You are currently reviewing an older revision of this page.
Is it possible to set up a control to change the relative closure of a valve?
You can set a control through the controls manager (Components > Controls). Controls created in this way will need to have an adjustment to the TCV headloss coefficient. This is the only method currently available to change valve settings through operational controls. If you need to change the setting on a TCV based on a tank settings, this method must be used, and use Headloss Coefficient as the "Coefficient Type" for the TCV.
If you do not have the headloss coefficient for the valve, it possible to derive it. First, use the fully open discharge coefficient along with the user-defined valve characteristics curve to determine the exact discharge coefficients that correspond to a range of relative closures (If you have the manufacturers discharge coefficient, you can use that as well). Then, you would take the valve diameter along with the discharge coefficients and use an equation to convert to a headloss coefficient (K). Here’s the equation with US units:
K = 39.693 * D^4/Cv^2
However, if you want to adjust the relative closure of a TCV based on time, you can create a pattern. Go to Components > Patterns and create a new pattern for "Valve Relative Closure." Set the starting relative closure to be the initial position of the valve. Then create the pattern that will be used by the program to adjust the relative closure of the TCV.
Note that this type of pattern works in conjunction with "Valve Characteristics Curve" selected as the "Coefficient type" for the TCV, and the pattern that you enter would be selected in the field called "Pattern (Relative Closures)". If you are using Headloss Coefficient or Discharge Coefficient as the Coefficient Type, your pattern needs to be entered under "Valve Settings" - in this case, the values entered in the pattern are multipliers, which multiply against the initial headloss coefficient. So, a value of "1" on the pattern will cause the program to use the original initial headloss coefficient at that time. Therefore in order to close the valve using this method, you would need to use a very high multiplier in the pattern, such as 999999999999. So, in a situation where you need to open and close a valve based on time, it would be better to use the Valve Characteristics Curve type, or logical controls.