Raw Water Intake Pumps for Process Cooling – Case Study

Raw Water Intake Pumps for Process Cooling – Case Study What is raw water abstraction? For a recent client we chose to provide pumps that would harness raw water abstraction from an open body of water. But what is abstraction? Raw water abstraction is the use of natural untreated water from open bodies. Any open body of water can be used, such as rivers, lakes, floodplains, excess groundwater, ponds, lochs, streams, and oceans which is often an economical water source for industrial use. As water can contain a variety of nutrients or contaminants ranging from minerals, ions, algae, particles, chemicals, bacteria, and parasites; consequently, it can require purification or treatment before industrial use or consumption. The Client/Application Background A client contacted us who were experiencing issues with their existing raw water intake pumps which were part of an aquaculture plant in a remote location. Their issues included: - The intake pumps were clogging, affecting the cooling of essential process equipment - The intake pumps were centrifugal design, and had to be dismantled for cleaning and blockage removal - Their duty/standby pumping arrangement was a single pump. Should that become clogged then plant operation would be stopped The use of raw water for process cooling provides various benefits. The two biggest benefits are: economic and environmental. An incident highlighted below shows the importance of a correct application. 'After recent water shortages in the UK, Thames Water discovered a data centre located within London using treated potable water for cooling. This led to public outcry and disapproval as water-saving measures were currently imposed.' As potable water is for human consumption, it requires far more processing. These associated processes add layers of engineering, which increase costs and environmental impact not required to undertake the application. There are various sources of water which can be used in a plant's process. As a comparison below you can see the cost, environmental impact, filtration requirements and how the quality can vary. 9 Raw Water Intake Considerations When constructing a raw water intake pipe in a plant there are 9 important considerations: Solid Handling and Filtration Often what’s drawn into the suction pipe can also pass through the pump. So careful consideration should be given to objects which may enter the inlet. Raw water intake screens can be used to screen out stones, aquatic life, or other objects. Over time these can become clogged and may need a backwash or manual intervention to clean. Sand Concentration Sand suspended within water, if pumped at high velocity, has the potential to damage pump parts. This can happen quickly to pumps fitted with soft mechanical seals. If sand is at high concentrations, it will very quickly wear pump parts. The solutions to this are a heavy-duty pump, a reduced pumping speed or slow working pump technology. Iron Content High levels of iron can be present in groundwater. This usually occurs in locations close to peat, clays, slurry pits, landfill, effluent discharge, and septic tanks. If pipework and pumps become exposed to air, it can cause the blocking and corrosion of pumps and pipework leading to pump stoppage. Tide or Water Levels Any pump selected for water intake has a required inlet pressure which must be met to deliver the performance required. If water levels vary on the intake due to tidal conditions or times of drought, this can affect the performance of the pump. Checks should be made regarding the minimum and maximum water levels. Additionally, having a pump that can operate at a variety of speeds will address times of lower water availability. Water Quality and Metal Recovery If raw water is being used as a source for potable water, the quality of drinking water derived from it will depend on the source water quality. Raw water sources are varied and can contain bacteria, parasites, legionella, chemicals, or metals. Considering this, water treatment should take place if water will come into contact with humans during normal plant operation or maintenance. There can also be opportunities for metal recovery in areas where water abstraction is performed close to areas of mining. Water Hardness Hard water is water which contains high ion or mineral deposits from chalk, limestone, or gypsum. This can have a detrimental effect on pump parts. Parts can become coated causing design tolerances to be reduced, hydraulic performance to be altered or units to seize. The addition of water softeners can prevent this. Aquatic Life Government guidelines may need to be followed if looking to undertake water abstraction to safeguard aquatic life. Protected species may include eels where maximum pump speed is regulated, or fish-friendly pumps being a requirement. When units are installed at seawater intakes, consideration should be given to mussels. Mussels are known to bio-fowl intake screens, blocking them, and starving the pump of required inlet flow, which affects the performance. Having a backwash filter can prevent this. Abstraction Limits The amount of water abstracted from open water sources is regulated to ensure that ecological systems or other users are not affected. If you plan on using more than 20M³ a day you will need a water abstraction licence. Harsh Environment Equipment can be in remote, hazardous, and hard-to-access areas. This could be humid saline environments or at locations far away from water intake sources. Having equipment specified for the environment it is situated in will ensure a problem-free pumping process. Our SolutionBoyser FMP50 Peristaltic Pump For our solution, we looked at the client’s requirements and existing issues. We also took into consideration future scenarios and planned to safeguard against them. We chose two non-clog peristaltic pumps (NRFMP50BA32VSD). The pumps are motor mounted inverters, capable of delivering between 1.5–5.2M³H, at constant pressure up to 8 bar. This meant regardless of cooling demand, the pump would deliver enough water through cooling loops for it to cool equipment with an operating range from 20-70Hz. The pumps selected are also self-priming, which was a big upgrade. This is due to the intake pipeline being immersed in the sea and subject to tidal fluctuations. A pump which was self-priming meant that the pump could operate above the water intake without having to be re-primed. Using a peristaltic pump as an intake pump also meant that intake screening was not required. This eliminated the need for a backwash system and manual intervention. Unlike centrifugal pumps which are used for intakes, the pressure generating capability of peristaltic pumps does not diminish when speed is reduced. Peristaltic pumps are well known for being of a non-clog design. This is down to their internal design which ensures particles and solids do not remain in the pump during working motion. The integrated VFD allows the user to alter the speed of the pump to match raw water intake demand or have it remotely controlled via a panel via the 4-20ma onboard control. They can also be reversed should a blockage occur, and if operated in remote areas, have the ability for a leakage sensor to be fitted ensuring pump operation is stopped should the hose leak. This unit was fitted with DN40 Stainless steel flanges for seamless connection to pipework. This aquaculture plant now has a robust heavy duty easy to maintain intake pump, which will stand the test of time.

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