Compressed air system design, layout and installation for optimum efficiency

For any given compressed air system, the right layout will depend on the relationship between the 5 design elements we discussed in part 1 of this blog post, being compressed air; demand, quality, supply, storage and distribution. 

It is quite often the case that the compressed air user will design and install the distribution system themselves. However, due to the complexities and the number of design criteria involved, it is worth bearing in mind that only experienced compressor professionals can provide the required information that will allow you to design a truly effective compressed air system. If you are wanting to optimise the performance and lifetime of your compressed air equipment, it is worth consulting with a compressed air specialist. 

When installing a compressed air system it is important to consider; adequate ventilation, the foundation requirements as well as the compressor room requirements and piping materials. 

You should ensure adequate ventilation of the compressed air system. Depending on the requirements of the compressed air system, this could be achieved by; natural ventilation, forced ventilation with an exhaust fan, ducted ventilation without a damper for air recirculation to the outside (a suitable option for ambient temperatures above 0^oC); ducted ventilation with circulating air damper for winter operation, mixing warm air with cold intake air (suitable for intake temperatures below 0^oC), or during the summer - an exhaust air duct vented to the outside, and space heating during winter. 

Where the compressed air system comprises of multiple compressors, there are two ways to ventilate the compressor room. One method would involve adding the kW power of all the single compressors together and ventilating the room as if there was a single compressor of that kW power in the room. Alternatively, you can provide each compressor with a separate intake air opening. You can determine the size of the intake opening by adding up the drive power of all the compressors, determining the cooling air flow and the required intake air opening for the total drive power. Once you have this information you can simply divide the area of this opening into smaller intakes, proportional to the relative size of the compressors. In general, no intake ducting will be required. The foundation requirements of the compressed air system will depend on the size and type of air compressor(s). Some types and sizes of compressors will be able to be installed without any special foundation, such as packaged rotary and small reciprocating compressors with drive motors of 18 kW or less. Base mounted rotary screw compressors that feature vibration insolation mounts will additionally not require special foundations. Larger compressors will usually require extensive foundations.

There are a number of factors that should be considered when planning the installation of a compressed air system. 

Compressed air equipment should be easy to access, with sufficient lighting, for service and maintenance tasks to be carried out. 

If you are installing a medium or large compressor it should ideally be installed in its own compressor house that is clean, dust-free, dry and cool. Machinery as well as all heat-dissipating pipes should be well insulated. The temperature in the compressor house should not fall below 4^oC in order to avoid frost and corrosion from condensate accumulation. 

The temperature of the compressor house should also be considered where air-cooled compressors are being installed. To allow for sufficient cooling air flow, the temperature in the compressor room should not exceed 35^oC.
Natural ventilation will generally be sufficient for compressors with drive powers up to 18 kW. However, forced ventilation will be required for larger compressors and/or smaller compressor houses. The ventilation of the compressed air dryers should also be considered to ensure the correct operation and a long service life. Proper placement and/or cooling ducts/fans may be required. 

How the compressed air lines will be installed should also be considered. The airline can be installed underground. This is often seen as a low cost option, however in the long run this method makes service and maintenance tasks more difficult. Materials will also need to be rust-proof.
Suspending the airline above the ground is another option. Whilst this method is fairly low cost, there may be construction obstacles to consider.
Finally, if the installation is going to be outside, it must be taken into consideration that the compressed air will need to be dried to a pressure dew point below the lowest outside temperature to avoid pipe freezing. 

The actual selection of piping will also be important in the compressed air system’s overall reliability and efficiency. Material choice, dimensions, layout, on-site conditions and future needs of the compressed air system should all be considered when selecting the piping.
Piping should be easy to maintain, robust enough for the existing work conditions and incur only minimum pressure loss and leakage. In terms of piping material, there are a number of options available such as; copper, stainless steel and galvanised. The advantages and disadvantages of each material should be considered in the selection process. 

References: KAESER Compressors, Inc. (June 2007): Designing your compressed air system: How to determine the system you need

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