New development in particle counters

Paul Boughton

The German company Pamas develops, manufactures and distributes Automatic Particle Counters for fluid contamination control. The product range includes measuring instruments for long-term condition monitoring of liquids such as hydraulic or lubricating oil and for contamination analysis of particulate matter in water, pharmaceutical suspensions and many other fluids.

Designed specifically for stationary online measurement of dark fluids, Pamas has developed a new particle counter: the Pamas S50DP. With its integrated dilution system, this online particle counter automatically dilutes dark sample fluids prior to measurement and thus reduces the sample’s turbidity level.

Fluid cleanliness (e.g. of oil, water or fuel) can be monitored through optical particle counting. An automatic particle counter detects and measures particulate contaminants in the fluid. Optical particle counters work with the help of light. In optical measurement proceedings, the light beams through the liquid.

The electromagnetic waves may be deflected or absorbed when meeting the particles in the measuring cell. The light effect on the particles is analysed with the help of a previously calibrated optical electronic hardware. The measuring result provides information on the number of particles per millilitre and on the size of each single particle.

This technique has its limitations. For example, in case of dark fluids, the sensor’s laser beam is not able to penetrate the medium. To enable particle counting of dark fluids, the sample fluid’s absorption needs to be reduced before analysis. The optical particle counting technique is also difficult to use if the level of contamination greatly exceeds the sensor’s maximum particle concentration level, if the fluid contains undissolved additives or if the sample’s viscosity is too high for an accurate measurement. In such cases, sample dilution with solvents helps to achieve reliable measuring results.

For batch and bottle sampling, the dilution agent can simply be added manually. However, if operating fluids are analysed online, an online particle counter is directly integrated as a fixed installation into the system (e.g. hydraulic/lubricating oil system or fuel tank). The sample liquid is drawn from the system via a bypass line and analysed directly online during operation.

To enable continuous condition monitoring of difficult fluids such as the above mentioned ones, Pamas has developed a new online particle counter: The Pamas S50DP online particle counter has an automatic dilution system that adds a programmable amount of solvent online to the difficult sample. The system’s inner structural design ensures that the solvent and sample fluid are thoroughly mixed. This helps to get a good homogeneity of the mixture and hence accurate, repeatable measuring results.

The Pamas S50DP online particle counter is well suited for the analysis of fuel containing free water: without prior dilution, free water in fuel would lead to false measurements. The diluting agent increases water solubility in the sample, so the water drops are no longer detected.

Another application example are highly contaminated liquids. Without prior dilution, the coincidence error quote of such sample fluids would be too high due to particle over concentration.