# Control Valves

FluidFlow contains a database of control valves which can be used when building a network. The user can also very easily add new control valves to the database for specific modelling applications. Note, you only need to add a component to the database once. It will then be stored for all future projects. This section of the help file outlines the information required when adding a new control valve to the database. Figure 1: Data Entry for a Control Valve. Name: Allows you to enter a descriptive name for this element. Manufacturer: The name of the valve manufacturer can be entered here. Materials: The materials used to manufacture the valve may be defined in this field. Options include: Brass, Copper, Steel, etc. Applications: This option allows you to list the specific applications in which the valve may be used. Options include: Chemical, Power, etc. Max Operating Pressure: If there is a maximum pressure rating for the control valve 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. Size: This refers to the diameter of the valve opening. Size Unit: This refers to the diameter/size units used in the above entry. Usage: If there are specific uses for the new control valve they should be selected here. Uses include: Steam, Liquids, Gases, Flow Control, Pressure Control, etc. Xt-Pressure Loss Ratio Factor: The pressure drop ratio (choked flow ratio) for gases (Xt) is used to predict the choking point where additional pressure drop (produced by lowering the downstream pressure) will not produce additional flow due to the sonic velocity limitation across the vena contracta (choked flow). This factor is a function of the valve geometry and varies similarly to FL, depending on the valve type. The value of Xt is determined experimentally and supplied by the valve manufacturer. FL-Liquid Pressure Recovery Factor: The pressure recovery factor (FL) predicts the amount of pressure recovery that will occur between the vena contracta and the valve outlet. FL is an experimentally determined coefficient that accounts for the influence of the valve's internal geometry on the maximum capacity of the valve. It is a function of the direction of flow through the valve, the valve position, and whether the valve has a full or reduced seated trim. The value of FL can be obtained from the manufacturer. High FL values indicate low pressure recovery and low FL values are an indication of high pressure recovery. Higher FL values result in better resistance to cavitation. Fs-Laminar Flow Factor: Laminar flow factor is a correction factor applied to the pressure drop of the valve when the flow is in the laminar region. Fd-Valve Style Modifier: Valve style modifier applied to the standard equations depending on the type of valve (butterfly, gate, globe, etc.). The value of Fd can be obtained from the manufacturer. Defined By: The valve performance curve characteristic can be defined as either Cv or Kv. Users can choose from the units as shown in Figure 2. Figure 2: Data Entry for a Control Valve Curve Characteristic. Curve Data: The valve curve coordinates can be defined in this field. 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. Notes: - By default, the software displays one row for % Open vs. Cv(Cv usgpm/psi) units in the "Curve Fit" editor. Use the "Down Arrow" key or Select "ADD" if you need to create additional rows for the curve coordinates. - The coordinate values must be entered directly into the cells. coordinates cannot be copied from other software tools and pasted into the FluidFlow "Curve Fit" editor. Figure 3: Data Entry for a Control Valve Curve Coordinates. Note, users can select the most accurate curve-fit and equation order from the top left hand corner of the Curve Fit dialog. It is also important to set the Min & Max Limits as these will form the basis of any warning generated when the valve is solved in a system, i.e if we solve a system such that the operating point for the valve is outside the min and max limits, we will get a warning in the Messages tab to that effect. If any of the above is unclear or you require any further information, please contact us at: support@fluidflowinfo.com.