May 2019

reaction needed for an accurate measurement to take place. As such, it is important to ensure that reagents are replenished as soon as they are exhausted. Checking reagent consumption regularly will help you predict the best time to carry out a changeover. As reagents have a shelf life, check the expiration date before exchanging the used reagent with the new one. In addition, regular maintenance will also help to show whether the reagent is being consumed at the rate that should be expected for the application. Under or over consumption can be indicative of a problem in the analyser’s fluid handling system, such as a blockage or restriction. Perform regular visual checks Analyser functions and readings should be thoroughly checked to ensure they work at optimum efficiency. Checking for leaks (pipe connections and tubing and liquid handling components), liquid levels (reagents, calibration and cleaning solution bottles) and potential obstructions to the sample flow should be performed as regularly as possible. It’s also worth remembering that erratic readings on the analyser display unit may not be indicative of a fault with the transmitter, but rather external factors such as unexpected changes in water quality. Where doubts arise, it is advisable to check the analyser’s historical log to compare the period during which erratic readings took place against the known operating conditions. In addition, always check the analyser’s high and low measured values. Any discrepancies in the measured values may be symptomatic of a number of potential issues. These could include incorrect calibration or variations in ambient temperature and humidity conditions that could be affecting the sample. If a filter is fitted prior to the analyser, there is also the possibility that some important parameters may be being filtered out. Check calibration Ensuring that your analyser is properly calibrated will have a material impact on its ability to deliver continued measurement accuracy. Errors can arise when changing A s the front line in any water quality measurement scheme, continuous water quality analysers need to be kept in good working order to provide accurate, reliable and repeatable performance. Tightening environmental legislation, coupled with customer expectations of quality and availability are seeing continuous water analysers being used to measure an extensive range of parameters, from dissolved oxygen in aeration processes through to chlorine and turbidity. Capable of taking ongoing readings which can be automatically relayed to a central monitoring system, continuous water analysers help to eliminate the delays and added uncertainties associated with extractive testing methods. Despite their advantages, however, the performance of continuous water analysers is only as good as the condition of the analyser itself. With the introduction of ever more stringent standards by the UK Environment Agency, it is particularly important to maintain analysers to the highest possible levels as a matter of best practice. In the event of a water quality incident occurring, operators must demonstrate that their monitoring and measurement equipment was being correctly maintained in accordance with recognised best practice. The following provides some recommendations for measures that can be put in place to help ensure continued effectiveness. Initial warning signs Many of the latest generation of analysers incorporate self-diagnostic features and alarm capabilities to warn when something is wrong. Although these signals are useful in determining when maintenance needs to be performed, it is nevertheless advisable to have a preventive maintenance regime in place to help extend the life of the instrument. Check reagent levels Reagents are crucial for producing the chemical Focus on: Water & Waste Management Energy, the Environment & Water May 2019 www.pwemag.co.uk Plant & Works Engineering | 35 Mike Sparrey, water & utilities sales manager for ABB measurement & analytics in the UK, puts forward some tips for looking after water quality instruments that can help to minimise potential problems and extend service life. Keeping continuous water quality analysers functioning