- December 10, 2019
- Posted by: khawaja senan
- Category: Heavy Equipment
What is the most likely cause of machine failure?
The machines fail for various reasons; Not all failures are the same. The term “machine failure” or “breakdown” usually implies that the machine has stopped doing the design function or what is expected of it. This is what is called “loss of function” of the machine or component. For example, if a pump is installed to pump 400 liters of oil per minute, but over time its function decreases, to the point that it can now only pump 300 liters per minute; This is the loss of the asset’s function.
This loss of function is divided into three main categories:
- Surface degradation.
Of the three, the degradation of the surface of the internal components is the cause of the loss of the function of the machines in the great majority of cases. This degradation of the surface is mainly due to corrosive wear and mechanical wear.
Corrosion of machinery components is quite common, especially for those who have problems with water contamination. Water not only causes rust on iron surfaces, it can also accelerate oil oxidation, creating an acidic environment within the component.
Acids can be formed as byproducts of the reactions between water and certain additives in the oil. Process substances can also enter through the seals, creating an acidic environment. Something as simple as having an extreme pressure additive in contact with yellow metals (copper, bronze, brass, etc.) can cause corrosion.
Mechanical wear occurs when machine surfaces wear out mechanically over each other. Abrasive wear is a method in which particle contamination causes most of the wear. Particles such as soil or wear particles can cause abrasion of three bodies or surface fatigue, which results in the surface being pitted or torn.
Adhesive wear involves two surfaces that come into direct contact with each other, transferring metal from one to the other. This wear occurs in areas where the lubricant cannot withstand the load or in areas where there is a shortage of lubricant.
Metal fatigue is similar to what happens when trying to cut a wire without using tools. As the wire bends back and forth, again and again, the metal begins to work more intensely and becomes fatigued. After several cycles of this type of stress, the metal eventually weakens and breaks. The same process occurs in machines. For example, a particle can cause stress to increase in the inner race of a bearing. With time and constant bending, the metal begins to fatigue, spreads and forms cracks in the material.
Thus, although the machines lose their functionality in different ways, the degradation of the surface of the machine components is the cause of most of these problems. By properly keeping the machines sealed to restrict the ingress of particles, and making sure that the lubricants you use meet or exceed the component’s operating requirements, you can extend the life of the machinery and reduce the total failures.
In recent times, we have begun to talk about the concept of reliability, to the extent that it was understood that it was not enough to achieve high availability, but also to minimize the probability of failure of critical machines during operation, that is to say, Achieve high reliability.
The consequence of failure can range from lost profits or lost production, through unproductive man-hours of operations, to the degradation and breakage of the machines themselves. In the case of heavy machinery, reliability will be the product of the individual reliability of each system that composes it.
When is there a fault?
- When the piece is completely unusable
- When it works, it does not fulfill its function satisfactorily
- When its operation is unreliable due to failures and presents risks
- Bad design, bad material selection
- Imperfections of the material, the process and/or its manufacture
- Errors in service and assembly
- Errors in quality control
- Environmental factors, overloads
3 stages of failures in heavy machinery
This stage is characterized by having a high failure rate that descends rapidly over time. These failures may be due to different reasons such as defective equipment, incorrect installations, equipment design errors, ignorance of the proper procedure.
This stage consists of a lower and constant error rate. The failures do not occur due to causes inherent to the equipment, but due to random external causes. These causes can be accidental accidents, bad operation or inadequate conditions.
Stage characterized by a rapidly increasing error rate. The natural wear of equipment causes failures due to the passage of time.
Any failure leaves some clues that allow you to find its origin. Every machine has its normal levels of noise, vibration, and temperature. When an abnormal increase in these levels is observed, the first indications are that there is a fault. Heavy machinery operators should be instructed to warn when they detect these symptoms that the machine presents.