Axial Flow Pump
An axial flow pump is a type of pump that uses an impeller with vanes to create a flow in the direction parallel to the pump shaft. This design allows for the movement of large volumes of water at relatively low heads. Axial flow pumps are commonly used in applications such as irrigation, drainage, and water supply systems.
7 Key excerpts on "Axial Flow Pump"
- Barbara Renner(Author)
- 2017(Publication Date)
- CRC Press(Publisher)
...The faster time of approximately one-half to two-thirds saves contractors costs. Also, a submersible pump is more “flexible” when being installed because it does not require as much alignment as the shaft does. VERTICAL TURBINE PUMP MAINTENANCE 12.81 Most water utilities do not perform any repair or overhaul maintenance on vertical turbine pumps. This generally involves having a well contractor who has the equipment necessary to perform the work. However, the utility personnel are responsible for the daily and routine preventive maintenance chores. This includes making sure that the pump and motor receive the proper lubrication and inspections, including monitoring of the electrical usage and discharge flow, which tells the operator how well the pump is performing. Figure 12.15. Axial Flow Pumps. Axial Flow PumpS 12.82 The use of Axial Flow Pumps in water or wastewater applications is generally limited to water transfer, for example, inlet or feed pumps that pump water from a reservoir into a treatment plant or for storm dewatering or irrigation purposes. Although they generally are considered low head, high-volume pumps, some styles do have high head capabilities. 12.83 Almost all of the pumps are driven by a line shaft, with the motor mounted on a platform that may be 5–20 feet above the fluid level. The impellers are designed to move a lot of water and are of the axial or mixed flow style and are located in a large bowl-shaped casing. A suction bell is placed below the casing and acts as an inlet pipe that directs the fluid into the impeller area (Figure 12.15). 12.84 An axial flow impeller (Figure 12.16) looks much like a ship’s propeller that has been cut off at the ends. However, much like a ship propeller, the impeller has the ability to move a lot of water. The use of a mixed flow impeller would permit a pump to have higher discharge head ratings while also moving a lot of water...
- Mei Zu-yan(Author)
- 2018(Publication Date)
- Routledge(Publisher)
...Chapter 13 Construction of Axial—Plow, Mixed—Flow and Tubular Pumps Masnji Matsumura 13.1 General Features of Low Head Pumps Axial-flow, mixed-flow and tubular pumps are the essential pump types used for water lifting under relatively low heads, Generally speaking, axial-flow pumps are used for head ranges from several metres to less than 10 m and are applied mainly in the medium to large capacity range, Mixed-flow pumps are used in somewhat higher head ranges and mostly in the small/medium capacities. Both types may be constructed in vertical or horizontal designs and occasionally in the inclined arrangement (S-type), but the majority of these are vertical pumps. There are specific reasons for choosing one type or the other on grounds of preference to hydraulic performance and/or mechanical construction. The tubular pump is an axial-flow pump set horizontally. Its main feature is that the water flowing through the pump has a straight-through passage with no inlet or discharge bends, consequently it has a higher hydraulic efficiency. The driving motor is either mounted vertically above the pump with transmission through bevel gearing or enclosed in a shell with water flowing around it as is know as a bulb-type pump in large installations. 13.1.1 Variable pitch blade and fixed blade impellers An example of a fixed blade mixed-flow impeller is shown in Figure 13.1. The impeller may consist of four to eight blades (the larger number for lower specific speed pump) with three-dimensional curvature, fixed to the conical surface of the hub as a one-piece casting. This figure shows the semi-open type of impeller which is used to handle sewage water that contains fibres or solid particles. In general, with decreasing specific speed a closed type impeller with a shroud is used. The ratio of passage breadth to the outlet diameter is higher than with a centrifugal impeller...
- Amithirigala Widhanelage Jayawardena(Author)
- 2021(Publication Date)
- CRC Press(Publisher)
...In the outlet side of the impeller, a set of stationary guide vanes is usually fitted − the purpose being to reduce the whirl velocity. Guide vanes on the inlet side are usually not provided because they do not improve the pump performance significantly. The equations derived for centrifugal pumps can also be applied to Axial Flow Pumps. The main difference is that the peripheral velocities at inlet and outlet are the same (same radii at inlet and outlet), which means u 1 = u 2 Work done on fluid/unit weight = u g (v w 2 − v w 1) = 1 2 g { (V 2 2 − V 1 2) − (R 2 2 − R 1 2) } (12.11) Usually, v w 1 is assumed to be zero; then, the above equation is independent of the radius. Impellers are usually designed to satisfy the ‘free vortex’ relationship which implies that the velocity of whirl at the outlet varies according to the equation v w 2 r = Constant (12.12) Therefore, the work done on fluid per unit. weight ω r (v w 2 − v w 1) = ω (v w 2 r 2 − v w 1 r 1) (12.13) With the further assumption v w 1 = 0 the above expression is independent of the radius because v w 2 r 2 is a constant (Eq. 12.12). Note : These equations are based on the assumption that uniform conditions exist at inlet and outlet. This is not so for positions close to the impeller because the blades are so widely spaced. Axial-flow pumps are high capacity, low head type. 12.6 Mixed flow (diagonal flow) pump This type is intermediate between the radial flow type and the axial flow type. The flow may go along the conical surfaces of revolution. In all these types, there must be a rotating member, usually called a rotor or an impeller which does the work on the fluid and one or more stationary members called a stator. Volute and guide vanes are to guide the flow before and after the impeller. In summary, positive displacement type pumps have the following characteristics: Unsteady delivery Clearance between moving and stationary parts is very small...
eBook - ePub- Barbara Hauser(Author)
- 2017(Publication Date)
- CRC Press(Publisher)
...Most centrifugal pumps are radial pumps, they are able to produce high pressures. The High Service Pump at a potable water treatment plant, which lifts water from the plant to elevated storage is usually a radial pump. Axial Pump Water enters and exits the pump on the same plane. Backwash pumps - and Low Service Pumps, which carry water from the source to the treatment plant, are usually axial pumps. pump types: suction condition Single Suction One suction line enters the pump casing. Double Suction The suction line splits in two as it enters the pump and water approaches impeller from both sides. This type minimizes head losses inside the pump. Double suction pumps are often seen as water distribution booster pumps. Figure 12.2 Double suction centrifugal pump. pump types: impellers Single Stage One Impeller is installed on the pump shaft. Multi-Stage Used where water must be delivered at high pressures (a high pressure pump); to feed boilers, membrane processes, and for deep wells. It is designed so that the discharge from one impeller is led through a passage in the casing to the suction of the next impeller. other important pump components Stuffing Box and Packing As the shaft extends to the outside of the pump, water is prevented from escaping by the stuffing box, which is filled with rings of packing. The packing acts primarily as a seal, and also as a lubricant for the shaft. It is pressurized by an external source of water at a higher pressure than the water inside the pump. Often this is a small flow of the pump discharge water which is directed back to fill the packing. This water pressure is increased because it has already passed through the pump. Pump seal water flow is small, but constant, and stuffing box is designed to allow a constant leakage. Mechanical Seals This is an alternate to sealwater and packing, and has two components: Rotating Assembly: attached to the pump shaft. Stationary Assembly: positioned permanently on the stuffing box...
- Ron Palgrave(Author)
- 2019(Publication Date)
- Butterworth-Heinemann(Publisher)
...These are known as Mixed Flow or diagonal flow pumps. The term centrifugal pump strictly relates to the first group only, those where the flow leaves radially. In these cases, centrifugal forces are by far the dominant contributor to the way in which pump pressure head is created. But this is not the only contributor. At the other extreme, in cases where the liquid leaves the impeller axially, it does so at the same radial distance from the shaft as when it entered. With no change of radius, there can be no obvious centrifugal force. Instead the pressure head is generated almost entirely by a different mechanism. In the case of mixed flow pumps, the contributions from both mechanisms might be comparable. In fact, most practical members of this part of the pump family generate head from combinations of these two mechanisms. However, the term Centrifugal Pump has come to describe any member of the family (Fig. 3.1). The main purpose of almost every centrifugal pump is to create flow in a liquid system. To do so they have to simultaneously generate pressure head in the liquid. This pressure head is then dissipated by the liquid system resistance while handling the above-mentioned flow. Though the pump still has to generate pressure head as a by-product, its chief purpose is to create a specified system flow. On very rare occasions, centrifugal pumps are installed for the main purpose of creating hydrostatic pressure. But generally, other classes of pumping machine are better suited to this aim. Fig. 3.1 The general appearance of rotodynamic pump impellers. Compared to many other machines, the inner workings of a centrifugal pump are largely invisible, except in certain laboratory research pumps. This means that the underlying physics are less than obvious. The detail physics of the liquid flow path are well covered elsewhere [3, 33], but at a level inappropriate to this volume. Therefore, a simpler description is given here...
eBook - ePubPumping Station Design
Revised 3rd Edition
- Garr M. Jones PE DEE, Robert L. Sanks PhD PE(Authors)
- 2011(Publication Date)
- Butterworth-Heinemann(Publisher)
...Multistage pumps usually have single-intake impellers that are arranged, when possible, in a back-to-back fashion to reduce the axial thrust. The impellers are equipped with radial wear rings. Bearings. The pump bearings are mounted in two separate bearing housings. One of the two bearings is locked in the housing and carries the radial as well as the axial loads. The other bearing is for the radial load only. The bearings may be lubricated with grease or oil. Seals. The two stuffing boxes contain either packing or single-face mechanical seals. For gritty liquids or for installations with low suction pressure, the packings are provided with lantern rings and buffer liquid injection. 11-6. Classification of Vertical Pumps Vertical pumps were originally developed for well pumping. The bore size of the well limits the outside diameter of the pump and so controls the overall pump design. Vertical pumps are very versatile and are often used for installations not related to well pumping. Vertical pumps can be subdivided into three major categories: (1) lineshaft pumps, (2) submersible pumps, and (3) horizontally mounted, axial-flow pumps (Figure 11-1b). Lineshaft Pumps In lineshaft pumps (Figure 11-24), the driver is mounted on the discharge head. The lineshafting extends through the column to the bowl assembly and transmits torque to the pump rotor. Lineshaft pumps can be further subdivided into the following three categories: Deep well lineshaft pumps, which are used for the pumping of deep water wells. Short-setting lineshaft pumps, which are used for the pumping of shallow wells or pump sumps. Barrel pumps, which are short-setting pumps equipped with their own barrels or ‘‘cans’’ in place of pump sumps. Submersible Pumps Submersible pumps (Figure 11-25) are driven by a submersible motor. The motor is mounted below the bowl assembly and is directly coupled to the pump rotor shaft...
eBook - ePubPump Wisdom
Essential Centrifugal Pump Knowledge for Operators and Specialists
- Robert X. Perez, Heinz P. Bloch(Authors)
- 2021(Publication Date)
- Wiley-AIChE(Publisher)
...Occasionally, high efficiencies are alluded to in a manufacturer's literature when bearing, seal, and coupling losses are not included in the vendor's test reports. Impellers and Rotors Regardless of flow classification centrifugal pumps range in size from tiny pumps to very big pumps. The tiny ones might be used in medical or laboratory applications; the extremely large pumps may move many thousands of liters or even gallons per second from flooded lowlands to the open sea. All six of the impellers in Figure 1.5 are shown with a hub fastening the impeller to the shaft, and each of the first five impellers is shown as a hub‐and‐disc version with an impeller cover. The cover (or “shroud”) identifies the first five as “closed” impellers; recall that Figure 1.3 had depicted a semiopen impeller. Semiopen impellers are designed and fabricated without the cover. Finally, open impellers come with free‐standing vanes welded to or integrally cast into the hub. Since the latter incorporate neither disc nor cover, they are often used in viscous or fibrous paper stock applications. To properly function, a semiopen impeller must operate in close proximity to a casing internal surface, which is why axial adjustment features are needed with these impellers. Axial location is a bit less critical with closed impellers. Except on Axial Flow Pumps, fluid exits the impeller in the radial direction. Radial and mixed flow pumps are either single or double suction designs; both will be shown later. Once the impellers are fastened to a shaft, the resulting assembly is called a rotor. In radial and mixed flow pumps, the number of impellers following each other, typically called “stages,” can range from one to as many as will make such multistage pumps practical and economical to manufacture...
