Of all the equipment that has changed concrete construction over the past 40 years, the concrete boom pump is number one for increasing productivity and reducing labor. While buckets may still be used in some situations, they have become rare on modern concrete projects. Concrete pumps have actually expanded the applications for concrete — think how difficult filling insulating concrete forms would be without a pump. And some recent high-rise concrete buildings would not have been feasible without the ability to pump the concrete hundreds of feet up to placing booms.
A concrete pump is a very large and powerful piece of equipment with its boom fully extended like a giant extraterrestrial insect. It has the ability to provide great benefits on a concrete project, but it can also be dangerous without proper set-up and safety procedures. The American Concrete Pumping Association (ACPA) has done many things to further the pumping industry, but the single most important is advancing pump safety. One big part of that is positioning the pump to assure safe operation.
In general, ACPA’s position is that the concrete contractor is responsible for providing a safe set-up area for the pump. The area must be large enough for the pump with outriggers, free of building materials, level enough that the pump can be leveled to within 3 degrees, far enough away from excavations and power lines, and with stable soil on which the outriggers can bear. Pumping contractors, however, will usually make sure that’s the case to protect themselves and their equipment and to do the best and safest job possible for their customers. “Every job is different,” says Joe Delehay, president of Dynamic Concrete Pumping, Calgary, Alberta, and also a concrete floor contractor. “So during the prepour meeting we make sure the site is safe by doing a hazard assessment to check for wires, trees, excavations, obstacles, and especially things like overpasses.”
Electrical lines are the most obvious hazard. “Like cranes,” writes ACPA, “the number one cause of fatal accidents with pumps is electrocution.” When the U.S. Department of Labor recently changed the rule for minimum clearance for cranes from power lines to 20 feet (no piece of the crane, load, or rigging can be within 20 feet of a wire), concrete pumps were specifically excluded, meaning pumps could continue to follow the previous 17-foot rule. But to simplify things, ACPA adopted the 20-foot rule anyway. For higher voltage situations (large transmission towers and lines), the rule is 50 feet minimum clearance. Pump operators should always refuse to operate the pump if it will violate the 20-foot rule.
The next most-important aspect of safely positioning a pump is to assure that it won’t tip over. When a boom is fully extended and full of concrete there could be ½ cubic yard of concrete or more in the line. That’s about one ton of concrete, enough to easily tip over a boom pump that is not properly stabilized.
Boom pumps are stabilized using outriggers, and properly deploying the outriggers is essential. The four outriggers must be fully extended and bearing on a solid surface. Never partially extend outriggers since not only is it dangerous, but the outriggers can be damaged. The foot of the outriggers alone is seldom large enough to support that load and must bear on cribbing. Operators will position the cribbing and then jack each outrigger individually to assure that the ground is strong enough to support the load. If not, dunnage will be added to increase the bearing area. The most dangerous situation for pump stability is fill or hidden voids below the surface. If you see a pile of dirt near the set-up area, that’s a sign that there could have been some excavation. Once the operator feels the outriggers are stable, he will slew the boom over each outrigger as a final safety check to see if any outriggers sinks into the soil.
Positioning near excavations is another danger. The rule is one-to-one, meaning for every vertical foot of excavation depth, the closest outrigger pad must be more than that distance horizontally from the base of the excavation. Closer than this can result in an overturned pump truck. Pump operators should carry a plumb bob to help determine the limits of the on-to-one rule.
Sometimes there is only enough room at a set-up for the outriggers on one side of the truck, such as when setting up in a street with only a single lane closed. This is called short rigging. The great danger with short rigging is in slewing the boom around to the side of the truck without fully extended outriggers, which can result in tipping over the pump. “Short rigging is not recommended,” says Schwing America Vice President of Sales and Marketing Tom O’Malley. “But it’s sometimes necessary.” He cautions that this practice should be avoided whenever possible.
“Our policy is that the superintendent must be present for a short rigging and must sign off in advance,” says Delehay. “There’s always a risk but it can be reduced if there are two sets of eyes on it.” Some pumps have automatic stops when the set-up is short-rigged to prevent the boom from slewing into the danger zone.