Page 417 - Compression Machinery for Oil and Gas

396 SECTION III Applications

structural steel only when the package must be kept within certain weight lim-
itations; however, the preferred base design is a steel frame filled with rein-
forced concrete, as this design is portable and eliminates the need for field
poured concrete within the structural steel skid.
The engine and compressor typically sit on an elevated pedestal on top of the
skid which is preferably filled with concrete. It is important that this pedestal be
fabricated as a solid and rigid component. In reciprocating compressor pack-
ages, the natural vibrating forces with a flexible pedestal can cause skid failure
or misalignment of the engine and compressor during normal operation.
A successful foundation design require a well detailed and managed design
and construction process. A typical teams consists of a company/owner as the
lead, specialized geotechnical engineers, facility “topside” mechanical and civil
engineers of record, a compressor packager, the specialized design-build foun-
dation contractors and the managing general contractor.
Owner’s responsibilities include but are not limited to: contract and manage
the coordination of schedules and information exchange between the mechanical
and civil engineer of record, geotechnical engineer, any specialized foundation
design-build contractor, compressor packager and all other major equipment sup-
pliers, contract and manage the scheduling, inspection, and coordination of all
third parties in addition to owner’s supporting project members and all governing
agencies, provide management of construction and design “punch lists,” provide
postinstallation feedback and test data as needed, coordinate schedules and infor-
mation exchange to complete all “as-built” drawings and reports related to foun-
dation systems and associated connection to the Owner’s system.
General Considerations for Onshore Foundation designs:
1. Types of static (weights) and dynamic (operating) loads, and how the loads
are supported and absorbed by the soils and structural foundation system
selected. With vibrating loads and granular soil material, soil consolidation
and/or shifting is a risk.
2. Cost—shallow foundations are less expensive than deep foundations.
3. If native soils near the surface have sufficient strength, then shallow foun-
dations may be used.
4. Deep foundation design options may be required if dynamic and vibrating
loads are applied on granular soils (sand, cobble, gravel).
5. Typically, foundations should be designed for the following:
l dead loads—weights (permanent)
l live loads—dynamic forces (side-to-side, bouncing, twisting, torsional,
etc.) created by heavy piston/crankshaft/compressor motion, unbalanced
engine forces, heavy equipment, etc.
l Geological loads—wind, snow, freeze/thaw, seismic activity, etc.
l All appropriate combinations of those loads as indicated in the building
code applicable to the area, such as the Uniform Building Code (UBC),
International Building Code (IBC) or ANSI A58.1 (“Minimum Design
Loads for Buildings and Other Structures”).