Choosing and safely operating powered hoists

Hoists are used to raise and lower or transport material throughout the plant and position components in process or assembly operations.

01/01/2000


Hoists are used to raise and lower or transport material throughout the plant and position components in process or assembly operations. They serve as standalone devices permanently attached to walls, floor, or ceiling in capacities from a few hundred pounds to 50 tons (usually less than 3 tons), to models that serve as the vertical lifting arm of traveling overhead monorail or crane systems handling over 400 tons (usually less than 30 tons).

Most hoists are designed for a particular application and specific set of load, duty, and travel requirements. The typical function requires less than 20 ft of lifting, less than 30 ft of horizontal movement, and less than 30 fpm of travel speed. Hoists use electricity or compressed air as the power source, and wire rope or chain to link the bottom hook with the hoist body. Pendant controls usually operate the hoists,

Plant Engineering magazine would like to thank Columbus McKinnon, Harrington Hoists, and Shepard Niles for their special contributions to the development of this article.

- Selection

- Operation

- Maintenance

- Inspection

ANSI hoist duty service classifications

Uniformly distributed work periods Infrequent work periods

Duty Max. on time, Max. Max. on time Max.

class Service Typical applications min/hr starts/hr from cold start, min starts

H2 Light Light machine shop and fabricating industries, and service or maintenance work where loads and use are randomly distributed and capacity lifts infrequently handled. Equipment running time does not exceed 12.5% of the work period. 7.5 75 15 100

H3 Standard General machine shop, fabricating, assembly, storage,and warehousing where loads and use are randomly distributed. Equipment running time does not exceed 25% of the work period. 15 150 30 200

H4 Heavy High-volume handling in steel warehousing, machine shops, fabricating plants, mills, and foundries; and manual or automatic cycling operations in heat treating and plating. Equipment running time normally approaches 50% of the work period, with loads at or near rated capacity frequently handled. 30 300 30 300

Inspection guidelines

How often?

Frequent inspection is visual examinations by the operator or other designated personnel with records not required.

- Normal service -- monthly

- Heavy service -- weekly to monthly

- Severe service -- daily to weekly

Periodic inspection is visual checks by a designated person who makes records of external conditions to provide the basis for a continuing evaluation. An external coded mark on the hoist is an acceptable identification in place of records.

- Normal service -- yearly

- Heavy service -- semiannually

- Severe service -- quarterly

What?

Frequent inspection

- Trace of slipping via braking

- Control functions for optimal operation

- Damage, cracks, and bends in hooks or noticeable openings

- Hook latch setting and operation

- Optimal lubrication, signs of wear, link damage, or adhesion of foreign matter to the load chain

- Load sheave and idle sheave engagement with load chain

- Load chain twisting

Periodic inspection

- All items included in frequent inspection

- Fastening of screws, bolts, and nuts

- Wear, corrosion, cracks, distortion, etc. of the hook block, gears, bearings, and chain pins

- Damage to, or excessive wear of, the load sheave chain pocket

- Friction discs

- Sticking of contactor or contact point deterioration for electric hoists

- Sticking of valves and airlines for air-powered hoists

- Imperfect insulation of cables, cords, and control station

- Damage to supporting structures

Six keys to maintenance success

1. Keep detailed records of all inspection and maintenance activities, whether they are performed by the inhouse staff or a professional hoist inspection and repair company.

2. Know the hoists inside and out. Manual hoists contain bearings, bearing points, gears, and other parts that require regular maintenance. Electric hoists also require maintenance on electrical parts such as fuses, push button switches, power contactors, and conductors.

3. Replace worn or failing components with new products, in accordance with the manufacturer's specifications. Keep in mind that different hoist models require different parts.

4. Use the proper type and amount of lubrication to help reduce friction and wear, and prevent parts from rusting. If maintaining an electric hoist, keep oil in the gearbox at the prescribed level and use the specified type of oil.

Be sure to lubricate the chain, gears, hooks, guide rollers, brake, and limit switch. Gear oil should be changed at least annually. The chain should be lubricated at least weekly, depending on the severity of use. Lubricate the chain more frequently if you use the hoist in a corrosive environment.

On trolleys, lubricate the handwheel shaft, side rollers, and suspender shaft.

5. Take proper precautions before performing maintenance. Follow applicable lockout/tagout procedures. Allow only qualified personnel to perform maintenance. Attach a tag stating "Danger: Do Not Operate; Equipment Being Repaired" to the hoist. Never perform maintenance on a hoist supporting a load.

6. Follow prescribed methods and use appropriate maintenance materials. Also, consult the manufacturer's operating and maintenance manual or check publications of technical societies such as ASME and ANSI. Operational and safety considerations

Do

- Read and understand applicable standards, such as ASME B30.16, NEC (ANSI/NFPA 70), and OSHA

- Understand and follow operating controls, procedures, maintenance, and warnings

- Ensure hook travels in same direction shown on controls

- Make sure limit switches function properly

- Maintain firm footing when operating

- Ensure load slings or other approved attachments are properly sized and seated in hook saddle

- Make sure hook latch, if used, is closed and not supporting any part of load

- Make sure load is free to move and clears all obstructions

- Take up slack carefully, check load balance, lift a few inches, and check load-holding action before continuing

- Avoid swinging load or load hook

- Make sure all personnel are clear of suspended load

- Warn personnel of approaching load

- Protect wire rope and load chain from weld spatter or other damaging contaminants

- Use OEM replacement parts

- Promptly report any malfunction, unusual performance, or damage

- Inspect regularly, replace damaged or worn parts, and keep appropriate maintenance records

- Use hook latches where possible

- Apply lubricant to wire rope or load chain according to manufacturer recommendations

- Assure hoist and load are in straight line

- Keep clean of dust, dirt, or moisture

- Choose the right product for the job

- Visually check regularly

- Provide current overload protection and grounding on branch circuit of electric hoists

- Lift loads gently

- Train operators

Don't

- Lift more than rated capacity

- Use load limiting device to measure load

- Use damaged hoist or one not working correctly

- Use with twisted, kinked, damaged, or worn wire rope or chain

- Lift load unless chain is properly seated in wheels or sprockets, or wire rope is properly seated in grooves

- Use wire rope or load chain as sling or wrap around load

- Lift load if any binding prevents equal loading on all supporting chains

- Apply load to tip of hook

- Operate unless load is centered under hoist

- Allow attention to be diverted when operating

- Operate beyond limits of wire rope or chain

- Use limit switches as routine operating stops; they are for emergency use only

- Lift, support, or transport people

- Leave suspended load unattended unless specific precautions are taken

- Lift loads over or near people

- Allow sharp contact between two hoists, hoist hook and body, or hoist and building obstructions

- Use chain, rope, or hook as a ground for welding

- Allow chain, rope, or hook to be touched by a live welding electrode

- Remove or obscure warning labels

- Attempt to adjust or repair unless qualified to perform the duties

- Attempt to lengthen or repair damaged chain or wire rope

- Install or operate in hazardous locations

- Touch live electrical parts

- Over lower load

For more information related to hoists, see the "Material handling" channel on www.plantengineering.com.





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