Blocking & Cribbing Raised Equipment
Mechanics and operators are crushed every year by a dump body, loader arm, blade or bucket that came down while they were under it. Hydraulics leak and hoses fail. Anything raised must be lowered to the ground or mechanically blocked before anyone goes under or between.
- Mechanics
- Equipment operators
- Truck drivers
The rule
OSHA says machinery or parts held up by slings, hoists or jacks must be substantially blocked or cribbed before workers go under or between them. Dozer and scraper blades, loader buckets, dump bodies and similar parts must be fully lowered or blocked when being repaired or not in use, with controls in neutral, motors stopped and brakes set.
Ways to block
| Method | Use |
|---|---|
| Built-in props and locks | Dump body props, loader arm supports, cylinder lock collars; use them every time |
| Rated stands | Equipment stands and jack stands rated for the load |
| Hardwood cribbing | Stacked in a crisscross (log cabin) pattern under the machine’s frame or lift points |
| Engineered blocking | Steel or composite blocks rated for the load |
Cribbing tips
- Use sound, solid hardwood timbers of the right size, free of rot, splits and oil.
- Build on firm, level ground, or on a solid base.
- Stack in a crisscross pattern, keeping the stack wide for its height.
- Place cribbing under solid frame points, not under hoses, pans or thin sheet metal.
- Lower the load onto the cribbing gently and check that it’s stable before going under.
- Don’t use concrete or cinder blocks, bricks, rocks or scrap; they can crumble or roll
- Don’t rely on the hydraulic system, a jack or a chain hoist alone
- Don’t put any part of your body under a load while placing blocks; use a push stick or place them from the side
Before going under
- Part lowered or mechanically blocked
- Engine off, key removed, controls in neutral and locked out
- Parking brake set and wheels chocked
- Stored hydraulic pressure released as the maker requires
- Blocking stable and rated for the load
- Coworkers know you’re under the machine
Two seconds can kill. Many crushing deaths happen during a “quick look” under a raised body or bucket. Block it, even for a minute.
Standards & references
- 29 CFR 1926.600(a)(3): Blocking raised equipment
- 29 CFR 1910.147: Control of hazardous energy (gravity is stored energy)
- See also: Hydraulic Hazards · Jacks & Jack Stands · Dump Trucks
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