Page 82 - Machinery Component Maintenance

Muchinery Foundations and Grouting 67

used in setting heavy machinery and in repairing concrete foundations.
Specifications for Portland cement grouting and epoxy grouting of ro-
tating equipment, as well as a checklist for baseplate grouting, can be
found in the appendices at the end of this chapter.
The need for a machinery grout is created by a combination of circum-
stances occurring in the construction of foundations. Many of these cir-
cumstances are unfavorable to concrete, thereby complicating its use.
This condition is brought about primarily because it is impossible to pour
a concrete foundation to within the tolerances usually required for preci-
sion leveling and alignment of dynamic equipment. Even if such exact
placement were possible it would be further complicated by the fact that
concrete shrinks while curing.
Furthermore, the laitance or weak surface created when simple con-
crete is cast or troweled would not provide sound support for machinery
requiring precision alignment. It has therefore become a standard prac-
tice in construction of foundations to pour the concrete to a level slightly
above the desired grade, and after curing, chip away the surface to re-
move the laitance. The machinery is then positioned on the foundation,
leveled and aligned to within proper tolerances with the aid of jack
screws, wedges, shims, etc., and the gap grouted in solidly to establish
integrity between the machine base and the concrete foundation below.
When improperly installed machinery breaks loose, the static forces to
which the foundation is subjected do not act alone. Vibratory forces of
high magnitude will also exist. Given enough time, this will usually
cause cracks in the foundation that allow lubricating oil to penetrate deep
into the foundation and proceed to degrade the concrete. It therefore be-
comes necessary to repair the cracked foundation, remove or repair oil-
soaked concrete and regrout in order to re-establish the integrity of the
system. Epoxy grouting materials have long been used for these repairs.
The specific use for which grout is intended should be taken into con-
sideration when evaluating the properties of a prospective grout. It is
equally important to ascertain the conditions under which a manufacturer
obtained his test data. This will allow the user’s engineer to correlate
these data with actual operating conditions. For example, most ASTM
test procedures do not specify the test temperature for determining the
properties of epoxy grout. In contrast to cement-based mortars, the prop-
erties of epoxy grouts are considerably different at the high temperatures
of operating machinery than at standard ambient temperatures. A list of
ASTM test procedures often used in testing epoxy grout properties is
shown in Table 3-1. Furthermore, in comparing compression test data it
is also important that the test specimens be of the same size and shape
because test data from cylindrically-shaped specimens is considerably