Page 105 - Machinery Component Maintenance

88 Machinery Component Maintenance and Repair

grow first as a result of thermal expansion because they are in contact
with the equipment base and conduct heat well. In order to prevent rail
growth, opposing forces must be created equal to the compressive
strength of the steel in the rail. Such forces would be well over 50 times
the tensile strength of the grout. If the grout has enough elasticity to al-
low rail growth without extensive cracking, it is probably too soft to
maintain support without creep. The grout should have adequate com-
pressive strength to maintain alignment without creep.
The obvious solution is to install expansion joints. Expansion joints, as
shown in Figure 3-7, can be cast into the foundation when the epoxy
grout is poured. After the foundation has been dressed, the surface of the
expansion joint and the outer periphery of the machine base is sealed with
silicone rubber. A photograph of the finished work is shown in Figure
3-8.

Figure 3-7. An oblique view of a foundation shoulder illustrating cast-in expansion joints
which have been sealed with silicone rubber. The outer periphery of the machine base is
also sealed with a fillet of silicone rubber (Courtesy Adhesive Services Company).