Washing Water Analysis with UV spectrometer allows to monitor the results of washing process during and after the cleaning.
The washing water analysis means taking samples from the washing water effluent during the washing process and analyzing the sample with a UV spectrometer. This allows a fast and efficient control of the cleaning process without interruption and confined space entry.

The underlying principle is the concentration measurement of cargo remainings in the wash water.
An effective cleaning method will remove cargo clingage from tank and pipeline surfaces. Thus the washing water will contain a certain amount of the cargo.
A small quantity from the wash water sample introduced into the UV spectrometer delivers a curve (UV Wavescan) that indicates both, the magnitude of the concentration and the type of the cargo. The height of the peak indicates the concentration, the shape of the curve is typical for the cargo that was in the tank.
Significant conclusions are possible from interpretation of this information.

Blue line: Sample after 15 min shows a significant concentration of previous cargo. This indicates that the cargo is transported by the washing water out of the tank.
Red line: After 30 min a remarkable reduction of the concentration is observed.
Yellow line: A nearly flat line after 45 min indicates that no cargo is transported anymore out of the tank.
The dashed lines are standards that are available for many cargoes. Comparison with those allows instantaneous assessment of the removed quantity. Sampling in regular time intervals allows monitoring of the progress. In this example the cleaning step can be finished after 45 min. No cargo is removed anymore. If this is water soluble cargo it means the tank is clean. If this a non-water soluble cargo it means continuation will not improve anything. It could mean go to the next step.