What happens if you run a positive displacement pump with close discharge

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  • Useful information on positive displacement pumps

    Positive-displacement pumps (Fig. 14.12) are quickly damaged by being run against a closed valve on the delivery side, and are not usefully controllable by throttling on either side. You can control them to some extent with a valve on a bypass to suction, but very accurate control can be given using an inverter drive.

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  • Positive Displacement Pumps - an overview |

    2021-5-7 · A Positive Displacement Pump, unlike a Centrifugal or Roto-dynamic Pump, will produce the same flow at a given speed (RPM) no matter the discharge pressure. A Positive Displacement Pumps is a 'constant flow machine' A Positive Displacement Pump must never operate against closed valves on the discharge side of the pump - it has no shut-off head ...

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  • Positive Displacement Pumps - Engineering ToolBox

    2015-6-4 · Positive displacement pumps use two opposing, rotating elements (rotors) to displace product from the suction side of the pump to the discharge side of the pump. As the rotors rotate, the chamber formed between the rotors, housing and cover collects the product on the inlet side of the pump and carries the product to the discharge side of the ...

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  • Positive Displacement Pump Basics - Fristam

    A positive displacement pump makes a fluid move by trapping a fixed amount and forcing (displacing) that trapped volume into the discharge pipe. Some positive displacement pumps use an expanding cavity on the suction side and a decreasing cavity on the discharge side.

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  • How do positive displacement pumps work?

    2003-5-1 · All, I need you opinion on this one. I'm HAZOPing a PD pump set-up. For the pump block-in condition (discharge valve close), is it sufficient to depend on the pump's internal relief valve or must we install a PSV upstream of the discharge valve with its outlet being recirculated into the suction line.

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  • 5 Reasons To Choose A Positive Displacement Pump

    2021-4-12 · You are experiencing rapid pump wear. There are abrasives in the liquid you are pumping that arecausing erosion problems. You may have to go to a larger pump running at a slower speed. There is some corrosion in one or more of the pump elements. There is a lack of lubrication. You have a severe pipe strain problem.

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  • How To Read A Positive Displacement Pump Curve

    2020-9-7 · If you google 'pump impeller', you'll get tons of photo and videos of what they look like. They aren't positive displacement; they throw water out via centrifugal force. If you shut the valve, the water just spins with the impeller, in place.

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  • Positive displacement pumps - PetroWiki

    2016-1-12 · Rotary pumps are self-priming but are not designed to run dry for long periods. For best operation, there must be enough fluid at the suction port to keep the pumping chamber completely filled. Fig. 2 illustrates the relationship between speed, volumetric efficiency, and displacement of a rotary positive-displacement pump. The principles of ...

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  • What will happen in case we close the outlet valve of a ...

    What will happen in case we close the outlet valve of a centrifugal pump and reciprocating pump. ... If it is positive displacement type, there will be high pressure and the fluid will not go back ...

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  • Positive displacement pumps for water services |

    2016-10-31 · Pulsation could be an issue in any positive displacement pump; this is a critical issue in a reciprocating pump. As an indication, distances between hold downs should vary with pulsation intervals and line sizes Major fittings, such as elbows, etc., relatively close to a positive displacement pump should have these hold downs.

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  • Rules to Follow to Avoid Pump Problems | Valin

    2014-8-5 · A final note before discussing NPSH. Pressure for centrifugal pumps (inlet and outlet) is measured in Feet of Head and pressure for positive displacement pumps is typically measured in psi. One of the exceptions is for air operated diaphragm (AOD) pumps, which is a positive displacement pump where discharge pressure is measured in Feet of Head.

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  • Centrifugal Pump Running with Throttled Discharge

    2014-12-26 · Throttling/restricti ng the discharge of a centrifugal pump lowers the motor amperage because there is less flow therefore less HP demand on the motor.. Increasing the opening of the discharge valve causes even higher amperage on the motor. If a centrifugal pump motor cannot run with the discharge throttled without tripping and the overload protection is set correctly, the odds are very …

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  • vfd pump selection constant pressure

    2016-11-12 · We will take a close look at a PRV and VFD controlled constant pressure application and provide some basic rules for pump selection. ... a positive displacement pump, due to its inherent operating ... of the centrifugal pump. As the pump’s discharge is throttled and its flow decreases, so does the power consumed. Unfortunately, this reduction ...

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  • GUIDELINES FOR PUMP SYSTEM DESIGNERS Jacques

    2011-8-12 · When you order your pump make sure that the motor is installed with spacer blocks so that the next largest motor frame can be installed. 17. Effect of viscosity on pump performance Viscosity is the main criteria which determines whether the application requires a centrifugal pump or a positive displacement pump. Centrifugal pumps can pump viscous

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  • How Does Pump Suction Limit the Flow? | Pumps &

    2011-12-17 · One of the advantages of centrifugal pumps over positive displacement pumps is an ability to operate with a wide flow range. Since a centrifugal pump operates at the intersection of a pump curve and a system curve, varying the system curve easily changes the pump's operating point (see Figure 1). Figure 1. Flow control of the centrifugal pump by the discharge valve

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  • 6 Basic Rules of Pump Piping - Crane Engineering

    2021-5-13 · Include a straight run pipe length equal to 5 to 10 times the pipe diameter between the pump inlet and any obstruction in the suction line. Note: Obstructions include valves, elbows, 'tees', and etc. Keeping the pump suction piping short ensures that the inlet pressure drop is as low as possible.

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  • Pump Troubleshooting Guide | JAECO Fluid Systems

    When this happens, you must discard the hydraulic oil and thoroughly flush the gearbox. Replace with fresh hydraulic oil. Discharge Pipe Tips. For long pipe runs, install a pulsation dampener as close to the pump discharge connection as possible to avoid the hydraulic shocks known a “water hammers”

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  • How do positive displacement pumps work?

    A positive displacement pump makes a fluid move by trapping a fixed amount and forcing (displacing) that trapped volume into the discharge pipe. Some positive displacement pumps use an expanding cavity on the suction side and a decreasing cavity on the discharge side.

    Get Price
  • Positive displacement pumps for water services |

    2016-10-31 · Pulsation could be an issue in any positive displacement pump; this is a critical issue in a reciprocating pump. As an indication, distances between hold downs should vary with pulsation intervals and line sizes Major fittings, such as elbows, etc., relatively close to a positive displacement pump should have these hold downs.

    Get Price
  • Positive Displacement Pumps in Series - Pump

    2010-6-15 · Good day, I need some insight into positive displacement pump theory. I realise the differences between a normal centrifugal pump and a positive displacement pump for example, but I want to know how they perform in a system e.g. in parallel or in series.

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  • Centrifugal pump behavior when the outlet is closed ...

    2020-9-7 · If you google 'pump impeller', you'll get tons of photo and videos of what they look like. They aren't positive displacement; they throw water out via centrifugal force. If you shut the valve, the water just spins with the impeller, in place.

    Get Price
  • GUIDELINES FOR PUMP SYSTEM DESIGNERS Jacques

    2011-8-12 · When you order your pump make sure that the motor is installed with spacer blocks so that the next largest motor frame can be installed. 17. Effect of viscosity on pump performance Viscosity is the main criteria which determines whether the application requires a centrifugal pump or a positive displacement pump. Centrifugal pumps can pump viscous

    Get Price
  • High Speed Pump - an overview | ScienceDirect Topics

    Positive displacement pumps can also be run in parallel with centrifugal pumps. A positive displacement pump has an H–Q characteristic which is almost vertical. Here again Q values for the same head are added, giving the combined characteristic plotted in Fig. 2.9. The intersection of the system head curve with the combined pump ...

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  • Engineering Essentials: Fundamentals of Hydraulic

    2012-1-1 · So if the load-pressure setting of a pressure-compensated pump is 1,100 psi, the pump will increase or decrease its displacement (and output flow) based on a 1,300-psi discharge pressure. A two-stage pressure-compensator control , Figure 14, uses pilot flow at load pressure across an orifice in the main stage compensator spool to create a ...

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  • Berkeley Type B end suction close ... - Water Pump

    Viscosity is the main criteria which determine whether the application requires a centrifugal pump or a positive displacement pump. Centrifugal pumps can pump viscous fluids however the performance is adversely affected. If your fluid is over 2000 SSU in viscosity consider using a positive displacement pump.

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  • Pump Troubleshooting Guide | JAECO Fluid Systems

    When this happens, you must discard the hydraulic oil and thoroughly flush the gearbox. Replace with fresh hydraulic oil. Discharge Pipe Tips. For long pipe runs, install a pulsation dampener as close to the pump discharge connection as possible to avoid the hydraulic shocks known a “water hammers”

    Get Price
  • Choking the Flow from a Pump Makes it Work Easier –

    Centrifugal pumps are counter-intuitive. As pressure on a pump increases, the power required decreases. In other words, if you put a valve on the discharge of a pump and begin to restrict the output flow, the power required by the motor will decrease. Most people already have it in their head that choking a pump …

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  • Solving Pump Inlet Problems - BLACOH

    2013-12-5 · Positive displacement pumps, specifically reciprocating and peristaltic types, create pulsating flow that results in damaging vibration and pressure spikes. These flow pulses occur because the pump’s liquid chamber or chambers are repeatedly filled with liquid on the inlet stroke and then expelled on the discharge stroke.

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  • Centrifugal pump behavior when the outlet is closed ...

    2020-9-7 · If you google 'pump impeller', you'll get tons of photo and videos of what they look like. They aren't positive displacement; they throw water out via centrifugal force. If you shut the valve, the water just spins with the impeller, in place.

    Get Price
  • Why Discharge Valve Closed During Starting of

    2021-5-14 · >As you know,the current will be high during the starting of any motor. If you start the pump with discharge valve open, the discharge head will act on the pump ie, more resistance, so the motor has to give more starting torque to the pump which means more current is drawn by the motor.

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  • Diaphragm Pump : Its Functioning, Advantages &

    2020-2-28 · The diaphragm pump definition comes under the classification of positive displacement pumps that utilize the grouping of the reciprocating operation of thermoplastic, rubber and Teflon diaphragm. The flowrates of these devices will not fluctuate much with that of discharge pressure which means the pump functions against the specified pump speed.

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  • High Speed Pump - an overview | ScienceDirect Topics

    Positive displacement pumps can also be run in parallel with centrifugal pumps. A positive displacement pump has an H–Q characteristic which is almost vertical. Here again Q values for the same head are added, giving the combined characteristic plotted in Fig. 2.9. The intersection of the system head curve with the combined pump ...

    Get Price
  • How Does Pump Suction Limit the Flow? | WQP

    2003-4-22 · Since a centrifugal pump operates at the intersection of a pump curve and a system curve, by varying the system curve the operating point of the pump easily is changed. (See Figure 1.) The convenience and simplicity of such flow control by the discharge valve throttling comes at a price because a pump is forced to run either to the left or ...

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  • Engineering Essentials: Fundamentals of Hydraulic

    2012-1-1 · So if the load-pressure setting of a pressure-compensated pump is 1,100 psi, the pump will increase or decrease its displacement (and output flow) based on a 1,300-psi discharge pressure. A two-stage pressure-compensator control , Figure 14, uses pilot flow at load pressure across an orifice in the main stage compensator spool to create a ...

    Get Price
  • Sizing Pressure-Relief Devices - AIChE

    2013-11-4 · discharge due to overfilling — instrumentation and/or procedural safeguards are used to mitigate the overfilling scenario. Pumps can be an overpressure hazard to downstream equipment. All positive-displacement pumps should be reviewed as a potential source of overpressure. Normally, the relief device on a pump discharges to the inlet side of the

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  • Diaphragm Pumps Ltd | FAQ Pumps and Pump Spares

    The pump will sound erratic with many false strokes. Close the throttling valve until the pump strokes uniformly and smoothly. How can I get a uniform non-pulsing discharge? Buy a pulsation dampener or if this is unsuitable:- At the pump discharge, add a flexible hose with internal diameter three or four times the pump discharge size. The ...

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  • Choking the Flow from a Pump Makes it Work Easier -

    2015-3-31 · While you can close the discharge valve to reduce the flow for operation reasons , you do reduce the overall efficiency of the pump, and in time if overdone the pump will overheat .the best way as Gary says is to size the pump for the flow required, that way the pump runs at peak efficiency,

    Get Price
  • Why Discharge Valve Closed During Starting of

    2021-5-14 · >As you know,the current will be high during the starting of any motor. If you start the pump with discharge valve open, the discharge head will act on the pump ie, more resistance, so the motor has to give more starting torque to the pump which means more current is drawn by the motor.

    Get Price
  • Pump FAQs

    Both positive displacement and rotodynamic pumps are used for food and beverage processing. A few positive displacement pumps that are used are: Controlled volume metering pumps, or simply metering pumps, pump fluid through reciprocating action. They are often used to pump a fixed amount of a mixture in situations where precision is crucial.

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  • E N G I N E E R I N G - Gear Pump Basics - Liquiflo

    2009-3-31 · 1 tel. 9 0 8 .5 1 8 .0 7 7 7 fax. 9 0 8 .5 1 8 .1 8 4 7 w w w. l i q u i f l o . c o m EXTERNAL GEAR PUMP PRINCIPLE OF OPERATION & ADVA N TA G E S E N G I N E E R I N G - Gear Pump Basics The external gear pump is a positive displacement (PD) type of pump

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  • Millwright-IP Questions Flashcards | Quizlet

    What happens on centrifugal people pump when you Close discharge while operating ? Maximum pump slip. ... How do you control pressure fluctuations in a positive displacement pump. Pulsation damper. ... What happens when you increase spring pressure on mechanical governor.

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  • Lift Water with an Archimedes Screw - Scientific

    2019-7-11 · A positive-displacement pump traps fluid from a source and then forces the fluid to move to a discharge location. The Archimedes screw is made up of a hollow cylinder and a spiral part (the spiral ...

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  • Understanding and avoiding pump cavitation | PI

    2017-5-2 · Discharge cavitation happens when a pump’s discharge pressure is inordinately high — In other words, the pump is running at less than 10 percent of its best efficiency point (BEP). High discharge pressure prevents fluid from easily flowing out, which leads to recirculation of fluid within the pump.

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  • CAFS On-Line Orientation

    2019-4-8 · Positive Displacement vs Non-Positive Displacement Pumps • Rotary-Screw Air Compressor • Positive Displacement • Needs Shaft Speed to produce volume and pressure • Impeller Driven Water Pump • Non-Positive Displacement • In cases where there is incoming pressure, pump …

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  • Choking the Flow from a Pump Makes it Work Easier -

    2015-3-31 · While you can close the discharge valve to reduce the flow for operation reasons , you do reduce the overall efficiency of the pump, and in time if overdone the pump will overheat .the best way as Gary says is to size the pump for the flow required, that way the pump runs at peak efficiency,

    Get Price
  • Pumps Flashcards | Quizlet

    When air is present (pump section line) the float drops and opens valve. Air goes in primer and discharged to atmosphere. When air is purged float will rise and close suction to primer. Cooling water: supplied from pump discharge to prevent overheating of sealing water. If coolant water overheats steam will form destroying the vacuum.

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  • What does 'Open Flow' mean for a pump flow rate?

    2015-6-15 · Pump flow rates are usually useless without the curves given in the diagrams. The flow rate and the pressure are linked. You will have to find the operating point for your application. For example, you know the pressure you want to achieve on the pressure side (e.g., hydrostatic pressure) and you know what pressure drop occurs in your pipe.

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