The first consideration is the nature of the liquid being pumped as this has a major impact on the type of pump. Important factors to consider include general composition, the concentration and size of suspended particles as well as the liquid’s pH level, temperature, and chemical content. For example, is it water with fine particles or a much thicker fluid, and how aggressive a media is it?
One of the most important performance considerations is the flow requirement, i.e. how much liquid needs to be moved and how quickly? For example, a pump with a maximum flow rate of 138m3/h (608 US gpm) (such as Atlas Copco’s WEDA D50) will remove water from a pool that is 36m3 in 15 minutes (158 US gpm in 15 minutes). However, a pump with a flow rate of 350m3/h (1,541 US gpm) (such as the WEDA D80) would empty the pool in just 6 minutes.
Over what height does the fluid need to be pumped and how far does it need to travel? This will have an impact on the pressure that the pump needs to deliver to ensure it can pump efficiently and reliably. The greater the distance the water needs to be pumped, the more friction is created, which results in pressure loss from the pump. Pumps need to overcome gravity resistance as well as friction losses. When specifying, check the manufacturer’s published pump curve, which shows head height against flow rate, to ensure it covers the required duty point.
If mains electricity is available, an electric pump will be the best and most efficient choice in most cases. Electric submersible pumps – such as Atlas Copco’s WEDA pumps – are the simplest, most energy-efficient and most economical approach, providing high power in light and compact packages. If the site is remote and prone to a fluctuating mains supply, consider a pump that has the motor and starter equipped with inbuilt electrical protection against varying voltage, phase failure and human error.
Apart from the type of fluid to be pumped, energy source, and flow and volume needs, other factors need to be considered when choosing a submersible pump such as energy economy, durability and servicing expense for each pump offered. Making the right choice is not a simple decision, but with expert guidance it can be achieved satisfactorily.