A submersible pump plays a vital role in moving water from one place to another since it can function even when totally immersed in water. The entire mechanism is meant to draw fluids through suction and push them out. Since different types of submersible pumps are available, users need to choose the right one based on their needs. One should consider some important factors while buying a submersible pump. The head and the flow rate are two major aspects that should be checked to buy the most suitable submersible pumps.
The importance of the head in a submersible pump
The vertical height to which water needs to be lifted by a submersible pump is termed the head. The pump needs to push up the water against gravitational force and friction in the pipes. The head height is also called total dynamic head (TDH). So, the pump should bear the capacity of creating enough pressure that can overcome the head and push out water.
- If the head is higher than the pushing capability of the submersible pump, it will not be able to perform as required.
- A more powerful submersible pump should be chosen for a higher head, as the resistance in pushing out water will be much greater.
- The head or the vertical height decides the amount of frictional force that a submersible pump needs to overcome. Hence, it directly affects the performance of the pumping system. If the head is not checked correctly, the pump will not function as expected, leading to the waste of money spent on buying it.
- The head height is comprised of the vertical lift and frictional force in the pipe. Hence, if water is 50 feet down in a 100-foot well, the head height will be 150 feet.
- The loss in frictional force depends on the length and width of outlet pipes, valves, and bends of pipelines. TDH counts the total friction loss, which is added to the height through which water should be raised to be pumped out.
- Only a very powerful submersible pump can fulfill the task of drawing up water for a higher head, as a huge amount of resistance should be overcome. For example, a deeper well needs a more powerful pump compared to a shallow well, as it has a much higher head (TDH).
The significance of flow rate in a submersible pump
The volume of water that should be pumped out by a submersible pump in one minute is termed the flow rate. It is measured as gallons per minute (GPM) or liters per minute (LPM).
- For a higher flow rate, a more powerful submersible pump should be chosen. This type of pump is required for the irrigation of large fields. It is also used in industries where accumulated water should be removed.
- A small submersible pump with a low flow rate is sufficient to take out water from a well or free up space from accumulated rainwater.
- The size of a submersible pump is directly related to its flow rate, which should be checked before buying this machine. If the pump is oversized than required, it will be a waste of money and electricity. On the other hand, an undersized pump will not be able to function as required.
- Normally, the flow rate is 10 – 15 GPM for domestic use, while it should range between 20 GPM and 30 GPM for industrial or agricultural purposes.
- The flow rate also depends on the size of the space from where water should be removed and the fixtures used there.
- It is essential to buy a submersible pump with the required flow rate to get the best result while using the pump.
Comparison between the head and the flow rate
Both the head and the flow rate determine the efficiency of a submersible pump. These factors also affect the fulfillment of the requirements of buying this pump. There are a few differences between head height and the flow rate in submersible pumps, which are listed below.
- The head and the flow rate are inversely related to each other. If the flow rate is high, the head height will be low. If the head height is the maximum, the flow rate may be zero or negligible, which is also termed the shut-off point. If a performance curve is drawn for a submersible pump, this relationship between its head and the flow rate can be illustrated clearly.
- If head height and flow rate do not match the functional requirement, the pump is more likely to be damaged soon.
- The head height does not depend on the density of fluid, while the flow rate depends directly on the density or quality of water.
Uses of submersible pumps using optimized head and flow rate
Submersible pumps with the perfect total head and flow rate can clear out water from low-lying water-logged places during heavy rainfall, mainly in basements of large buildings. Small-sized pumps are also used to draw water from wells in rural areas. Large submersible pumps are used in the irrigation of large fields, supplying water for the growth of crops. Wastewater and liquid sewage can be drawn out from septic tanks by using submersible pumps.
Conclusion
Both the head and the flow rate are very important factors that should not be overlooked while buying a submersible pump. Water transfer is carried out more efficiently only if the pump has the accurate head and flow rate. However, the selection of a submersible pump also depends on other factors apart from the head and flow rate.
The diameter of the outlet pipes, design of the pump, and material used for the pump body should be checked as well for satisfactory performance of the pump. The quality of fluid, the source of electrical power, and the environmental conditions should be considered as well.
It is best to consult an expert engineer regarding all these aspects before selecting a submersible pump. Then a satisfactory result can be guaranteed from this pump.