One of the handiest pieces of equipment designed for construction sites has to be the concrete boom pump. Generations of construction workers who pushed wheelbarrow loads of concrete from the mixer to the pouring location, or carefully swung bucketloads from one place to another and did their best not to strike anything in between would clearly have appreciated the convenience and time savings these handy devices offer.
The booms on these pumps give the operators a great deal of flexibility and allow concrete to be delivered quite a distance away. However, that flexibility creates a significant hazard on the jobsite. In addition to the possibility that the boom will strike workers or stationary objects while it is being deployed, the process of deploying it dramatically changes the pump’s center of gravity.
Boom pump manufacturers have prepared for that shifting center of gravity by including built-in outriggers that provide stability through the full range of the boom’s travel. However, those outriggers provide that stability only when they are deployed correctly on surfaces that provide adequate support.
Determining where and how to deploy those outriggers is one of the pump operator’s most critical responsibilities. Failing to follow the procedures specified by the manufacturer can cause the pump to tip over, creating the potential for serious damage and injury, as well as major disruption on the jobsite. In most cases, tip-over accidents are completely avoidable.
Sometimes the cause is obvious. I’ve seen two tip-overs on jobsites that occurred when the operator retracted the outriggers while the boom was still raised. That’s the result of simply not paying attention and ignoring the manufacturer’s procedures. Operators should never retract the outriggers until the boom is completely lowered into its housing.
Other causes of tip-overs involve the way the outriggers were extended, or the condition of the surface below them. If the soil is poorly compacted, has hidden voids, or has been backfilled, the outrigger will move once the center of gravity shifts. In wet conditions, the soil under the outrigger can be washed out. That’s why it’s critical to test the integrity of the soil before relying upon it as a safe base for the outriggers.
Many construction sites are uneven, and setting a concrete boom pump up in an area that isn’t level, or using it next to an excavated or sloped area, creates a much greater risk for tip-over. A good rule of thumb is to ensure that the outrigger is one foot from the edge of the drop-off for every foot of vertical drop. If an operator is setting up next to a six-foot-deep excavation, the outrigger should be at least six feet from the edge.
If the surface itself isn’t strong enough to support the pressure from the outrigger, cribbing may be a solution, but it also has to be used correctly. Always compute how much cribbing will be needed, and never use less than that amount. You just can’t have too much cribbing. If you’ve computed a need for five pieces of cribbing, but the outrigger’s foot is only touching three of them, you can expect it to sink into the soil. You can place dunnage on top of the cribbing to overcome this. There is one exception to the use of cribbing: never use it to bridge a hole. If there is an open area beneath the cribbing, it could collapse.
Finally, if the operator is unable to get the outriggers to stabilize, the boom should not be unfolded. Instead, the pump must be moved to a surface that will be able to support the weight of the outriggers. The same holds true if the operator notices that the outriggers are beginning to sink.
As with so many other aspects of workplace safety, proper training is critical. Everyone who works with the concrete boom pump is responsible for making sure that the hose person and other workers in the area are protected. Workers should avoid climbing under the boom, too.
If the proper procedures are followed and the surfaces on which the outriggers are extended are found to be strong enough to support them securely, the concrete boom pump will be able to live up to its promise of helping everyone get more done in less time — with no damage or injuries.