Simulating Pump Transients through InfoSurge

Power outage and Pump trips cause the pump operation changes. Power outage is the most severe case for pump transient events. There are two ways to simulate pump operations within InfoSurge.

1- Pump Speed Change with creating speed ratio curves is the easiest way to simulate the pump operation change. The Pump Operation Change Data window is accessed by selecting a pump and selecting the Pump Operation Change   button in the Attribute Browser. This function is used to describe the pump/turbine operational changes during transient analysis.  A turbine is represented by the pump element with turbine-specific parameters in a surge model. A wicket gate can be specified for the turbine element to simulate the transients due to wicket gate changes.

2- Applying real pump operations with Pump Files
If there is a pump trip, we always don’t know how speed changes exactly, in this case we can use the pump file to calculate the actual speed changes. The Pump Surge Data is accessed from the Pump Surge Data   button from the Attribute Browser when a pump is selected. This dialog box is used to specify the properties of the pump/turbine which are to be used in a surge analysis. If you intend to have pump trip or ratchet during the surge analysis it is necessary to specify a Pump File. In the Select Pump File Provided option, select the appropriate pump file (a Pump File Selector tool is provided to assist in the pump file selection) from the menu, include the necessary Pump File Settings.

A Pump File is a table defining head and torque as a function of flow and speed. These are based on experimental data and 8 files are available to use. The Pump Files contain the information about pump performance in both normal and abnormal operating conditions. There is a calculator provided, Pump File Selector    to help you select the most appropriate pump file.

The Pump Inertia Calculator calculates the pump and motor inertia based on the rated conditions using curves fit to a large quantity of data (Thorley, 1991).

Suter diagram defines the pump behavior for each zone. During a hydraulic transient event, a pump may experience either a reversal in flow, rotational speed, or both, depending on the situation. It is also possible that the torque and head may reverse in sign during abnormal zones of performance. In extreme cases, the full four quadrant characteristics representing the eight possible zones of operation (four normal and four abnormal) must be used.

In summary, when you use the speed change curve, only one speed change curve is going to be applied for different situations. However, with Suter pump file curve method, pump speed curve is not going to be linear and InfoSurge makes the interpolation based on the pump files.

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