Water & Wastewater Treatment

WWT June 2017

Water & Wastewater Treatment Magazine

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Page 27 of 47

28 | JUNE 2017 | WWT | www.wwtonline.co.uk 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 fl uid handling system, such as a blockage or restriction. 3 Perform regular visual checks Analyser functions and readings should be thoroughly checked to ensure they work at optimum effi ciency. 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 fl ow should be performed as regularly as possible. It's 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 aff ecting the sample. If a fi lter is fi tted prior to the analyser, there is also the possibility that some important parameters may be being fi ltered out. 6 Replace components regularly Follow the manufacturer's recommendations regarding the replacement of any key components. Depending on the type of analyser being used and its application, consider changing parts such as tubing, measurement cells and seals and diaphragms on a yearly or bi-annual basis. 7 Create a maintenance routine Given the diverse range of parameters that are measured in water and waste treatment processes, it is diffi cult to set a universal rule when it comes to setting the frequency of maintenance checks. In most cases, it is possible to create a maintenance routine by monitoring the nature of past breakdowns with any issues that have been recorded, such as fouling, abrasion or measurement variations. By using these as a guideline, it will then be possible to create a maintenance routine that can help to safeguard against 4 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 reagents, with potential failures arising if the reagents are not fi tted properly, if tubing is blocked or restricted or if the reagent lines were not properly primed. Failure of a routine calibration can also be symptomatic of issues within the analyser, such as blocked tubes and valves, leaking seals or contamination of the reference standard. 5 Check the sensor It is worth checking analyser systems that are in direct contact with the process, as sensors can become obstructed or damaged as they o en bear the brunt of any adverse conditions. In waste water treatment processes in particular, sensors can quickly become fouled by the build-up of organic matter or subjected to abrasion by sediment. The accuracy of electrochemical sensors used in dissolved oxygen monitoring applications, for example, can quickly become impaired due to fouling of the sensor membrane. The knowledge: analyser maintenance future occurrences. In addition, information from the device manufacturer should also be taken into account in order to further optimise performance. 8 Consider the lifecycle Another factor that can aff ect the way that an analyser is maintained is where it sits in its lifecycle. This should take into account the model, age and make of the analyser. Models that are at the start of their product lifecycle will be well- supported, with ready spares availability. This may diff er for models from older product ranges, where spares and the expertise to service them may not be as readily available. Dealing with reputable manufacturers can help to minimise this, as they are more likely to be able to support older products or else to recommend a suitable upgrade path with an alternative replacement.

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