Page 125 - Machinery Component Maintenance

108 Machinery Component Maintenance and Repair

Figure 3-23. Jack screws resting on circular disks are the preferred method of pump base-
plate support prior to grouting.

Prior to the baseplate placement on the foundation, the concrete must
be chipped to remove the cement-rich concrete (called laitance) and to
expose the aggregate. This provides a strong concrete/epoxy grout bond,
because the strength of the concrete depends on the aggregate. The
chipped surface must be blown clean with oil-free air and kept dry. Mois-
ture and oil are the big enemies of good epoxy grout/concrete bonding.
Experience shows that 2.0 to 3.0 in. of epoxy grout are required under
the pump baseplate flanges to reach the desired compressive strength.
Thinner pours do not generate enough exothermic reaction heat to fully
cure the epoxy. Before leveling, the baseplate should be high enough for
the 2.0 to 3.0 in. of grout.
Using jack screws for leveling is much faster than the more common
application of square steel plates and shims. Jack screws also eliminate
the problem of removing the leveling shims after grout placement. As
mentioned, the baseplate should be totally supported by the epoxy grout
and not point-supported at the leveling shims. Sharp-cornered shims
should not be left in epoxy grout because they form stress concentrations
that cause cracking. Once the epoxy grout has cured, the jack screws are