News News Mechanical seal pumps Magnetic drive pump Centrifugal pumps 29 September 2026

Higher than expected energy consumption: the first warning sign
Abnormal vibrations and noise indicate an incorrect pump sizing
Cavitation: one of the most obvious signs of incorrect pump sizing
Frequent breakdowns in the seals and mechanical components
When they flow rate do total head not meet the needs of the process
Relying on a specialized partner to verify the correct sizing of the pumps
Most common FAQ about pump sizing problems

The correct sizing of the centrifugal pumps is a fundamental aspect to ensure high performance for the entire system. The choice of the appropriate product must take into account specific and precise parameters such flow rate as total head the characteristics of the fluid to be moved, temperature, pressure and operating conditions. When all these aspects are selected with precision, the pump operates at its maximum efficiency, ensuring reliability, low consumption and a longer lifespan for the components, even in heavy-duty applications.

An oversized or undersized pump is not always easy to identify, however, as it can continue to operate for a long time without highlighting immediate failures. This often leads to underestimating the problem, while at the same time energy costs increase, the wear of mechanical parts accelerates and the risk of unexpected plant shutdowns increases.

Recognizing the signs that indicate a dysfunctional operation Best Efficiency Point (BEP), The pump’s maximum efficiency point allows for intervention before small anomalies turn into extraordinary maintenance or the early replacement of the machine. For this reason, it is important to regularly monitor the pump’s behavior and verify that the actual performance is in line with those predicted during the design phase.

In CDR Pompe We pay great attention to the sizing of our pumps, from the design phase to the installation and commissioning, in order to guarantee high performance and a long product lifespan.

Higher than expected energy consumption: the first warning sign

Among the most evident indicators of a possible Incorrect sizing This includes the increase in energy consumption. If, for example, a centrifugal pump consumes more energy than the values estimated during the design phase, it is advisable to verify that it is operating under the conditions for which it was selected. Very often, in fact, the problem does not depend on the motor or the wear of the components, but on the fact that the pump is forced to operate outside its maximum efficiency point, requiring more “effort” and therefore more energy. This situation is particularly common in plants that have undergone changes over time, or in those where the actual requirement has changed compared to the initial conditions.

An oversized pump tends to generate flow rate more power than the process requires. To adjust its operation, it is often adjusted flow rate by partially closing the valves: this solution allows the system to remain operational, but it introduces load losses that result in greater energy consumption and a reduction in overall efficiency.

The main signs are:

Electrical consumption higher than the design values, Even in the presence of an apparently stable system.
Constant use of the control valves to limit the flow rate excessive production by the pump.
Operation away from the Best Efficiency Point (BEP), resulting in a decrease in hydraulic yield.
Increase in operating costs, This is due to the energy consumed without any real benefit for the production process.
Reduction of the overall efficiency of the system, This can also affect the performance of other connected equipment.

Periodically monitoring the electrical absorption of the pump and comparing it with the design data represents one of the most effective methods for identifying an incorrect sizing. A timely technical analysis allows evaluating whether the problem is related to the operating conditions or whether it is necessary to intervene on the configuration of the system or even on the choice of the pump itself.

Abnormal vibrations and noise indicate an incorrect pump sizing

One centrifugal pump Properly dimensioned equipment operates under hydraulic and mechanical equilibrium conditions, with contained vibrations and a noise level compatible with the characteristics of the system. When, however, unusual vibrations or persistent noises begin to appear, it is necessary to verify that the pump is operating within its ideal operating range.

Vibrations and noises not only cause discomfort during exercise, but are often a sign of stresses that over time compromise the reliability of the entire system. Identifying the cause at the root of the problem allows for intervention before component deterioration leads to higher maintenance costs or production downtime.

The main conditions that can generate abnormal vibrations and noise, related to an incorrect sizing of the pumps, are:

Flow rate less than the expected one, This causes the pump to work in an area of the curve for which it was not designed, resulting in flow instability.
Operation away from the Best Efficiency Point (BEP), a situation that alters the balance of power hydraulic forces acting on the impeller and increases the mechanical stresses on rotating components.
Internal circulation of the fluid, These are caused by abnormal operation, which produces turbulence and pressure variations inside the pump, resulting in an increase in noise and vibrations.

These conditions can have significant effects on the lifespan of the machine:

Accelerated wear of the bearings, subjected to loads higher than those provided for during the design phase.
Damage to mechanical components, This is due to the continuous stresses and abnormal movements of the shaft.
Reduced pump lifespan, which requires maintenance interventions They are more frequent and increase the risk of sudden breakdowns.

For this reason, vibrations and noise should never be considered a normal consequence of the pump’s operation. A technical inspection allows verifying whether these phenomena are due to a sizing error, a change in operating conditions, or other critical issues with the system.

Cavitation: one of the most obvious signs of incorrect pump sizing

Among the phenomena that deserve greater attention is the cavitation, A condition that we have already extensively discussed and that can quickly compromise the performance and integrity of the product. Cavitation occurs when, within the pump, the fluid pressure drops below the vaporization value, causing the formation of vapor bubbles that implode in the areas of higher pressure. This process generates continuous micro-impacts on the impeller and the internal surfaces of the pump, accelerating wear.

Recognizing cavitation in its early stages is crucial to avoid more extensive damage. The most common signs are:

Metallic noise similar to the grinding of gravel or pebbles, easily perceptible during the operation of the pump.
Abnormal vibrations, These increase progressively as the phenomenon worsens.
Reduction of flow rate or total head, This results in a loss of process efficiency.
Intermittent performance, These systems are characterized by irregular operation and fluctuations in the operating parameters.

Cavitation does not depend solely on the pump sizing (other causes are explained in this article), but a machine selected without properly considering the actual operating conditions may be more susceptible to this phenomenon. Even modifications made later to the system, changes in the fluid characteristics, or changes in production requirements can favor its occurrence.

Frequent breakdowns in the seals and mechanical components

The recurrent replacement of mechanical seals, bearings or joints is often attributed to the normal wear of the components. In reality, when these interventions become “too” frequent, it is advisable to verify whether the pump is operating under the conditions for which it was designed. In fact, improper pump sizing subjects machines to continuous stresses that accelerate the deterioration of mechanical parts and increase the number of maintenance interventions required.

Vibrations, operation away from the Best Efficiency Point (BEP), internal fluid recirculation, and cavitation generate additional loads that are transmitted to the shaft and rotating parts. Over time, these conditions compromise the pump's stability and reduce the lifespan of the most stressed components.

Among the elements that may be most affected by an inadequate operation are: the mechanical gears, subject to premature wear due to vibrations and pressure variations; the bearings, those that work with loads higher than those intended, increasing the risk of failure; Transmission joints, Exposed to continuous mechanical stresses that can cause abnormal movements and misalignment; The pump tree, which can undergo deformations or repeated stress when the operation deviates from the point of maximum efficiency.

When the same components are replaced several times within close intervals, it clearly means that the intervention is solely focused on the effects and not on the root cause of the failure. A verification of the sizing and operational conditions, on the other hand, allows identifying any critical issues and planning truly effective interventions.

When they flow rate do total head not meet the needs of the process

The problem is particularly evident in undersized pumps, which are unable to provide flow rate or the other total head necessary to ensure the continuity of production. However, there is also the opposite situation: an oversized pump can deliver performance exceeding actual needs, forcing the system to undergo continuous adjustments that reduce overall efficiency.

Some signs make it easy to identify this condition:

Flow rate insufficient, With longer times for the transfer of fluids or for filling the systems.
Total Head not adequate, This prevents the fluid from reaching the pressures required by the process.
Intermittent performance, This is due to the difficulty of the pump in maintaining constant operating conditions.
Frequent changes to the system settings, necessary to compensate for performance that is inconsistent with production requirements.
Reduction in the efficiency of the entire system, This can also involve equipment connected to the pump.

These situations can be due to an initial selection that was not correct, but also to modifications made later to the plant, to an increase in production capacity, or to variations in the characteristics of the treated fluid. For this reason, it is advisable to periodically check that the working point of the pump is still compatible with the actual operational requirements.

Relying on a specialized partner to verify the correct sizing of the pumps

A centrifugal pump can continue to operate even when its operating point is now far from what was intended. It is precisely this situation that makes it more difficult to identify a sizing problem for the pumps: the system remains operational, but consumption, vibrations, wear, and maintenance interventions increase. Sometimes the first warning is a higher energy bill; other times it’s a fixture that fails frequently, an unusual noise, or one flow rate that no longer meets the requirements of the process.

At CDR we pay enormous attention to the correct sizing of the pumps, from the initial design stages to the kick-off meeting, to ensure our customers optimal operation throughout the product’s entire lifecycle. We also provide assistance with the installation and commissioning of the pumps, a periodic and scheduled maintenance service, and a High-level service department to support customers with any questions, problems or information.

Contact us for a consultation and to learn about all the applications, parameters and functions of our pumps magnetic drive and mechanical seal.

Most common FAQ about pump sizing problems

1. Why is the Best Efficiency Point important in pump sizing?

The Best Efficiency Point, Generally referred to as BEP, this point in the curve is where a centrifugal pump reaches its maximum hydraulic performance. Working near it normally allows for maintaining a good balance between performance, consumption, and mechanical stresses. When the working point moves significantly away from BEP, radial forces on the impeller, internal turbulence, and vibrations can increase, while performance may decrease.

The BEP should not, however, be interpreted as a single mandatory value to which the pump must operate at all times. The machines can operate within a certain operating range; the problem arises when they are used permanently in areas of the curve that are not favorable. Therefore, during sizing, it is important to verify the position of the flow rate demand relative to the yield curve and also to assess any changes in demand during the different stages of production.

2. Does an oversized pump always consume more energy?

Not necessarily in every condition, but an oversized pump It may result in higher consumption than necessary to achieve the required performance. The problem becomes particularly evident when it flow rate is restricted through a partially closed valve. In this case the machine continues to develop pressure, while part of the energy is dissipated through the regulation. The actual consumption must however be evaluated considering the pump curve, the working point, efficiency, absorbed power and characteristics of the circuit.

Even a pump with an under-sized capacity can have high consumption if it is continuously pushed into conditions that are not suitable for achieving performance beyond its capabilities. Therefore, simply comparing the nominal engine power is not sufficient to determine which machine is more efficient. It is necessary to analyze how much energy is actually used to meet flow rate the total head demands, taking into account the entire operation of the pump and the circuit.

3. How do you know if a pump is working too far from its maximum efficiency point?

To understand where a pump is actually working, it is necessary to compare it with flow rate and total head effective with the characteristic curve provided by the manufacturer. Just listening to the machine or observing the vibrations can provide useful indications, but they do not allow for determining the exact point of operation with precision.

The verification can include measuring the pressure in suction and discharge, the electric absorption flow rate, and, when necessary, the vibrations. By entering the measured values on the pump curve, it is possible to understand in which zone the machine is operating and how far the point deviates from the BEP. It is also important to repeat the evaluation under conditions representative of normal operation, especially when the demand varies during the day or during the different production phases. A single measurement could in fact only describe one of the possible conditions and not the actual behavior of the pump over time.

How to determine if a centrifugal pump is oversized or undersized