# PD Pumps or Compressors

FluidFlow contains a database of Positive Displacement (PD) Pumps & Compressors which can be used when building a network. The user can also supplement this database by adding new pumps or compressors for specific applications. This section of the help file outlines the information required when adding a new PD pump/compressor to the database. Firstly, define the main pump parameters by selecting: Database | Boosters | Positive Displacement Pump or Compressor and select "Add". Give your new pump a (unique) Name and enter the main operating parameters for the pump (see Figure 1). Figure 1: Data Entry for a Positive Displacement Pump or Compressor. Name: Allows you to enter a descriptive name for this element. Manufacturer: The name of the pump manufacturer can be entered here. Materials: The materials used to manufacture the pump may be defined in this field. Options include: Steel, Stainless Steel, Bronze, etc. Applications: This option allows you to list the specific applications in which the pump may be used. Options include: Chemical, Power, etc. Max Operating Pressure: If there is a maximum pressure rating for the pump you should enter this value here. Leaving the value at 0 means that FluidFlow will not make an overpressure check. Pressure Unit: The pressure units used when defining the Max Operating Pressure. Suction Size: This refers to the diameter of the pump suction connection. Discharge Size: This refers to the diameter of the pump discharge connection. Size Unit: This refers to the diameter/size units used in the above entries. Max Operating Speed: This refers to the maximum operating speed of the pump which is available from pump manufacturers. Efficiency (%): This refers to the pump efficiency which is available from pump manufacturers. Displacement Vol/Rev: This refers to the volumetric quantity of fluid displaced per pump revolution. This information is usually available from pump manufacturers. Volume Unit: This refers to the volume units used in the above entry. Use Internal Eff. Correction: There are two options to choose from, "Yes" or "No". Choosing "No" requires the user to define the curve relationship for performance degradation factor. Choosing "Yes" allows FluidFlow to automatically apply a correction factor for pump efficiency. Performance Factor: This represents the performance degradation factor which is a function of pump speed and typically has a range of 0 - 1. The degradation factor takes into account the pump slippage and performance "tail-off" with pump speed. A major effect on PD pump performance is the loss of flow due to slip conditions. The expanding cavity on the inlet side of a PD pump creates a low pressure area that requires it to be filled with fluid. This cavity can then be filled with fluid from the inlet pipeline under ideal operating conditions. However, if slip occurs, the cavity may also be partly filled with fluid on the discharge side flowing back through the pump clearances to the inlet side, thus affecting the overall pump performance. In general, the pump performance is dependent on the slip which occurs in a pump. The performance factor takes this into consideration and is plotted along the curve y axis. Figure 2 provides an illustration of a typical performance factor curve. Figure 2: Data Entry for Performance Factor for a Positive Displacement Pump or Compressor. To create the curve-fit, simply enter the coordinates as provided by the manufacturer in the columns on the left hand side. FluidFlow will automatically create the curve-fit once a minimum of three coordinates have been defined. Curve Fit Type: You can select the most accurate curve-fit from the top left corner of the dialog. There are two options to choose from: Linear and Polynomial. Equation Order: You can select the most accurate equation order from the top left corner of the dialog. There are a number of options available including: Linear, Quartic, Cubic, etc. If any of the above is unclear or you require any further information, please contact us at: support@fluidflowinfo.com.