COMPRESSED AIR QUALITY AND PURITY INSTRUMENTS

Compressed air is used in almost any industrial process, ranging from food and beverage to medical applications. Thereby, the compressed air is sometimes in direct contact with the products, for example in packing processes, where packing containers are blown out using compressed air. Considering that the compressed air system is part of the process and can be in direct contact with the products, it is very important to monitor the air quality.

The ISO 8573-1 has defined quality classes for the 3 major parameters, as they are oil contents, particle concentration and pressure dew point (water concentration), this helps users to define the air quality which might be in contact with the end product, according to defined standards. Modern filtration systems are capable to filter out any unwanted contamination of the compressed air used, most likely introduced by the compressors. But in case filters fail or degrade, users must have a reliable real-time monitoring to react on these failures, otherwise production output might be contaminated or even has to be called back from consumers.

In such cases, the damage on the product but also on the brand reputation can have a huge impact. Only a continuous monitoring of the compressed air quality helps to prevent this from happening.

The ISO 8573-1 offers users are guideline to classify the impurities of the compressed air. Therefore, the ISO 8573-1 has defined contamination limits for the three parameters oil, particles and water. These limit values are represented in classes of 1 to typically 5 or 6. Each parameter is considered as a single measurement value, so systems can have different ISO 8573 classes throughout the different parameters.

For example, if a system is classified as 1.2.1 according to the ISO 8573-1 it is typically meant that the particle concentration is class 1, the dew point is class 2 and the oil concentration is class 1. For particle concentration, the measurement is divided into 3 channels in regard to the particle size “d”: 0.1 < d ≤ 0.5 µm; 0.5 < d ≤ 1.0 µm; 1.0 < d ≤ 5.0 µm. Each size channel has its own defined limit values according to the ISO 8573-1. The water or humidity concentration is defined as pressure dew point, representing the humidity levels in the compressed air.

Oil concentration is measured in milligrams per cubic-meter (mg/m3) of air. The ISO 8573-1 helps operators of compressed air systems to define the quality of the air and unifies the references and limit values to be used, making it easy to classify systems.

SUTO oil vapor sensors used in the S120, S600 and other products are PID (Photo Ionization Detectors) sensors. PID sensors are using UV lamps to ionize the hydro-carbon molecules in the air passing by the sensor element, through the ionization the electrical charge of the molecule changes, this change can be detected by the sensor and the unit are able to quantify the value of hydro-carbons in the air. The measurement of oil vapor is mandatory according to the ISO 8573-1, it represents the oil contamination in the compressed air system. PID sensors are the state of the art when it comes to real-time oil measurement in compressed air systems.

SUTO particle counters are based on laser optical sensors. A high efficient laser beam is crossing the air stream, if now an airborne particle passes through the laser beam it will scatter the light. The light-sensitive sensor will detect this scattering and count the particles. Based on the different scattering of different particle sizes, the sensor is able to not only give a quantification but also able to detect the size range of the particles as defined and according to the ISO 8573-1 and ISO 8573-4.

Over the past years, it was a common practice to take on-site air samples and analyze them in external labs for quality audits. These external analyzes have one very big drawback, results are available within weeks and there is no monitoring or real-time measurement of the compressed air quality possible. This means, by realizing the measurement with probe sampling and external lab analyzes, the compressed air quality is always only a snapshot of the air quality at this particular date and time. But if in between two compressed air quality audits something would degrade or filters would fail, it could not be detected by the operators.

SUTO systems are offering live on-site monitoring solutions for a real-time measurement of the air quality. This enables to react in time when something is going wrong. By real-time compressed air quality measurements, operators are enabled to act on changes the moment they are happening and not when it’s already too late.

A modern compressed air system consists of a compressor which is then followed by filters and air dryers, a so-called filtration system. These filters are needed, because compressors are sucking in ambient air and introduce any impurity of the ambient air into the system. So even an oil-free compressor might introduce oil into the system, since oil vapor can already be part of the intake air.

Furthermore, water and particles in the ambient are also sucked in, compressed and introduced to the system. Multiple filters after the compressor are used to remove unwanted contamination, but small particles, water vapor and oil vapor will still pass these filters. Therefore, driers and activated carbon filters are needed to further filtrate the air.

But also the piping system itself contains components which might introduce impurities. Valves, sealing, connections, quick couplings or other components are often sources of contamination.