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  • Lawrence Matusek

The Art & Science of Pump Sizing and Selection: CPQ for Pumps, Part 1

Get the Right Pump

Pumps are the most widely used process equipment in the world.  Applications vary widely, and determining the best pump for a given need is one of the best opportunities for knowledge based guidance to get the right pump for the job.  Selecting the best pump involves trade-offs between efficiency and several other factors including cost and maintenance.  For high energy and critical services (high pressure, temperature, dangerous fluids, etc.) proper sizing and fit to the application needs is of paramount importance.  The knowledge base for pump selection has been codified by industry experts, and while there is no single standard, there are many proven tools for sizing and selection.  These tools can be integrated with sales and product configuration systems to allow for a seamless digital experience.  Other rotating equipment including mixers, fans, blowers etc. can similarly be automated for sizing, selection and configuration.

Properly balancing these considerations is both an art and a science. The pump industry has some of the most demanding customer facing business requirements of any manufacturing vertical, and they go well beyond traditional CPQ. These requirements start with selection. There are dozens of different pump types across several technical categories. Selecting "the right pump for the job" requires vast expert knowledge, and industry leaders can encapsulate nearly all this knowledge into expert systems.

Most customers can only explain the problem they are trying to solve. For example, I need to pump a truck filled with molasses three miles up the side of a mountain in coastal Alaska within one hour. What kind of pump should I buy?  

Our team could write an entire blog on just this selection problem. Beyond the basic head (pressure) and flow (rate) criteria, there are considerations for viscosity, altitude, head loss, ambient temperature, inlet temperature, heat imparted, food grade components and lubricants, mechanical seals, corrosion, available power, efficiency, serviceability, maintenance, durability, and more. As you may have guessed, this is a fictitious example but it gets "pumpoligists" revved up about the nuances of selecting the best pump family and then optimally sizing and configuring for its intended purpose. 

Can technology really be used to select the best pump family, or is this more art than science? One of our customers did an exercise where they asked ten of their experts to select the best pump for a given application like the example above. To everyone's surprise, they came back with ten distinctly different recommendations. So, who was right? The answer was… no one. As they discussed the reasoning behind their recommendation, each person had overlooked or improperly accounted for one or more considerations. There were a lot of "oh right, I didn’t think about that" comments. When they added it all together, the consensus recommendation was different from the original ten. So technology actually is *required* to consistently select the right pump family leveraging *all* of a company's expertise.

Curve Ahead

Once you have a selected the right pump family, you then need to choose the right size in that family for your desired duty point(s), i.e. required performance. The basics of sizing a centrifugal pump (which is the most common type in most industrial applications) are choosing the casing size and impeller type, and trim. Casings are graduated in size (e.g. 4", 6", 8") and have corresponding pump curves with a full-size impeller installed. Impellers are the rotating part of a centrifugal pump, and they have a number of veins that impel a fluid through the pump (thus the name). Impellers can be trimmed (i.e. reduced in diameter) which lowers the pump performance curve (and power consumption) to the specific performance required.

Pump curves are used to predict the performance of a pump across a wide range of operating duty points. Curves are generated from a limited set of duty points that are validated through bench testing. eLogic has worked with practically every commercial pump sizing application as well as a few custom applications. We understand the techniques and complexities of dynamically generating curves from data points to account for impeller trim and other influences. We have integrated curve generation functionality into numerous commercial CPQ solutions.

If it sounds simple enough, it isn't. There is a lot of science and a bit of art that goes into pump selection and sizing. There are also complex interdependencies that affect the overall performance of a pump. For many pump companies, selection and sizing is their "secret sauce" that differentiates them in the marketplace. Getting the optimal pump for an application yields the most efficient and trouble-free operation. Choosing a larger pump than needed results in excess power consumption. Choosing a smaller pump than needed results in insufficient performance for a given application. Choosing the wrong pump family can lead to recurring maintenance problems (and warranty claims). It is a complex balancing act that makes all the difference in the eyes of the end user.

I will be continuing this topic in a series of blog posts about pumps and CPQ. Up next, we’ll cover getting the pump right with selection, sizing, and configuration.

For more on this topic, as well as a deep dive into pump configuration, sales, aftermarket, and more, you can download my eBook “Pumps and CPQ: Solving CPQ for Pumps with Industry Best Practices” by clicking the button below:


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