November 1, 2015, 05:31 AM

While putting the setting in the Flow Control Valve, its releasing more flow than the setting.
For e.g my setting for FCV is 4373 m3/hr but its releasing around 5500 m/hr with an error message "open but cannot deliver the flow".
Isnt it suppose to restrict the flow to 4373 m3/hr .
In another scenario its doing the reverse, its reducing the flow much below than the setting instead of maintaining the setting flow.
Please help me to resolve this error.

Best Regards,

Patrick Moore
November 2, 2015, 01:42 PM
Hello Saurabh,

One of the first things to check with both valves is to see if they have any control values or initial status that would set them to "open" or that would override the valve setting. Unlike a pump an "open" value on a valve control statement will make the valve act like an open pipe and not like a valve.

When the valve is active (by using a setting on the valve without any control or without an initial status setting it to open) the valve will limit the flow downstream to the value of the setting, unless there is not enough head difference between the up and downstream points of the valve that can be used to "drive" the flow requested through it. In the model when a FCV is used it calculates what head value at the downstream of the valve that is needed to push exactly the flow requested by the setting. As long as this head is lower than the upstream head at the valve, the valve will maintain the requested flow by inducing headloss on the valve to match the desired flow. If the head upstream is lower than what is necessary for that flow, a yellow light will show and the text run report (if warning messages are checked to be issued, will show a warning for that valve that it was "open, but could not deliver flow". This means there was not enough head to drive the requested flow, but the model gave as much flow as would be possible based on the available upstream head. This is the same answer you would see if the valve was set to fully open under these specific head conditions. In other words, the valve will not have any headloss under these conditions and will not restrict the flow in any way.

For a valve to provide more flow that what is requested by the valve setting has to be either a simple or logical control that is changing the valve setting to a different value than the one listed under the valve "setting" when the valve is viewed in the model explorer, or the valve has been set to "open" by a control statement and is acting like a pipe and there is sufficient head to push more flow that the setting intended to be used by the valve. For the periods where the valve is flowing more than expected setting, check to see what the valve status and setting is when you graphically plot the output results and look at the tabular output data. This coupled with the output text report set to use a full status report and to generate warning messages (see below) can usually help identify if the valve is operating as expected or not. If you find the status is not shown as "active" and/or the setting is not as expected check your logical (rule based controls) or the simple controls associated with the valve to see if one or more controls is causing the valve to be "open" or have a different setting for the valve.

Where to set the report options in the run manager:
(Click if need larger image)
Setting the report options for a full status report with warning messages:
(Click if need larger image)


To make a closed valve "active" properly within the software simply use a control statement that assigns a "setting" to the valve rather than making it "open"
See below for an example of both statements and how to properly make a valve active using a setting.

Valve control examples
(click for larger image if necessary)

If you need further information or if we misunderstood your question, please reply back in this thread.

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