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408 Delaying Flow
Controlling a Valve’s maximum rate
The following screenshot shows how the Production Gate’s quantity goal has been configured on its Flow Control tab:
Flow Control tab, goal is quantity
• ThevaluefortheGoalquantityisreceivedthroughtheGinputconnector.(Inthismodel,the goal is 5000 gallons because each item has a Quantity attribute value of 5000.)
• ThepopupmenuoptionStartrunwithgoalOffhasbeenselected.(Thiscausesthegoalto be in the Off state at the start of the simulation.)
• TheValvehasbeeninstructedtoStopflowwhenthegoalisOff.
• Thepopupmenuoption“StartrunwithgoalOff”hasbeenselected.(Thiscausesthegoalto
be in the Off state at the start of the simulation.)
• If a new goal is received before the previous one is finished, the new goal will be ignored. (In this model, a new goal cannot arrive before the previous one is finished.)
An interesting aspect of this model is that the Production Gate valve has been set to have an infinite maximum constraining rate. This means that it will, in and of itself, not limit the rate of the flow moving through it. However, the block’s effective (actual) rate will be determined by the two upstream Valves. One of these Valves is connected to a Lookup Table block (Value library) that changes its maximum rate depending on the time of day. The other upstream Valve is connected to a Shutdown block (Item library) that causes the movement of flow to be stopped periodically for specified durations. This sequence causes some interesting effects in the model, and the Production Gate’s effective rate ranges between 80 and 0 gallons/minute.
Discrete Rate

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