Rotary Positive Displacement Pumps vs. Centrifugal Pumps: Which is Best?
Positive displacement pumps are commonly used to transfer fluids that are viscose, such as chemical or food ingredients. They are typically employed in applications that require precise measuring.
They function by switching back and forth strokes of a piston, diaphragm or helical rotation. They can transfer a certain volume for each shaft rotation.
Positive displacement pumps with the rotating sprayer
A positive displacement pump draws a fixed amount of fluid into the pump and then forces it out via an outlet valve. These pumps can transport liquids of all viscosities and sizes, ranging from thicker than water, to emulsions or sludges. These pumps can operate at high pressures and are ideal for applications that require precise dosing. They are also preferred for fluids containing solid particles or abrasives. The most common types of positive displacement rotary pumps are piston, diaphragm, gear and screw pumps.
Because these pumps do not make use of impellers, they are not as susceptible to the issues that affect centrifugal pumps, such as wear and cavitation. However, abrasive feed can still cause excessive wear to the components of certain positive displacement pumps. This is particularly true when rotary pumps use plungers or pistons to trap and displace fluid. Therefore, avoid abrasive feed as much as possible.
The discharge that pulsates is another problem that is associated when using rotary pumps with positive displacement. Cavitation and noise may result from this, and it can damage the pipes. However, this issue can be minimized by using multiple pump cylinders and pulsation dampers.
Another benefit of a rotary positive displacement pump is that it can typically self-prime. This is due to the tiny clearances that exist within the pump. It is essential to not let the pump be running dry for long durations because this can reduce its efficiency and life expectancy.
Positive displacement pumps that have a reciprocating pump
They draw and pressurize fluid using pistons inside a cylindrical. When the piston is moved between its sides, it entraps liquid between the inlet and outlet valves, causing the possibility of a differential pressure which overcomes the valve at the inlet to allow fluid to leave. In contrast to centrifugal pumps which are sensitive to changes in viscosity, positive displacement pumps maintain their flow rate independent of the pressure in the system.
The ability to work at a consistent pressure makes these types of pumps perfect for applications that require accurate metering and transfer, and also for abrasive or dangerous materials. Additionally, these pumps are self-priming, which decreases downtime and cost of labor because they do not require manual re-priming.
However, a drawback of the pumps is that they could continue to build pressure within the pipework of delivery until a source of relief reduces the pressure. This may be the pump or the liner, which can lead to excessive vibration and noise when in use. To mitigate this problem they require additional components like pulsation-dampeners to the pipework as well as discharge lines. Furthermore, the internal structure of these pumps tends to make them more expensive and difficult to maintain than centrifugal pumps. Their ability to handle dangerous or corrosive liquids and their ability to perform consistently even at low pressures overcomes these issues. These pumps are perfect for use in high-viscosity applications in the drilling industry, pharmaceutical and chemical processing industries.
Gear Pumps
In contrast to diaphragm pumps and gears, they don’t cause shear to the fluid. They are great for moving fluids with shear-sensitive properties including emulsions Microbial cultures, as well as food products. Gear pumps may bom ly tam truc ngang are ideal for liquids with a tendency to change viscosity.
They are very small and cost-effective. These pumps can be made out of stainless steel or other components. They have high efficiency levels of up to 85% or more. They are reversible meaning they operate in both directions to make sure that the entire contents of a hose are emptied. They also self-prime, which means they don’t require an external air supply. They are typically Atex certified (explosion proof) and are able to handle solvents.
The shafts are housed in sleeves that are bonded with a recirculating plastic providing lubrication. The recirculating polymer is produced through the pressure difference between the two gears. It is not recommended for them to dry out and must be properly lubricated to stop grinding of the gears. This may occur when the melt of polymer is too tough, or if the shear heat is too high.
The gears spin in opposite directions picking up the polymer, then transferring it to the edges of the meshed cogs. Lubrication grooves are included to ensure that the gears are in good condition. They are double or single jacketed and equipped with various seals – such as mechanical, gland packing/stuffing, or magnetic coupling if there is no seal.
Diaphragm Pumps
Diaphragm Pumps are one of the most flexible pumps in the world. They are able to be moved to any location. Just attach the liquid and air lines, and you’re good to go. They are capable of handling any application, whether it’s low viscosity spraying or massive solid handling.
Diaphragm Pumps contain two chambers of compressed air that expand and contract in alternating volumes. This creates the pumping effect. The pump can transfer, compress, and then evacuate fluids without need for lubricant.
During the suction stroke when air pressure is applied to the left diaphragm to transform it from flat to a convex shape and opens the inlet check valve and draws fluid into the pump. Then, as the shaft of the pump is moved to the right side, the right diaphragm changes from a concave shape to a convex shape and closes the check valve for outlet while fluid is pumped out into the discharge valve.
The air pressure is controlled by an input regulator. The pumps stop when the air pressure is greater than the pressure at which they discharge. The pump will not damage its own system pipes or. This type of high-pressure, air driven pump can achieve an ultimate pressure of 30 psi, however the actual pressure is less since the diaphragm can break over the pressure.
