Compressor room design: Key to efficient operation
August 12th 2011

Although most of today’s compressors and all relevant accessories are purchased as fully-integrated, plug and play packages, it is important to remember that the installation method and siting may still have a significant influence on a compressor system’s performance and reliability, as Sean Fairest of Atlas Copco Compressors explains

The main rule for an installation is first and foremost to arrange, where possible, a dedicated and centralised compressor plant. Atlas Copco’s experience dictates that centralisation is preferable, regardless of the application industry. The subsequent benefits are improved operating economy, a better-designed compressed air system and service provision, and greater user friendliness, combined with effective noise control, better opportunities for controlled ventilation, and protection against unauthorised access.

While it is true that a demarcated area in a building that is used for other purposes can be used for the compressor installation, there can be associated problems and inconvenience which should be borne in mind. For example: disturbance due to noise or the compressor's ventilation requirements, the risk of overheating, the provision of drainage for condensation, hazardous surroundings, e.g. exposure to dust or flammable substances and aggressive materials in the air, not to mention accessibility for service and extra space requirements for future expansion.

However, direct installation in a workshop or warehouse close to the point of use not only enables energy savings due to minimum pressure drop, achieved through reduced pipework requirements, but can also provide a viable opportunity for energy recovery.

If space restrictions demand that the compressor is sited under a roof structure outdoors, stringent measures must be taken to ensure all-weather protection, provision of adequate firm foundations and again minimum risk of ingress of dust, flammable or aggressive substances, and security against unauthorised access.

Placement and design

Essentially for large installations with lengthy pipework runs, and ideally for other applications, the centralised compressor facility should be sited for optimum routing of the distribution system. Proximity to auxiliary equipment such as pumps and fans – even to the boiler room – can be advantageous for service and maintenance procedures.

The building should feature adequate clearance height and lifting equipment capable of handling the compressor’s heaviest components, such as the electric motor and/or have access to a forklift truck. It should also have sufficient floor space for installation of an extra compressor for future expansion.

Provision of floor drainage is equally important in order to handle condensate from compressors, aftercoolers, dryers, air receivers, etc and disposal methods must comply stringently with local regulations.

Foundations

Normally only a flat floor of sufficient weight-bearing capacity is required to set up the compressor plant. In most cases, vibration damping is integrated into the equipment. However, it is usual to cast a concrete plinth for the compressor package to allow for floor cleaning and provide a base for new installations.

Large piston and centrifugal compressors can require a concrete slab foundation anchored to the bedrock or on a solid soil base. The impact of externally produced vibration has been reduced to the minimum for advanced, complete compressor plants. In systems with centrifugal compressors it may be necessary to vibration dampen the compressor room’s foundations.

Intake air

For trouble-free, efficient operation, compressor intake air must be clean and free of solid and gaseous contamination.

Particles of dust and dirt can cause wear and corrosive gases are particularly damaging. The compressor air inlet is usually located at an opening in the sound-reducing enclosure, but can also be placed remotely in a place in which the air is as clean as possible. Gases from vehicle exhaust fumes can be lethal should they contaminate a breathing air supply. A pre-filter, either a cyclone, panel or rotary band filter, should be used on installations where the surrounding air has a high dust concentration. In such cases, the pressure drop caused by the pre-filter must be accounted for during the design phase of an installation.

It is also beneficial for the intake air to be cold. It may therefore be appropriate to route this air through a separate pipe from the outside of the building into the compressor. It is important that corrosionresistant pipes, fitted with mesh over the inlet and designed so that there is no risk of drawing snow or rain into the compressor be used for this purpose.

The design of piston compressor inlet pipes is particularly critical. Pipe resonance from acoustic standing waves, caused by the compressor’s cyclic pulsating frequency, can damage the piping as well as the compressor, cause vibration and affect the production environment through irritating low-frequency noise.

Compressor room ventilation

Because compressors generate heat, adequate compressor room ventilation is an important consideration.The ventilation air for air-cooled compressors contains close to 100% of the energy consumed by the electric motor in the form of heat. The ventilation air for water-cooled compressors contains some 10% of the energy consumed by the electric motor. So the heat must be removed to maintain the temperature at an acceptable level in the compressor room. Most compressor manufacturers provide detailed information on the required ventilation flow.

One way to deal with heat build-up problems and to realise economic benefits into the bargain is to install heat recovery systems at the outset or apply retrofit solutions to recover the waste heat and apply it to premises or production processes.

Ventilation air should be drawn in from the exterior of the building at a maximum velocity of 4m/s, preferably without extensive ducting and, where possible, the inlet should be positioned on a north-facing wall to provide shade in the hotter months of the year. Grille and air stream damper units prevent foreign objects from entering and they eliminate cold draughts. The intake needs to be positioned as low as possible on one wall while thermostaticallycontrolled ventilation fans should be sited at the highest point on the opposite wall.

In order to ensure the optimum performance and reliability of compressor equipment, as a vital part of the production process, it is important to take all of these considerations into account when designing a compressor room installation.

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