Positive displacement and centrifugal pumps are the two most common types of pumps. What's the difference between the two?
A centrifugal pump is a pressure-creating device. Centrifugal pumps are used to transport fluids by converting rotational energy driven by some sort of motor or engine into energy moving the fluid. The fluid enters the impeller of the pump by the rotating axis, where it is accelerated by the impellor towards a diffuser or scroll. As pressure goes up, flow goes down in direct correlation.
A positive displacement pump is a flow-creating device. It transports fluids by trapping a fixed amount of the liquid and forcing it into the discharge pipe. It moves fluid at the same speed regardless of the pressure on the inlet end. The movement is started by two or three spindles that move in opposite directions of each other; pumping and thus displacing the liquid.
How do centrifugal pumps work?
The most popular type of pump in use today is centrifugal pumps. They are commonly used to transport low viscosity fluids through a piping system. There are many centrifugal pump designs and configurations, but all work on the same basic principle. They convert velocity to flow and pressure.Fluid enters the pump and is propelled as it flows outwards through the vanes to a volute by an impeller. The fluid exits the pump at a higher pressure. The kind of impeller used by centrifugal pumps can be used to identify them.
Radial flow centrifugal pumps are one of the most popular. To transport fluid, they use a revolving impeller that produces a vacuum. To lower pressure at the intake, this fan-like impeller spins within the pump housing. The fluid is then pushed to the outside of the housing, raising the pressure to the point where it may be discharged.
A curved propeller-shaped impeller is used by axial flow centrifugal pumps. They pull fluid into their axis and send it out the opposite side through the impeller.
Centrifugal pumps are utilized in a variety of sectors, including water, wastewater, petroleum, and petrochemical pumping. About 60% of all rotating equipment in the world are pumps, and of those, about 85% are centrifugals!
What are positive displacement pumps and how do they work?
A positive displacement pump moves a fluid by repeatedly enclosing a fixed volume, with the aid of seals or valves, and moving it mechanically through the system. The pumping action is cyclic and can be driven by pistons, screws, gears, lobes, diaphragms or vanes.
Positive displacement pumps are classified according to the fluid-moving mechanism they use.
Rotary positive displacement pumps uses a revolving mechanism creates a vacuum, which draws in and captures the fluid. Gear, screw, vane, peristaltic, rotary lobe, and progressive cavity pumps are all common examples. Progressive cavity pumps are used to transport very viscous fluids or those containing particles, such as dirt, grit, or sludge, in difficult applications.
Reciprocating positive displacement pumps use one or more oscillating pistons, plungers or diaphragms. Valves restrict the fluid’s motion to the correct direction. Reciprocating positive displacement pumps are typically used for applications that need to maintain low flow rates against high resistance. Some may be used to pump highly viscous and heavy fluids, like sludge and slurry. Diaphragm valves are often used when pumping toxic and hazardous fluids.
Linear positive displacement pumps have been used to draw water for ages all throughout the world. Examples include rope pumps and chain pumps.
Whether you need a centrifugal or positive displacement pump, choosing the right one for your application can be tricky. Let our team of Experts in GIL Automation help - contact us today!
