Dec 30, 2015 there are many benefits of positive displacement pumps for varying applications. Jan 22, 2018 positive displacement and non positive displacement pump comparison. However, we will briefly present the positive displacement pump in section. Definitions and terms density density is the mass of a substance per unit volume. In this video, adam breaks down the different types of positive displacement pump. Driveroperator 1b september 2003 slide 212 types of fire pumps positive displacement. With this pump, the volume of liquid delivered for each cycle depends on the resistance offered to flow. We will discuss here the difference between positive and nonpositive displacement pump. For very high pressure, low flow applications, positive displacement pumps are more suitable. Centrifugal and turbine pumps are examples of non positive displacement. Positive displacement pumps are generally used for specialist applications such as for pumping viscous liquids or liquids that contain suspended or fragile solids. 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. Other rotary nonpositive displacement pumps pumping installations or systems f04d 2500 definition statement this place covers. Throttling valves are used with non positive displacement pumps.
Centrifugal pumps develop pressure by increasing the velocity of the liquid liquid is literally flung out of the cutwater. When to use a centrifugal or a positive displacement pump pd pump is not always a clear choice. Non positive displacement pumps for elastic fluids. A positive displacement pump moves a fixed volume of fluid within the pump casing by applying a force to moveable boundaries containing the fluid volume. What is positive displacement pump definition, types and. Pressure positive displacement pumps work for high pressure applications, pressure might be upto 800 bar.
Nonpositive displacement pumps find more use in lower. What is the difference between the positive and non. In case of non positive displacement pump, flow is not constant but also it varies with variation in pressure. 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. Like most pumps, a centrifugal pump converts rotational. Difference between positive and nonpositive displacement pumps.
Throttling valves are used with nonpositive displacement pumps. Positive displacement means that liquid is discharged as soon as the pump operates and continues as long as the pump operates. Centrifugal and positive displacement pumps cedengineering. A pump is a device that moves fluids liquids or gases, or sometimes slurries, by mechanical. Sep 02, 2003 for example, positive displacement pumps must have a safety relief valve added to the pump discharge pipe to prevent excessive pressure buildup. To make a good choice between these pump types it is important to understand that these two types of pumps behave very differently. These pumps maintain a constant volume and positively displace any liquidsuch as juice, fats, oil, gelatin, mayonnaise, syrup, creams, milk products, automobile paint and polymersfrom a fixedvolume container. When using a positive displacement pump care needs to be taken to ensure the flow is not restricted causing pressures in excess of the pump or system design andor power requirements in excess of the design. Many manufacturersincluding those in the food and beverage, personal care, cosmetics, dairy or meat processing industriesbenefit from a positive displacement pump. A principal advantage of hydraulic power is the high power density power per unit weight that can be achieved. For more information, we recommend taking the hydraulic institute s new positive displacement pd pumps. Nonpositive displacement pumps have more clearances between the moving and stationary parts than positive displacement pumps. Pumps can be classified into three major groups according to the method they use to move the fluid. A hydraulic pump that uses an impeller or propeller to move fluid by momentum, as opposed to a positive displacement pump, which moves discrete quantities of fluid with each rotation.
Selecting a positive displacement pump using performance curves. Positive displacement pumps features and a positive. Non positive displacement pump non positive displacement pump are also known as hydro dynamic pump. Each cycle encloses a certain volume of fluid and moves it mechanically through the pump into the system. Do not let a nonpositive displacement pump run at zero flow. Pumps operate via many energy sources, including manual operation. These pumps are able to handle viscous fluids, which flow at lower speeds and create more resistance, more efficiently than kinetic dynamic pumps. What is the difference between the positive and nonpositive. Cpc definition f01d nonpositive displacement machines. Flow and pressure relationship of a nonpositive displacement pump when the flow increases, the discharge pressure of the pump decreases, and when the flow decreases the discharge pressure increases ref. The operation of this type of pump is holding a fixed volume of fluid that needs to be displaced and then forcing it from the inlet section into the discharge pipe. Positive displacement pumps are a category of pumps designed to move fluid at a steady rate through a system. Centrifugal and turbine pumps are examples of nonpositive displacement. If they are not properly plumbed with a prv the system will continue to build pressure until something bursts.
The lower speeds reduce seal wear, extend pump life, reduce suction pressure requirements and produce quieter operation. Nonpositive displacement pumps are basically used for low pressure applications and are designed to work for a maximum pressure of 18 to 20 bar. Different types of pumps positive displacement pumps. Positive displacement pumps performance and application by david b. Nonpositivedisplacement pumps engine fuelinjection. These pumps need no priming, but must have some means of relief when the discharge control valve is.
Basic hydraulic systems pump valve free 30day trial. The pump and motor assembly must be securely fastened to the base, and the base must be securely attached to the ground. Cpc definition f04b positivedisplacement machines for. It is not always possible to use a standard stuffing box to seal the shaft of a centrifugal pump. Most non positive displacement pumps operates by centrifugal force, they. For every stroke pumping chamber opens to an outlet port. Aug 25, 2016 brought to you by the machine tech video blog.
Positive displacement pump applications and benefits. Centrifugal pumps and propeller pumps are the best example. Pd pumps handle flow rates from less than 1 gpm to 15,000 gpm and pressures from a few psi to more than 70,000 psi. Nonpositive displacement pumps for nonelastic fluids. Nonpositive displacement pumps summary these pumps are also known as hydrodynamic pumps. The yoke can be positioned with a variety of controls, i. Positive displacement pump includes reciprocation pump, rotor pump, etc. Lobe pumps work on the similar principle of working as that of external gear pumps. The composite curves are based on the maximum speed of the pumps. The difference in performance of a centrifugal pump non positive displacement, compared to a rotary pump and a reciprocating pump is illustrated in figure 1. A positive displacement pump, unlike a centrifugal pump, will produce the same flow at a given rpm no matter what the discharge pressure is. Fundamentals, design and applications elearning course. Rotarypiston, or oscillating piston, positive displacement.
About positive displacement pumps hydraulic institute. Jun 5, 2017 difference between positive and non positive displacement pumps. However in lobe pumps, the lobes do not make any contact like external gear pump see figure 5. The foundation area should be rigid and level for maintaining pump alignment. Pressure affects the output only to extent that it increases internal leakage. The pump curves referenced in this article could not be reproduced online. Positive displacement pumps frequently are used in hydraulic systems at pressures ranging up to 5000 psi. Mechanisms and mechanical devices sourcebook pdf mechanisms and mechanical devices sourcebook pdf file. Nonpositive displacement example if you designed a lift where a hydraulic cylinder is extended by flow from a nonpositive displacement pump, the performance would be terrible. Fundamentals of positive displacement pumps the hydraulic institute provides an overview of positive displacement pumps performance characteristics. Generally, we express density in units of pounds per cubic inch. They also provide a fixed displacement per revolution and.
Positive displacement pumps selection guide engineering360. Fundamentals of positive displacement pumps plant services. Positive displacement pump handbook pdf grundfos has developed the pump handbook, which in a simple manner deals. They cover gear, screw and reciprocating pumps in different configurations that guarantee reliable and efficient pumping processes. A vendor manual for a specific pump usually contains a curve of. Flowserve positive displacement pumps comply either with asme or api standards.
This disambiguation page lists articles associated with the title positive displacement. Positive displacement and non positive displacement pump. Pumps machines for liquids, or pumps, of rotarypiston or oscillatingpiston type f04c. Positive displacement pump non positive displacement pump 1.
Positive displacement pumps move fluids with pistons, gears or vanes and flowrate is a function of rotational speed and has. Below we outline the main reasons many operations choose to use them. This subclass does not cover combinations of nonpositivedisplacement pumps with other pumps, which are covered by. A nonpositive displacement pump can slip, making it a good choice for any application that does not put high pressure on the pump s outlet. Positive displacement pumps have been used in fire protection for many years. Positive displacement pumps are self priming because there will be very close clearance between rotary and stationary components of pump. Specific gravity specific gravity is used to compare the density of a product to the density of water. Other rotary nonpositivedisplacement pumps pumping installations or systems f04d2500 definition statement this subclassgroup covers.
These pumps can be fitted with a smaller motor than would be required by many much bigger reciprocating pumps for equivalent flows and pressures. In fact, they were the first pump type to be utilized for mobile fire truck applications, long before centrifugal pump designs were used for pumping fire water. The extra clearance allows more oil to be pushed back between the parts as the outlet pressure resistance to flow increases. On a test stand the flow rate is determined for various speeds and total head i. Reciprocating pumps are tolerant of small solids, resistant to chemical and corrosive attack. 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. Centrifugal and propeller pumps are examples of nonpositivedisplacement pumps. A positive displacement pump uses a mechanism like a piston and valves so that the amount of volume moved is matched by the swept volume. A positive displacement pump cannot be operated against a closed valve on the discharge side of the pump, i. When it works, its piston will move forward and backwa. Positive displacement pumps are excellent for applications that require high pressure, with some models producing over 1,000 psi 2,300 ft. Combinations of nonpositive displacement pumps with other pumps. F04d 1700f04d 270292 details, component, parts, or accessories.
Understanding positive displacement pumps pumpscout. F04d 100 f04d 15029 non positive displacement pumps for elastic fluids. It delivers water through the change of its volumes. Categorize common models of pump as positive or non. Difference between positive and non positive displacement pump.
Positive displacement pump is a type of pump used to displace or force oil and petroleum products into pipelines or into various equipment installed in refineries. If an internal link led you here, you may wish to change the link to. Positive displacement and non positive displacement pump comparison. A positive displacement pump is a machine used for the. A rotodynamic or non positive displacement pump imparts velocity energy to the fluid, which is converted to pressure energy upon exiting the pump casing. The pumping action is cyclic and can be driven by pistons, screws, gears, rollers, diaphragms or vanes.
Centrifugal pumps are the most common type of pumps found in doe facilities. These designs of pumps cannot be deadheaded, meaning that the fluid has to have somewhere to go. This subclass covers nonpositivedisplacement pumps for liquids, for elastic fluids, or for liquids and elastic fluids whether rotary or not having pure rotation this subclass does not cover combinations of nonpositivedisplacement pumps with other pumps, which are covered by subclass f04b, except that the use of such other pumps for priming or boosting nonpositivedisplacement is covered. A positive displacement pump must not be operated against a closed valve on the discharge side of the pump because it has no shutoff head like centrifugal.
Driveroperator 1b september 2003 slide 2 positive displacement pump. 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. Types of fire pumps positive displacement centrifugal. 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. In addition, positive displacement pumps generally operate at rpms well below centrifugal pumps. Positive displacement pumps operate with a series of working cycles. Hydrodynamic or non positive displacement pumps such as centrifugal. Nonpositive displacement pumps definition statement. Positivedisplacement pumps frequently are used in hydraulic systems at pressures ranging up to 5000 psi. When selecting, keep in mind that it is best to run a positive displacement pump at no more than 400 to 500 rpm. Combinations of nonpositive displacement pumps with other pumps positive displacement machines for fluids. Due to the positive displacement pumps design however, if kept in operation against a closed discharge valve, it will continue to build pressure until the line bursts, the pump is damaged, or both. Any rotary non positive displacement which does not have radial, axial or helico centrifugal flow, pumps adapted for conveying or for handling specific elastic fluid, and pumps with circumferential or transverse flow. 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.
Depending on which of these pumps you are dealing with, a small change in the pumps counter pressure results in differences in the flow. In these pumps the fluid is pressurized by the rotation of. 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. Positive displacement pumps they cover gear, screw and reciprocating pumps in different configurations that guarantee reliable and efficient pumping processes.
Nonpositivedisplacement pumpsmodern industrial hydraulics. Depending on the type of pump and the liquid being handled, this happens with little influence from the back pressure on the pump. An increasing volume is opened to suction, filled, closed, moved to discharge. Pumps operate by some mechanism typically reciprocating or rotary, and consume. Positive displacement machines pdf combinations of positive displacement and nonpositive displacement pumps are. 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.
Useful information on positive displacement pumps what is a positive displacement pump. The displacement of fluid takes place by some parts like plunger, piston, diaphragm etc. F04d 2900 f04d 29708 in the part related to details, component, parts, or accessories i. Driveroperator 1b september 2003 slide 215 positive displacement pumps can pump air has a small amount of slippage ability of water to pass through the inner workings of the pump, not allowing 100% discharge. Non positive displacement pumps summary these pumps are also. Any rotary non positive displacement which does not have radial, axial or helico centrifugal flow, pumps adapted for conveying or for handling specific elastic fluid, and pumps with circumferential or. There are many pump designs that fall into the positive displacement category but. Oscillatingpiston type f04c nonpositive displacement phd thesis in project management pdf pumps f04d. A positive displacement pd pump moves a fluid by repeatedly enclosing a fixed volume and moving it mechanically through the system.
1317 442 237 53 21 54 539 812 63 480 1084 693 229 1488 164 1255 991 434 367 625 1572 1097 1167 1434 660 154 1351 1198 799 1417 1306 661 1129 325 420 623 872 731 471 804 975 1463 1463 547 334 714 1033 795 721 712