INDUSTRY FOCUS WATER & WASTE TREATMENT A LONGER TERM VIEW ON MAINTENANCE


Graham Ward, sales and marketing director, at WES, discusses the potential risks and costs associated with the inadequate maintenance of chemical dosing systems, and offers suitable solutions in the form of proactive maintenance regimes and regular audits


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eliable and efficient chemical dosing systems are vital to the regulatory


compliance, safe management and cost- effectiveness of water and wastewater treatment operations. To optimise performance, avoid equipment failures and minimise related costs, these systems must be properly maintained. Over recent years, there has been an


increasing trend of ‘run-to-failure’ maintenance, where businesses operate reactively rather than proactively. This is the case in wastewater as much as anywhere else and with increased business pressures, reduced operating budgets and a growing backlog of urgent maintenance, proactive and preventative maintenance are becoming ever more challenging. However, no matter what the reasons


for operating a ‘run-to-failure’ maintenance programme, these regimes cost more in the long run. The costs include more downtime which leads to rising business costs, increased capital expenditures through reduced equipment lifespan and decreased availability of vital services. In the case of a breakdown in the chemical dosing equipment, there is the added potential for environmental harm and a company’s trade effluent consent being put at risk, if the composition of their wastewater doesn’t meet specific criteria. A deteriorating or faulty dosing system could also endanger the safety of employees or customers. When it comes to chemical dosing


maintenance, particular attention must be paid to the condition and performance of the dosing pumps. There are three broad types of metering pump, diaphragm, peristaltic and progressive cavity. Each has particular characteristics, advantages and drawbacks that affect maintenance: • Diaphragm pumps are very accurate


and have a long operating life, as the diaphragm is supported by hydraulic fluid rather than a mechanical linkage, but such systems also have additional maintenance requirements associated with the hydraulic components and fluid. • Progressive cavity pumps work well


with slurries, viscous materials and chemical products, but have a limited range of capacity adjustment and the


28 SEPTEMBER 2020 | PROCESS & CONTROL


complex geometry and requirement for extremely precise manufacturing tolerances means high capital and maintenance costs. • Peristaltic pumps feature a rotor


moving over a flexible tube which squeezes the chemical out. Robust and easily designed for tolerance to the pumped chemical, peristaltic pumps do however produce limited discharge pressures and require periodic replacement of the pump tube. Servicing goes a long way towards


extending the life of pumps, no matter which type is being used in the chemical dosing system. To move from a reactive to a more proactive maintenance schedule, the typical elements that need to be included in a regular programme are: • Checking pump calibration and


recalibrating where appropriate • Inspecting and replacing worn pump


components • Examining and clearing inline filters • Cleaning and removing blockages


from injection quills • Flushing sludge or solids from


chemical storage tanks • Identifying leaks in any part of the


system • Assessing condition of all equipment • Testing performance • Confirming bund security (this crucial


second line of defence against leakage is the focus of a WES white paper, ‘The definitive guide to chemical bunding in the water industry’) • Routinely reviewing the equipment’s


specification to ensure it is still suitable for the application It’s important to remember that


changes in operating conditions, such as the quantity and quality of wastewater received, or the types of chemicals used,


Experts at WES regularly carry out free, no- obligation, initial on-site surveys, so that operators and their maintenance teams have an understanding of the state of their chemical dosing equipment and what their short and longer-term maintenance needs might be


may necessitate a different set-up - the WES white paper on ‘Selecting the right chemical dosing system’ offers further advice on this. Specific maintenance needs vary


between sites, applications and the nature of the existing equipment. However, to determine what is required in each case, an audit of the chemical dosing system is advised. Regardless of the system’s age or manufacturer, a baseline needs to be set, so that the equipment can be measured against current standards and best practice. This not only highlights potential maintenance problems in the short term, but it also gives an idea of what upgrade work might be needed in the longer term to ensure efficient site operation. Experts at WES regularly carry out these


When it comes to chemical dosing maintenance, particular attention must be paid to the condition and performance of the dosing pumps


free, no-obligation, initial on-site surveys, so that operators and their maintenance teams have an understanding of the state of their chemical dosing equipment and what their short and longer-term maintenance needs might be. Following such a survey, an assessment of the equipment’s general condition is produced, along with recommendations on any repair or upgrade work needed. Based on these reports, WES can then recommend a service package appropriate to the process, the operational regime and the operators specific needs. A chemical dosing system must be


properly maintained to ensure it remains reliable, efficient and delivers 24/7. Shortcuts to maintenance will not only have cost implications, but potential environmental and regulatory ones as well. However, putting in place a robust servicing schedule is possible and with the help of experts such as WES, external support can be maximised in a way that suits any company’s maintenance needs and budget.


WES www.wes.ltd.uk


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