Several Common Factors Affecting The Service Life Of Centrifugal Pumps

Jun 14, 2025

Users often ask, "How long will the pump run?" The standard answer is, "It depends on the situation

In the formula for pump reliability life expectancy, almost every factor depends on the end user, especially the operation and maintenance methods of the pump. For example, if a standard L-shaped ANSI pump operates near its optimal/design operating point and is properly maintained, it is expected to operate for 15 to 20 years, and in many cases over 25 years.

What factors can the end user control to extend the service life of a given pump design? Although not an exhaustive list, the following 13 noteworthy factors are important considerations for extending pump life.

 

1. Radial force

 

Industry statistics indicate that the biggest reason for the discontinuation of centrifugal pumps is the failure of bearings and/or mechanical seals. Bearings and seals are early indicators of pump operation and also a precursor to what is happening inside the pump system.

The first best practice for centrifugal pumps is to operate them at or near their optimal efficiency point (BEP). At the BEP point, the pump design will withstand the minimum radial force.

High radial force and subsequent shaft deflection are the killers of mechanical seals and factors that shorten the life of bearings. If it is high enough, the radial force will cause the shaft to deflect or bend. If the pump is stopped and the shaft runout is measured, no problems will be found because this is a dynamic occurrence.

For example, a bending shaft running at 3600 RPM bends 7200 times per minute. High cycle deflection will make it difficult for the sealing surface to maintain contact and the fluid layer required for proper sealing operation.

 

2. Lubrication pollution

 

For bearings, over 85% of bearing failures are caused by the entry of pollutants, whether it is dirt, foreign objects, or water. Only 250 parts per million (ppm) of water can shorten the lifespan of bearings by four times.

The service life of lubricating oil is crucial. Continuous operation of a pump is similar to driving a car continuously at a speed of 100 kilometers per hour. It doesn't take long to enter some mileage on the odometer 24 hours a day, 7 days a week -2400 kilometers per day, 870000 kilometers per year.

 

3. Inhalation pressure

 

Other key factors that affect bearing life include suction pressure, alignment of driving equipment, and a certain degree of pipeline strain.

For single-stage horizontal cantilever process pumps, the axial force on the rotor is directed towards the suction, so offsetting the suction pressure (to some extent and with limitations) actually reduces the axial force, thereby reducing the load on the thrust bearing and extending its service life. four Equipment alignment

The misalignment of the pump and drive equipment causes overload of the radial bearings. The service life of radial bearings is exponentially related to misalignment. For example, due to a misalignment of only 1.5 mm, end users may encounter some kind of bearing or coupling problem during three to five months of operation; However, within a deviation of 0.025mm, the same pump may operate for more than 90 months.

 

5. Pipeline strain

 

Pipeline strain is caused by the misalignment between the suction/discharge pipeline and the pump flange. Even in robust pump designs, the resulting pipeline strain can easily transfer potential stresses to the bearings and their respective bearing seats. Force can cause poor bearing fit/or misalignment with other bearing positions.

 

6. Fluid characteristics

 

Fluid characteristics such as pH, viscosity, and specific gravity are key factors. If the fluid is acidic or corrosive, the components in contact with the liquid, such as the casing and impeller materials, require special design. The amount of solids present in the fluid, their size, shape, and abrasive quality are all factors.

 

7. Service

 

The severity of the service is another major factor, how often does the pump start within a given time? For example, a pump that starts and stops every few seconds has a much higher wear rate than a pump that runs continuously under the same conditions.

Under the same conditions, submerged suction pumps will operate more reliably than lift suction pumps. Improving conditions requires more extra work and provides more opportunities for air intake or worse conditions (drying up).

 

8. Net suction head

 

The higher the margin between the available net positive suction head (NPSHA) and the required net positive suction head (NPSHR), the less likely the pump will experience cavitation. Cavitation can cause damage to the pump impeller, and the resulting vibration can affect the seals and bearings.

 

9. Pump speed

 

The operating speed of the pump is another key factor. For example, the wear rate of a 3550 rpm pump is 4 to 8 times faster than that of a 1750 rpm pump.

 

10. Impeller balance

 

Unbalanced impellers on cantilever pumps or some vertical designs can cause shaft agitation, which can cause the pump shaft to deflect, just like the radial force of the pump when running away from BEP. Radial deflection and agitation can occur simultaneously.

It is recommended that the impeller be balanced at least according to the International Organization for Standardization (ISO) 1940 Level 6.3 standard. If the impeller is modified for any reason, it must be rebalanced.

 

11. Geometric shape of pipeline

 

Another important consideration for extending pump life is the geometry of the pipeline or how the fluid is' loaded 'into the pump. For example, elbows on the vertical plane of the pump suction side cause less harmful effects than elbows on the horizontal plane. The hydraulic load on the impeller is more uniform, so the load on the bearings is also uniform.

 

12. Pump operating temperature

 

Whether it is high or low temperature, the working temperature of the pump, especially the rate of temperature change, will have a significant impact on the lifespan and reliability of the pump. The working temperature of the pump is very important, and the pump needs to be designed to adapt to this issue. More importantly, the speed of temperature change.

Suggest controlling the rate of change to below 2 ℃ per minute. Different materials expand and contract at different rates, which can affect the gap and stress.

 

13. Pump casing penetrations

 

Although not often considered, the number of pump casing penetrations can have some impact on the lifespan of the pump. Many end users wish to drill and tap the pump casing, such as installing vibration sensors. Every time drilling and tapping on the pump casing, it becomes the origin of stress cracks and the starting point of corrosion in the pump casing