When seeking a suitable pump for a given situation, the essential thing is not just to find one that will move the desired quantity of liquid.
It is necessary to consider the system and its performance in detail and ensure that the selected equipment will be appropriate for the conditions and perform its task reliably.
A wrongly selected pump, whether due to an incorrectly calculated head or simply due to improper consideration of suction conditions, can incur high running costs and cause significant damage to the process.
Therefore, the process of choosing a pump always starts with a detailed understanding of the system.
That is why Delflow Industries offers an Industrial Pump Sizing Toolkit for Excel, which allows users to perform pump selection, hydraulic calculations, determination of total dynamic head (TDH), net positive suction head (NPSH), pump performance assessment, and economic analysis.
It is necessary to examine the pumping system and its needs in detail since it is the pump’s operating environment. The pumping system always has a combination of static heads, pressure requirements, friction losses in pipes, and losses in auxiliary devices, and the sum of these elements is the total dynamic head.
However, it is not always necessary to increase the total head: production requirements vary, filters clog, valves freeze, and levels fluctuate.
Therefore, a pump that seems to meet all the requirements at a particular point in time may not be suitable for the process due to the changes in the system.
By looking at the system curve and knowing the pump curve, we can find out at which point the pump will work, and therefore whether it will really be suitable.
One of the most common mistakes of novice engineers is the belief that the higher the flow rate and head of the pump, the better its performance will be. Actually, this is not the case: the pump that will suit the job is the one whose characteristics most closely approximate the working conditions.
While oversizing in terms of flow rate and pressure seems like a safe choice, pumping equipment operating with an excessive reserve will have higher losses, require more power, and create additional vibrations, which will make maintenance more challenging.
Therefore, it is crucial to understand what pump will be needed and not to choose one that is too powerful.
Click Here to Download Readymade Engineering/Process Equipment Design, Continuous Improvement, Quality, Production, ISO 9001, ISO 14001, ISO 22000, ISO 45001, FSSC 22000, HACCP, Food Safety, Integrated Management Systems (IMS), Lean Six Sigma, Project, Maintenance and Compliance Management etc. Kits.
The total dynamic head is the main characteristic that shows how well the pump will perform its duties.
However, another parameter, the net positive suction head, is no less important since it characterizes the condition of the suction line.
These two values seem to be closely related: total dynamic head shows the pressure that the pump must overcome in order to function, and the net positive suction head is the difference between the pressure at the pump inlet and the liquid vapour pressure.
However, engineers often confuse these two characteristics. The calculation of the total dynamic head is needed to choose the pump that will best meet the requirements of the system. Meanwhile, the net positive suction head calculation is needed to ensure that the pump will have enough suction to avoid cavitation.
If the pump’s inlet pressure is lower than the fluid vapour pressure, bubbles will form and reduce the flow rate. Moreover, cavitation will cause additional stresses on the impeller, and the pump’s performance will deteriorate.
Therefore, when selecting a pump, one should examine not only the total dynamic head but also the net positive suction head.
The main cause of cavitation is the use of incorrect or imprecise data, since the available suction head directly depends on the source vessel pressure, temperature, liquid level, and losses in the suction line.
Therefore, it is vital to check the calculations and ensure that there is a sufficient safety margin.
The Delflow Industries toolkit includes a set of calculations that allows one to assemble a pumping system, determine the pump performance, calculate TDH and NPSH, and determine the efficiency of the pump.
In addition, the toolkit examines a multi-pump configuration and the impact of various factors on the system. Moreover, the toolkit helps to estimate consumption, energy, and life-cycle costs, as well as check preliminary design against API 610 standards and prepare an engineering summary.
It becomes clear that the toolkit provides a wide range of opportunities for engineers. Nevertheless, the question arises: why is it so important to use these tools?
First of all, consistent results are obtained when using standardized methods and performing calculations within the same document.
Moreover, the toolkit allows engineers to easily try different combinations and visualize how changing one value or another will affect the system.
Finally, economic analysis is crucial when selecting a pump: even if a certain pumping system seems to be the best choice in terms of flow rate and pressure, it is subject to operate with high energy consumption and therefore can be economically unjustified.
A thorough examination of the system using the toolkit can help to choose a pump that will best suit the specific operating conditions.
Nevertheless, one should remember that an Excel file is always just an auxiliary tool that helps to explore the possibility of selecting a pump.
The accuracy of the results will always depend on the accuracy of the entered data and the correct choice of formulas.
Therefore, it is vital to examine the assumptions and verify the calculations, check the performance of the pumps selected using the toolkit with the pump manufacturers’ data, and consult with specialists in the case of complex systems.
Proper selection of a pump always starts with a detailed study of the system and its requirements.
A good engineer understands that it is not the pump that is more important but the system in which the pump operates.
y looking at the system curve and comparing it to the performance of the pumps available, one can select the equipment that will have the best efficiency at the operating point. This approach will alleviate the problems associated with the use of pumps operating with an offset from the BEP.
Therefore, when selecting a pump, it is vital to examine not only the total dynamic head but also the net positive suction head.
Since cavitation is one of the most dangerous phenomena that can occur in a pump, verifying the correctness of the NPSH calculation is crucial to ensure that there will be enough suction pressure.
By using the Delflow Industries toolkit, engineers can not only perform a set of calculations that will help select the best pump, but also analyze the system as a whole and examine the impact of various factors on it.
For a process engineer, mechanical engineer, plant operator, consultant, or EPC team, determining the pump’s suitability using the toolkit is a convenient and reliable way to ensure that the selected equipment will best meet the requirements of the system in which it will operate.
Good pump engineering is about delivering the right flow and pressure with the reliability and economy in mind.