Vertical pump designs are similar to conventional pumps, with some unique differences in their applications. Pumps use centrifugal force to convert mechanical energy into kinetic energy and increase the pressure of the liquid. Vertical pumps move liquids in the vertical direction upwards through a pipe. All pumps pressurize liquids, which are mostly incompressible. Unlike compressible gases, it is impossible to compress liquids, therefore the volumetric flow rate can not be reduced. Therefore liquids are transported by pumping and the inlet volume flow rate is equal to the exit volume flow rate.
Vertical centrifugal pumps are simply designed machines, and have similarities to their horizontal counterparts. A casing called a volute contains an impeller mounted perpendicularly on an upright (vertical) rotating shaft. The electric drive motor uses its mechanical energy to turn the pump impeller with blades, and imparts kinetic energy to the liquid as it begins to rotate. These pumps can be single stage or multistage with several in-line stages mounted in series.
The centrifugal force through the impeller rotor causes the liquid and any particulates within the liquid to move radially outward, away from the impeller center of rotation at high tangential velocity. The swirling flow at the exit of the impeller is then channeled into a diffusion system which can be a volute or collector, which diffuses the high velocity flow and converts the velocity into high pressure. In vertical pumps, the high exit pressure enables the liquid to be pumped to high vertical locations. Thus the pump exit pressure force is utilized to lift the liquid to high levels, and usually at high residual pressure even at the pipe discharge.
Applications of Vertical Pumps
An “in line” vertical pump is illustrated in Figure 1 (Reference 1), where the flow enters horizontally and exits horizontally and can be mounted such that the center line of the inlet and discharge pipes are in line with each other. This is a centrifugal pump with a tangential scroll at the inlet that redirects the flow by 90 degrees and distributes it circumferentially and in the axial direction into the impeller eye. The discharge is a simple volute that collects the tangential flow from the impeller exit, and redirects it into the radial direction.
Figure 2 shows a vertical pump that has a vertical intake that directs the flow straight into the eye of the pump rotor. At the impeller exit, the tangential flow is collected by a volute and diffused in an exit cone. An elbow after the exit cone redirects the flow into the vertical direction to lift the liquid to the desired altitude. (Reference 2).
A multistage vertical pump also referred to as a turbine pump is shown in Figure 3 (Reference 3). Vertical turbine pumps can be radial flow or axial flow type, multistage featuring double casing. The stages are in line and can be stackable, depending on the required lift pressure, or pressure head. They can be used for continuous duty at a variety of high-pressure services, operating at temperature extremes and handling difficult liquids. These are utilized in the following industries: Mining, Water Resources, Power Generation, Oil and Gas. Some applications for vertical turbine pumps include Agriculture, Condensate Extraction, Crude, Product and CO2 Pipeline, Dewatering and Water Supply (mining), Gas Treating and Sulfur Recovery, Ground Water Development and Irrigation, Water and CO2 Injection, Nuclear Service, Offsites and Waste Treatment, Snowmaking, Water Supply and Distribution (water), Water Treatment, and for pumping LNG.
There are a wide range of applications for vertical pumps, ranging from domestic use to industrial uses (Reference 4). Vertical pumps can be constructed from stainless steel, aluminum or cast iron and must be strong enough to withstand internal and external pressures. These pumps are most often used for lifting and transporting water, an application that finds many uses in residential, general purpose, industrial and commercial situations. Vertical centrifugal pumps are used in waste water and sewage treatment plants to handle trash and refuse; abrasive slurries. Certain heavy duty models can pump mixtures of solids that are suspended in liquid. As water pumps, vertical pumps are used for deep well pumping and move water from its underground source to buildings for human use or to prevent flooding or drainage issues. If vertical pumps are made of strong corrosion resistant materials, they are able pump chemicals and acids which is a useful way of transporting hazardous liquids throughout a processing plant. Vertical pumps can also be utilized in the pharmaceutical, food and beverage industries, as well as for HVAC applications.
Depending on the application, vertical pumps can feature several different types of sealing arrangements, which effect their design. Some pumps are “sealless”, shaft sealed or magnetic drive, where zero leakage is a requirement.
Designing Vertical Pumps with AxSTREAM
AxSTREAM® can be utilized to design impellers and diffusion systems for single stage or multistage vertical pumps. Figure 4 shows a single stage vertical pump with a centrifugal impeller, vaned radial diffuser and volute. Note that this design is similar to the vertical pump configurations shown in Figures 1 and 2.
AxSTREAM® can also be utilized to design vertical turbine pumps (VTP) as well, either single stage or multistage as illustrated in Figure 3. These types of pumps can feature mixed flow impeller rotors and mixed flow crossover diffuser – deswirler vanes that lead the flow into the next stage. A typical VTP designed with AxSTREAM® is shown in Figures 5 and Figure 6.
The capabilities of the AxSTREAM® code includes a fully integrated system of modules for the preliminary design and analysis of vertical pumps. The system of modules includes conceptual and preliminary design optimization module, 1D/2D streamline flow analysis module, structural analysis module for thermal, steady stress and dynamic analyses of blades and disks, and the CFD and Rotor Dynamics analysis module. The AxSTREAM® modules are seamlessly integrated into one system which share the geometric and fluid/thermal boundary conditions and provide a user-friendly design platform for the design of a wide variety of turbomachinery.