SAFE LIFTING

The following factors are basic guidelines to perform safe daily crane operations:

1. Determine the weight to be lifted and the crane required to make the lift safely.

2. Travel the proposed route the crane will follow to and from the project site, and complete the Crane Lift Checklist.

3. Obtain the travel permits if required.

4. Brief operators and riggers on the specifics of the lift and travel conditions.

5. Inspect the crane area setup for stability and safe operating area

6. Fully extend the outriggers and use them according to the manufacturer's instruction.

7. Check the crane for levelness.

8. Inspect all rigging hardware.

9. Select the proper sling with sufficient capacity rating.

10. Center the sling in the base (bowl) of the hook to avoid hook point loading, and ensure the hook block is always placed over the center of the load to eliminate shock loading of the slings or cranes, resulting from load shifts when a lift is made.

11. Make ample safety allowances for unknown factors.

12. Stand clear of and do not walk under suspended loads.

13. Boom deflection. _{All crane booms have} deflection. When the load is lifted off the ground, the boom will deflect, causing the radius to increase. Increased radius may cause overloading of the crane.

14. An uncontrolled swinging load can cause the radius to increase.

15. Clean operating area. Water coolers, excess tools, grease, soda cans, and other unnecessary items should be kept outside of the operating area of the crane. Water coolers must be kept off the crane to prevent

Figure 12-47.-Typical crane capacity chart.

_{people from} congregating around the crane when in operation.

NOTE: Safe lifting is paramount! Project _completion must not interfere with safe crane operations.

CLAMSHELL OPERATIONS

The clamshell bucket is an attachment used with a crane for vertical digging belowground level and for placing materials at considerable height, depth, or distance. You can also use it for moving bulk materials from stockpiles to plant bins, loading hoppers, and conveyors. It can be used to dig loose to medium compacted soil.

Clamshell operating procedures are as follows:

1. Position and level the crane, ensuring the digging operation is as close to the radius as the dumping operation. This prevents you from having to boom up and down, resulting in a loss of production.

2. Select the correct size and type of bucket for the crane.

3. When lowering the clamshell bucket, if too much pressure is applied to the closing line brake, the bucket will close and an excess amount of wire rope will unwind from the holding line hoist drum. To avoid this, you should release the holding line and closing line brakes simultaneously when lowering the open clamshell into the material for the initial bite. Engage the closing line control lever to close the bucket. Control the digging depth by using the holding line control lever and brake.

4. If, during hoisting, the hoist line gets ahead of the closing line, the bucket will open and spill the material. (This could also be caused by having too much wire rope on the hoist drum.) The operator must hoist both the closing and holding lines at the same speed to keep the bucket from opening and spilling material.

5. When the clamshell bucket is raised enough to clear all obstacles, start the swing by engaging the swing control lever. Hoisting the bucket can be performed, as it is swung to the dumping site. The spring-loaded tag line will retard the twisting motion of the bucket if the swing is performed smoothly.

6. Dumping and unloading the clamshell is performed by keeping the holding line brake applied while the closing line brake is released. Apply the closing line brake quickly after the load is dumped to prevent the closing line from unwinding more wire rope than is needed to dump the material. After the bucket is emptied, swing the open clamshell back to the digging site. Then lower the open bucket and repeat the cycle.

The clamshell operating cycle has four steps: filling (closing) the bucket, raising the loaded bucket, swinging, and dumping. The boom angle for clamshell operations should be between 40 to 60 degrees. Be careful when working with higher boom angles, as the bucket could hit the boom. A clamshell attachment is not a positive digging tool.

The height reached by the clamshell depends on the length of the boom used. The depth reached by the clamshell is limited by the length of wire rope that the hoist drum can handle. For the safe lifting capacity for the clamshell, refer to the operator's manual and the crane capacity load chart.