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 device reveals trends between regular laboratory tests and enables the investigation of deviations.
This is always important whenever compressed air or other media can affect the product, the process, or sensitive surfaces, such as in the following areas:
- Pharmaceutical industry
- Food and beverage industry
- Electronics
- Biotechnology and cosmetics
- Technical gas supply
Indicative Measurement According to ISO 8573-5 (2025)
Indicative measurement according to ISO 8573-5 provides transparency exactly where it matters most in operations: directly in the compressed air system and without having to wait for lab results. It continuously monitors residual oil levels and immediately highlights changes in the process, ensuring greater safety and faster response times. It focuses on gaseous components—particularly oil vapors—and thus complements 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 proper calibration of the measurement system. The Class 1 limit 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—exactly where it matters most. Calibration at 7 additional points ensures that even high residual oil levels can be reliably measured.
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 being measured. If the signal remains stable under varying pressures, a zero-point correction can be reliably performed; if it increases, 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 vapor measurement can increase the measured value even when no relevant contamination is present in the measurement gas. The OIL CHECK 500 is specifically designed to have low cross-sensitivity to the two commonly present interfering 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. Since modern compressed air systems may feature heat recovery, it is possible that the compressed air temperature during measurement in the compressor room is below 20 °C, but rises above 20 °C again further down the production line. This can result in less oil vapor 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-validated by the Fraunhofer Institute for Measuring Technology IPM, an external research laboratory, and demonstrated an excellent detection limit of 0.0015 mg/m³ at 6 Sigma. It thus 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. As a result, the OIL CHECK 500 reliably covers oil classes 0 through 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 station 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 oil from the compression stage; in 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 vapor phase.
For very low oil vapor contents, such as those relevant to Oil Class 1, such an adsorption stage is often part of the treatment process, depending on the intake air and system design. During operation, three factors are particularly relevant:
- Intake air: Exhaust gases , a generator on the premises, or solvents from the facility can alter the intake load, along with traffic, weather, and shift operations. In a field measurement, switching from outdoor to indoor intake doubled the oil vapor value from approximately 0.003 to 0.006 mg/m³.
- Operating conditions:Alternating between load and idle, starting and stopping individual machines, operating hours, and maintenance history can influence the measured oil vapor profile.
- Activated carbon:Its service life depends, among other things, on oil loading, humidity, temperature, and operating mode. The differential pressure does not indicate the remaining adsorption capacity for oil vapor. A measurement taken downstream of the activated carbon indicates the outlet concentration and provides early detection of an increase, such as when saturation begins.
Dryers, filters, and activated carbon—a measured value summarizes the total output and describes the air fed into the network. Immediately downstream of the compressor or receiver, humidity and aerosol content may exceed the measurement gas conditions (≤ 40% 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 generator with a filter or catalyst. Test gases are used only during factory calibration of the sensor unit.
Not alone. For classification according to ISO 8573-1, the laboratory determines all oil phases: aerosol and liquid oil according to ISO 8573-2, and oil vapor via gas chromatography according to ISO 8573-5. The OIL CHECK 500 continuously monitors the oil vapor 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 progression between them.
The warning threshold and action threshold are derived from the specifications of the draw-off point, the initial value after commissioning or cartridge replacement, the measurement uncertainty, the proportion of aerosol and liquid oil in the total oil volume, and the desired advance warning time; there is no standard value.
No. For particles (ISO 8573-4) and pressure dew point, the PC 400 particle counter and the FA 510/515 dew point sensors complement it; a DS 500 equipped with the appropriate features records all three measured variables and monitors the limit values.
