Masonry Magazine August 2016 Page. 33
It has a full-flow internal fluidway. This allows the S-tube to work with material mix designs containing coarse aggregates. For example, masonry contractors wanting to use a 3,000 psi (207 bar) mix design containing aggregates up to 1/2-inch (12.5-mm) diameter would select a masonry grout pump with S-tube valve design to ensure those larger aggregates pass through the pump. Maximum aggregate sizes stated by the manufacturer may be as high as 3/4 inch (19 mm), although pumping these large aggregates may require a higher compressive strength mix design and large-diameter material delivery hoses.
S-tube pumps are especially suited to pumping grout from ready-mix trucks because oftheir ability to keep pace with the yardage coming out of the truck. They can also be used with mortar mixers, although it is important to con�sider that a grout pump will almost always pump faster than the mixer can produce materials.
Bottom line: the S-tube is the choice for high-production, continuous pumping offine or coarse grouting materials �especially when sourcedfrom ready-mix providers.
Pumps with ball-valve or ball-check designs are also used for masonry grouting. These designs are used
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Masonry Grout Pump on jobsite in Perth, Western Australia.
Photo courtesy ofBrunswick Safes
on mechanically driven and hydraulic grout pumps. The ball-valve design uses two balls made of either steel or hard plastic to create suction between the hopper and material cylinder in the pump. One ball is located below the material hopper, and the other at the discharge of the pump. The material cylinder contains a piston, which forces material from the hopper valve toward the discharge. This cylinder is constantly cycling forward and backward when the pump is switched on. As the cylinder cycles back during the retract stroke, the discharge ball is seated, sealing off material from flowing out of the discharge. At the same time, the hopper ball is "unseated," allowing material to flow from the hopper into the cylinder. The opposite is true in the forward stroke: the hopper ball is seated, sealing off material from entering the cylinder from the hopper, and the discharge ball is unseated, allowing material to pass out the discharge into the grout hose.
Ball-check pumps may include a single cylinder or may combine a main cylinder with a compensating cylinder to reduce the surge effect caused by the retracting and extending of the piston. Contractors wanting to use maximum aggregate sizes published by ball-check pump
August 2016 � MASONRY I 31