K Concrete Welded Base

Concrete bases are recommended under pumps as they are more rigid and a better choice in maintaining alignment. They need not be selected for the additional mass that is needed under highly unbalanced machines such as slow speed horizontal or vertical compressors. If the building can handle the added weight, floating concrete installations always look better and the shielding reduces air borne noise transmission. The K designs are a neat way of building these bases as the contractor receives a complete package consisting of a steel form with reinforcing bars and anchor bolt templates in place ready for pouring. Concrete foundations need not have quite the same depths as steel bases since stiffness is provided by the entire width. Therefore, we have reduced the depth requirement to 1/12th the longest dimension. We have limited the mandatory depth to 12 inches(300mm), as compared to our older specification which had no depth limit. If the vibration manufacturer feels that the 12 inch depth is not sufficient, he may increase it at his option. An open ended requirement of 1/12th of the longest dimension led to thicknesses that were completely impractical on long bases where there was no particular alignment, inertial or loading problem.

The steel form may be bolted or welded, structural or formed metal if it does not deform during the pour. When the concrete hardens, the structural strength and rigidity is provided by the reinforcement and has little or nothing to do with the perimeter steel.


Vibration isolation manufacturer shall furnish rectangular steel concrete pouring forms for floating concrete bases. Bases for split case pumps shall be large enough to provide support for suction and discharge elbows. Bases shall be a minimum of 1/12 of the longest dimension of the base but not less than 6”(152mm). The base depth need not exceed 12”(305mm) unless specifically recommended by the base manufacturer for mass or rigidity. Forms shall include minimum concrete reinforcing consisting of 1/2”(13mm) bars welded in place on 6”(152mm) centers running both ways in a layer 11/2”(38mm) above the bottom. Forms shall be furnished with steel templates to hold the anchor bolt sleeves and anchor bolts while concrete is being poured. Height saving brackets shall be employed in all mounting locations to maintain a 1”(25mm) clearance below the base. Wooden formed bases leaving a concrete rather then a steel finish are not acceptable. Base shall be type BMK or K as manufactured by Mason Industries, Inc.