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Reactive versus Preventative Maintenance

Updated on February 7, 2012

While no one would argue that fixing things as quickly as possible when they break is important, few realize the high costs associated with solely practicing this mode of operation. A good preventive maintenance program preserves assets, keeps things running in optimum condition, and helps insure that maximum life expectancy is achieved. It also helps managers anticipate failure thereby allowing time to plan and budget for replacements as well as perform work at more convenient times. All of these factors make Preventive Maintenance a more predictable and cost effective way to operate.

BRAC brings upheaval, opportunity to San Antonio 090812 by familymwr, on Flickr
BRAC brings upheaval, opportunity to San Antonio 090812 by familymwr, on Flickr | Source

Classifying Work

One of the most important things you can do in your maintenance operation is to categorize work into various classifications. This allows you to quantify the types of work orders being created and where your technicians’ time is being spent. This is needed so you to determine the effectiveness of any operational modifications made by monitoring changes to the amount of work performed in each classification. There is no right or wrong, set terminology, or acceptable number of work types. The only rule of thumb is to create classifications that will allow you to measure the parts of the operation that are important to you. For example, in order to determine the effectiveness of a PM program, you should establish work classifications that separate preventive work from reactive work.

Reactive Work: Is nothing more than reacting to failed equipment by restoring its intended function. There are many organizations that solely rely on this type of maintenance and shun any form of PM. While it’s acceptable to work in this manner in limited circumstances, it’s generally a costly way in which to operate. Failures and outages are unpredictable, labor and material resources may not be readily available or may entail paying premium rates, and equipment life is not being maximized. There are also indirect costs associated with non-functioning and unreliable equipment that can impact reputations, budgets, compliance to regulations, safety, and the ability to generate revenues.

Preventive Maintenance: Preventative maintenance consists of formal procedures and tasks that help prevent unplanned breakdowns and insure equipment is operating properly. Tasks and intervals are pre-determined by owner's manuals, industry standards, guidebooks, environmental conditions, equipment criticality, location, impacts on safety and mission, past experience, work order histories, and predictive maintenance tasks. Some examples of Preventive Maintenance tasks include lubrications, consumable parts replacements, cleaning, adjustments, Inspections and testing.

Predictive Maintenance: Predictive maintenance tasks are those that can indicate deterioration conditions, rates of decay, and clues to tasks and frequencies needed in the preventive maintenance program to slow it down or eliminate it, and maximize remaining useful life. Some examples of PdM tasks include vibration and oil analysis, infrared testing, leak detection, and engineering surveys.

Reactive Maintenance

Studies show that Reactive Maintenance or the “run until it breaks” mode of maintenance is still the predominant method of operation in the US. There are advantages and disadvantages to working this way.

Advantages & Disadvantages of Reactive Maintenance

Advantages:

  • Lower initial costs
  • Requires fewer staff

Disadvantages:

  • Increased costs due to unplanned equipment downtime
  • Increased labor costs, especially if overtime is needed for untimely repairs/replacements.
  • Increased costs due to paying premiums for expedited manufacturing and shipping
  • May result in secondary equipment or system losses.
  • Is an inefficient use of staff resources.

An operation that solely relies on Reactive Maintenance generally expends more labor and material resources than if they had a Preventive Maintenance program (and the right facility management software). Their failures also seem to occur at inopportune times, often at the expense of delaying or eventually foregoing planned work.

A blur of car problems by maureen lunn, on Flickr
A blur of car problems by maureen lunn, on Flickr | Source

Preventive & Predictive Maintenance

Some use the terms Preventive and Predictive Maintenance interchangeably but they’re actually two separate and distinct types of work.

Just by their names alone, Preventive Maintenance consists of tasks that are designed to prevent breakdowns, failures and unplanned outages. Predictive Maintenance consists of tasks designed to predict when breakdowns, failures and unplanned outages may occur and detect when they actually happen

Let’s look at an example…

The owner’s manual for your car tells you the preventive maintenance tasks that need to be done and in what time frame in order to keep it in optimum running condition. It may also tell you what to expect if you don’t perform these tasks. They’re based on the engineering standards of the car and decades of collecting historical data on past models. So in essence the car manufacturer can predict what will happen and when based on performing trending and analysis on historical data gathered over many decades. Often this is expressed in a graph called a “Bathtub” curve. Ever wonder why things always seem to breakdown just after the warranty expires? It’s usually test and analysis results mapped on a Bathtub curve that tell engineers how long something will last before breakdowns can be expected.

Preventive Maintenance

Studies show that Preventive Maintenance can save as much as 12% to 18% over Reactive Maintenance methods. There are advantages and disadvantages to working this way.

Advantages & Disadvantages of Preventive Maintenance

Advantages:

  • Cost effective in many capital intensive processes & equipment.
  • Provides flexibility for adjusting maintenance frequencies.
  • Increases component life cycle.
  • Generates energy savings.
  • Reduces equipment and/or process failures
  • Results in 12% to 18% cost savings over Reactive methods.

Disadvantages:

  • Does not eliminate catastrophic failures
  • More labor intensive.
  • Includes some invasive activities that have the potential to cause incidental damage to components.

A common misconception in the industry is that good preventive measures are enough to maximize useful life. This couldn’t be further from the truth. We’ll use the bearing example again. A good preventive practice is to lubricate the bearing based on the manufacturer’s guidelines. While this will reduce unplanned outages and result in savings over no maintenance at all, lubricating the bearing does nothing to indicate the condition of the bearing or the rate at which it’s deteriorating. You may not be using the proper lubricant, technicians may not be adding the right amount, and the environmental conditions the motor is operating in may demand attention more often. Only by performing an infrared scan of the bearing (Predictive Maintenance) will you know the effectiveness of your Preventive Maintenance efforts and be able to use that data to make appropriate adjustments.

Predictive Maintenance

Studies show that Predictive Maintenance can save as much as 8% to 12% more than Preventive Maintenance strategies alone and 30% to 40% over Reactive Maintenance depending on asset condition. There are advantages and disadvantages to working this way

Advantages & Disadvantages of Predictive Maintenance

Advantages:

  • Increased component operational life and availability.
  • Allows for preemptive corrective actions.
  • Results in decreased equipment or process downtime.
  • Lowers costs for parts and labor.
  • Provides better product quality.
  • Improves worker and environmental safety.
  • Raises worker morale.
  • Increases energy savings.
  • Results in 8% to 12% cost savings over Preventive Maintenance

Disadvantages:

  • Increases investment in diagnostic equipment.
  • Increases investment in staff training.
  • Savings potential is not readily seen by management.

By performing predictive tests and analyzing trends and results, we can take preemptive actions to slow deterioration, prevent unplanned failures, and reduce replacement costs. Predictive maintenance maximizes useful life and in some cases can extend it. This does require purchasing somewhat costly diagnostic tools, equipment and training, but their return on investment is very high and happens over a very short period of time.

How do PM/PdM Programs Help Me?

  • Predictive Maintenance helps determine the frequencies and tasks to be used in a Preventive Maintenance program, which reduce unplanned or unforeseen outages and breakdowns that result in Reactive work.
  • Predictive Maintenance also helps determine when equipment will eventually fail and allows time for proper planning and budgeting.

When planning and budgeting can be done in advance, costs go down because of a reduced need for overtime, thereby reducing the need for more expensive emergency procurements and expedited shipping charges, a reduction in downtime, reduced interruptions to normal missions and business functions, and reduced chances for negative domino effects on dependent pieces of equipment, systems and components.

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