Whether it’s relocating a petrochemical tank, raising an elevator or adjusting sensitive electrical switchgear, work environments and loads can vary greatly across jobs. To manage these, you may require an overhead hoist capable of adapting its design and configuration to match the task at hand.
Continue reading to discover the different variables in overhead hoist equipment and methods.
Firstly, overhead hoists are powered or manual.
- Powered hoists are typical for machine shops and mechanics and include hoists driven by hydraulic, electric or pneumatic motors. Powered hoists work using a control device that’s mounted in a remote radio-control transmitter or suspended from the hoist. This device controls a motor, which the controls the hoist drum or hoist load chain sprocket to lower or lift the hoist load hook. Electric hoists plug easily into the closest wall outlet, whereas pneumatic chain hoists are generally used to lift heavy equipment in dusty, flammable or dirty environments.
- A manual (hand chain) hoist typically means the hoist is levered, ratcheted or hand cranked. It works once the operator pulls a roller load chain or welded link load chain made of a series of interwoven links fitting the sprocket (hoist hand chain wheel). Once the operator pulls the chain, the hand chain wheel rotates and transmits lifting power.
Overhead hoists are typically trolley-mounted, hook-mounted or lug-mounted.
- Trolley-mounted crane hoists are clevis-mounted, lug-mounted or hook-mounted crane hoists suspended from trolleys.
- Hook-mounted hoists are either suspended from the suspension pin of a trolley via a top hook on the hoist frame of the crane, or the clevis (a forked or U-shaped metal connector). They may also be suspended from a fixed device mounted on the permanently attached on-site or on a beam. These hoists usually use roller load chains or welded link load chains as the lifting medium.
- Lug-mounted crane hoists can also be suspended from a building structure or beam and can be trolley-mounted. These hoists have a lug mounting fastened to the hoist frame.
Hoists usually use wire rope or chain (roller load chain or welded link load chain).
- Wire rope is made up of strands, a core, and fits into the grooves of a hoist drum. Do not use these hoists on crane equipment that’s manually-operated such as hand-push bridge cranes, jib cranes or small gantry cranes, as it can be dangerous if it becomes unseated from the grooved drum.
- Roller load chain consists of alternately assembled pin links and roller links. The pins connect inside buildings, while the rollers rotate freely on the bushings. The links fit the teeth of the hoist load sprocket roller load chain. Roller load chain must also meet special requirements for particular hoists to guarantee reliable, safe operation.
- Welded link load chain consists of a series of welded and interwoven formed links. These links fit into the hoist load sprocket (a.k.a. “lift wheel, load wheel, pocket wheel or load sheave”), which transmits motion to the load chain. This type of load chain is made to meet special requirements for particular material strength and dimension requirements for a specific hoist.
Hoist Manufacturers Institute (HMI) Hoist Duty Classifications
The Hoist Manufacturers Institute (HMI) created hoisting equipment standards for ratchet lever hoists, air wire rope hoists, electric wire, hand chain hoists, electric chain hoists, air chain hoists and trolleys. Their “hoist duty classifications,” which you can view below, will give you an idea of what the duty cycle ratings look like for different electric hoists.Google+