Positive Displacement Pumps are utilized for transferring fluids with high viscosity such as food ingredients, fuels or even chemicals. These pumps are commonly employed for applications which require precise measuring.
The piston, diaphragm or helical-rotor is moved forward and back in a cycle. They can transfer the same amount of liquid with each shaft revolution.
Positive displacement pumps that have an rotary, nozzle
Positive displacement pumps pull a particular amount of fluid into the pump before forcing it out using the outlet valve. These pumps can transport liquids of any viscosity and sizes, ranging from thicker than water to emulsions and sludges. They can operate with high pressures and are suitable for applications requiring precise dosing. They are also preferred for fluids that contain hard particles or abrasives. Common types of Rotary positive displacement pumps comprise diaphragm, piston, gear rotary, and screw pumps.
These pumps are less prone to issues like cavitation and wear that can occur with centrifugal pumping systems. However, abrasive feed could cause excessive wear on the components in certain positive displacement pumps. This is particularly true for rotary pumps that use plungers or pistons for the purpose of capturing and dispersing fluid. Avoiding feeds with abrasive particles wherever possible.
Pulsating discharge is a different issue when using rotary pumps with positive displacement. This could cause noise and vibration in the system and cavitation, which could damage pipes. However, this can be minimized by using multiple pump cylinders and the use of pulsation dampers.
A rotary positive displacement pump may also self-prime. The pump has very small clearances. But care must be taken to ensure the pump is not run dry for prolonged durations of time since this can reduce the efficiency and lifespan of the seal.
Positive displacement pumps that have an reciprocating pump
By using pistons in the cylinder which create pressure and draw fluid. When the piston rotates around, it holds a volume of liquid between the outlet and inlet valves, causing an increase in pressure that overtakes the valve at the inlet to allow the liquid to flow out of. In contrast to centrifugal pumps which are sensitive to viscosity changes and positive displacement pumps keep their flow rate independently of the pressure of the system.
These pumps are ideal for use in applications that require accurate metering or transfer of materials such as abrasive and dangerous substances. These pumps also self-prime, that eliminates the requirement to manually reprime.
But, one drawback to these pumps is that they may continue to build pressure within the pipework of delivery until an event relieves the pressure, which may be the pump itself or the liner, leading to a lot of noise and vibration when in use. In order to mitigate this, these pumps typically require accessories like an acoustic damper in the pipework and discharge line to ensure safety and reliability. They are also expensive to maintain and costly because of their internal design. Nonetheless, their capacity to deal with corrosive or hazardous fluids, as well as their capacity to perform consistently at low-pressure settings, offset these challenges. These pumps are perfect for high viscosity requirements in the oil drilling, chemical processing and pharmaceutical industries.
Gear Pumps
Gears, unlike diaphragm pumping they do not shear the liquid. They are great for moving fluids with shear-sensitive properties like emulsions, Microbial cultures, as well as food products. Gear pumps are ideal for liquids that have the tendency to change their viscosity.
They are extremely small and cost-effective. They are constructed from a range of materials like stainless steel and have a high level of effectiveness, with 85 percent or more being achievable. Reversible, they are able to be operated in any direction to drain the entire contents of the tube. They self-prime, and don’t need external air. They are usually atex-rated (explosionproof) and can handle solvents.
The shafts are contained within sleeves bearing on each other with a recirculating polymer providing lubrication. The recirculating plastic is formed through the pressure difference between the two gears. They are only able to run dry for a certain amount of time and should be kept clean and lubricated to prevent gears galling. This could happen in the event that the melt of polymer is too hard or shear temperature is too high.
Gears are rotated in opposite directions, absorbing the polymer. The polymer is then conveyed to the outer cogs. Lubrication grooves are incorporated to keep the gears well-lubricated. They can be double or single jacketed and are fitted with various seals – such as sealing, mechanical, gland packing/stuffing or magnetic coupling when no seal is present.
Diaphragm Pumps
Diaphragm Pumps are the most flexible pumps available worldwide tu dieu khien may bom. They can be easily moved to any location. Just connect the air and liquid lines, and you’re set to go. They are capable of handling every kind of application, be it low viscosity spraying or large solid handling.
The Diaphragm Pump has two air chambers, which are supplied with compressed air whose the alternating expansion and contraction of volume causes the pumping effect. A hermetic seal between the diaphragm drive mechanism, and compression chamber allows the pump to transfer to, compress and expel a medium without requiring the use of lubricants.
In the suction process, air pressure is used to convert the left diaphragm from flat to convex, which opens the inlet valve and allows fluid to flow into the pump. Then, the pump shaft shifts to the right and the right diaphragm transforms from a concave to an convex form and shuts the outlet check valve as the fluid is pumped through into the discharge valve.
The pressure of the air is controlled by an input regulator. If the air pressure exceeds the discharge pressure, the pumps will stop. The pump will not damage its own system pipes or. This type of high-pressure air driven pump is able to reach the ultimate pressure of 30 psi, although the actual maximum attainable is lower as the diaphragm will break above the pressure.
