Hire and Rental News - November 2018

POWER & PUMPS The ins and outs of pump selection By Kevin Ennis – Redstar Equipment General Manager Sales, & David Buttigieg – Redstar Equipment Queensland Branch Manager. There are a multitude of choices when it comes to selecting a pump and much of the discussion should focus on application. So what are the things you should be considering when selecting a pump? Electric or diesel? When it comes to the choice of power sources, the debate is becoming increasingly prevalent. It is a decision that also applies to the choice of dewatering pump technologies. However, it is not a contest of technical supremacy. It is a common-sense selection process based on matching equipment performance and capability to all aspects of dewatering applications. Decisions should take into account critical factors such as required volume, flow/ head specifications and the constitution of water and materials to be pumped. Pump capability has to encompass the variables of operational conditions, site access, project duration, environmental issues, equipment autonomy and more. Here are five key considerations when buying or renting a diesel or electric pump. 1. Power and Flow Sturdily built for endurance and reliability, diesel powered centrifugal pumps are designed for handling high volumes of water discharge. The operating flow range is typically between 50 to 830m3h with a head of up to 51m. These pumps are able to operate in a high variable speed range, which enables them to cover different applications and flow/head combinations. By comparison, medium-to-large electric submersible pumps offer maximum power ratings in the region of 54kW and can typically manage flows from 225 to 16.500 litres per minute with a maximum head of 85m. These are the typical range; however, some higher- head pumps are available. 2. Solids handling Diesel driven centrifugal pumps can work with water that is clean or dirty as well as handle trash and fibrous materials. Their solids handling capacity can reach up to 76mm in size thanks to features such as semi open impellers and abrasion-resistant pump casings. Discharge connection diameters typically range from 75 – 200mm. In contrast, electric submersible pumps can handle abrasive materials and solids up to 12mm (higher with sludge pumps), although it’s recommended to equip them with hardened impellers when handling suspended solid. 3. Applications Electric submersible dewatering pumps offer portability, easy handling and are generally available in a power rating and capacity range that make them well suited to ground water control applications; including emergency duties. Fully automatic self-priming diesel centrifugal pumps are the de facto choice for delivering fast dewatering solutions to sites where an alternative power source, such as a generator or mains feed, is not available. They are the ideal solution for transporting or raising water with large abrasive solids in suspension. Transportation and storage handling at remote sites is simplified if these pump units feature forklift slots and a built-in lifting eye. 4. Performance Providing hours, and even days, of unattended dewatering pump operation, submersible pumps can meet the demanding requirements of raising water from great depths or lowering water tables even in the toughest environments; with some models capable of running for up to 2,000 hours without attendance. Sub- surface units, they can continue working under ice in freezing conditions; as long as the pump is completely submerged. Where appropriate to the task, electric pumps offer environmental compatibility, eg: quiet running. When equipped with a reliable engine and high capacity cooler, centrifugal pumps will ensure continuous and safe running even at high ambient conditions. Together with fuel autonomy of around 40 hours, continuous drainage is made possible even with significant volumes of air (snore conditions) thanks to an oil-free diaphragm vacuum pump’s automatic priming. Some pumps can be equipped with an extra-large fuel tank that allows them to run for longer periods without refuelling. 5. Maintenance and service Electric submersible pumps offer high-wear resistance and modular construction provides for simplified maintenance procedures. Some models can also be equipped with on-site servicing and parts replacement kits, including seals and impellers. With the exception of replacing wear parts and engine filters, maintaining centrifugal pumps is easy and simple, and they can include advanced controllers with data monitoring capabilities that flag up when service interventions are required. Conclusion It all comes down to the nature of the application and questions such as where is the site, how deep is the access point, what is the nature of the water/material mix to be pumped and how long will the equipment need to run to complete the operation? Making the correct pump selection will depend upon the physical parameters – the static head height, the required hose length and its diameter and interpretation of published flow rate v head height performance curves to find the BEP (Best Efficiency Point), and thus the pump best rated to deliver this performance. Visit: www.cfc.com.au There are a multitude of choices when it comes to selecting a pump 58 HIRE AND RENTAL NEWS • NOVEMBER 2018