gearbox output drives either a rope drum or a rotor with a spiral groove.
Two consequences follow directly from that arrangement. The first is that the brake is normally closed, so the load is safe if power fails, and the hoist cannot move at all if the brake fails to release when the operator commands a lift. The second is that the motor must develop enough torque through the gearbox to overcome the brake before any lifting happens, which is why a heavily loaded hoist may hum and fail to move while the brake is still closed but the motor is healthy.
A further group of hoists uses a planetary or helical gear motor integrated with the hoist body. These are common in modern chain hoists and are more compact, but the same logic applies: control power, brake release, motor rotation and load path remain the four things to test.
Each component has a characteristic set of symptoms. Recognising the pattern narrows the fault before opening a panel.
| Component | Function | Typical symptom of failure | First check |
|---|---|---|---|
| Power supply and cable | Delivers energy to the hoist | Nothing operates, no indicator or hum | Supply voltage and continuity |
| Control pendant or radio | Issues the lift command | Hoist responds to one direction only, or intermittently | Buttons, connectors and battery or transformer |
| Overload protection device | Limits load and prevents over-winding | Lift stops part way, resetting required | Setting and mechanical latch |
| Motor | Supplies lifting torque | Hum without movement, unusual noise or heat | Voltage at the terminals, winding resistance |
| Gearbox and bearings | Reduces speed and multiplies torque | Grinding, rattling, oil leakage, slow creep | Oil level, temperature, listening |
| Mechanical brake | Holds the load | Load drifts, brake will not release, squeal | Air gap, lining wear, spring tension |
| Load chain or rope | Transmits load to the hook | Stretch, elongation, wear at the links | Gauge measurement and visual wear |
| Limit switches | Stop over-travel of the hook | Hoist stops at an unexpected height | Actuation and adjustment |
Installation problems are easier to prevent than to fix. Selection depends on the load, the duty cycle and the environment, and on the mounting arrangement that carries the load through the hoist into the structure.
| Selection factor | What to check | Consequence of getting it wrong |
|---|---|---|
| Rated capacity | Maximum load the hoist may lift | Brake and gearbox overload, reduced service life |
| Duty cycle | Starts per hour and hours of operation per day | Thermal damage to the motor if undersized |
| Suppression of the load factor | How the load is picked up and released | Shock loading of the chain and brake |
| Chain or rope length | Maximum hook travel needed plus fall | Two-speed limit switches and drum capacity |
| Supply | Voltage, phase and frequency | Reduced torque, overheating, no start |
| Environment | Dust, moisture, temperature, washdown | Corrosion of gearbox and brake parts |
| Mounting | Suspension or trolley, beam capacity and deflection | Beam failure or unstable suspension |
One point deserves emphasis. A hoist is only as strong as the structure carrying it, and the structure is only as strong as its beam deflection. A trolley on a beam with excessive deflection gives the impression that the load is unstable even though the hoist performs correctly.
Installation should start with the suspension point rather than the hoist. The supporting structure must be checked for strength, for freedom from vibration, and for the dynamic effect of a load being picked up.
Suspension hoists hang from a fixed point, a hook or an eye, and the verticality of the hoist matters. The load chain must hang plumb, because a tilted hoist introduces a sideways load into the gearbox and the brake, and it causes the load to swing as the hook rises. Trolley hoists run on a beam and must be checked for correct positioning, adequate travel, and end stops in place. The trolley wheels should sit on clean rail with the correct flange arrangement, and the beam should be level within limits across the travel direction.
The electrical side of installation should follow a deliberate order. Mount the hoist mechanically first, with the chain free and the brake in its released condition as the manufacturer specifies, then bring in the supply. The supply should be protected by an appropriate isolator and overcurrent device, with an earth connection made before the hoist is energised for the first time. Pendant cables and radio controls should be routed so that they cannot be cut by the load chain or by a moving trolley, and they should never be run across a travel path.
Commissioning should be methodical and written down. Begin with a dead test: isolate the power, check the control device responds, check that the brake releases and re-applies correctly with the supply energised but no load, and confirm that the limit switches operate at both the upper and lower positions.
During the loaded test, the operator should confirm that the hoist starts smoothly without a jolt, that the brake releases promptly, that the load is held when the command is released, and that the hook block stops cleanly at the limit switch. A load that creeps downward for even a fraction of a second indicates a brake problem and should stop the commissioning process rather than be noted for later. The manufacturer's test load and commissioning record should be completed and retained with the equipment documentation.
Inspection is what keeps an electric hoist available rather than down. The daily check is short and is done by the operator; the periodic check is a thorough examination by a competent person at the interval required by the applicable standard and the manufacturer.
| Interval | Items to examine | What counts as a defect |
|---|---|---|
| Before each shift | Control device, brake release, chain or rope condition, hook and latch, unusual noise | Sticky buttons, twist in the chain, damaged hook throat, missing latch |
| Weekly | Limit switch operation, suspension and fasteners, chain lubrication, cable and plug condition | Chained or missing shackle, damaged plug, chain lubrication overdue |
| Monthly | Brake wear and air gap, gearbox oil level, trolley wheel wear, overload device setting | Brake lining worn, oil below minimum, wheel flange wear, altered setting |
| Periodic thorough examination | Full strip of wear parts, electrical test of pendant and earth continuity, load test, records | Any cracked or deformed component, failed earth continuity, missing record |
Records are the point of the exercise. A log recording what was checked, what was found and what was replaced allows a trend to be seen, such as accelerating brake lining wear, and it demonstrates compliance at audit.
Electrical faults are best approached from the supply inward, since the supply is the most common source of problems and the easiest to rule out.
| Symptom | Likely causes | Checks in order |
|---|---|---|
| Hoist does nothing at all | No supply, isolated isolator, tripped protection, cut cable, dead pendant | Voltage at the isolator, then at the hoist terminals, then the pendant connector |
| Hoist hums but does not lift | Brake not releasing, gearbox jammed, load above rating, wrong phase | Check brake release, free rotation of the chain, actual load weight |
| Lifts in one direction only | Failed pendant button, broken control wire, faulty direction contactor | Test at the hoist terminals with the pendant disconnected |
| Stops part way through the lift | Overload protection operated, limit switch triggered, low voltage, phase loss | Compare load with rating, check voltage under load, check switch actuation |
| Runs hot at the motor | Duty cycle exceeded, undersized motor, brake drag, low voltage | Measure current, compare with rated data, inspect brake gap |
| Erratic or intermittent operation | Loose connection, damaged cable at a flex point, poor earth, interference | Check connectors, inspect cable at the pendant and trolley |
Mechanical symptoms usually give away their cause through noise, movement or a visible condition. The table pairs the most frequent complaints with the checks that confirm them.
| Symptom | Likely causes | Confirmation and remedy |
|---|---|---|
| Load slips or creeps | Brake lining worn or contaminated, spring weakened, air gap incorrect, overload | Measure air gap and lining wear, clean or replace, verify load against rating |
| Brake will not release | Brake coil failed, control circuit open, misaligned or seized brake | Check coil supply at the terminals, then check mechanical freedom of the brake |
| Grinding or rattling | Dry or low gearbox oil, worn bearings, damaged gear teeth | Check oil level and condition, listen for changes with load, dismantle if needed |
| Chain binds or runs off the sprocket | Chain twisted, links stiff, sprocket worn, load chain not hanging plumb | Inspect chain for twist and wear, check sprocket profile and hoist verticality |
| Hook twists or does not seat fully | Side load, rotating load, damaged hook throat | Quarantine the hook, measure for twist, investigate how the load was picked |
| Operation slow under load | Brake dragging, low supply voltage, gearbox wear, overload | Measure voltage at the motor under load and compare with rated current |
Technical competence does not remove the need for discipline at the hook. Loads should be picked up vertically wherever possible, since side loading multiplies the effective load on the chain and the hoist structure by a factor that grows quickly as the sling angle opens up. Nobody should stand under a suspended load, and the load should not be dragged along the ground or used as a pulling point.
The pendant or radio control should be operated by a trained person who can see the load, and the operator should be able to stop the hoist from any position. Emergency stops and isolators should be identified on the layout of the equipment, and the isolation point must be reachable without climbing over the load. If a hoist has been overloaded, subjected to a shock load, or has been involved in a collision, it should be taken out of service and examined before it is used again, because the visible damage is rarely the whole of the damage.
Electric hoist reliability comes from the same routine every time: match the machine to the load and the duty, mount it on a structure that can carry the dynamic effect, commission it with a progressive load test, inspect it on a fixed schedule, and diagnose faults in a fixed order from the supply inward to the gearbox. When a hoist fails to lift, check the power and the pendant before assuming the worst. When a load drifts, look at the brake and at the actual load. When the control behaves strangely, check the connections and the supply rather than the mechanism. Keep the records, keep the inspection interval honest, and treat any overload or shock event as a reason to examine the equipment instead of a reason to return it to service. Handled this way, an electric hoist remains one of the most dependable pieces of equipment on any workshop floor.
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