The correct sizing of a centrifugal pump

Factors to consider when choosing the right pump for your application

When sizing a centrifugal pump, it is important to consider it as part of a hydraulic system, taking care to size it correctly from both a hydraulic and mechanical perspective. In fact, if a pump that is not suitable for the intended use is installed, problems can occur that result in maintenance costs, loss of dangerous/expensive liquid, and plant shutdowns.

Size a centrifugal pump among the countless options available, it can be very complicated, so it is good to identify first of all:

• system pressure and liquid characteristicsare very important to ensure the correct casing of the pump and its configuration;
• an accurate estimate of the budget and purchase costs, considering the actual pump usage time: This is necessary to avoid selecting an unsuitable, undersized, or oversized product, which would lead to increased operating costs.

Choosing a low-cost pump doesn't make much sense if it turns out to be inefficient, as it's prone to frequent breakdowns or expensive to maintain.

Essential factors for the correct sizing of a pump

From a hydraulic perspective, identifying the correct centrifugal pump for the system means ensuring that some important factors are considered.

The capacity and prevalence of a pump

To know how to calculate the Centrifugal pump head it is necessary to know the amount of liquid that must flow into the pump and at what distance the same liquid must be re-pressurized within the system. In the prevalence calculation, it is essential to also consider any pressure losses related to fluid friction, the possible presence of valves, reductions, and elbow bends in the piping.

What are the characteristics of the fluid being pumped that should be considered for the proper selection of a centrifugal pump?

  The main characteristics of the fluid to be pumped that are important for correct pump selection are:

• The nature and temperature of the fluid  influence the selection of pump material. Each material, in fact, has different mechanical/chemical compatibility with the pumped fluid and, at the same time, has a resistance to operating temperature. Therefore, knowing the type of fluid being pumped, its concentration, and its temperature allows for the correct selection of compatible materials.
• Fluid density and viscosity they influence the engine power to be selected and at the same time the correct sizing of the impeller cut, to ensure the achievement of the required performance.
• The presence of solid suspensions in the pumped liquid: this information is important for choosing the type of centrifugal pump to select.

The Magnetic drive centrifugal pumps are generally suitable for working with clean or lightly contaminated liquids.

CDR Pompe, thanks to its design team—which has decades of experience in the field of magnetic drive—has managed to overcome this limitation by developing the XTN and XTS pumps, magnetic drive pumps specifically designed for pumping liquids with high concentrations of solid suspensions.

What is the maximum pump efficiency and its optimal use?

From a technical standpoint, it is advisable to run the pump ideally in the Best Efficiency Point (B.E.P.) Efficient Point, that is, between 50 and 110% of the pump’s maximum efficiency point, and in any case never at the extremes of the Q-H curve. This operating point, in fact, minimizes vibrations, insufficient lubrication, and cavitation, and therefore breaks of the pumps themselves.

CDR can offer solutions to safeguard pump operation even in operating conditions far from the BEP, for example by configuring the pump through the installation of bushings with a special surface treatment.RunSafe SICself-lubricating and capable of counteracting poor lubrication.

Another deciding factor: maintenance cost

A relevant role in Choosing the ideal pump it is also covered by the cost of maintenance of the same in the medium-long term, not just the purchase cost. CDR magnetic drive pumps, especially when compared to mechanical seal pumps, are in fact simple to dismantle and reassemble and, if used at the right operating point, achieve a Useful life of approximately 10/15 years (hundreds of CDR pumps installed can easily reach 25/30 years of service).

Contact us In case of doubts about the sizing of the centrifugal pump for your application. Our sales representatives, thanks to their experience, are able to assist you in choosing the right ideal pump, discussing the various aspects listed above and delving into the details of each specific application.