Common Causes of Machine Failures

Noria Corporation

Machines fail for a variety of reasons. Likewise, not all failures are the same. The term "machinery failure" or "malfunction" usually implies that the machine has stopped functioning the way in which it was intended or designed.

This is referred to as “loss of usefulness” of the machine or component. For instance, if a pump is installed to pump 100 gallons of oil per minute but over time can no longer keep up and now only pumps 75 gallons per minute, this is a loss of usefulness of the asset.

This loss of usefulness is broken down into three main categories: obsolescence, surface degradation and accidents. Of these three, surface degradation of machine parts results in the machine’s loss of usefulness in the vast majority of cases. Surface degradation is comprised mainly of corrosion and mechanical wear.

Particle contamination is a major cause of mechanical wear and one that can be addressed with the right combination of contamination exclusion and removal methods. In-service lubricants will become dirty over time, but innovative new solutions are beginning to change the way we see machine lubricants, opening up the potential of oil regeneration and long-term re-use of oil without impacting performance or machine reliability. 

Corrosion

Corrosion of machine parts is quite common, especially for those with water-contamination issues. Water not only rusts iron surfaces, but it can also increase the oil’s oxidation rate, leading to an acidic environment within the component.

Acids can also be formed as byproducts of reactions between certain additives in the oil and water. Product contamination through seals can create caustic environments and corrosive wear as well. Something as simple as having an aggressive extreme-pressure additive in contact with a yellow metal (copper, bronze, brass, etc.) can produce corrosive damage.

Mechanical Wear

Mechanical wear occurs when machine surfaces mechanically wearing against each other. Abrasive wear is a method in which particle contamination causes the majority of the wear. Particles such as dirt or wear debris can lead to three-body abrasion or surface fatigue, which results in the surfaces becoming pitted and scored.

Adhesion

Adhesive wear involves two surfaces coming in direct contact with each other, transferring material from one face to the other. This appears in areas where the lubricant can no longer support the load or in areas of lubricant starvation.

Fatigue

Metal fatigue is similar to what happens when you try to cut wire without any tools. As you work the wire back and forth, the metal begins to work harder and fatigue. After enough cycles of this type of stress, the metal finally becomes brittle and snaps.

Abrasion

The same process occurs in machines. For example, a particle can cause a stress riser on the inner race of a rolling-element bearing. Over time and with constant flexing, the metal begins to fatigue. This propagates into a spall of the material.

So as machines can lose their functionality in a variety of methods, it is the surface degradation of the machine parts that causes the majority of these problems. By keeping your machines properly sealed to restrict the ingress of particles and making sure the lubricants you use meet the operating demands of the components, you can extend machine life and see fewer total failures.

Combatting Particle Contamination

In order to address the problem of solid particle contaminants in lubricants, the first step is to set targets or limits. To establish the allowable particle count for a given machine, an ideal value must be determined based on what can actually be achieved by employing cost-effective measures. If the goal is not achievable, it has little value.
 
The second step is to employ the appropriate methods to achieve the identified goals. Particle contamination control has several components, but it begins with good lubricant storage, handling and application methods. New oil is a common source of particle contamination because it is typically dirty upon arrival.
 
In the average plant, new oil is often further contaminated by being dispensed into a dirty container with unsanitary transfer equipment, and finally applied to the machine through a soiled funnel. By properly storing, filtering and applying new lubricants, along with the use of simple contamination exclusion methods such as high-quality breathers and seals, an appropriate level of cleanliness can often be maintained for even nonfiltered systems.
 
When these exclusion methods are insufficient, methods to remove contaminants must be used. The right combination of contaminant exclusion and lubricant filtration together is often what is needed. Some facilities are taking a more holistic approach, using service partners to achieve proper contamination control. SKF RecondOil's "Oil as a Service" is one such example, delivering oil that meets target cleanliness levels from the start. No matter how you achieve highly clean oil, the benefits to machine reliability and machine service life are well-established. Take contamination seriously, and you will find significant cost savings can be achieved over time.
 
 Of course, it is more cost-effective to practice good contamination exclusion methods, and therefore exclusion should be the first method considered.

Subscribe to Machinery Lubrication