Failure Modes in Pumps

Introduction to Pumps

Pumps are among the most essential workhorses in all industries, ranging in size and type, operating in anything from small waterworks to massive paper mills. When pumps fail, the impact on production and the company’s performance can be critical.

Pumps handle all kinds of liquid or semi-liquid materials and substances that may be intermediate states between gas and liquid.

They are designed in many different ways depending on factors such as the medium, flow, pressure, and temperature. As such, they can be categorized based on their physical design and operating principles.

Different types of pumps have unique physical characteristics. Aspects like medium, temperature, pressure, and flow influence the failure modes they are most susceptible to. The combinations of these parameters are so numerous that general failure modes cannot be calculated—they must typically be assessed individually for each pump.

Fortunately, there are several common failure modes that apply regardless of pump type. Examples include bearing failures, leaks, cavitation, motor malfunctions, misalignment, blockages, dry running, pressure instability, resonance, general wear and tear, structural damage, loose foundations, and overheating.

This guide covers typical failure modes and helps you choose the right sensors to monitor those most important to your operations. While it focuses on common industrial and rotary pumps, it’s also a useful starting point for analyzing failure modes in other pump types.

About Failure Modes

The term “failure modes” is used to describe the ways in which equipment can break down or end up in a state where it no longer performs as intended or at the desired quality.

Failure modes often represent the first step in processes like FMEA (Failure Modes and Effects Analysis) and FMECA (Failure Modes, Effects, and Criticality Analysis), where the focus is on studying what can go wrong, its effects, and the consequences of the failure.

Learn more about FMEA here: FMEA – How to use Failure modes and effect analysis

Contents

Introduction to Pumps 2

Table of Common Pump Failure Modes 4

Failure Modes 5

Bearing Failures 5

Leaks 5

Cavitation 5

Impeller Damage 6

Motor Failures 6

Misalignment 6

Blockages 6

Dry Running 7

Pressure Instability 7

Resonance 7

Loose Foundations 7

Faulty Dampers 7

Structural Damage 8

General Wear and Tear 8

Table of Common Pump Failure Modes

Failure Modes

Bearing Failures

Bearing failures are the most significant cause of pump malfunctions, accounting for 40–50% of all breakdowns. Bearings are generally very stable when operating under optimal conditions but become vulnerable under suboptimal conditions. This can be caused by lubrication issues, misaligned shaft loads, contamination by dirt or fluids, high vibration, or extreme temperatures.

Lubrication issues are the primary cause of problems, whether insufficient lubrication, excessive lubrication, incorrect lubricant type, or aging lubricant. Regardless of the cause, lubrication issues will result in heated bearings or increased vibration.

Detection of bearing failures is done using vibration and temperature monitoring, for instance, using Neuron Vibration RMS, which combines vibration and temperature measurement in one device. In some cases, separate temperature measurements using Neuron Temperature may also be suitable.

Leaks

Leaks are the second most common cause of pump failures, responsible for 20–25% of incidents. This isn’t surprising, given that pumps are designed to move liquid media.

Leaks can occur internally—between the pump chamber and bearing housing—or externally, where the liquid escapes to the surroundings through cracks.

Common causes include gasket issues from improper installation, overloading the pump’s capacity, or exposure to extreme temperatures beyond the pump’s tolerance.

Internal leaks are harder to detect but may show up as unusual vibrations or pressure fluctuations, which can be measured with Neuron Vibration RMS and Neuron Gauge Pressure sensors. 

External leaks are easier to spot and can be monitored as fluid accumulation under the pump, such as in a catch tank. Tools like the Neuron Water Detector are effective for this purpose.

Cavitation

Cavitation occurs inside the pump housing during suboptimal operation and involves small air bubbles forming and collapsing in the liquid flow due to vacuum conditions. These failures account for 10–15% of pump breakdowns.

Cavitation wears down the pump housing, impeller, and other components in contact with the cavitation process. Over time, cavitation can erode holes in the pump housing or destroy the impeller, leading to a loss of function.

Cavitation can be detected by monitoring vibrations in the 1000–1500 Hz range, for which Neuron Vibration RMS is well-suited.

Impeller Damage

Cavitation is often a contributing factor to impeller damage. However, erosion, corrosion, deposits, and collisions with fluid flow objects are typical causes. Impeller damage is estimated to contribute to 5–10% of pump failures.

Damaged impellers affect the pump’s performance and can be detected through shaft imbalance or general performance losses, such as pressure drops. Neuron Vibration RMS and Neuron Gauge Pressure are suitable tools for detecting these types of failures.

Motor Failures

Pumps are mechanically driven by an energy converter, most commonly an electric motor. These motors are subject to the physical laws of maintenance and will develop their own failure conditions over time. Addressing these failures is critical to ensuring uptime and optimal maintenance. In fact, 5–10% of pump issues are related to the motor or its power supply.

Read more about motor failure modes here: Failure modes for electric motors

Misalignment

When rotating shafts are not perfectly aligned, it is called a misalignment. This condition is particularly challenging for pumps because it can damage seals and lead to leaks. Approximately 5–8% of pump issues originate from misalignment between the motor and the pump. Misalignment can also damage the bearings and motor components.

Improper installation, loose fasteners, overheating, or material fatigue often cause misalignment.

Misalignment detection is primarily done using vibration sensors sensitive to frequencies in the 20–500 Hz range, measured in all three axes. Neuron Vibration RMS is well suited for this.

Blockages

The pump’s task is to move a medium through physical action, and sometimes, objects become lodged either in the pump or its associated filters, slowing or halting the flow.

Blockages can be identified through changes in vibration, pressure, temperature, and electrical current. These indicators make blockages relatively easy to detect.

Neuron Vibration RMS, Neuron Gauge Pressure, Neuron Temperature, and Neuron Ampere are effective for identifying this failure mode.

Dry Running

If the pump lacks sufficient media filling, this is referred to as dry running. It is often a critical condition for certain types of pumps, as they rely on the medium to maintain the impeller’s correct position or to serve as part of the bearing’s cooling system.

Dry running is detected using pressure sensors, vibration sensors, temperature sensors, or by monitoring the motor’s current draw. There are many ways to identify this failure mode.

Neuron Vibration RMS, Neuron Gauge Pressure, Neuron Temperature, and Neuron Ampere  are effective for detecting dry running.

Pressure Instability

In pressurized systems, certain conditions can cause pressure fluctuations that stress the pump and surrounding components. These instabilities may lead to leaks or inconsistent pump performance, increasing the risk of failure.

Pressure instability can be detected by measuring pressure and identifying unusually high spikes or low-frequency vibrations. This can be detected using vibration sensors such as Neuron Vibration RMS.

Resonance

All rotating equipment has one or more rotational speeds that trigger self-amplifying oscillations, also known as resonance. These rotational speeds are typically avoided to protect the pump from unnecessary stress, which can lead to bearing failure or material fatigue in the pump housing.

Resonance vibrations can also propagate further into the hydraulic system, affecting processes and even causing feedback to the motor and its bearings.

Resonance is detected using vibration sensors sensitive to a broad frequency spectrum, such as neuron Neuron Vibration RMS or Neuron Vibration RMS High temperature .

Loose Foundations

Pumps and their associated motors often produce strong vibrations that need to be anchored securely to their foundation. If the anchoring fails, the pump can vibrate excessively and, in some cases, become dislodged, resulting in catastrophic failure. Dislodged pumps often lead to significant leaks and pose risks to safety and health.

Loose foundations can be identified by measuring low frequencies in the vibration spectrum. Typically, the entire pump and motor assembly (rig) will shake when this occurs. Neuron Vibration RMS is well-suited for detecting failure modes related to loose foundations.

Faulty Dampers

Pump vibrations are often isolated from the foundation using dampers. These dampers reduce vibration transfer while keeping the pump properly positioned. Vibration dampers protect surrounding components from the intense vibrations generated by the pump.

Faulty vibration dampers can result in the pump being improperly positioned or allow vibrations to spread to sensitive components, such as valves, frequency converters, or other electronics. Issues with vibration dampers can be detected using vibration sensors such as Neuron Vibration RMS.

Structural Damage

All pumps are composed of mechanical parts that can suffer structural damage due to impacts, corrosive fluids, fatigue, and similar factors. Structural damage can manifest in various ways, such as leaks or performance issues, and may be very difficult to detect until they lead to more specific failure modes.

General Wear and Tear

Most pumps perform according to their specifications and operate efficiently for many years. However, everything has a defined lifespan, even under ideal conditions. To stay ahead, installing hour counters (Neuron Hour Meter) can track the exact number of hours a pump has been in operation. This allows for better estimation of the remaining lifespan and facilitates timely replacement planning.