Pumps can be classified into three major groups according to the method they use to move the fluid. The volume is a constant given each cycle of operation. Sep 07, 2017 positive displacement pump pdp is a type of pump in which a moving fluid is captured in a cavity and then discharges that fixed amount of fluid. Pumps are used to move any substance which flows or which can be made to flow. Definitions and terms density density is the mass of a substance per unit volume. Positive displacement pumps they cover gear, screw and reciprocating pumps in different configurations that guarantee reliable and efficient pumping processes. A film of the liquid being pumped prevents contact of the rotating elements and the bore. A diaphragm pump is a particular type of positive displacement pump that uses the reciprocating action of a flexing diaphragm to move fluid into and out of the pumping chamber. Useful information on positive displacement pumps what is a positive displacement pump. On a test stand the flow rate is determined for various speeds and total head i. This article deals exclusively with centrifugal pumps. Pumps come in many forms, but can generally be categorised according to two main operating principles. Dynamic pumps can be subclassified as centrifugal and special effect pumps. These pumps are typically not capable of such a high flow rate as say, a centifrugal pump, but they are capable of producing much higher pressures.
These two categories of pump movement type are called. Each time the pump spins, a specific amount of water is moved. The fluid is positively moved from a set quantity container. Displacement pumps can be subclassified as rotary or reciprocating pumps. Selection of a positive displacement pd rotary pump is not always an easy choice. Precise metered displacement of fluid typically gph or. Best practices in selecting and applying positive displacement. Numerous sizes, hydraulics and material combinations are particularly well suited for use in applications where uncompromising reliability and efficiency over a wide flow range are key.
Positive displacement pump applications and benefits. Aug 25, 2016 brought to you by the machine tech video blog. Most pd pumps can be adapted to handle a wide range of applications, but some types are better suited than. Positive displacement rotary pumps can be grouped into three main types. This document has been reproduced directly from the best available copy. In this video, adam breaks down the different types of positive displacement pump. Types positive displacement pumps a lobe pump a positive displacement pump causes a fluid to move. A positive displacement pump has an expanding cavity on the suction side and a decreasing cavity on the discharge side.
As the rotors rotate, the chamber formed between the rotors, housing and. Sep, 2007 positive displacement pumps is a current reference guide for positive displacement pumps for both traditional and state of theart testing methods, and serves as a bridge between textbooks and manufacturers literature by providing equipment testing practices based on technical knowhow, practical experience, and academic theory. The pumping action is cyclic and can be driven by pistons, screws, gears, rollers, diaphragms or vanes. Positive displacement pumps operate by forcing a fixed volume of fluid from the inlet pressure section of the pump into the discharge zone of the pump. To make it a bit easier to understand, we have broken down the most common positive displacement pumps into nine basic types based on their mechanics. Types of positive displacement pumps are reciprocating, metering, and rotary pumps. Based on direction of fluid flow relative to shaft. Feb 26, 2018 all types of positive displacement pumps involve a mechanism that falls into two categories depending on the type of motion it utilizes.
A pump is a device that moves fluids liquids or gases, or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic energy. For instance, the positive displacement pd pump provides a continuous flow. The compressor increases the pressure energy of a gas by reducing its volume. Positive displacement pumps features and a positive displace. Positive displacement pumps have a very close clearance between rotating and stationary parts and. They can be classified according to their basic operating principle as dynamic or displacement pumps. The flexing diaphragm creates a vacuum at the inlet of the chamber that draws the fluid into the chamber. Positive displacement pumps positive displacement pumps, in contrast, have very little slips, are selfpriming and pump against very high pressures, but their volumetric capacity is low. Stand alone metering capabilitystand alone metering capability. So, rotary systems require some type of safety pressurere lief valve at or immediately downstream of the pump to protect against overpressure.
Figure 12 reciprocating positive displacement pump operation. A positive displacement pump must never operate against closed valves on the discharge side of the pump it has no shutoff head like centrifugal pumps. Positive displacement pumps are another category of pumps. Positive displacement pumps are generally used for specialist applications such as for pumping viscous liquids or liquids that contain suspended or fragile solids. If positivedisplacement pumps are properly installed and operated, satisfactory performance can be realized for a long time. Positive displacement pumps and their different types. Hydraulic pumpmotor division positive displacement pumps fixed displacement flow varies only with shaft speed typical types gear pumps and vane pumps variable displacement flow can be varied at a given shaft speed typical type is variable piston pumps hydraulic pump basics. What are the basic types of positive displacement pumps. Pressure relief valves that are usually fitted to the delivery side of the pump to provide safety protection against high pressures also limit maximum pressures possible. Positive displacement pumps use an expanding cavity on the suction side and a decreasing cavity on the discharge side. Dec 30, 2015 definition of positive displacement pumps. What is positive displacement pump definition, types and.
These pumps generally tend to be larger than equal. Positive displacement pumps are classified into different types but some of them are discussed below like diaphragm, gear, peristaltic, lobe, and piston pumps. Positive displacement pumps allow liquid to flow into an open cavity trap the liquid in the pump transport liquid from the suction to discharge port mechanically force liquid out of the pump. A vendor manual for a specific pump usually contains a curve of pump. Understand the difference between centrifugal pumps and positive displacement pumps. Different types of pumps positive displacement pumps. The displacement of fluid takes place by some parts like plunger, piston, diaphragm etc. These pumps are commonly called as constant volume pumps.
Alhough certain system head parameters are calculated the same way whether the driving force for flow is a pump or gravity, this. Because of this action, positive displacement pumps are capable of delivering constant flow at very high pressures at a constant speed. Centrifugal and positive displacement pumps cedengineering. In addition to an extensive range of sizes, pumps also come in several different types. Centrifugal pumps serve many purposes in residential buildings. Now, pdps is a form of viking pump which can be further categorised into three. They are classified by the way they add energy to a fluid. Dynamic and positive displacement aka displacement. Positive displacement pumps with positive displacement pumps the flow rate q is linear dependent on the pump speed n. All types of positive displacement pumps involve a mechanism that falls into two categories depending on the type of motion it utilizes. The major disadvantage of piston positive displacement pumps is that material volumes are determined by the piston stroke which is manually set with an adjustable collar. Centrifugal pumps are the most common type of pumps found in doe facilities. Centrifugal pumps develop pressure by increasing the velocity of the liquid liquid is literally flung out of the cutwater.
Types positive displacement pumps a lobe pump a positive displacement pump causes a fluid to move by trapping a fixed amount of it then forcing displacing that trapped volume into the discharge. Screw pumps are a more complicated type of rotary pumps, featuring two or three. Radial centrifugal pumps axial boat propellers mixed. Diaphragm pumps also known as aod pumps air operated diaphragms, pneumatic, and aodd pumps.
These pumps are manufactured in a variety of designs for many different services. Pump maintenance michigan water environment association. When we think of pumping, we ordinarily think of moving water, oil, air, steam, and other common liquids and gases. Following is some of the pumps under both categories it is impossible to list all. Generally, we express density in units of pounds per cubic inch. Most pd pumps can be adapted to handle a wide range of applications, but some types are better suited than others for a given set of circumstances. Liquid flows into the pump as the cavity on the suction side expands, and the liquid flows out of the discharge as the cavity collapses. Specific gravity specific gravity is used to compare the density of a product to the density of water. A positive displacement pd pump moves a fluid by repeatedly enclosing a fixed volume and moving it mechanically through the system. Types positive displacement pumps a lobe pump a positive displacement pump causes a fluid to move by trapping a fixed amount of it then forcing displacing that trapped volume into the discharge pipe. Apr 29, 2017 heavy duty sand suction dredge pump tobee tg dredge pump are the most comprehensive range of centrifugal gravel sand pumps for use in mining, chemical and general industry applications. There are two different types of pumps, positive displacement and centrifugal. Positive displacement pumps selection guide engineering360. Positive displacement pumps or pd pumps are one kind of pump and the designing of these pumps can be done long before centrifugal pumps.
Positive displacement pumps are a category of pumps designed to move fluid at a steady rate through a system. These pumps are able to handle viscous fluids, which flow at lower speeds and create more resistance, more efficiently than kinetic dynamic pumps. A positive displacement pump operating against closed discharge valves continues to produce flow until the pressure in the discharge line is increased until the line bursts or the pump is. Most process pumps are rotodynamic pumps, so you need to know the required outlet pressure to specify the pump that will provide the required flow. There are, of course, other types of pumps and compressors, in particular positive displacement pumps whose advantage is that they deliver a particular. These pumps are competent in expanding high pressures while working at little suction forces. There is a new document prepared jointly by europump and the. How a positive pump operates positive displacement pump operation assuming sufficient nipr 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.