Compressed air quality - mobile "All in one solution"
Residual oil - particles - residual moisture. Compact trolley with wheels.
Details
Description of the measuring device:
The OIL CHECK 500 continuously monitors the oil content in compressed air and other gases. The instrument highlights trends between regular laboratory tests and enables deviations to be investigated.
This is always important whenever compressed air or other media may affect the product, the process or sensitive surfaces, such as in the following sectors:
- Pharmaceutical industry
- Food and drink industry
- Electronics
- Biotechnology and cosmetics
- Technical gas supply
Indicative measurement in accordance with ISO 8573-5 (2025)
Indicative measurement in accordance with ISO 8573-5 provides transparency exactly where it matters most in operations: directly within the compressed air system and without having to wait for laboratory results. It continuously monitors residual oil content and immediately highlights changes in the process, ensuring greater safety and a faster response. It focuses on gaseous components, particularly oil vapours, thereby complementing quantitative laboratory analysis with a practical online monitoring system. This provides operators with a powerful tool for consistent compressed air quality, reliable processes and operational safety.
11 calibration points, 3 within Class 1
The most important factor for an accurate measurement is the correct calibration of the measuring system. The Class 1 limit value specified in ISO 8573 is 0.01 mg/m³. This corresponds to a volume concentration of 2.5 ppb, which means 2.5 parts per billion. The OIL CHECK 500 is calibrated with 3 adjustment points in Class 1, precisely where it matters most. Calibration at 7 further points ensures that even high residual oil readings can be measured reliably.
Forced Pressure Variation
The Forced Pressure Variation test uses targeted pressure changes in the measuring chamber to verify whether the zero air used is truly free of the gases to be measured. If the signal remains stable when pressures are varied, a zero-point correction can be carried out reliably; if it rises, this indicates contamination of the zero air and a zero-point adjustment is not permitted. This prevents creeping errors caused by contaminated zero air. This results in greater measurement reliability in the critical lower measuring range, fewer external calibrations and consistently reliable measurement results.
Easy-to-replace sensor unit
The sensor unit can be easily replaced on site. This eliminates the need to return the entire instrument for recalibration.
Low cross-sensitivity to humidity and ethanol
Cross-sensitivity to gases that are not target gases for oil vapour measurement can increase the measured value even when there is no relevant contamination in the measurement gas. The OIL CHECK 500 has been specifically developed to minimise cross-sensitivity to the two commonly occurring interference gases: humidity and ethanol. This improves the reliability of the measured values.
Controlled gas temperature
ISO 8573 specifies a reference temperature of 20 °C for residual oil measurement. As modern compressed air systems may be equipped with heat recovery, it is possible that the compressed air temperature may be below 20 °C during measurement in the compressor room, but rise above 20 °C again further down the production line. This can result in less oil vapour being present in the compressor room at low temperatures than at the consumer. The optional integrated heating element ensures a measurement temperature > 20 °C. The measured value can thus be reliably converted back to the reference temperature of 20 °C.
External verification by the Fraunhofer IPM Institute
The OIL CHECK 500 was cross-checked by the Fraunhofer Institute for Physical Measuring Technology IPM, an external research laboratory, and performed impressively with a very good detection limit of 0.0015 mg/m³ at 6 Sigma. It therefore delivers reliable measured values and high measurement resolution within the ISO 8573-1 Class 1 range.
Its wide measurement dynamic range, spanning more than three orders of magnitude, enables precise measurement across an exceptionally broad concentration range. The OIL CHECK 500 thus reliably covers oil classes 0 to 4 of ISO 8573-1 and supports safe compressed air monitoring.
Compressed air quality is the result of the entire system: intake air → compression → drying and filtration → activated carbon (if applicable) → internal piping and fittings → OIL CHECK 500 at the supply point.
Vaporous hydrocarbons from the intake air can pass through the compression, drying and filtration stages. Oil-free compression prevents the introduction of lubricating oil from the compression stage; in the case of oil-lubricated compressors, additional oil may be introduced from the compression stage. Coalescing filters are designed for liquid droplets and aerosols; activated carbon is used for the targeted reduction of the vapour phase.
Where oil vapour content is very low – as is the case with oil class 1 – such an adsorption stage is often part of the treatment process, depending on the intake air and the system design. During operation, three factors are particularly relevant:
- Intake air: Exhaust gases , a generator on site or solvents from the workshop can alter the inlet load, alongside traffic, weather and shift work. In a field measurement, switching from external to internal air intake doubled the oil vapour value from approximately 0.003 to 0.006 mg/m³.
- Operating conditions:Changes between loaded and idle operation, the switching on and off of individual machines, operating hours and maintenance history can influence the measured oil vapour profile.
- Activated carbon:Its service life depends, amongst other things, on oil loading, humidity, temperature and operating mode. The differential pressure does not indicate the remaining adsorption capacity for oil vapour. A measurement taken downstream of the activated carbon indicates the outlet concentration and provides an early indication of an increase, for example as saturation begins.
Dryers, filters and activated carbon: a single measured value summarises the total output and describes the air fed into the network. Immediately downstream of the compressor or receiver, the humidity and aerosol content may exceed the measurement gas conditions (≤ 40 per cent relative humidity, pressure dew point max. +10 °C, non-condensing, with upstream aerosol separation).
No, not during operation. The OIL CHECK 500 checks the zero point internally using forced pressure variation; there is no need for a separate zero air supply with a filter or catalyst. Test gases are only used during the factory calibration of the sensor unit.
Not on its own. For classification in accordance with ISO 8573-1, the laboratory determines all oil phases: aerosol and liquid oil in accordance with ISO 8573-2, and oil vapour by gas chromatography in accordance with ISO 8573-5. The OIL CHECK 500 continuously monitors the oil vapour content on an indicative basis in accordance with ISO 8573-5:2025, Annex B; its class indicator classifies this content. The measurement data support decisions regarding additional laboratory samples and – when connected to a data-logging system – document the trend between them.
The warning threshold and action threshold are derived from the specification of the sampling point, the initial value following commissioning or a cartridge change, the measurement uncertainty, the proportion of aerosol and liquid oil in the total oil, and the desired advance warning time; there is no standard value.
No. For particles (ISO 8573-4) and pressure dew point, it is supplemented by the PC 400 particle counter and the FA 510/515 dew point sensors; a suitably equipped DS 500 records all three parameters and monitors the limit values.
