Positive displacement pumps are commonly employed to transfer fluids that are viscose, such as fuels, chemicals or food ingredients. These pumps are commonly used in applications which require precise metering.
The diaphragm, piston, or helical-rotor is moved back and forth in an arc. They can transfer the same amount of liquid every time a shaft turns.
Rotary Positive Displacement Pumps
A positive displacement pump draws an exact amount of fluid into it and pushes it out using an outlet valve. These pumps can transport liquids with all viscosities that range from thinner than a drop of water to sludges or emulsions. These pumps can operate at high pressures and are ideal for use in applications requiring precise dosage. These pumps are preferred when working with fluids that contain hard particles or abrasives. There are a variety of rotary pumps that are positive displacement such as piston as well as gear rotary, screw and pumps.
These pumps are less prone to problems such as cavitation and wear that could happen with centrifugal pumps. However, abrasive feeding can cause wear to the components of some positive displacement pumps. This is especially the case for rotary pumps that use pistons or plungers in order to trap and displace fluid. It is recommended to avoid abrasive feeds whenever possible.
Another issue associated with Rotary positive displacement pumps is that they may create pulsating discharge. This can cause noise and vibration in the system, as well as cavitation that can damage piping. This is a possibility to be reduced by using multiple pumps cylinders and pulsation-dampers.
Another advantage of a rotary positive displacement pump is that it can typically self-prime. This is due to the small clearances within the pump. However, care must be taken to ensure the pump does not run dry for extended periods of time as it can affect the performance and life span of the seal.
Positive displacement pumps that have an reciprocating pump
These pumps pressurize and draw fluid using pistons inside the cylindrical. When the piston is moved around, it holds a volume of liquid between the outlet and inlet valves, causing a differential pressure that overcomes the valve at the inlet to allow the liquid to flow out of. Unlike centrifugal pumps that are sensitive to viscosity changes and positive displacement pumps keep their flow rate in line with system pressure.
The ability to operate at consistent pressures makes these types of pumps ideal for applications requiring precise metering and transfer as well as abrasive or hazardous materials. Additionally, these pumps are self-priming which can reduce downtime and labor costs due to the absence of manual revoking.
However, a drawback of these pumps is that they can continue to build pressure within the pipework of delivery until an event relieves the pressure, which could be the pump or the liner. This can lead to excessive vibration and noise during operation. In order to mitigate the effects of this, they typically require additional components such as pulsation dampeners in the pipework and discharge line to ensure safety and may bom ly tam truc ngang dependability. These pumps are also difficult to maintain and cost more due to their design. Nonetheless, their capacity to handle dangerous or corrosive fluids, as well as their ability to operate consistently at low pressure levels, help overcome these issues. They’re an excellent choice for high-viscosity applications in the pharmaceutical as well as chemical processing and oil drilling industries.
Gear Pumps
In contrast to diaphragm pumps and gears, they don’t create shear in the fluid. They are ideal for transferring fluids that are sensitive to shear, such as emulsions, microbial cultures, and food products. Gear pumps are ideal for liquids that have an ability to change viscosity.
They are small and cost-effective. They are made out of stainless steel or other components. They offer high efficiency levels of 85% and more. They’re reversible which means they operate in both directions, ensuring the full contents of the hose are empty. They also self priming ensuring they do not require an external air supply. They are usually Atex rated (explosion proof) and are able to handle solvents.
The shafts are enclosed in sleeves that rest on one the other. Lubrication is provided through a recirculating lubricant. The recirculating polymer is created due to the different pressure between the two gears. They are only able to run dry for a short period of duration and must be properly lubricated to avoid galling, which can occur in the event that the melt of polymer is hard enough or the shear temperatures are too high.
Gears rotate in opposite directions, absorbing the polymer. The polymer is then transferred to the outer cogs. Lubrication grooves are included to keep the gears well-lubricated. They may be single or double jacketed and equipped with various types of seals, including sealing, mechanical, gland packing/stuffing, or magnetic coupling if there is no seal.
Diaphragm Pumps
Diaphragm Pumps are among the most flexible pumps worldwide. They can be easily transportable to any place. Simply connect the air and liquid lines, and you’re good to go. Whether your application calls for low viscosity spraying or large solid handling, or chemical and physical aggression, these pumps are able to manage it.
The Diaphragm Pump has two air chambers that are supplied by compressed air whose alternating volume contraction and expansion creates the pumping action. A hermetic seal between the diaphragm drive mechanism, and compression chamber allows the pump to move the pressure, compress and then evacuate an air-filled medium without the need for a lubricant.
In the suction process the air pressure is utilized to change the left diaphragm to convex, which opens up the inlet valve and allows fluid to flow into the pump. Then, the pump shaft shifts to the right while the right diaphragm shifts from a concave form to an convex form and shuts the check valve for outlet, while fluid is released from the discharge valve.
The pressure of the air is controlled by an input regulator. The pumps stop when the air pressure is greater than the pressure at which they discharge. This will prevent the pump from damaging its own system or piping. This kind of high-pressure air driven pump can achieve an ultimate pressure of 30 PSI, however the actual pressure is lower as the diaphragm can break over this.