18.3 Scrap and Material-Handling Grapples
Key Takeaways
Crane demand includes the grapple and applicable adapters in addition to the retained material.
Jaw geometry and closure determine whether irregular contents can remain secure.
Keep workers clear of falling pieces as well as the complete suspended load.
Retain the material, not just its calculated weight
A grapple closes around material using designed tines, jaws or shells. Scrap and material-handling grapples differ from slings because they may handle irregular, loose or shifting contents rather than a single solid object with known lifting points. Capacity selection must address both structural load and the ability to retain the actual material.
An orange-peel grapple uses multiple tines around irregular scrap. A timber grapple is intended for the approved size and arrangement of logs. Clamshell-type material handlers enclose suitable bulk material with shells. Jaw shape, opening, tine coverage and operating mechanism affect what each can retain. A product intended for loose scrap is not automatically suitable for delicate finished machinery or an intact structure.
The blueprint calls for selection and use of scrap and material-handling grapples. Learn to recognize their purpose, check their lifting connection and control system, and plan a protected pick-to-discharge sequence. Do not substitute excavator digging specifications for an overhead lifting rating.
Separate capacity, volume and closing force
A manufacturer's data may list payload capacity, device weight, jaw opening, volume, hydraulic pressure and closing force. These values answer different questions. A large closing force does not certify that a grapple can lift that numerical amount of payload. A volume rating also does not establish the weight of a bucketful without the material's applicable bulk density.
| Data | Use |
|---|---|
| Payload or rated load | Maximum permitted material load under stated conditions |
| Self-weight | Added demand on crane and suspension |
| Jaw opening and tine/shell arrangement | Geometric suitability and retention |
| Hydraulic pressure and flow | Compatible power and controlled operation |
| Rotator rating | Capacity and permitted reaction at the connection |
| Bulk density | Estimate of contents weight, with actual fill considered |
Scrap density can vary substantially with shape, packing and composition. A grapple that looks half full may contain a heavy solid piece among light hollow sections. Use a reliable weight determination or the approved operating procedure, not a visual percentage applied to an arbitrary density.
Inventory example
A hypothetical grapple is rated for 3,000 lb of payload and weighs 900 lb. Its approved load contains 2,400 lb of material. The grapple's payload demand is 2,400 lb, while grapple plus contents contribute 3,300 lb to the crane inventory before other applicable suspended items. The lift is not evaluated as a 2,400-lb crane load merely because the grapple has its own rating.
If a rotator and adapter are separate components, their ratings, weight and connections must also be verified. The weakest permitted capacity in the assembled load path governs. A 5,000-lb rotator cannot increase the 3,000-lb grapple payload limit.
Connect and inspect the system
Identify the correct suspension, pins, retaining devices, swivel or rotator and hydraulic or electrical connections. Verify that supply pressure, flow and controls match the device. Excess pressure, incompatible couplers or altered valves can change operation and create failures; do not modify settings to obtain more grip.
Inspect tines or shells, pivots, cylinders, welds, pins, hoses, fittings, stops and connection points. Check control function using the manufacturer's unloaded procedure in a protected area. Look for leaks, uneven movement, damaged teeth, loose pins or an inability to hold the selected position. A leaking line is not repaired by having someone hold the control continuously under the load.
Consider stored hydraulic energy when maintaining or disconnecting the attachment. Follow isolation and pressure-relief procedures. Never place a hand over a suspected high-pressure leak or stand between closing jaws. Inspection and repair must be performed by persons authorized for the equipment.
Pick, retain and travel
Select a capture arrangement that actually encloses or securely grips the material. Avoid loose pieces perched above the jaws or protruding items likely to fall. Close fully as directed and verify retention during the planned low trial lift from a safe position. If material slips or the device closes unevenly, land and correct the condition.
Keep workers outside the material fall zone and the swinging attachment's path. Irregular pieces can fall without the whole grapple releasing, and sharp ends can sweep a wider area than the crane hook. Plan the route around that complete envelope. A spotter or signalperson needs a clear position outside both the drop area and pinch points.
Avoid sudden acceleration, impact and unauthorized side pulling. Do not use the grapple to tear a fixed object free unless that use is expressly approved and the additional forces have been assessed. A stuck piece can suddenly break loose, changing load, stability and trajectory.
Discharge and stow
Confirm the receiving container or pile can accept the load without striking people, equipment or unstable material. Lower to the approved release position, then open according to the procedure. Do not swing a loaded grapple over workers to reach a convenient discharge spot, and do not ask someone to pull loose material from suspended jaws.
After discharge, verify that no pieces remain trapped before travel. For storage, lower the attachment onto a suitable stable support, release hydraulic or electrical connections by the prescribed isolation sequence and protect exposed couplers and hoses. Keep the device's identification and records available so its capacity and intended material application remain clear for the next operation.
Sources: CCO grapple selection and execution topics, KINSHOFER crane attachment catalog, CCO reference manual, ASME B30.20.
A 900-lb grapple carries 2,400 lb of scrap and has a 3,000-lb payload rating. What is the combined weight of grapple and contents?
2,400 lb
3,300 lb
3,000 lb
1,500 lb
Sections you finish are checked off in the contents.