In a submersible pump, the drive motor and electrical components are completely enclosed in a watertight and sealed compartment that enables the unit to operate while totally submerged. Because of its proximity with the liquid being pumped, less energy is required. As it is easier to push rather than ‘pull’ liquids, the submersible pump uses direct pressure to force the fluid through the hose as opposed to utilising above-ground suction power. Factors such as site access, excavation depth or height can also create suction lift challenges for most types of above-ground pump.
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. For instance, 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 suited for applications where diesel pumps cannot be used, for example in underground mining environments or where emissions are not allowed
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. Submersible pumps have been known to run up to 10,000 hours without attendance (although 2,000 hours is the recommended service interval). As they are 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. For instance, quiet running is an essential feature of their performance when they are sited in populated areas or employed in night-time operations.
Superior build quality is a major benefit of more recent electric submersible pump designs, which can be equipped with valued added features such as sealing systems, adjustable wear-resistant nitrile rubber diffusers and hardened high chrome clog-free impellers to enhance durability. The lifetime of a submersible pump can be further extended if it is fitted with advanced features, such as temperature gauges, to prevent the motor from overheating. Another feature is rotation and phase failure protection technology. This technology prevents the risk of the impeller rotating in the wrong direction and will stop the pump in the event of phase failure
Positioning a pump into water in a safe and efficient manner is critical to achieving straightforward dewatering operations. For this reason, manufacturers are striving to develop submersible pumps that are increasingly light and easy to handle; with smaller models now available that weigh just 9 kg. You can even achieve a flow of around 1300 litres per minute with a pump that only weighs 20 kg. Part of this reduction in weight is down to the fact that electric-driven units are increasingly being constructed with aluminium bodies that are made to resist and reduce the amount of corrosion that can form. This results in easier handling, installation and servicing, which makes a world of difference when a user is on the water’s edge and needs to start pumping quickly.
For ease of maintenance, it’s advised to consider submersible pumps based on modular design principles. This helps to simplify the separation of major parts and provide easy access to electrical components. Ideally, all stainless steel fastenings should be the same size so that one tool can be used to change seals, impellers, and other parts in a matter of minutes. Some models can also be equipped with on-site servicing and parts replacement kits, which are essential for remote operations.
Current 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. However, higher-head pumps are also available on the market. For tougher applications, electric submersible dewatering pumps can be equipped with clog-free hardened impellers, with some units capable of handling suspended solids of up to 50mm dimension; dependent upon the model and specification.
Pump operation is not about pumping water at any cost and it’s important that energy efficiency isn’t ignored. For this reason, electric submersible pumps are now being fitted with high efficiency electric motors, which require a reduced start current and, in some cases, can consume up to 20 per cent less energy than previous models.