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2016SummerShotcreteEMag

Shotcrete Corner Advantages of a swing tube pump: • Highest pumping pressure for harsh materials and long distance pumping; • Pump will run in reverse for safety in case of hose plug; and • Infinitely variable pumping speed for high and low output. Disadvantages of a swing tube pump: • Higher cost to purchase; and • Requires a trained and experienced operator. Squeeze Tube or Peristaltic Pumps A squeeze pump (Fig. 2) operates on the same principal as filling a straw with a milkshake and using your thumb and index finger to squeeze the milkshake out of the straw. Two squeeze rollers are mounted on a roller assembly inside a drum. Pairs of “following rollers” are mounted between the two squeeze rollers to keep the pumping tube in alignment. A rubber pumping tube is mounted on the inside circumference of the drum housing. A heavy-duty shaft is connected to the assembly that holds the squeeze rollers and follower rollers in place, and this shaft is held in place by the pump housing. A heavy-duty gear box powered by a hydraulic motor turns the rotor shaft, which turns the squeeze roller assembly. As the rollers turn and make contact with the tube, the rollers squeeze the tube closed, which causes the material to fill the tube on the suction side and discharge from the tube on the discharge side. The speed the rollers turn is directly related to the pump output, which is infinitely variable from 0 to 30 rpm. The pump can be reversed to pump in either direction. The pump also can be run dry without damage to the pump. Squeeze pumps come in three sizes: 2 x 22 in. (50 x 560 mm) diameter with an output of 0 to 5 yd3/h (0 to 3.8 m3/h); 3 x 28 in. (75 x 710 mm) diameter with an output of 0 to 12 yd3/h (0 to 9 m3/h); and 3 x 36 in. (75 x 910 mm) diameter with an output of 0 to 25 yd3/h (0 to 19 m3/h). A rollerdriven pump, where the squeeze rollers are under power rather than the rotor being under power, is also available in a 3 x 36 in. (75 x 910 mm) pump with 0 to 25 yd3/h (0 to 19 m3/h) output. Squeeze pumps provide the lowest output pressure when compared to swing tube, rotor stator, or ball seat pumps. The maximum output pressure at pump discharge is 500 psi (3.4 MPa). As a result, squeeze pumps would not be recommended for pumping larger than 0.5 in. (13 mm) aggregate, exceeding 50 ft (15 m) vertically and 250 ft (76 m) horizontally. The slump of the material should not be less than 3 in. (75 mm). Squeeze pumps are preferred for cellular concrete Fig. 2: A squeeze pump operates on the same principal as filling a straw with a milkshake and using your thumb and index finger to squeeze the milkshake out of the straw because the lower pressure does not damage the bubbles in this material. Squeeze pumps have also been used successfully to pump shotcrete with steel and synthetic fibers. The lower pumping pressure makes a squeeze pump the safest to operate and, in many cases, customers with no concrete pumping experience can safely operate a squeeze pump. The squeeze pump’s wear part is the rubber pumping tube, and the tube can be replaced in about 30 minutes. The pumping tube should be lubricated on the underside where the squeeze rollers make contact with the tube to reduce friction and improve the life of the tube. The squeeze pump is the only concrete pump that is available as a skidsteer work tool. The squeeze pump work tool is the least expensive concrete pump on the market. Advantages of the squeeze pump: • Lowest cost to purchase and maintain; • Low pumping pressure friendly to cellular concrete and low-velocity spray-up as well as standard shotcrete; • No nozzle blowback, which is much less stressful to a nozzleman; • Most simple and safe to operate and available as skidsteer work tool; and • Pumps in both directions without priming. Disadvantages of the squeeze pump: • Limited to 50 ft (15 m) vertical, 250 ft (76 m) horizontal, and over 3 in. (75 mm) slump material. Hydraulic Ball Valve Pump The hydraulic ball valve (also known as ball seat) (refer to Fig. 3) is similar to the swing tube or “S” tube pump in that both use two hydraulic cylinders as differential cylinders to load and unload the material inside two 24 in. (610 mm) long by 4 in. (100 mm) diameter pumping cylinders. The hydraulic cylinders are attached to Shotcrete • Summer 2016 57


2016SummerShotcreteEMag
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