Applies To Product(s): Bentley HAMMER Version(s): 08.11.XX.XX Environment: N/A Area: Layout and Data Input Subarea: Original Author: Terry Foster, Bentley Technical Support Group When I run a pump shut down using the pump shut down after time delay setting, the residual flow through the pump(s) is different from when the pumps is set to the variable speed/torque pump type. What is the difference between these two types of pumps? Background The difference between the pump shut down after time delay and the variable speed/torque pump type options are the shut down after time delay assumes that the electrical torque applied to the pump impeller suddenly drops to zero, whereas with the variable speed type, you enter the pattern of pump impeller speed so you are directly controlling the speed of that impeller. With the shut down after time delay, the impeller will take some time to spin down once power is cut based on the inertia/momentum. Steps to Accomplish If you wanted to have the variable speed/torque pump type act like the shut down after time delay pump type (cutting off the power instead of having to manually control how the speed changes), then you could set it to use "Torque" as the control variable instead of "Speed" (this is the default). This is done in the pump properties. If you want to use the variable speed type (instead of variable torque), you would first need to decide how long it takes for the pump impeller to slow to a stop, after it shuts down. If you need help in doing this, you could do a trial run using the "Shut after time delay" transient pump type with a number in the "Report Period" field. After computing the transient simulation, look at the bottom of the transient analysis details report to see the pump speed over time. Next, you will need to define a transient pump pattern (Components > Patterns) based on that delay and when you want the pump to restart. You'll need to decide how long it takes for the pump to turn back on as well. In the pattern, 1.0 represent full speed and 0.0 represents fully stopped. Model the pump as being on in the initial conditions, set the transient pump type to variable speed, then select the pattern that you created.
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