Pure dry air

The applications for pure, dry compressed air in cleanroom environments range from pressurisation airlocks and the operation of automatic door-opening mechanisms to data sampling equipment, analytical processes and the operation of laboratory instrumentation and robotics.

Oil-free compressors are also used in medical cleanrooms, which require the highest standards of cleanliness; applications include the hygienic sterile facilities used to prepare medical equipment for the treatment of patients receiving chemotherapy. To minimise the introduction, generation, and retention of particles inside the room, and to ensure that other relevant parameters such as humidity and pressure are controlled, the compressors can be fitted with a wide range of accessories which ensure appropriate standards are achieved. The requirement for pure air means that compressors have to be equipped with air-intake filters, post-compression filters and dryers to minimise the risk of contamination. Where stringent levels of cleanliness are required, systems can provide HEPA filtration down to 1µm and bacterial filtration to 0.01 µm. To meet the growing demand for clean, dry compressed air in cleanroom environments, Jun-Air produces a range of oil-less air compressors and accessories that meet such industry classifications as Federal Standard 209, British Standard 5295, ISO Standard 209 and the Pharmaceutical Cleanroom Classification. They offer a combination of low noise levels, reliability, long life and low maintenance, the company says. Humidity control With the control of humidity in cleanrooms also becoming increasingly important in areas such as semiconductor and pharmaceutical manufacturing, dehumid-ification units (mechanical coil or desiccant types) are also available. Mechanical coils dehumidify the air by cooling it; as cooler air holds less humidity, lowering the temperature causes water to condense out. However, to dehumidify a cleanroom to the fine tolerances necessary for semiconductor fabrication, a specialised process such as desiccant dehumidification is essential. The water vapour in atmospheric air condenses to water droplets when the compressed air cools; at the same time, moisture and heat from the compressor create favourable conditions for the growth of bacteria. Adsorption dryers are recommended to remove water vapour before compressed air accumulates in the receiver; they can ensure a constant and absolute pressure dew point as low as –40ºC. Bacteria become inactive at a pressure dew point below –23ºC and may subsequently be removed, while the risk of corrosion is eliminated at –30ºC. By removing particles, water and vapour from the air line, this additional equipment ensures that the air supply is of the highest quality. The slide (shown top) provides a typical sample from a compressor without a dryer, where contamination in the air has provided ideal conditions for bacterial growth. The sample below it was taken from an oil-less compressor fitted with a dryer that has eliminated the risk of bacterial growth.¹ For many applications the air compressor is located in a "grey area" next to the cleanroom, which allows the air supply to be piped into the working environment. In the case of stand-alone compressors operating within the cleanroom environment, noise can be a concern; however, with decibel ratings as low as 47-55 dB(A) when housed in a soundproof cabinet, models in Jun-Air's oil-less range have some of the lowest noise levels available, making them suitable for installation in or near individual workstations. To ensure the highest air quality throughout the lifetime of the oil-less compressor range, receivers are internally powder-coated to avoid corrosion. Dryers are located upstream of the receiver, meaning that it will store only dry air. Units feature a cooling system and wear-resisting piston rings, and are designed for 100% continuous operation at up to 10 bar maximum pressure, although higher-pressure units are available.