The principle measurement techniques used for on-line continuous measurement of produced water are video microscopy and fluorescence. Both these techniques use optical measurements and as such are prone to fouling.

Traditional methods of cleaning include use of surfactants, chemicals, back flushing with water and even manual cleaning – all requiring operator intervention and/or consumables.  Advanced Sensors uses patented automatic ultrasonic cleaning for its analyzers.

Sensor Cleaning

Both the in-line probe and side stream formats are fitted with ultrasonic cleaning. A sound wave is passed along the sensor head and through the sapphire window. Cavitation on the surface of the window causes tiny bubbles of water to burst, effectively jet washing the sensor head. The diagram below shows how this works in the probe.

As every produced water setup is different, the intensity and frequency of the ultrasonic bursts can be varied to cater for the effects of different concentrations, oil types, flow rates and temperatures. Each analyzer is set to autotune its output frequency periodically to ensure optimum performance.

Sample Homogenization

With the side stream version of the analyzers, use of the ultrasonic cleaning has an added benefit. When the sample valve is closed, use of the ultrasonics ensures that the oil particles are broken down to a standard size and distributed evenly around the sample chamber.

A representation of the ultrasonics at work is shown below.

Creating an homogenised sample in this way allows Advanced Sensors to cater for any variance in fluorescence caused by fluctuations in oil droplet size.