# Centrifugal Pumps #

FluidFlow contains an extensive database of centrifugal pumps which can be used when building a network. The user can also supplement this database by adding new pumps for specific applications. This tutorial demonstrates how to add a new centrifugal pump to the database. Defining a pump capacity curve in FluidFlow using head units is straightforward (m fluid, ft fluid, etc.). If however you wish to define a pump capacity curve which has been developed by the manufacturer using pressure units (Kpa, bar, etc.), it will be necessary to convert the coordinates to head units. This example takes us through the steps required to define this type of pump. Pump Data: Operating Speed = 1780 RPM Operating Impeller Diameter = 393.1mm Min. Impeller Diameter (D3) = 380mm Max. Impeller Diameter (D3) = 475mm Maximum Operating Pressure = 25.3 bar g Suction Size = 200mm Discharge Size = 150mm Figure 1 provides an illustration of a typical pump capacity curve and Figure 2 details the curve coordinates. Figure 1 – Pump Capacity Curve. Figure 2 – Pump Capacity Curve Coordinates. The first step is to convert the pressure units to head units using the equation P = ρ*g*h. H = P/ρ*g. Figure 3 provides details of this conversion. Note, the value for density was obtained from the manufacturer's technical datasheet and is the density value for the fluid from which the curve was developed. Figure 3 – Pump Capacity Curve Coordinates. Now we have calculated the head units, we are ready to define the pump in the components database. Firstly, define the main pump parameters by selecting 'Database | Boosters | Centrifugal Pump' and clicking 'Add'. Give your new pump a Unique Name and enter the main operating parameters for the pump (See Figure 4). Figure 4 – Pump Operating Data. Note, if we had defined a min and max speed for the pump operating data, we would have the ability to model the effect of changing the pump speed from the input tab of the data palette. Now we can define the pump capacity curve using the flow units provided by the manufacturer and the head units as calculated in Figure 3. Figure 5 below provides an illustration of the defined pump curve coordinates based on available manufacturer's data. Note, the Min & Max Limits (Vertical Red Lines) have been set based on the actual curve data available from the manufacturer. An Important point to note is the entry at Head = 0. You are unlikely to get this information from any manufacturer, so you MUST make an estimate. The estimate you make can be guessed (this is OK because we will never operate the pump anywhere near to this condition). When you make the guess at head of zero, ensure that you do not "upset" the shape of the curve for the valid data points by selecting a value that lies on a smooth curve. If you do not make this guess you run the risk of using the pump in a system that is difficult to solve (converge). Figure 6 shows how an additional row has been added where we have made an estimate of the flow at 0 head. As you can see, the curve still intersects the coordinates and is an accurate representation of the manufacturer's data. The Max Limit is retained as 2816.8 usgpm. If we solve this pump in a system and the duty point is beyond the Max Limit of 2816.8 usgpm, we will get a warning message to that effect. This informs us that we are operating outside the range for the pump based on available manufacturer's data. We would therefore need to investigate the pump performance further with the vendor. Note, by default, the software displays one row for Flow vs. Head units in the "Curve Fit" editor. U se the "Down Arrow key" if you need to create additional rows for the curve coordinates. Figure 5 – Pump Capacity Curve. Figure 6 – Pump Capacity Curve Defined Across Full Quadrant. Enter the pump efficiency curve using the same method as above, taking care to review the Min & Max Limits. Figure 7 – Pump Efficiency Curve. Finally, enter the pump NPSHr curve using the same approach, again taking care to review the Min & Max Limits. Figure 8 – Pump NPSHr Curve. Once the above steps have been completed, the new centrifugal pump will be available in the database for all future modelling projects. If any of the above is unclear or you require any further information, please contact us at: support@fluidflowinfo.com.