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.
Operating the pump efficiently is critical. The first decision is determining the size of the boom. Ideally the pump will be set up as close to the placement as possible and be sized so the entire placement can be reached with a single set-up. Booms have become so huge (the current record is Sany’s 86-meter boom) that covering the entire job with a single set-up is often possible. “Contractors have become complacent,” says O’Malley. “They think a really big boom pump is always the answer.” Often it is.
When asked what reduces productivity with a boom pump, Doug Rhiel, Schwing sales director for the eastern U.S. and Canada, says one word: moves. It’s not quite that simple, but poorly planned moves, or more moves than necessary, can squeeze a lot of profit out of a job. “Nothing kills productivity more than moving a pump in the middle of a pour,” says O’Malley. “It’s often necessary, but an unplanned move is the worst since it will take longer and you then have to worry about cold joints. Planning and timing a move with the ready-mix producer and other subcontractors is key.”
Jim Bury, director of engineering, production, and quality for Putzmeister America, notes that when there are delays during a move, the contractor often then wants to increase the volume of concrete to make up for the lost time. “You end up using more fuel to increase the flow rate and wearing out some of the wear parts, which increases maintenance costs,” he says.
“We go over all the moves in the prepour conference with the contractor and the ready-mix supplier,” says Delehay. “We document where the pump will sit, we emphasize the staging to get the pump in and out, and make sure everyone is up to speed.” The worst case, everyone I spoke with for this story described, is the nightmare of arriving at the jobsite with the pump, or preparing to move the pump, and finding the set-up location blocked or under use.
Dynamic Concrete Pumping establishes a complete performance schedule and delivery rate schedule in advance. Everything is built into the schedule, including the moves. For a big 55-meter boom pump, they allow a 45-minute window to move the pump during which concrete delivery will stop. A sponge is pushed into the hose at the delivery end and the concrete in the boom is sucked back into the hopper. “We never move the truck with concrete in the boom,” insists Delehay. “The operator must fold the boom first.” Folding the boom, moving the pump truck, setting the outriggers, and redeploying the boom takes about 45 minutes for the big pumps. For smaller pumps, they can reduce that to only about 15 minutes. “On those moves we may not even interrupt the concrete flow,” he says.
Access for the pump truck to get to the set-up location and set-up is a big concern. But even more important from a productivity standpoint is staging and access for the ready-mix trucks to deliver the concrete and get back off the site. Make sure the trucks have room to wait briefly if necessary and then to safely back in and get back out or, even better, to deliver the concrete and drive out via another route. There should be room near the pump hopper for at least two ready-mix trucks to unload at the same time to keep up a consistent supply to the pump. “With the pumps being able to deliver up to 150 yards per hour, and it taking two and a half minutes to unload a truck, we prefer to have room for three trucks at the hopper to maintain the flow,” says Delehay.
There also must be room for the ready-mix trucks and the boom pump to wash out at the jobsite and many will want a place to dump the last material in the boom and hopper. With all the environmentally sensitive projects in their area, Dynamic Concrete Pumping, however, has invested in a complete concrete recycling system. Delehay explains, “The driver brings the last half-yard in the hopper back to our shop and it goes into the recycler where it is separated into sand and gravel and clean water. There is zero discharge.” Dynamic even invites other pumping companies to use its recycler. And to take its environmental consciousness a step further, Dynamic uses only biodegradable hydraulic fluid. “We were working over a trout stream and the last thing we wanted was a spill of conventional oil,” says Delehay.
As a contractor, keep your pumping contractor happy and you will minimize your costs on this vital service.
This story originally appeared in Concrete Construction, TCP’s sister magazine.