Cranes have been used since the first century – in that time, they were powered by humans or animals to lift heavy loads. Cranes have adapted and come a long way since – they now use an assortment of crane equipment and hardware to lift, lower and even sometimes move horizontally.
Read on to learn more about the modern variety of crane equipment available and Hercules SLR’s tips for using it.
CRANE EQUIPMENT: an overview
For rigging with cranes, different types of lifting equipment (also known as tackle) are used. These include:
- Wire Rope Slings
- Synthetic Slings
- Snatch Blocks
- Chain Hoists
- Chain Pullers
- Eye Bolts
- Lifting Beam
- Spreader Beams
- Beam Clamps
- Plate Clamps
CRANE EQUIPMENT: wire rope slings
Pay special attention to wire rope slings as they are susceptible to server wear, abrasion, impact loading, crushing, kinking and overloading – small changes in the slings’ angle affect the safe working load of the sling. Care should be taken around rough edges and wire rope slings – even an edge you might not consider ‘sharp’ can make considerable damage to your wire rope sling, making it unsafe and ineffective. Use sleeves, wear pads or corner protectors to protect your wire rope sling from damage.
Be sure to not drop a load or run a load over the sling – this will crush the sling. Also, don’t stop and start suddenly while you lift and lower with a wire rope sling, as this increases the slings’ stresses and increases possible failures.
WIRE ROPE SLING SPLICES
WIRE ROPE SLING IDENTIFICATION
There are three ways to identify wire rope slings: the SWL, I.D. number and certificate number.
- Hard-stamped on ferrule
- A tag which has a wire running through the tag and eye of the sling
- Large metal washer where the wire of the sling is passed through when you make the eye of a sling
WIRE ROPE CONFIGURATIONS
There are three main wire rope sling configurations:
- Double-Choker Hitch
- Pair of Double Wrap Chokers
- Single Choker Hitch
Round slings’ are versatile – they’re strong, yet delicate to the load to lift. They’re light, flexible in many directions and malleable which is especially helpful when lifting an awkward or delicate load.
CRANE EQUIPMENT: synthetic round slings
Round slings’ are not easily damaged by sunlight, humidity, grease, dirt or seawater. Round slings’ are identified by the colour of the label, and also have the SWL on it.
CRANE EQUIPMENT: web slings
Web slings are suited for particularly those that can be easily damaged. They’re easy to damage if you use them improperly – your web sling shouldn’t touch a sharp edge, heat or chemicals that will cause damage.
CRANE EQUIPMENT: hardware
For crane lifting, two different shackles are typically used – bow and d-shackles. When using synthetic slings with a crane, two types of shackles are available, wide sling shackle and a round sling shackle. Web sling shackles are wider and bow out in the middle, and round sling shackles are narrow and sometimes have small valleys in the shackle bow, which supports the synthetic strands better.
These prevent the sling from bunching and pinching, which can be an issue with bow or d-shackles – it also reduces the SWL capacity of the sling.
To use shackles for crane lifting safely, follow these tips:
- Don’t replace the shackle pin with a bolt – only the proper fitted pin should be used. Bolts aren’t meant to take the bend that a pin can handle.
- Pins must be straight and all-screw pins must be completely seated
- Cotter pins should be used with all round pin shackles
- Shackles worn at the crown or pin by over 10% of original diameter should be removed from service and destroyed.
- Don’t pull your shackle at an angle with a sling or hoist rope – this reduces the shackle’s capacity by 50%. Spacers can be used to centralize the load on the pins with spacers.
- Don’t use screw pin shackles if the load can roll under load and unscrew
A sheave block is a single, or multi-sheave block which opens on one side – this opening allows a rope to be pulled over the sheave and eliminates the need to be threaded through the block. When crane lifting with wire rope, sheave blocks can be purchased with configurations for hook, shackle, eye and swivel fittings.
- Sheave blocks are normally used when it’s necessary to change the direction of pull on the line. When this happens, the stress on the sheave block is significantly greater than the angle between the lead and load lines.
- When the lines are parallel, 1000lbs on the lead line results in double the weight on the block—2000lbs on block, hook and whatever the connection points are attached to. As the angle between lines increases, the stress on the block and hook is reduced.
Many different hooks are available for lifting and rigging operations – check with manufacturer instructions and warnings before using in a crane application.
When using hooks to lift with a crane, follow these tips:
- Ensure hoisting hooks are fitted with safety latches (except grab and sorting hooks)
- Inspect hooks often, looking for wear in the hook’s saddle – check for cracks, corrosion and if the hook’s body is twisted.
- Inspect the shackle’s throat opening – if the hook’s been overloaded or is weak, the throat will open. If this is the case, remove from service and destroy so no one else attempts to use it.
- Inspect for cracks in the hook’s saddle and neck
- Be sure the hook is stamped with its SWL
- Note that the SWL applies when the load is in the saddle of the hook, as this reduces the SWL.
Turnbuckles are sometimes called rigging screws and can be supplied with eye end, jaw end, stub end fittings and/or a combination of these.
- Use turnbuckles fabricated from alloy steel with weldless construction.
- If turnbuckles have end fittings, ensure hooks are fit with safety latches.
CHAIN HOISTS / CHAIN BLOCKS
Chain hoists are often used with cranes to move larger equipment and machinery. Chain hoists vary in size and length, and require little effort to execute a lift.
Chain hoists are durable, but can be damaged easily. To prevent damage, check:
- The SWL is right for the application/load
- The chain hoist has been inspected or certified by a third party
- The hoist’s body is free of cracks or broken castings
- The hook isn’t deformed and is fit with a safety latch
- Anchor pins are in place correctly, and are the right type
- Chain is in good working condition
- SWL is clearly marked on the chain hoist block
A lever hoist is similar to a chain hoist, but operates slightly different with a lever to lift and lower the load – it can also be used to pull loads.
When lifting with a crane and eye bolts, ensure eye and ring bolts are made of alloy steel and have shoulders or collars.
Do not load eye bolts at an angle – angular loading reduces the weight of the load they can safely support.
A tirfor is a mechanical device, equipped with a level handle to operate. They’re used to pull and add tension, and can also be used to lift if they have blocks.
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