Pumping Operations, Line and Boom Placement, and Placing Techniques
Pumping Operations, Line and Boom Placement, and Placing Techniques
This domain covers the run itself: priming, matching pump output to the line, unfolding and positioning the boom, and placing concrete without segregating it or overloading formwork.
Start and run
- Prime the line with grout or slurry; never start a dry mix into a dry pipe.
- Keep the hopper charged. Letting it run low pulls air in, and an air pocket comes back as a pressure spike or a plug.
- Start slowly and build speed. Output that is fine in a 5 in. line is punishing in a 4 in. line: halving the area doubles velocity and roughly quadruples friction per foot of pipe.
- Put reducers at the discharge end, not at the pump.
Boom and hose
- Unfold and stow in the manufacturer's sequence; never rest the boom tip on rebar, scaffold, or a wall.
- Keep the boom and hose clear of power lines, and keep everyone out from under the boom and the discharge hose.
- Use the shortest practical rubber hose, secured with a whip check; the steel line carries the pressure.
Worked example
A crew wants to neck a 5 in. line down to 4 in. right at the pump to save hose weight at the placement point. At the pump, that 4 in. section sees full pump pressure and the highest velocity in the system, and every elbow downstream takes the extra wear. Moving the reducer to the last 20 ft before the discharge keeps the high-pressure, high-wear section short.
Traps that cost marks
Adding water on site to "make it pump"; running high engine speed with a long, small line; letting the hose end whip unsecured; resting the boom on structure; placing from height so the mix segregates; losing sight and radio contact with the nozzleman.