*TM 5-810-4/AFM 88-8, Chap. 3
a. A properly designed and constructed compressor
should be consulted for seismic considerations.
foundation performs the following functions:
(1) Maintains the compressor in alignment and at
proper elevation.
(2) Minimizes vibration and prevents its transmission
to the building structure.
(3) Provides enough mass to support the compressor*s
weight plus disturbing forces.
(4) Provides for the installation of sufficiently long
foundation bolts to insure good anchorage.
b. Concrete foundations must provide a permanently
rigid support for the machinery. Where the foundation is
exposed to freezing temperatures. its depth should extend
below the frost line. Isolating the foundation from any
building footings. walls, or floors will help to prevent
vibration from being carried into the building structure. TM
5-805-4/AFM 88-37 should be consulted for the
recommended vibration isolation practices. Each machine
requires an independent foundation. Operating platforms
must be isolated from the machinery foundations. Drawings
will be prepared for compressor foundations, and all
conditions surrounding the foundation will be made uniform.
The foundation should rest entirely on natural rock or
entirely on solid earth, but never on a combination of both.
If the foundation substructure rests on bedrock, a vibration
damping material should be interposed between the
substructure and the bedrock. If a foundation or foundation
substructure rests on piling, the piling should be covered
with a heavy, continuous, concrete mat. Foundation anchor
bolts hold the compressor down firmly and prevent it from
sliding laterally.
c. Horizontal and vertical reciprocating air compressors
will have a spring-mounted concrete inertia base installed on
a concrete foundation block. Limit stops will be provided for
seismic considerations. For compressor sizes 25 horsepower
and larger, it becomes necessary to engage the services of a
foundation specialist to:
(1) Test the ability of the soil to carry the load.
(2) Consider the elastic characteristics of the ground on
which the foundation rests, since reciprocating machines
exert a dynamic loading as well as a static loading on the
foundation. The unbalanced forces of the compressor are
available from the manufacturer.
(3) Check wet season and dry season soil characteristics
(static loading limits and elasticity).
(4) Determine need for piling, either vertical or batter
piles (piles driven at an angle at the foundation ends).
d. Rotary machines have considerably less vibration, and
may have a spring-mounted structural steel base supported
on a concrete foundation block, with limit stops provided for
seismic considerations. Some rotary package compressors
may be mounted on existing concrete floors, depending on
size and manufacturer*s recommendations, requiring only lag
bolts to keep the machine in place.
e. Chapter 10, Seismic Design for Mechanical and
Electrical Elements. of TM 5-809-l0/AFM 88-3. Chapter 13
1-3
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