Positive Displacement Pumps | How Positive Displacement Pumps Work

Successfully completing this lesson you'll be familiar with the operation of reciprocating pumps single and double acting reciprocating pumps the operation of several different rotary positive-displacement pumps the relief valve in positive-displacement pumps the lesson will end with a test positive-displacement pumps have one of two basic designs either reciprocating or rotary it's time for a quick quiz as we've seen positive-displacement pumps have two basic designs rotary and reciprocating which of these two pumps is a rotary pump click on the correct illustration if you're not sure go to the previous screen to refresh your memory correct the pump to the right is a rotary pump positive-displacement pumps differ from centrifugal pumps in that they use mechanical energy to transfer fluid if the displacement is on the forward stroke only then the pump is single-acting this pump is double acting because it displaces liquid both on the forward and return stroke it's time for a quick quiz is this pump a single acting or a double-acting pump if you're not sure go to the previous screen to refresh your memory correct the pump is a double-acting pup since it displaces liquid on both the forward stroke and the return stroke here's an illustration of a reciprocating pump system positive-displacement pumps are capable of delivering very high pressures these pressures can be much an excess of the design pressure and so a relief valve must protect the pump positive-displacement pumps are self priming as the section and delivery are positively separated pumping however in order to reduce wear and ensure quick starting an external priming connection from above the pump should be available reciprocating pumps can produce pressure fluctuations in the discharge pipelines a damper either gas or air filled can help to even out the pressure fluctuations the damper stores some of the energy as the pressure rises and releases this energy as the pressure Falls it's time for a quick quiz drag the relief valve to its corresponding pipe if you're not sure go to the previous screen to refresh your memory correct most positive-displacement pumps and use our of the rotary type rotary pumps operate in a circular motion and displace a constant amount of liquid with each revolution of the pump shaft this is accomplished by the pumping elements moving in such a way as to expand volumes to allow liquid to enter the pump these volumes are contained by the pump until the geometry causes the elements to move to reduce the volume and force the liquid out the clearances of the elements within the pump separate the suction from the discharge and are critical for efficient operation rotary piston type positive-displacement pumps are found in hydraulic systems there are two types radial piston and axial piston you can see that the Pistons rotate eccentrically to the rotor axis this causes the cylinder volume to increase as the Pistons past the suction port and decrease as the Pistons past the delivery port in some applications such as steering gear applications the pump can have a variable discharge this is achieved by increasing and decreasing the eccentricity of the Pistons thereby change the amount of cylinder volume increase the nature of the ports can also change by moving the piston eccentricity past the pump centerline an axial piston pump is sometimes known as a swash plate pump the principle is the same as for the radio type an axial piston pump can also be used as a variable delivery pop gear pumps rely on the meshing of gear wheels to separate the suction and delivery ports they come in two configurations either internal gear or external gear internal gear pumps use the same principle as the external type in this case the driven gear has internal teeth and meshes with the idler which has external teeth the external gear pump has two gearwheels one driven by the motor and the second or idler which is driven by the meshing of the gears the gears carry the liquid around the outside and the meshing of the teeth cause the liquid to be discharged it's time for a quick quiz as we've seen gear pumps come in two configurations internal gear and external gear which of these two pumps is an external gear pump click on the correct illustration if you're not sure go to the previous screen to refresh your memory correct the pump to the left is an external gear pump screw-type pumps usually have either two or three screws they can operate at high speeds and give a smooth discharged with almost no pulsations they come in two configurations either twin screw pump or three scoop up the twin screw pump uses a similar principle to the gear pump in that the liquid is carried between the screw and the casing the meshing of the screws also the liquid to be discharged due to the imbalance of forces this type of pump often has the suction arranged at the center of the screws and the delivery at either end and is often driven through timing gears which keep the screws from contacting each other 23 screw pump is usually arranged so that the central screwdrivers the two outer screws a special type of screw pump is the single screw or progressive cavity pump this pup has a single-screw rotating in stator the stator is made of an elastomeric material the stator has an internal helix of different pitch to the rotor the geometry means that the rotor moves vertically whilst turning so the meshing of the rotor and stator causes the cavity to progress to the discharge the screw is an interference fit in the stator so this pump must always have liquid present to prevent overheating and failure it's time for a quick quiz which part of a progressive cavity pump is called a stator click on the stator if you're not sure go to the previous screen to refresh your memory correct vane pumps come in two configurations either flexible vane pump or sliding vane pump the rotor is made of an elastomer and as the veins past the cam they deflect decreasing the cavity and so discharging the liquid the veins are a sliding fit in slots cut in the rotor the rotor turns eccentric to the casing causing the cavities to decrease in volume veins can be four stop by centrifugal force use springs or utilize the pressure of the discharge liquid it's time for a quick quiz where are the veins located click on the veins if you're not sure go to the previous screen to refresh your memory correct

Channel: Marine Online

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Keywords: Marine Online, Marine Online Courses, 4. Positive Displacement Pumps, laney college, oakland, positive displacement, pump, piston, plunger, diaphragm, gear, lobe, vane, peristaltic, screw, progressive cavity, pumps, positive displacement pumps, rotor type pump, reciprocating pump, hydraulic pump, relief valve, operation of a reciprocating pumps, Single and double acting reciprocating pumps, animation

Id: ySbtksESFUc

Length: 9min 29sec (569 seconds)

Published: Sat Jan 07 2017