More ball-valve pumps are in use than any other kind of concrete pump.
HOW THE BALL VALVE WORKS
A ball valve is actuated entirely by flow of the concrete. On the intake cycle, ball movement at the feed hopper is limited by bars or an off-center cam. On the discharge cycle, concrete flow seats the ball. The ball at the discharge cylinder seats during intake and opens during discharge. Balls with differing weights are used for pumping concretes with differing unit weights--lightweight, cellular, heavyweight, and normal-weight concrete.
DRIVE MECHANISMS FOR BALL-VALVE PUMPS
Many ball-valve rigs are mechanically driven. These have one concrete pumping piston driven off a series of belts, chains, and a crank. Hydraulic-drive ball-valve pumps use a two-cylinder hydraulic drive much like those on large-rock pumps. Hydraulic pumps can pump concrete at a faster rate and at higher pressures than mechanical pumps.
Small-diameter delivery line and hose are commonly used for ball-valve pumps. Depending on drive mechanisms, maximum concrete line pressures may range from 300 to 900 psi.
USING THE PUMP EFFICIENTLY
Almost any gain in pumpability as a result of aggregate blending also improves concrete finishability, surface appearance, and strength. Uniformity is the key word for ball-valve pump mixes. Consistent concrete makes the pump and the job run smoothly.