Particle Concentration Measurement in Compressed Air

Particle contamination in compressed air can originate from wear in the compressor, airborne particles at the air inlet or corrosion and swarf in the ring main. These particles can be a combination of metallic, plastic and organic materials in sizes ranging from several millimeters to a fraction of a micron and can all be problematic when ingested by pneumatic components or mixed with process materials. The particle removal process takes place in the main filtration system after the compressor but depending on the serviceability of the filters and the level of filtration, some particles may remain in the airstream.

Once in the air stream, tiny particles can accumulate into solid masses at pipe walls and junctions and reduce the efficiency of the distribution system through reduced flow and pressure. Point of use filters or filter regulators can help to prevent particles getting into areas where they can cause problems but excluding the very smallest particles and dusts requires much more effective filtration to protect sensitive equipment or processes. Determining the effectiveness of the filtration employed or identifying the level of contamination can only be done through measurement.

Why do I need Particle Measurement?

Dust and particle elimination through increasingly fine levels of filtration is common place at the compressor plant but further contamination throughout the distribution system can occur, which makes point of use filtration and measurement essential for maintaining compliance with plant or international standards.

ISO 8573-1 defines a range of purity classes for compressed air including solid particles. ISO 8573-4 is the section that defines measurement methods for particles and ISO 8573-8 covers test methods by mass concentration.

Measuring the particle concentration can be achieved through laboratory analysis of diaphragms that have been fitted into the system at suitable test points. The process of using microscopy to determine the particle sizes and concentration is expensive, time consuming and doesn’t allow instant results for the test engineer.

A frequently used method is to employ laser particle sensors to measure an air stream directly and this can give both accurate and fast results. Laser particle sensors can be permanently mounted for continuous monitoring or used as portable test instruments for plant audits and quality verification.

Monitoring the particle sizes and concentration is a key indicator of system health that can be used to guide maintenance tasks as well as contribute to plant compliance with the purity classes set in ISO 8573-1.

Laser Particle Sensors