Compressors foundation design

Foundation designers, particularly ones who are familiar with reciprocating compressors, will often ask about the shaking forces exhibited by... 

The dynamic compressors, axial and centrifugal, exhibit one other non-steady force, which is often questioned by foundation designers. This is the torque reaction force at the casing feet and, thus, the foundation due to surge. As a rule of thumb, a value of A the maximum steady-state torque reaction at the casing feet can be used. The frequency is the surge frequency, which is less than operating speed but not readily predictable, because it is heavily dependent on the connected system. 

Satisafactory compressor installations many times depend on how well the foundation or support structure was designed. An inadequate foundation design can result in equipment damage due to excessive vibration. The money saved by cutting comers on foundation design effort may be spent many times in costs associated with high maintenance and lost production. 

Depending upon size and type of unit, the mounting may vary from simply bolting to the floor to attaching to a massive foundation designed specifically for the application. A proper foundation must (1) maintain the alignment and level of the compressor and its driver at the proper elevation, and (2) minimize vibration and prevent its transmission to adjacent building structures and machinery. There are five steps to accomplish the first objective ... 

Separately driven centrifugal compressors are adaptable to low-pressure cryogenic systems because they can be coupled directly to steam turbine drives, are less critical from the standpoint of foundation design criteria, and lend themselves to gas turbine or combined cycle applications. Isentropic efficiencies of 80 to 85% are usually obtained. 

Arya, S.C., Drewyer, R.P. and Pincus, G. Foundation Design for Reciprocating Compressors. Hydrocarbon Processing, May 1977, p. 223. 

Due to the basic design of the compressor, its rotating and reciprocating masses produce inertia forces and moments tha cannot be completely eliminated and must be absorbed by the foundation. The manufacturer has the ability to minimize the magnitude of these forces and moments by adding counterweights to the crossheads but cannot totally eliminate them. 

Because of the vibration problems ever present with reciprocating compressors, pipe supports have a very important role in piping design. Supports independent of any other foundation or structure are almost mandatory. Pipe systems firmly fastened close to grade are much preferred. 

The blowers are designed as compact uncooled radial compressors of horizontal barrel-type construction They are installed on a steel foundation with an integrated oil system. Drive speed-controlled electric motors with intermediate gearing are provided. 

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