Page 119 - Machinery Component Maintenance

102 Machinery Component Maintenance and Repair

the foundation to the other end. This series of holes is placed at an eleva-
tion of approximately two feet below the oil pan trough. High tensile al-
loy steel stud bolts are inserted in the holes along with small-diameter
copper injection and vent tubes. The ends of the hole are then sealed and
overcome before the crack could possibly recur. In this case, the repair
relies not only on bond of the adhesive between the two segments but also
on the prestressed condition of the concrete. As a result, the repaired
foundation is often much stronger than the original foundation. This tech-
nique is frequently used when the concrete is of poor quality.
When access to the foundation is limited or downtime is critical and
stud bolts are not immediately available, an alternate method can be used
where holes are drilled after the existing grout has been removed. These
holes are drilled into the foundation perpendicular to the crankshaft and
at an angle to intersect the crack at an elevation of approximately two feet
below the oil pan trough. Heavy reinforcing steel, usually 1V2 in. in di-
ameter, is inserted into the hole along with the small-diameter copper in-
jection and vent tubes. The entrance is then plugged and the equipment
regrouted. After equipment regrouting, the annular space around the
reinforcing steel is filled, the vent tube plugged and the crack pressure
injected from the inside out.
A similar procedure for repairing cracks perpendicular to the crank-
shaft can be carried out by rotating the drilling angle 90" (Figure 3-19).
The reinforcing steel in this case would be in positions skew to the crank-
shaft.
Figure 3-20 illustrates a method of repairing cracks between concrete
pours. These cracks often appear between the block and the mat below or
between the pours when blocks are so large that a monolithic pour cannot
be easily made.
As one word of caution to equipment owners, these techniques require
special epoxy formulations and a great deal of care. Repairs should be
carried out by experienced specialists using products manufactured spe-
cifically for such applications. Note that there are approximately 100 dif-
ferent types of curing agents available to the epoxy formulator. Only a
few impart satisfactory properties to the cured epoxy resin. The choice of
curing agent is based on such criteria as pot life time, nonshrink capabil-
ity, ability to bond through oil films, creep resistance at the operating
temperature, etc. Because all jobs are slightly different, the applicator
should be experienced with available products.