What You Need to Know About Submersible Pumps
A submersible pump, like any other pump, is used to move liquids from one point to another. The major difference between a submersible pump and any other type is that it is completely submerged in the liquid that it is required to pump.
These pumps can be used in many different applications. They also have their advantages and disadvantages, which must be taken into consideration when making a pump selection.
What is a Submersible Pump?
As the name suggests, a submersible pump is designed to work with the entire assembly, consisting of pump and motor, fully submerged in the liquid or medium to be processed. This type of pump has a hermetically sealed motor which is close-coupled to the pump body. The water-tight enclosure around the motor is usually filled with oil to protect it from damage by preventing the entry of any liquid which may cause a short circuit.
A submersible pump operates by pushing, as opposed to drawing, liquid during the pumping process. This is extremely efficient because the pump uses the head of liquid in which it is submerged to operate and no energy is spent in drawing the liquid into the pump. The motor is cooled by the liquid around it, preventing overheating.
Many submersible pumps in the oil and gas industry operate according to the Electric Submersible Pumping (ESP) principle. This is a cost-effective method of lifting large volumes of fluids from deep wells. The motors used in an ESP system are designed to operate under high temperatures and pressures. They require special electricity cables and can be expensive to run.
Advantages and Disadvantages of Submersible Pumps
The submersible pump offers several major advantages over other types of pumps:
Priming: They don’t have to be primed. They are self-priming because they operate below the surface of the fluid being pumped.
Cavitation: Because they are fully submerged, submersible pumps are not prone to cavitation. This can be a problem with centrifugal pumps and other types of positive displacement pumps.
Efficiency: A submersible pump has the head pressure of liquid on the suction end to help it operate. It doesn’t need to use as much energy in drawing liquid into the pump and is, therefore, more efficient.
Noise: Being submerged, these pumps are very quiet in most applications.
There are also some disadvantages to contend with:
Accessibility: Submersible pumps are often not easily accessible for routine inspection or maintenance, especially in deep well applications. This makes it difficult to perform preventative maintenance and in many applications pumps are left to run until they break down and need to be replaced.
Corrosion: Prolonged exposure to a liquid of any sort will lead to corrosion. Submersible pumps are often used to handle liquids that are corrosive and abrasive. Seals are especially prone to corrosion, which leads to leaks and damage to the motor. To counteract corrosion these pumps need to be made of corrosion-resistant material, which can make them more expensive than other types of pumps of the same capacity.
Wherever possible, submersible pumps should be inspected as often as possible. In this way, any necessary repairs can be carried out to prolong the life of the pump.
Submersible Pump Applications
Submersible pumps are generally very reliable and able to operate well in harsh conditions. They are made with robust iron castings and protected against corrosion with coated epoxy.
These are some of the main applications for these pumps:
Wastewater: Submersible pumps are widely used in the grit and wastewater industry. They are often used in pump and lift stations because they are compact and are less costly to install than other pumps.
Sewage treatment: This application requires submersible pumps, such as grinder pumps, that can transport solid material without obstruction from entry to discharge. These pumps often reduce sewage material to particles for easier handling and downstream treatment.
Sump pumping: Submersible pumps are often used to remove a liquid from a particular area at no great depth. This could include emptying tailings ponds from mining operations or pumping out water from a building following flooding.
Dredging: These pumps are used by port authorities to dredge a harbor. They have to be specially designed to handle liquids with a high solid content.
Wells: Water wells and boreholes employ these pumps to lift water to the surface. The oil and gas industry uses ESP submersible pumps extensively to lift oil to the surface from deep wells.
Mining: Mines use ESP submersible pumps that are designed differently from those used in the oil and gas industry. They have to contend with severe conditions because mine water is highly acidic and carries suspended solids.
Marine applications: Submersible pumps are used by all seagoing ships to deal with onboard flooding and barge unloading.
Submersible pumps can be truly indispensable. In some of these cases, industries would not be able to operate without them.
Submersible pumps have a wide range of ratings for capacity, pumping speed and energy use. Some of them can be used interchangeably for a variety of applications when pumping thin liquids. More viscous liquids and pumping applications at greater depths require stronger pumps that are designed to enable them to function properly.
Liquids with a high solid content, corrosive and abrasive fluids pose a particular problem, as do liquids containing solid material that can cause damage to a pump. Each application poses its own challenges. To ensure you have the right pump for your application, contact a leading submersible pump manufacturer to discuss your needs.
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