Machine foundations must fulfill certain requirements before their detailed design can be carried out. The first requirement is that the foundation must be able to support the weight of the machine without causing shear or crushing failure. Secondly, the permissible limit of settlements must not be exceeded. The combined centre of gravity of the machine and foundation should be in the same vertical line as the centre of gravity of the base plane as much as possible. Thirdly, resonance should be avoided, which can be achieved by ensuring that the natural frequency of the foundation-soil system is either too high or too low in comparison to the machine’s operating frequency. For low-speed machines, the natural frequency should be high. Fourthly, the amplitudes under service conditions should be within the permissible limits, which are set by the machine manufacturers. Fifthly, all rotating and reciprocating parts of a machine must be well balanced to minimize unbalanced forces or moments. Lastly, if possible, the foundation should be designed in such a way that it can be altered in the future by changing the base area or mass to achieve the desired natural frequency.
Fig: Machine Foundation
To ensure practicality in machine foundation design, certain requirements must be met. First, the groundwater table should be kept as low as possible, and the groundwater level should be at least one-fourth of the width of the foundation below the base plane. This is necessary to limit the propagation of vibration since groundwater is an efficient conductor of vibration waves.
Secondly, it is important to separate machine foundations from adjacent building components through the use of expansion joints. This helps to prevent any potential damage that may arise due to differential movement between the machine foundation and the adjoining building components.
Thirdly, any steam or hot air pipes embedded in the foundation must be properly isolated to avoid heat transfer from the pipes to the foundation. This is essential in preventing any potential damage that may result from thermal expansion or contraction.
Fourthly, the foundation must be protected from machine oil by applying an acid-resisting coating or suitable chemical treatment. This is crucial in preventing the deterioration of the foundation due to chemical reactions that may occur between the machine oil and the foundation.
Lastly, machine foundations should be taken to a level lower than the level of the foundations of adjoining buildings. This helps to prevent any potential damage that may arise from differential settlement between the machine foundation and the adjoining building foundation.