Compressed air is used as a medium in numerous applications: for cleaning, ventilation and transporting chemical products, controlling production lines, manufacturing nitrogen or as an air curtain for separating safe and clean areas. Since the chemical-pharmaceutical industry works with toxic, corrosive and changeable substances, high quality requirements and safety standards are in place there for the compressed air, because even the slightest carelessness during the production of chemicals can lead to reactions and have a decisive influence on the manufacturing process. The contamination of compressed air by oil particles, for example, can cause a great deal of damage from increased scrap to machine downtime with all the ensuing economic consequences.
Contamination in the compressed air
At the start of a compressed air line is a compressor. Quite often, the compressor itself can be a source of contamination in the compressed air, since it is generally oil-lubricated, meaning that aerosols and oil vapours can enter the system. Yet, even an oil-free compressor is not completely safe, because if the intake air is already charged with steam, dirt or micro-organisms, it can carry those pollutants into the compressed air system. Even excessive humidity in the compressed air – caused by high humidity in the intake air on hot summer days, for example – endangers the air quality and has impacts on production.
Insufficiently designed compressed air treatment, inappropriate operation and inadequate maintenance of compressors and treatment components can also lead to contamination through dirt particles as well as residual humidity or oil vapour. During the manufacture of pills, for example, the compressed air which is used to transport the products comes into direct contact with them. The pills can potentially become contaminated if the air is not sufficiently treated. This can lead to cracking or to fluctuations in colour and entails health risks for the consumer.
Oil-free as a result of treatment
To avoid this, the compressed air must be absolutely oil- and germ-free and also of top quality. This is the only way to achieve safe, stable processes and products in the chemical-pharmaceutical industry. Compressed air is hence subject to strict requirements and checks. Various regulations such as the GMP (Good Manufacturing Practice), the implementation of which is regulated by rules governing medicinal products and active ingredients in the European Union, as well as DIN ISO 8573-1 and the European Pharmacopoeia define compressed air classes which are oriented towards applications.
For an application to be safe, it is important that the compressed air be treated by means of filtration, drying and process technology (catalysis), as well as by condensation, and monitored throughout the process. This permits the quality of the air to be checked against the specified requirements. The catalytic process of a Bekokat by Beko Technologies delivers absolutely oil- and germ-free compressed air with a scarcely measurable maximum residual oil content of 0.001 mg/m3. The process exceeds the stringent requirements of ISO 8573-1 (Class 1 oil content), in other words, with the kind of quality that is stipulated in particularly demanding production processes.
Cracking hydrocarbon chains
In the Bekokat, all oils contained in the air after compression are removed, whether in gaseous, vapour or aerosol form. These problematical substances are completely converted into carbon dioxide and water during the catalysis by means of total oxidation.
Following the principle of heat recuperation, the compressed air is heated to 150 °C in the heat exchanger before entering the insulated reaction tank. The sheath heating of the tank then only has to heat it slightly, so that the Bekokat is very energy-efficient.
A granulate which works as a catalyst in combination with the heat starts the reaction and enables long-chain oil molecules (from oil-lubricated compressors, for example) to be cracked into ever smaller molecules until only H2O and CO2 are left. After cooling, these are precipitated as condensate and discharged. Thanks to the catalysis process, the condensate is oil-free and can thus be safely disposed of via the sewerage system without any further treatment. The exothermic reaction also produces thermal energy. A measuring and control circuit constantly monitors the temperature, ensuring the safety of the process. If oil entry, and with it the temperature, increase due to a compressor fault, the inlet and outlet valves close immediately, so that contamination of the downstream compressed air systems is ruled out.
Monitored compressed air quality
In order to guarantee this compressed air quality in the long term, all crucial air parameters such as the residual oil vapour content, volume flow, pressure, relative humidity and dew point can be monitored using appropriate measuring systems. Quality is always the result of controlled processes. The measuring devices deliver a sound data basis for evaluation. The compressed air measurements and checks are generally automated.
A Metpoint OCV compact, for example, measures and monitors the residual oil content. Every 4 s, it records and displays a value which is a running mean of the past 80 s. This prevents the results from being distorted by outliers owing to unexpected internal or external disturbances.
Increased measuring reliability regardless of the operating conditions is ensured by the patented reference gas which is produced by a catalytic converter. In contrast to other measuring devices, the gas from the converter is absolutely oil-free zero air. If, on the other hand, reference gas is produced using activated carbon, there is always a risk of residual oil being contained in the compressed air in the event of a non-ideal design or insufficient maintenance.
The modular design of the Metpoint OCV compact simplifies assembly on site and restricts subsequent maintenance to a minimum, as all components can be exchanged quickly and easily. Servicing and maintenance cycles are indicated automatically. In addition, the measuring device can be adapted to different operating pressures from 3 to 16 bar via a controller. The operating condition and compliance with the ISO 8573 oil class is shown by red or green LEDs.
Alarm contacts can be configured individually to allow instant information if the residual oil vapour content increases. Production managers can then take appropriate action before the compressed air becomes contaminated.
Thus, industrial companies always work with the compressed air quality that is best suited for their process. If they combine comprehensive compressed air treatment with continuous monitoring of the compressed air parameters, maximum process reliability and resource efficiency will result.
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