Rigging and Load Handling
Rigging and Load Handling
This domain tests whether you can connect a load to the crane without overloading the rigging or losing control of the load. The exam stresses load weight, center of gravity, sling angle, hitch type, inspection, and load control rather than memorized hardware names alone.
Core rules
- Determine the load weight and center of gravity before selecting rigging. An off-center pick shifts more load to one leg and can tilt the load.
- Use only rigging with a known working load limit and current inspection. Remove tags that are missing or unreadable.
- Sling tension increases as the angle from horizontal decreases. Two legs do not each carry half the load unless the geometry and center of gravity are symmetrical.
- Protect slings from sharp edges and from being choked at a tight radius. Check the D/d ratio when a wire rope sling bends around a pin or shackle.
- Use tag lines where needed to control rotation. Never place hands on the load or rigging to stop a swing.
- Do not side-load hooks or use a hook with a damaged latch. Avoid shock loading.
Worked example
A 10,000 lb load is lifted by two symmetrical legs at 60 degrees from horizontal. Each leg carries a vertical share of 5,000 lb. Tension equals 5,000 divided by sine 60 degrees, or 5,000 divided by 0.866, which is about 5,774 lb per leg. If the same load is rigged at 30 degrees from horizontal, tension becomes 5,000 divided by 0.5, or 10,000 lb per leg. The reasoning: vertical share stays the same, but a flatter sling has a smaller vertical component, so tension rises sharply.
Traps
Assuming two legs always share equally; ignoring the center of gravity; using a sling at a flatter angle than its rated configuration; and trusting a sling that was not inspected after previous edge damage.