Excavator Lift of Concrete Pipe With Tangled Tag Line
A contractor is lowering a 24-inch reinforced concrete pipe section into a 10-ft-deep trench with a hydraulic excavator. The delivery ticket lists the section at 2,600 lb; the two-leg chain sling and shackles add 180 lb. Each sling leg is rated 5,000 lb for a vertical lift, and the legs form a 90-degree included angle. The excavator capacity chart at the planned 18-ft radius and 12-ft height shows 5,200 lb. A laborer plans to stand in the trench to guide the pipe by hand because the tag line is tangled at the spoil pile. The operator has not checked the automatic swing brake, and the trench is 12 ft wide with the spoil on the far side. The crew needs to set four sections before the concrete truck arrives.
1. Evaluate the lift: is the load within the excavator's capacity? Show the load and rigging comparison, and identify any missing capacity allowances.
Read the worked answer
The suspended load is 2,600 + 180 = 2,780 lb. The excavator chart allows 5,200 lb at the planned radius and height, so the static load is about 53% of chart capacity. For the sling, a 90-degree included angle puts each leg 45 degrees from vertical. Each leg carries (2,780 / 2) / cos 45 = 1,966 lb. Even after derating the 5,000-lb vertical rating for the 45-degree angle, the sling is adequate. However, the operator must confirm the chart is the machine's lift-capacity chart, not the bucket breakout rating, and must account for the actual attachment point, any dynamic load, and the weight of the rigging. The lift is acceptable only if all rigging and attachment points are rated and the load is kept under control.
2. What rigging and personnel changes are required before lowering the pipe?
Read the worked answer
Replace the tangled tag line and use two tag lines on a 24-inch pipe so the load can be controlled from outside the trench. Clear all personnel from the trench before the pipe is moved over it. The operator should test the automatic swing brake and confirm it holds before lifting. Use a spotter, barricade the swing radius, and keep the load close to the machine to avoid side loading. Lower slowly and do not use the bucket to catch or stop a swinging load. The laborer must not enter the trench to guide the pipe by hand while it is suspended.
3. If the pipe still needs guidance, how should it be done safely?
Read the worked answer
Guidance should come from tag lines operated by workers standing outside the trench and outside the swing radius. If a guide pole is used, keep hands away from pinch points and never stand under or against the pipe. The pipe should be lowered to the bedding, checked for alignment, and only then released. A worker may enter after the pipe is landed and stable and the excavator controls are locked or the machine is shut down. No worker should be in the trench while the load is suspended.