Articles, Tribology

How to diagnose faults in mechanical components

When failures occur in mechanical components of mobile or industrial equipment. Evidence of the failure is often destroyed along with the mechanical component that has failed.

The initial evidence of the flaw is so deformed by the actual flaw that it becomes indistinguishable from other evidence. The destruction of the initial evidence of failure usually leads the investigator to accuse the lubricant because of failure caused by another mechanism.

In reverse. Failures that have been caused by the use of improper lubricant or ineffective lubrication are mistakenly attributed to other factors. There are many potential cause and effect situations where evidence about the cause of failure is lost in evidence about the effect.

The absence of good evidence is what leads to costly erroneous decisions about whether or not to act in a particular breakdown of mobile or industrial equipment. In most cases, one can not even determine whether the malfunction occurred was in any way avoidable or if it was something accidental and should be accepted as such.

mechanical components

Many maintenance professionals have encountered recurring failure modes in machine mechanical components without having a clue as to the root cause of the malfunction. Because you can not pinpoint the root cause of the crashes. The solution is to create complex and often innocuous and unnecessary preventative maintenance procedures (PMs). Implementing a set of preventive maintenance procedures (PMs) is a fairly common response. When you can not really explain why mobile or industrial equipment has failed.

It is relatively common that, once innocuous and unnecessary preventive maintenance procedures (PMs) are introduced into the maintenance system, they become a permanent part of maintenance practices. No longer being discontinued even if its ineffectiveness is evidenced.

Over time, it will no longer be remembered why those innocuous, unnecessary, costly and cumbersome preventive maintenance (PM) procedures were instituted. The process of rationalizing maintenance practices through the removal of ineffective practices will always require lengthy and heated discussions.

mechanical components

 

Lubrication failure occurs when the lubricant no longer effectively separates the metal surfaces of the mechanical components in relative motion. However, there are numerous reasons why this can happen.

There are totally different situations in this aspect and we can cite by way of example:

  • vibration leads to loosening of the sump drain plug of mobile or industrial equipment, total loss of lubricating oil and, consequently, catastrophic failure
  • the mobile or industrial equipment operates in extremely dusty environment, the lubricant is contaminated with abrasives and there is acceleration of abrasive wear

Both situations will cause lubrication failure from a maintenance and prevention perspective. But they are totally different events.

mechanical components

How, then, can one improve the quality of evidence and the skills to examine them? In the vast majority of cases where there are failures, catastrophic or otherwise, in mobile or industrial equipment the evidence of the malfunction. Still, they can be found either in the lubricating oil or in the lubrication system. Even if the evidence in the mobile component has been destroyed. The important thing is not to discard the evidence. And yes, try to preserve them. For the root cause search of the problem.

Componentes mecânicos

Let us consider, then, some ways of studying the evidence of failures in mechanical components:

Analysis of lubricating oil in use in mobile or industrial equipment

In spite of the degraded appearance of the mobile component that failed. The lubricant still holds the evidence for the time period preceding the failure until the time of the catastrophic event. Sometimes sampling of reservoir and reservoir funds can help in the investigation process.

Wear residues accumulate in the bottom of casings and reservoirs. Making it possible to set the history of the machinery operation since the last change of the lubricating oil load or flushing of the tank. Many of the wear particles deposited in reservoir and reservoir bottoms are initial evidences of the failure process or catastrophic failure.

Wear particles are pieces of a puzzle. That can help the maintenance professional, in assembling them, in assembling a logical and understandable context of what happened.

A word of caution: the analysis of particulate material from the bottom of the sump or reservoir does not allow, for the most part, to accurately classify which mobile component originated the wear residues or when they were generated, in the case of more than one analysis of an informative nature.

mechanical components

Lubricant Oil Filter Analysis

The lubricating oil filter is a valuable log book as it captures the solid particulate material generated from the last replacement to the failure event.

mechanical components

 

Open the filter for inspection. Release the wear particles from the filter element by ultrasonic bath, depositing them on an inclined slide or retaining them in a filtering membrane, evidence of the incipient failure event until catastrophic failure can be evaluated. In the same way as crankcase or reservoir bottom sampling, this method does not classify the wear particles with respect to the composition or generation time.

mechanical components

Completely inspect the mobile components in response to monitoring based on the condition of the machinery

Condition-based maintenance technicians often detect early-stage failure in the moving component of the machinery, but when maintenance mechanics remove the moving component and inspect it, they can not find any evidence of failure.

The mobile component is then assembled. Again, in its original position, the mobile or industrial equipment is put into operation and, a few weeks later, the equipment is paralyzed by catastrophic failure or not. It arises, of course, the assumption that the intrusive act of machine inspection caused the failure and the monitoring technicians based on the condition are in delicate situation.

mechanical components

 

Typical inspection on a rolling bearing is visual and often performed with the lubricant still present. As a general rule, the maintenance mechanic moves the rolling bearing to check that it rotates freely. Solid particulate material from wear with dimensions of 5 micron – 50 micron. It can be studied through techniques of analysis of residues of wear using a microscope or other types of instruments suitable for evaluation of solid particles.

In the face of this the question arises: how can the maintenance mechanic observe pits or grooves with microscopic dimensions. With approximately, the aforementioned dimensions to the naked eye? Once the mobile component fails event. Progression accelerates rapidly. Ideally, inspect the metal surfaces of the moving parts removed from the machinery after cleaning. So that you can check in more detail what is really happening in terms of wear.

Maintenance Staff Training

Training programs for PCM technicians, maintenance mechanics, and machine operators focus on restoration or repair techniques. It is necessary to train these professionals. Also, in analysis of failure mechanisms so that they can understand how the machines arrive at the state of failure, methods and techniques for reduction of failures (proactive maintenance), proper lubrication techniques, the monitoring of the machinery by the condition and fault analysis techniques.

Such training will enable maintenance staff to find and analyze evidence of failures in mobile or industrial equipment. And how to employ practical knowledge and experience in the pursuit of continuous improvement.

mechanical components

 

Fact is we are living a new era in issues of mechanical components maintenance, mobile and industrial equipment. Many companies have completely overhauled their old maintenance practices by replacing them with completely new ones. It is not possible to seek to eliminate the root cause of problems without accurate evidence of what actually caused the failure. Lubricating oils and greases and lubrication systems. They offer valuable clues even though the evidence of failure regarding the machinery or the mobile component has been completely destroyed. It is of fundamental importance to learn how to access and use this evidence as the basis for sound decisions.

mechanical components

 

Article originally published in: http://portallubes.com.br/2017/10/componentes-mecanicos/

 

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