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How do I model a pump shut down transient event?
1) Set the pump Status(Initial) to 'On'
2) In the Transient (Operational) section of the pump properties set the pump type (transient) to 'Shut Down After Time Delay'.
3) Set the Time (Delay until Shut Down) property. The time you enter is the time at which the power to the pump motor is shut off. It should also be noted that a linear closure is assumed for this case.
4) Set the Pump Valve Type to check valve or control valve depending if the pump has one of these type of valves. If your pump has a control valve you'll need to enter the time it takes for the valve to close. This is the time taken for the pump discharge control valve to close after the transient simulation begins. The check valve assumes instant closure on the first detection of reverse flow. If you want neither a control valve nor a check valve, choose control valve and enter a large number such as 99999 seconds. If you want to control the closure time of the check valve use the steps from the last sentence then insert a check valve node element from your layout toolbar just downstream of the pump. See screen shot below:
2) Set the Pump Type to "Variable Speed/Torque".
3) In the Time (Valve to Operate) property you enter the time to close the check valve or to open it if initial flow is zero. If the check valve allows flow only in one direction enter 0 (i.e. the pump has a built in check valve). To simulate a pump with no check valve enter a very small number like 0.1 seconds, so the valve closes immediately.
4) For the control variable properties you can choose either speed or torque. For more information on the difference between the variable speed and torque setting please refer to this wiki article. Here the default value is to control the speed of the impeller by the using the pattern. If you want to control the speed using torque, so the momentum of the impeller is accounted for like with the shut down after time delay type you have the option to do that too. Doing this you will need to enter the nominal torque of the pump before it shuts down. The nominal torque is then multiplied by the operating rule pattern multiplier that will result in the torque values the engine uses. To simulate the same behavior as the "shut after time delay", you would have the multiplier in the pattern drop from 1.0 (full applied torque) to zero in one timestep, at the time that you want the shutdown to occur.
5) Define the operating rule the pump will shut down based on. Click the dropdown button in the entry box and choose <Edit...> to create a pattern.
6) Under the Operational(Transient, Pump) section you'll right click to create a new pattern and set the starting multiplier equal to 1.000. In the section of the window under that enter the "Time from Start" , which is the time the valve starts to close. In the multiplier column enter 0 for when the valve is closed. If you have the valve close between time steps 5 and 10 seconds it will incrementally close over that period. Keep in mind the ending multiplier needs to be equal to the starting multiplier, so if you want to have the pump shut down through the entire simulation please make sure to enter a time from start the is longer than the simulation duration. (i.e. 9999) then enter the starting multiplier in the cell next to it.
Modeling a pump start up transient event in Bentley HAMMER