Old age catches up

In our search to discover the root causes of failure, we have now discussed the first six elements of failure in the previous chapters. We are now going to turn our attention to the final batch of three reasons in terms of ‘why does equipment fail?’

Why Does Equipment Fail?

• Aged and Non-Aged Related
• Misalignment
• Sabotage

Aged and Non-Aged Related

Age catches up with all of us ‘eventually’ and perhaps some parts do not function as well they once used to. Energy and capacity levels may start to fade and diminish. If this happens to us, why then should we get surprised when some equipment we work with starts to display age-related performance.

Age-Related Equipment failure refers to equipment that fails due to time in service and needs to be replaced.

Non-Aged Related Equipment refers to equipment where failure is not related to time in service.

Some equipment has a life that is directly related to time, while other equipment is not directly related to time and may fail after a month, year, or multiple years of service. This equipment doesn’t wear out, it fails for other reasons.

Aged Related Equipment Failure

Age-Related Equipment Failure generally relates to equipment that is in direct contact with a product being manufactured and will age due to shock, fatigue, corrosion, oxidation, and evaporation. Random failures can be expected as time moves toward the wear-out zone.

The probability of failure will increase as equipment moves from one period to the next and the wear-out zone equipment failures will multiply. Generally, there will be a long period of smooth running and the failures will start to happen as can be seen in this graphical image.

Non Aged Related

Non-Age Related Equipment Failure refers to equipment where failure is not based on time in service. It is normally associated with high stress from operational errors or external damage and the probability of failure is the same regardless of the time period. Equipment failure is random and equipment that experiences more non-age-related failures tends to be complex pieces of equipment or systems. As can be seen from the graphical image, there is no trend as it just keeps running and the failure rate or time cannot be forecasted.

Misalignment

Misalignment is the deviation of relative shaft position from the collinear axis of rotation when equipment is running under normal operating conditions. There are typically three major problems relating to misalignment conditions

• Bearing Failure
• Metal Fatigue
• Infant mortality

Misalignment is recognized as the leading contributor to machinery failure. Due to the parasitic axial thrust, misalignment can significantly reduce the life of a bearing and it exists when the center lines of two neighboring machines deviate from each other. Pulleys, drives, sprockets, and tracks are only a few of the mobile components that need to be kept in proper alignment to prevent premature wear and tear on their related components. Misalignment is a major cause of equipment breakdown and a big part of a machine’s routine maintenance program should include regular checks on component alignment. Realigning is far easier and more economical than letting breakdowns occur from this lack of care.

This image shows both a Parallel and angular misalignment and highlights that Strain + Stress + Force = Vibration.

Bearing Failure

If bearings fail, so can the equipment you are operating. Premature bearing failure is most commonly caused by the contamination or loss of bearing lubricant. Mechanical defects such as the unbalance or misalignment of bearings can also lead to bearings failing prematurely. Paying attention to what your bearings are telling you is vital to ensuring your facility runs efficiently.

Metal Fatigue

Another leading reason industrial machinery can fail and stop working is metal fatigue. Metal fatigue occurs when you attempt to cut wires without the use of tools.

As the operator makes their way through the wire, the metal works harder to harder, creating fatigue. When several cycles of such stress have occurred, the metal typically becomes brittle and snaps off. To help prevent machinery failure and the stress and loss of earnings equipment breakdown typically creates, it is important to keep machinery and internal parts well lubricated, well maintained, have parts regularly replaced, keep it stored in an appropriate place and only operated by those trained to do so.

Infant Mortality

This special failure mode relates to equipment that has been rebuilt by trade/craft personnel or where a service has been provided that has invaded the system. The probability of failure is highest when equipment is first started and the probability of failure levels off after a time period. The most dangerous failure time is when equipment is first started. Once past that stage, things settle down as can be seen on this graph.

Sabotage

We often think this subject is reserved for Hollywood movies but we may be surprised how often it does happen in the workplace for multiple varieties of reasons. Sabotage in the workplace refers to the destruction of an employer’s property, tools, equipment, and products to hinder the manufacturing process and impact profits.

One factory worker threw a bucket into a conveyor and shut down production for a half-day due to drugs. This was essentially an employee ‘game playing’.

Another employee nicknamed “Edward Scissorhands” by factory workers, would often cut plant power to halt production resulting in frustration and anger as this resulted in employees working longer hours to meet production schedules.

Employees do bring their problems to work!

Failure Causes

To remind us of where we started, if we want to get to grips with minimizing the destructive force of failure in our lives, our careers, and our organizations, then we need to understand what the root causes of failure are and be able to answer the question, ‘why does equipment fail?’. Over the last few chapters, we have worked our way through a total of nine elements of failure to help us to identify the root cause of why equipment fails.

Equipment failure happens and the impact ranges from easily fixed with minimal losses to catastrophic with huge losses, depending on factors such as repair costs, total downtime health and safety implications production and delivery of services

Our response has to be Proactive Maintenance in order to

• Reduce the risk of failure to acceptable levels
• Minimize costs of downtime
• Ensure the level of availability and the function necessary to avoid exposure to multiple failures

For more information email us at info@strobe-al.co.za or visit www.strobe-al.co.za