One of the Pipeline’s Boundary Conditions that can be defined in Ariete, our software for water hammer calculation in pipeline systems, is that of a water Pumping Station in which there exists one or more Centrifugal Pumps with similar characteristics and operating in parallel (two or more units).
Once you’ve created the Analysis Longitudinal Profile of the pipeline to model with Ariete, the next step is to establish the boundary conditions at its start and end chainages. In this case, what you will be selecting is Pumping Station so you must activate the corresponding option in the Devices menu → Upstream Device → Pumping Station:
After that, the Pumping Station dialog will be shown for defining the necessary information:
From this dialog it is not only possible to enter specific information about the Centrifugal Pumps installed in the pumping station, but also how the pumping system is expected to operate when modeling the water hammer occurrence can be indicated on it, specifically in regards to the sudden stop in the case of electricity supply failure into the pumping station.
Let’s review below the minimum information required in the fields on Data and Operation tabs of the Pumping Station dialog.
Pumping Station Data Tab
Modeling of Pumping Stations feeding pipeline systems with Ariete is done by adjusting the values of the installed centrifugal pumps’ characteristic curve to a quadratic equation of the type:
Where:
| HB: | Is the net head or head pressure generated by the centrifugal pump. |
| QB: | Pumped flow by the centrifugal pump |
| A, B, C | Data adjustment coefficients. |
This adjustment is made from the information provided by the user on the Data tab of the aforementioned Pumping Station dialog and for which there are two options:
- Enter the values of the centrifugal pump’s characteristic curve to consider in the water pumping station, specifying at least three operation points:
- Automatically generate, from the values of flow, head, efficiency, and power at the Best Efficiency Point (BEP), the theoretical centrifugal pump’s characteristic curve. In this case, you must press the button to the right of the table to show the dialog for entering this information, after which the table is created with the respective values:
After setting the table with the characteristic curve of the pumps installed in the water pumping station, it is necessary now to enter, at the bottom of the Data tab, the values of Water Level in the station’s Suction Tank, the pump’s nominal rotational speed, and the moment of inertia of the Motor-Pump couple, as well as the number of similar equipment operating in parallel:
When you click OK to close the Pumping Station dialog, the station symbol will be drawn in the Ariete’s Main Window, at the starting chainage of the Longitudinal Profile:
Pumping Station Operation Tab
In Ariete, the operation of the equipment in the modeled Pumping Station is performed by varying the rotational speed of the pumps at the station and for which you have two options:
- Specifying the pumps power failure rundown starting time. This is the option to model the condition of the water hammer when a sudden stopping of pumping occurs, and in which case the entered value of equipment’s moment of Inertia, in the dialog’s Data tab, plays an important role in the way that will vary (decrease in this case) the rotational speed of Centrifugal pumps during the simulation of transitory analysis.
- Setting the Pumps Rotational Speed’s Law of Variation over the simulation time. With this option, you can manually specify how the rotational speed of the Centrifugal pumps during the water hammer simulation will vary, by specifying the percentage with respect to the nominal rotational speed (which was entered on the dialog’s Data tab) for each specific moment of the simulation. This condition is useful for modeling the pipeline system’s behavior under steady state conditions (100% of rated speed throughout the simulation), among other conditions:
Thus, with the specific information of the Pumping equipment inside the station as well as its operational regime during simulation, Ariete is ready to generate results from water hammer calculation.
In this article, you will see the Water Hammer Analysis with Ariete in a pumping pipeline system when an electrical supply failure in the respective pumping station occurs.