Page 262 - Reciprocating Compressors Operation Maintenance

Overhaul and Repair of Reciprocating Compressors 247

As has been pointed out in Chapter 2, reciprocating compressors expe-
rience alternating movement of the reciprocating parts. The resulting
shaking or inertia forces must be contained by mounting these machines
on properly designed foundations.
Regrouting of oil soaked concrete is very often required on old com-
pressor installations. The new grout material should be an epoxy.
When regrouting on oil saturated concrete, the expected results
should be comparable to the properties of good concrete because these
properties were the criteria for the original design.
Experience has definitely shown that the best method of preparing a
concrete surface for bonding is through mechanical scarification to
remove surface iaitance. This can be accomplished by chipping away the
surface at least % inch. Sandblasting the surface on reciprocating equip-
ment foundations is not acceptable. At one time, acid washing was wide-
ly accepted as a means of surface preparation, but this practice has not
proved reliable.
Concrete can absorb oil and once oil has been absorbed, a gradual
reduction in both tensile and compressive strengths will follow. Given
enough time, the compressive strength of the concrete may be reduced to
the point where it can be crumbled between the fingers. Fortunately, the
deterioration process is slow and it may take many years for complete
degradation. When total deterioration has occurred, the damaged con-
crete must be replaced with either new concrete or epoxy grout.
There are measures that can prevent this problem, such as sealing the
concrete with an epoxy sealer to provide an oil barrier. Sealing of the
foundation is usually done at the time of original construction. Concrete
foundations that are oil-soaked but have not undergone total loss of
strength can be salvaged with proper regrouting techniques. When conta-
minants such as oil or grease are present, special consideration should be
given to surface preparation and epoxy thickness.
Proper epoxy grout thickness is important. It should be recognized that
in solid materials, forces resulting from compressive loading are dis-
persed throughout the solid in a cone-shaped pattern with the apex at the
point of loading. Consequently, the weaker the concrete, the thicker the
epoxy covering should be in order that loads can be sufficiently dispersed
before they are transferred to the concrete.