TYPES OF ROTARY PUMPS

 TYPES OF ROTARY PUMPS

The rotory pumps classified into six general types these are, 

1. GEAR PUMP
2. LOBE PUMP
3. VANE PUMP
4. PROGRESSIVE CAVITY PUMP
5. PERIPHERAL PUMP
6. SCREW PUMP

1). GEAR PUMP:

The hear pump classified into two different types these are, 

1. EXTERNAL GEAR PUMP
2. INTERNAL GEAR PUMP

a). EXTERNAL GEAR PUMP:

• In external gear pumps, two identical gears rotate against each other.

• The motor provides the drive for one gear. This gear in turn drives the other gear. A separate shaft supports each gear, which contains bearings on both of its sides As the gears come out of the mesh, they create expanding volume on the inlet side of the pump.

• Liquid flows into the cavity and is trapped by the gear teeth while they rotate. Liquid travels around the interior of the casing in the pockets between the teeth and the casing. The fine side clearances between the gear and the casing allow recirculation of the liquid between the gears. 

• Finally, the meshing of the gears forces liquid through the outlet port under pressure. As the gears are supported on both sides, the noise levels of these pumps are lower and are typically used for high-pressure applications such as the hydraulic applications. 

b). INTERNAL GEAR PUMP:

• Internal gear pumps have only two moving parts.They can operate in either direction, which allows for maximum utility with a variety of application requirements. 

• In these pumps, liquid enters the suction port between the large exterior gears, rotor, and the smaller interior gear teeth, idler. The arrows indicate the direction of the pump and the liquid. 

• Liquid travels through the pump between the teeth of the ‘gear-within-a-gear’ principle. The crescent shape divides the liquid and acts as a seal between the suction and the discharge ports. 

• The pump head is now nearly flooded as it forces the liquid out of the discharge port. Rotor and idler teeth mesh completely to form a seal equidistant from the discharge and suction ports.

• This seal forces the liquid out of the discharge port. The internal gear pumps are capable of handling liquid from very low to very high viscosities. 

• In addition to superior high-viscosity handling capabilities, internal gear pumps offer a smooth, nonpulsating flow. Internal gear pumps are self-priming and can run dry. 

2). Lobe Pump:

What is Lobe Pump?

• A lobe pump, or rotary lobe pump, is a type of positive displacement pump. It is similar to a gear pump except the lobes are designed to almost meet, rather than touch and turn each other.

OPERATIONS OF LOBE PUMP:

• The operation of the lobe pumps is similar to the operation of the external gear pumps. Here, each of the lobes is driven by external timing gears. As a result, the lobes do not make contact. 

• Pump shaft support bearings are located in the gearbox, and since the bearings are not within the pumped liquid, pressure is limited by the location of the bearing and shaft deflection. 

• As the lobes come out of mesh, they create expanding volume on the inlet side of the pump. The liquid then flows into the cavity and is trapped by the lobes as they rotate. 

• The liquid travels around the interior of the casing in the pockets between the lobes and the casing and it does not pass between the lobes. 

• Finally, the meshing of the lobes forces the liquid through the outlet port under pressure. Lobe pumps are frequently used in food applications because they can handle solids without damaging the product. 

• The particle size pumped can be much larger in lobe pumps than in any other of the PD types.

3). Vane Pump:

• A vane pump too traps the liquid by forming a compartment comprising of vanes and the casing . As the rotor turns, the trapped liquid is traversed from the suction port to the discharge port. 

• A slotted rotor or impeller is eccentrically supported in a cycloidal cam. The rotor is located close to the wall of the cam so a crescent-shaped cavity is formed. The rotor is sealed in the cam by two side plates. Vanes or blades fit within the slots of the impeller. 

• As the impeller rotates and fluid enters the pump, centrifugal force, hydraulic pressure, and/or pushrods push the vanes to the walls of the housing. 

• The tight seal among the vanes, rotor, cam, and side plate is the key to the good suction characteristics common to the Vane pumping principle. 

• The housing and cam force fluid into the pumping chamber through the holes in the cam. Fluid enters the pockets created by the vanes, rotor, cam, and side plate. 

• As the impeller continues around, the vanes sweep the fluid to the opposite side of the crescent where it is squeezed through the discharge holes of the cam as the vane approaches the point of the crescent. Fluid then exits the discharge port. 

• Vane pumps are ideally suited for low-viscosity, non lubricating liquids.
  

4). Progressive Cavity Pump:

• A progressive cavity pump consists of only one basic moving part, which is the driven metal rotor rotating within an elastomer-lined (elastic) stator. 

• As the rotor turns, chambers are formed between the rotor and stator. These chambers progress axially from the suction to the discharge end, moving the fluid. By increasing the pitch of the rotor and stator, additional chambers or stages are formed. 

• The Vane pumps are solutions to the special pumping problems of municipal and industrial wastewater and waste processing operations. Industries, such as, chemical, petrochemical, food, paper and pulp, construction, mining, cosmetic, and industrial finishing, find these pumps are ideally suited for pumping fluids with nonabrasive material inclusion. 

5). Peripheral Pumps:

• The impeller has a large number of small radial vanes on both of its sides. 

• The impeller runs in a concentric circular casing. Interaction between the casing and the vanes creates a vortex in the spaces between the vanes and the casing, and the mechanical energy is transmitted to the pumped liquid. 

• Peripheral pumps are relatively inefficient and have poor self-priming capability. They can handle large amounts of entrained gas. They are suitable to low flow and high pressure applications with clean liquids. 

6). Screw Pump:

• In addition to the previously described pumps based on the Archimedes’ screw, there are pumps fitted with two or three spindles crews housed in a casing. 

• Three-spindle screw pumps, are ideally suited for a variety of marine and offshore applications such as fuel-injection, oil burners, boosting, hydraulics, fuel, lubrication, circulating, feed, and many more. 

• The pumps deliver pulsation free flow and operate with low noise levels. These pumps are self-priming with good efficiency. These pumps are also ideal for highly viscous liquids.