Foundation design

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

This represents a shaking force at a frequency equal to rotor speed. For foundation design, a value of 5 to 10 times the residual unbalance or A to 1 times rotor weight at operating speed would be a reasonable design value. The direction of the force is perpendicular to the shaft, and operates as a rotating vector which can be centered between the bearings. 

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. 

Foundation Loads and Pressures. Foundations should be designed to support the weight of the structure, the live load, and the load effect on the structure and its foundation due to such other loads as v. ind. In general, for foundation designs, a safety factor of 3 is used for dead loads or live loads independently. A safety factor of 2 is used for combination loads including transient loads [38,40]. 

Where an under-slung condenser has been specified, the provision of a basement to the engine room offers the attraction of compactness at the expense of enhanced civil works, while alternatively, the specification of pannier condensers can obviate the need for a basement and will simplify the foundation design, but will considerably increase the floor area requirements. The condensing plant itself consists essentially of banks of tubes through which cooling water flows and around which exhausted steam from the turbine is condensed to form a vacuum. Such tubes have traditionally been made of brass, but where severe corrosion conditions exist, cupro-nickel is sometimes used. 

Centrifugal pumps require a rigid foundation that prevents torsional or linear movement of the pump and its baseplate. In most cases, this type of pump is mounted on a concrete pad or pedestal having enough mass to securely support the baseplate, pump and its driver. The following general mles apply to foundation design. 

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 ... 

Soil quality may vary seasonally and such conditions must be carefully considered in the foundation design. No foundation should rest partially on bedrock and partially on soil it should rest entirely on one or the other. If placed on the ground, make sure that part of the foundation does not rest on soil that has been disturbed. In addition, pilings may be necessary to ensure stability. 

Although there is no substitute for individual action based on a firm philosophical and ethical foundation, designers have developed guidelines for professional conduct based on the experience of many of them who have had to wrestle with troublesome ethical questions and situations previously. These guidelines can be found in the published codes of ethics for designers and engineers of a number of industry and technical societies such as the Industrial Designer societies. 

ORNL, Building Foundation Design Handbook, Oak Ridge National Laboratory, Oak Ridge, TN, 1988. 

The above lateral forces were determined from the combination of front and rear wall peak reactions neglecting any difference in time phasing. A more numerically complex approach would have been to determine lateral and vertical loads at each time step, and use the maximum value for foundation design. Such an approach would have resulted in lower toads. 

There are two basic approaches to foundation design equivalent static and dynamic. The equivalent static approach is almost always selected because of its simplicity. However, sometimes an overly conservative design could result. The dynamic approach involves a very complex analysis, although it should result in a more realistic design. 

Install and maintain a tank foundation design that will provide for early detection of releases of crude oil or its fractions before reaching the groundwater ... 

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. 

One of the most important aspects in structural design for the process industries is a correct foundation design with allowances for heavy equipment and vibrating machinery used. The purpose of the foundation is to distribute the load so that excessive or damaging settling will not occur. The type of foundation depends on the load involved and the material on which the foundation acts. It... 

Marshall, V.O. The Design of Foundations for Stacks and Towers. Hydrocarbon Processing, May 1958, p. 238. Czerniak, E. Foundation Design Guide for Stacks and Towers. Hydrocarbon Processing, June 1969, p. 95. Brown, A.A. An Easy Way to Compute Tower Foundation Flexure." Hydrocarbon Processing, January 1971, p. 121. 

Molnar, I.J. Foundation Design for Elevated Towers. Hydrocarbon Processing, April 1971, p. 129. 

Brown, A.A. Foundation Design for Pile Supported Tanks. Hydrocarbon Processing, September 1973, p. 175. Brown, A.A. A New Approach to Tank Foundation Design. Hydrocarbon Processing, October 1974, p. 153. 

Arya, S.C., Drewyer, R.P. and Pincus, G. Foundation Design for Vibrating Machines. Hydrocarbon Processing, November 1975, p. 273. 

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