Page 95 - Machinery Component Maintenance

78 Machinery Component Maintenance and Repair

Communication links between the equipment manufacturer, grout
manufacturer, design engineers, and construction and maintenance per-
sonnel are poor. Equipment manufacturers sometimes provide minimum
foundation mass and unbalanced forces data but they do not design foun-
dations. Data provided by grout manufacturers are often misinterpreted.
Design engineers seldom are provided feedback data on performance of
their design once the project is completed. Maintenance personnel rarely
have the opportunity to provide input during the planning stage.
The consequences of improper installation are severe. Machinery in-
stallation costs can approach $1,000 per horsepower and the loss of reve-
nue due to idle machinery has advanced at a pace even higher than the
rise in fuel costs. Large reciprocating compressor crankshafts are prone
to break if the machine is poorly supported on its foundation. Crank-
shafts are not “hardware store” items. With some equipment manufac-
turers now relying on foreign sources for their larger crankshafts, logis-
tics of spare parts supply are getting more complex. All the more reason,
then, to protect the machinery by doing an adequate grouting job.
Concrete is the most widely used construction material in the world.
Because it is so common it is often taken for granted, and therefore it has
also become one of the most abused materials. For good foundation de-
sign, these factors must be considered:

Proper chemistry
Proper water/cement ratio
A quality aggregate
Low amount of entrained air
Proper placement
An acceptable temperature range for curing
Moist curing conditions

A detailed analysis of each of these considerations would be beyond the
scope of this text; however, the listing serves to illustrate the fact that
concrete is a complex material. For our purposes, a brief description of
the mechanism of concrete curing will suffice.
Concrete is composed of a graded aggregate, held together by a hard-
ened paste of hydraulic cement and water. The thoroughly mixed ingredi-
ents, when properly proportioned, make a plastic mass which can be cast
or molded to shape, and upon hydration of the cement, becomes rock-like
in strength and hardness and has utility for many purposes, including ma-
chinery foundations. Fresh cement paste is a plastic network of cement
particles in water. Once the paste has set, its volume remains approxi-
mately constant. At any stage of hydration the hardening paste consists of
hydrates of the various ingredients in the cement which are referred to