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2016SummerShotcreteEMag

Shotcrete Corner the pumping cylinders on end and the pumping cylinders are attached with a heavy-duty clamp to a pump manifold. The manifold is bolted to the material hopper. The pump manifold includes four balls and four seats. Each hydraulic cylinder has a proximity switch that leads to an electrical control box to automatically shift the cylinder to load and unload the pumping tube. When the pump is loading with material from the material hopper, the suction causes the ball to move to a stop to allow material to be sucked inside the pumping tube. When the hydraulic cylinder reverses to unload the pumping tube, the pressure of the material moves the ball into the seat and the material in the pumping cylinder is pushed up and out of the manifold, which serves as a housing for the balls and seats. The discharge outlet is reduced from 5 in. (125 mm) to 4 in. (100 mm) to 3 in. (75 mm) at the pump outlet, where the 3 in. (75 mm) delivery line is attached. The manifold is attached to the pumping cylinders with heavy-duty clamps. The manifold is bolted to the receiving hopper on the opposite side of the manifold where the material loads into the manifold from the receiving hopper. When the clamps are removed from the pumping cylinders, the manifold becomes a part of the receiving hopper assembly. A hydraulic cylinder attached to the receiving hopper moves this entire assembly up and away from the pumping cylinders for easy access for cleaning and maintenance. The ball valve pump delivers up to 1100 psi (7.6 MPa) pumping pressure; however, it is limited to 3/8 in. (10 mm) aggregate and a slump that is not less than 3 in. (75 mm). The ball valve pump will not run in reverse; therefore, extreme caution must be taken to relieve the pressure on the delivery line should the line plug. There is a small ball valve on the discharge pipe of the manifold to manually relieve this pressure. Materials such as gypsum flooring materials, which are very plastic in nature, tend to build up over time in the receiving hopper and manifold. Shotcrete materials do not have these same characteristics and will work well provided the aggregate does not exceed 3/8 in. (10 mm) in diameter. Advantages of a ball seat pump: • Lower cost to purchase than swing tube pump; and • Simple and quick to maintain. Disadvantages of ball seat pump: • Cannot run in reverse so caution must be taken with hose plugs; and • Oversized aggregate will not pass between ball and seat. Rotor Stator, Screw, Progressive Cavity, or Worm Pump Rotor stator pumps (refer to Fig. 4) are available in many sizes. The eccentric screw pump or rotor stator is a progressive cavity pump. The design of the progressive cavity pump consists of a singlethreaded screw or rotor, turning inside a doublethreaded stator. The rotor seals tightly against the rubber stator during rotation, forming a set of fixed-size cavities in between. The cavities move when the rotor is rotated but their shape or volume does not change. As the rotor rotates inside the stator, cavities form at the suction end of the stator, with one cavity closing as the other opens. The cavities progress axially from one end of the stator to the other as the rotor turns, moving mortar through the pump. New spaces/cavities are created when the rotor is turning that move axial from the suction side toward the pressure side. The suction side and the pressure side are always sealed off, and a continuous flow of material is created. The material exits the pump and is conveyed hydraulically, under pressure through a rubber hose or steel pipe, to the point of placement. The benefit of a rotor stator pump is there is no pulsation when material is continuously fed. Most applications for rotor stator pumps use the low- Fig. 3: The hydraulic ball valve, or ball seat, uses two hydraulic cylinders as differential cylinders to load and unload the material inside two 24 in. long by 4 in. diameter pumping cylinders 58 Shotcrete • Summer 2016


2016SummerShotcreteEMag
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