Determining the operating point on the pump characteristics curves goes beyond finding the respective flow and pressure that are required by the centrifugal pump to “move” the water between two points within a system.
Studying the effect that local as well as friction head losses have on the performance of the centrifugal pump is needed, as is establishing how it relates to the system’s resistance curve.
The PUMPS Online’s Project menu is where you can set the specific characteristics of the pipeline system where the pumping equipment will be installed and where you will specify what type of pump’s connection, serial or parallel, you require in order to obtain the system’s design point for your project’s requirements.
Let´s check the Project page’s features here.
When you access the Project’s page of PUMPS Online, besides the buttons Save Changes and Calculate, you can identify three panels:
Each one of them is oriented to reflect the typical configuration of a pumping system: A Suction Pipeline – one or more pumping pipes – and a discharge pipeline or pumping main. The diagram, assuming that the centrifugal pumps inside the pumping station are connected in parallel, would be similar to that of the figure below, in which three pumping pipes are presented:
The Suction and Discharge Panels
At each panel, you will find a field to enter the water elevation value in the suction and discharge tanks. Additionally, you must enter the geometric characteristics of the suction and discharge pipelines, specifically:
- Friction Coefficient (Hazen-Williams)
Note that using the button at the top of each pipeline’s data table, you can include in the calculation several “pipeline sections,” each with different characteristics (material, diameter, fittings, etc.):
In this case, the respective pipeline’s resistance curve is obtained, assuming that all its sections are connected in a series.
When you access the pipeline’s sections editor, pressing the yellow button at the respective row of the section to edit, you´ll find the text boxes to enter the values previously referred to and, if you’ve enabled the calculation of head losses through the using of fittings’ local loss coefficients (on the Settings page), you will find a table for you to select the quantity of each type of fitting installed in the edited section:
The Pumping Pipe Panel
In a similar way to the suction and discharge pipelines, you must specify, at least, one pumping pipe in each project in order to get any results with PUMPS Online.
For PUMPS Online purposes, each pumping pipe consists of a suction piping, one centrifugal pump (selected from the available models in your account’s database), and a discharge piping. For each piping section, you must specify a diameter, length and friction coefficient as well as the quantity and type of fittings installed in it.
You will see that, in this panel, there are two options for you to select how the pumping pipes (each with its respective pump model) will be connected: in a series or in parallel.
You will also find the button to add additional pumping pipes to your project, so analysis with pumps of different characteristic curves is possible.
When you edit any pumping pipe from its editor page (yellow button on each table’s row), you will find, besides the fields to specify the suction and discharge pipes’ properties, the list of available pumps models in your account’s database, from which you will select the one that will be used in the edited pumping pipe:
Note that it is possible to generate results for any number of similar pumping pipes; to do this, just specify the number of lines in the Quantity field. Therefore, if your pumping station, for example, consists of four similar pumping equipment operating in parallel (or in a series), you can create only one pumping pipe and then set the value in the Quantity field to four.
Finally, at the bottom left of the pumping pipe editor page, you’ll see a chart where the characteristic curve of the selected pump model is compared with the characteristic curve of the pumping pipe, i.e., the first curve minus the total head losses (pipes and fittings) in the suction and discharge sections:
Thus, you can visualize how much the selected pump capacity is reduced by the effect of the head losses in the flow path through the pumping pipe.
Saving the Changes and Performing the Calculation
Every change you do in the Project’s page (specifically: suction and discharge levels, type of pumps connection and number of similar items for pumping pipes) should be saved by pressing the Save Changes button at the top of the page.
For saved changes, just click on the Calculate button and PUMPS Online determines the operating point of the whole system. If everything is okay, a message like the following will be shown:
At this point, you can go to the Results page to see the system’s operating point as well as the ones for each centrifugal pump modeled in your project. In this presentation, you can watch the entire process of an example project’s creation and results analysis using PUMPS Online.
Finally, if no solution is obtained, a message will appear upon detection of errors such as:
- The pumping characteristic curve does not intercept with the system’s curve.
- The pumping pipes characteristic curves cannot be associated in a series or in parallel, by not being in the same range of pumping heads in the case of parallel connection, or in the same range of flow rates when connected in a series.
- The maximum head of the pump characteristic curve is below the specified elevation for the discharge tank.
Then the following message will be shown and you will also see, below the Calculate button, the description of the detected error: