Trench Shield Components Can Be Dangerous
Because of the size and weight of trench shields, the processes of unloading, assembling, disassembling, and loading them can be dangerous. It is imperative that:
When handling trench shield components, everyone involved must work carefully, and use the proper rigging.
- No person is ever underneath an overhead load.
- Everyone watches for pinch points that are created with spreaders, sidewalls, etc.
- A properly rated and inspected sling or chain (approved for overhead lifting) is used for handling.
- Tag lines are used to control the shield.
- Everyone watches overhead utilities and objects.
- The crane or excavator that’s doing the lifting is rated to properly handle the load. As a rule-of-thumb, the crane or excavator must be rated to handle 1½ times (150%) of the weight of the trench shield, at the desired radius.
Coming up . . .
In the coming weeks we will review 4 Key Points to remember when working with trench shields.
Safely and carefully installing and moving trench shields is paramount. Steel shields can be heavy, and that means there is a high potential for danger. Aluminum shields are considerably lighter, but can be easily damaged by excavation equipment.
Using a Steel Trench Shield
There are a several techniques for using steel trench shields.
In stable soil, there are two steps:
- Excavate in front of the shield.
- Place excavator bucket around front spreader or use a chain/sling with pulling lugs, being careful not to damage the spreader or the collar. Pull the shield forward. Then promptly back fill behind the shield.
In unstable soil, there are a few more steps:
- Excavate a pilot hole as deep as possible. Set the shield in position.
- Excavate inside the shield.
- Continue digging, allowing the shield to descend as soil is removed. Use the bucket to push down on the shield. But don’t beat on the shield!
- To move forward, place excavator bucket around the front spreader, being careful not to damage the spreader or the collar. Pull upward and forward at a 45-degree angle.
- Excavate inside of the shield and repeat the previous steps.
Using an Aluminum Trench Shield
Because of the typical applications for aluminum shields, and the fact that aluminum is a softer metal, use of an aluminum shield is different. Typically, the hole is dug and the aluminum shield is set in place. When the work is complete, and it’s time to move the shield, the shield is lifted out of the hole and set in its new position.
This is an aluminum
trenchshield. The side
panels, which are
available in a variety
of sizes to match
of a wide range
of jobs, are
In our next installment — Part 5, coming in a couple of weeks — we’ll look at how to unload, assemble, disassemble, and reload trench shields.