Wednesday, April 18, 2012

Submersible Pumps

 A submersible pump is a type of hermetically sealed pump device that operates by pushing, rather than pulling, water during its pumping process. It is able to function in this manner because, like the name suggests, the pump is fully submerged in the liquid to be pumped. This allows the pump to be lowered down into a deep hole for pumping needs without running into problems like pump cavitation, which can damage moving parts by developing vapor bubbles. Submersible pumps are used in a wide variety of industrial and commercial use applications.

Submersible Pump Design

Submersible pumps can feature a single stage or multiple stages. Each stage consists of a motor in a casing, closed with mechanical seals to prevent leakage. The motor is connected to a cable that generates power to run the motor, and the casing extends to some sort of pipe or hose leading to the surface. Submersible pumps can be connected to various types of pipes, flexible hoses or wires, depending on the job and the liquid being pumped.

The submersible pump casing can be composed of different kinds of metals, like chrome or stainless steel, or polymers. The most important aspect of the casing is that it is hermetically sealed. If any liquid were to leak into the casing, the motor could short out easily and pose high repair costs. Some casings are fitted with double mechanical seal construction for more strenuous jobs. The cable powering the motor is usually 50 feet in commercial use applications and can be much longer in larger scale industrial situations, such as oil wells. Many casings are also affixed with a float switch, which automatically activates the motor when the pump is fully submerged.

Submersible pumps come in various strengths, both in energy use and pumping speed. Most submersible pumps are rated as effective for a wide variety of liquids, but more viscous liquids at greater depths pose pressure problems that require stronger pumps for proper function. Additionally, some jobs can feature random bits of solid detritus and debris in the liquid, so it can be important to choose a submersible pump rated capable of handling solids. Generally, a submersible pump capable of handling solids will feature an agitator or a spray hole to mix solid particles into the liquid and make it easier for the machine to pump them out of the ground.

Submersible Pump Function

Many submersible pumps operate under the principle of Electric Submersible Pumping (ESP). This is achieved by lowering flowing pressure, which decreases the pressure at the bottom of the shaft in which the submersible pump sits. The motor of an ESP system is also designed to function under high temperatures (up to 300 degrees Fahrenheit) and high pressures, so it is used in situations where very deep wells are common, such as oil wells. They can be relatively expensive to run because they require special electricity cables, although new developments have seen the introduction of coiled tubing umbilicals to supply energy to the deep motors. Additionally, electric usage is much higher than other submersible pump motors and the pump functions on tight tolerances that don’t allow for solids and sand.

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