Water & Wastewater Treatment Magazine
Issue link: https://fhpublishing.uberflip.com/i/877922
32 | OCTOBER 2017 | WWT | www.wwtonline.co.uk The Knowledge Pumps and pumping systems Electric submersible dewater- ing pumps offer portability, easy handling and are gener- ally available in a power rating and capacity range that make them well suited to mining, construction and ground water control applications including emergency duties. For in- stance, flooding, construction and mining sites or instances where a pump with a small footprint is needed, such as when draining a sediment tank. They are also useful for ap- plications where diesel pumps cannot be used, for example underground mining or where emissions are not allowed. Providing hours, and even days, of unattended dewater- ing pump operation, submers- ible 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. As they are sub-surface units they can continue working under ice in freezing conditions; as long as the pump is completely sub- merged. Where appropriate to the task, electric pumps offer environmental compatibility. For instance, quiet running is an essential feature of their performance when they are sited in populated areas or employed in night-time opera- tions. Extreme durability is also guaranteed as electric submersible pumps offer high- wear resistance. Meanwhile, the modular construction of these types of pump provides for simplified maintenance procedures. Some models can also be equipped with on-site servicing and parts replace- ment kits, including seals and impellers. Current manufacturers' medium to large capacity ranges offer maximum power ratings in the region of 54 kW and can typically manage flows from 225 to 16,500 litres per minute with a maximum head of 85 metres. These are the typical range; however, some higher-head pumps are avail- able on the market. In addition, electric submersible dewater- ing pumps used in the tough- est applications should be equipped with hardened impel- lers and to handle suspended solids, current supplier design has a clog-free impeller for solids of 8-12 mm dimensions. BenefiTs of elecTric suBmersiBle PumPs: l Continuous operation in all types of weather – with water temperature at up to 40°C l Compact dimensions, low weight and portability l Ability to handle abrasive materials and solids up to 12mm l High head capability l Environmental compatibility – quiet running in populated areas and night operations l Wide range of output power and low to high head specification options l Cost effective solution elecTric suBmersiBle PumPs Conclusion There is no one-size-fits all criteria for which type of pump works best in a given applica- tion – an electric pump might best suit a flood water removal situation but it may neces- sitate employing a diesel unit because of lack of access to mains power. Equally, diesel power may be ruled out be- cause of emission problems in an enclosed environment. 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/ma- terial mix to be pumped, and how long will the equipment need to run to complete the operation? In every case, making the correct pump selection will depend upon the physical parameters - the static head height, the required hose length and its diameter. It will need interpretation of equip- ment manufacturers pub- lished flow rate v head height performance curves to find the BEP (Best Efficiency Point), and thus the pump best rated to deliver this performance. What's more, there are also considerations to be made of friction losses and cavitation issues. So, overall, making the right choice is not a simple is- sue, but with expert guidance from equipment suppliers or renters it can be achieved satisfactorily. What is certain is that water industry plants cannot function without the ef- ficient use of pumps to ensure continuity and safety within their operations. l Note: Figures quoted are average values; actual specifica- tions of products may vary Electric submersible dewatering pumps offer portability & easy handling Smaller and lighter pumps are now being developed, as well as models that are easier to move and transport