Is there any way of analysing the reverse rotational speed of a pump impeller if slow closing check valves are being used at pump discharge and non reverse ratchet is not being used? I am primarily trying to analyse if the impeller and shaft reaches the critical speed during reverse rotation.
I guess you can have a look at the Extended Node Data in the Transient Results. If you are not using a ratchet to stop the reverse spin (i.e. reverse spin is allowed) then you can view the pump speed throughout the transient simulation i.e. before your transient event occurs and after it. In this case you can observe the speed of the impeller in the pump "after" the transient event has occurred (viz. shut down after time delay). This can give you an idea of the rotational speeds when the pump shuts down.
If you have selected "Reverse Spin Allowed?" you can check this. However, when the pump shuts down, the flow is going to reduce drastically and keep on reducing unless you have defined a pump start-up event after shut-down. I am not sure how the reverse spin on impeller will reach critical speeds though as the flow would reduce due to valve closure.
Here are some articles which you might find useful;
"Reverse spin allowed" limitation with pumps in a transient analysis
Does HAMMER assume a check valve in the pump?
Hope this helps.
Bentley Technical Support
I concur with Yashodhan - enter a number in the "report period" field of the pump (1 = report at every timestep), re-compute, then look at the speed graph in the Extended Node Data tab of the Transient Results Viewer.
Jesse DringoliTechnical Support Manager, Haestad ProductsBentley Communities Site AdministratorBentley Systems, Inc.