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Washington Crane School Use Of Slings

 

Crane Hitches

How should you use a vertical hitch?

• In most cases use more than one sling. A single rope sling load tends to rotate in a twisting action that unwinds cables causing them to weaken.
• Do not use for lifting loose materials, long or unbalanced loads. How should you use a turning hitch?
• Use a doubled choker to turn loads.
• Place both sling eyes on top of the load pointing in the direction opposite to the direction of the turn. This sling will remain tight while the load is turning.
• Never use a basket hitch to turn a load. How should you use choker hitches?
Choker hitch
• The sling tightens on a load as it is lifted.
• Do not use on loose bundles.
• Use choker hitches at 75% or less of rated sling capacity.
Doubled choker hitch
• Provides more contact area to secure a load.
Double Wrap Choker Hitch
• This hitch compresses the load and prevents it from slipping out of the sling.
• Where overhead space is limited, a double wrapped choker hitch is acceptable. How should you use basket hitches?
Basket hitches
• Provide relatively good control and eliminate the tendency of the load to twist, compared with a vertical hitch.
• Do not use on a load that is difficult to balance.
Double basket hitches
• Balance loads by keeping slings apart.
• Prevent sling slippage by keeping the angle between the load and sling 60° or more.
Double Wrap Basket Hitches
• Provide more contact for handling loose material and pipe.
• Tend to draw the load together. How should you use bridle hitches?
Bridle hitches
• Are made of 2, 3 or 4 single leg hitches.
• Are used for hoisting an object that has lifting lugs or attachments.
• Position the hook over the center of gravity of the load.
• Adjust sling leg lengths with turnbuckles to level raised load.
• Check each sling leg angle to ensure sling is not overloaded. How does the angle of hoisting affects a sling load limit?
• The angle affects the working load limit. The smaller the angle, the less load a sling can carry.


Synthetic Web Slings

What should you know about using synthetic web slings?

• Synthetic web slings are easily cut and have poor abrasion resistance when compared with chain and wire rope slings.
• Nylon slings are damaged by acids, but resist caustics.
• Polyester slings are damaged by caustics but resist acids.
• Sunlight, moisture, and temperatures above 90°C (194°F) damage both nylon and polyester slings.
• Use slings made of the right material for the job.
• Check the manufacturers' slings for their code number and the rated capacity. Reference charts showing slings and hitch rated capacities are available from manufacturers.
• Inspect slings before using them.
• Keep an inspection record for each sling.
What should you check when selecting slings?
• Refer to the manufacturer's reference chart for the capacity rating.
• Check a sling before using it.
• Determine the weight of the load.
• Prevent loading more than the rated capacity by considering sling angle.
• Protect webbing from sharp corners, protrusions, or abrasive surfaces.
• Ensure that the sling choking action is on the webbing, not the hardware.
• Have slings repaired by a sling manufacturer only.
What should you avoid when using slings?
• Do not drag slings across floors or other abrasive surfaces.
• Do not drop slings with metal fittings.
• Do not set loads down on top of slings.
• Do not pull slings from under loads when the load is resting on the sling.
• Do not weld anything hung from a sling.
• Do not lengthen or shorten slings by tying knots.
• Do not place stitch patterns (laps) on hooks, around sharp corners, or at choker bearing points.

What kinds of damage make a synthetic web-sling unusable?
• Increased stiffness of sling material.
• Acid or caustic burns.
• Melted, burned or weld spatter damage.
• Holes, tears, cuts, snag.
• Broke or worn stitching.
• Excessive abrasive wear.
• Knots in any part of the sling.
• Crushed webbing or embedded particles.
• Bleached sling color.


Chain Slings

When should you inspect chain slings?

• Inspect chain slings every working day. Check for visible faults in links and hooks.
How should you check chain slings during the periodical inspection?
A competent person should inspect chain slings periodically, according to the manufacturer's recommendations. For record keeping purposes it is useful if each chain has a metal tag with an identification number and load limit information. Information about the chain length and other characteristics and a inspection schedule should recorded in a log book.

• Clean sling before inspection.

• Hang the chain up or stretch the chain out on a level floor in a well-lighted area. Remove all twists. Measure the sling length. Discard if a sling has been stretched.

• Make a link-by-link inspection and discard if:
a. Wear exceeds 15% of a link diameter.
b. Cut, nicked, cracked, gouged, burned, or corrosion pitted
c. Twisted or bent.
d. Stretched. Links tend to close up and get longer.

• Check master link, load pins and hooks for any of the above faults. Hooks should be removed from service if they have been opened more than 15% of the normal throat opening, measured at the narrowest point, or twisted more than 10° from the plane of the unbent hook.

• Manufacturers' reference charts show sling and hitch capacities. Record manufacturer, type, load limit and inspection dates.

How should you use chain slings safely?

• Find out load weight before lifting.
• Lower working a load limit if there may be severe impact.
• Balance the load to avoid overstress on one sling arm or the load slipping free.
• Pad sharp corners to prevent bending links.
• Replace broken safety latches.
• Reduce the load limit when using chain in temperatures above 425°C (800°F).
• Keep hands and fingers from between load and chain.
• Store chain sling arms on racks in assigned areas.

What should you avoid using chain slings?

• Avoid impact loading: do not jerk the load when lifting or lowering the sling. This increases the actual stress on the sling.
• Do not drag chains.
• Do not splice a chain by inserting a bolt between two links.
• Do not shorten a chain with knots or by twisting.
• Do not force a hook over a link.
• Do not use homemade connections. Use only attachments designed for the chain.
• Do not heat treat or weld chain links: the lifting capacity will be reduced drastically.


Wire Rope Slings

How should you select the proper wire rope sling?

• Follow the manufacturers' charts and tables on sling types, angles, and rope diameters.
• Follow the manufacturers' recommendations on clips and clamps of suitable size and design for ropes of different size.
• Attach using methods outlined by the manufacturer.
• Remember that a socket and clip fittings used to attach the rope determine the sling's load limit. Fittings have 75% to 100% of the breaking load of the rope.
• Remember that the safe load limit of a sling also depends on the hitch (method of applying a sling to the load). The type of hitch depends on the kind of material to be lifted, the safe load limit of the sling, the presence (or absence) of lugs on the load, the headroom, and other factors. Check with the manufacturers instructions.

How should you use wire rope slings safely?

• Use wire rope slings at rated limits.
• Examine slings for wear, fatigue, crushed or broken wires, kinking, ballooning or "bird-caging", heat damage, etc. Check both before and after using slings to detect any damage or defects.
• Inspect and tighten fittings regularly.
• Check the manufacturer's chart for sling properties.
• Reduce rope stress with slow starts and stops.
• Keep wire rope slings well lubricated and inspect them often.
• Remove damaged slings from service and tag appropriately.
• Store slings on racks in a clean, dry place.
Center the sling load to prevent the load from shifting suddenly and causing a high impact load.

What should you avoid when using wire rope slings?

• Do not bend slings around sharp edges. Protect them by using corner saddles, padding, or wood blocks.
• Do not use slings with knots.
• Do not slide the load along a rope.
• Do not use a single leg hitch on a load that cannot be controlled. Rotation of a load can undo the wire rope strands and weaken the rope.