Maintenance Intervals
Mechanic's Mate CMMS Asset Maintenance Management Software

Maintenance Intervals - Too Often or Not Often Enough?

At the end of the day all maintenance organizations strive to reduce their break-down or unplanned work.  Simply put, if you have an effective ongoing maintenance plan in place, most break-down work can be avoided.  Maintenance managers operate in an environment that is very much like the slogan of the popular hotel chain in America …”The best surprise is no surprise.”

There is a fine line in the world of maintenance when we look at the factors that influence our decision as to how often we schedule maintenance.  Let me provide an exaggerated example to illustrate the point.

We could do something as ridiculous as check the tread depth of our car tires on a daily basis.  Eventually, we could determine the exact time to rotate our tires or replace them.  We could perhaps determine a trend that indicates a wheel realignment is in order.  Or we could choose to simply ignore checking our tread depth for a couple of years.  We all know that we can add substantial risk to our life and the lives of others as a result driving on worn-out tires.

The example above is a simple over exaggeration of a typical maintenance check.  In the above case, a daily check is overkill; on the other hand, delaying the check a couple of years is much too long.   Somewhere between the interval of daily to every two years lies a reasonable period of time for the check.

Surprisingly enough, maintenance intervals throughout industry continue unchallenged.  Checks are being made too often, or not often enough: the result; a dereliction of proper maintenance or a simple waste of resources.  In my personal experience, I have noticed situations where there is more attention paid to the interval for repainting the lines on the company parking lot than the interval for changing filters on air handlers.  I sense this is an innocent oversight: one can see parking stripes; whereas, air filters are typically hidden.

Where do we begin to make it right?

Manufacturers’ Recommended Maintenance:  Manufacturers’ documentation should be your primary source for maintenance interval information.  Normally, manufacturers provide the task detail as well as the recommended interval.  But is this the perfect world?  Are manufacturer recommended intervals too conservative?  The supplier will specify maintenance tasks that include the manufacturer supplied parts and fluids.  Sometimes the tasks require labor that is manufacturer supplied.  Their intervals are most likely based on many years of testing and machine runtime.

Compare your own maintenance intervals to those recommended and routinely performed by the dealerships for high-end cars in America .  Certainly, if you let the dealership drive the “maintenance bus” for your high-end car, you will most likely never experience the need for a tow truck for as long as you own your car.  This is because many dealers go above and beyond what the manufacturer recommends.  What does all this cost?  Is it practical?  Is it a good investment?  We all know that 3,000 mile oil changes when using synthetic oil is overkill; however, thousands of our citizens follow this regimen succinctly.

Industry Organizations:  Another source for the suggested maintenance intervals can be industry groups.  As an example, all areas of maintenance for ammonia refrigeration related equipment can be obtained from the International Institute of Ammonia Refrigeration (IIAR).   IIAR specifies the type of maintenance, the interval, and in some cases they include a detailed procedure.  There are plenty of other industry groups within the US that may offer a good point of reference.

Predictive Maintenance Technologies:  There are countless forms of predictive technologies from which to choose.  In many cases, these technologies allow you to see malfunctions before they fully develop into full-fledged equipment failures.  They include:


Operating Histories:
  By far, the most reliable source for maintenance task interval information may be your company’s own experience.  However, proceed with caution.  Your own success may be predicated on years of “too much” maintenance or pure maintenance overkill. 

If you have extensive maintenance histories for your assets, intervals can be established based on fact – not fiction.  Look for trends.  More importantly, look specifically at breakdowns.  Then look at the maintenance intervals for the preventive tasks related to the assets that have failed.  Try and identify any tell-tale indicators if possible.

If we examine a simple bearing failure, the common factors that can contribute to a failure are listed below.  Please note, as in many maintenance issues, some of the contributors have nothing to do with the frequency for a maintenance task. 

Generally bearings fail due to:


Which of the above can be associated with the interval of the maintenance task?  We can actually specify:


Some of the contributors to component failures have nothing to do with how often maintenance is performed.  How often one addresses an issue may simply be one of the many factors in the demise of a component.  To determine the specifics of why a failure occurred, root cause failure analysis (RCFA) can be applied.

RCFA identifies the basic source or origin of your problem.  RCFA is a step by step approach that leads to the identification of a fault's first or root cause.  Every system, equipment, or component failure happens for a reason.  There are specific successions of events that lead to a failure.  A RCFA investigation follows the cause and effect path from the final failure back to the root cause.

The RCFA procedure investigates the failure using facts left behind from the initial flaw. By evaluating the remaining evidence one can identify both the contributing and non-contributing causes that contributed to the event. 

RCFA provides a methodology for investigating, categorizing, and eliminating root causes of incidents with safety, quality, reliability, and manufacturing process consequences.

What is the price of poorly planned maintenance intervals?

Equipment failure is the ultimate price.  We need to ensure the maintenance performed within a task is effective and that the task is performed at the right interval.  Again we need to ask ourselves, “What is the impact to the overall operation if the equipment were to fail?”

 It is not unusual to have economic restraints in any maintenance organization.  Maintenance managers should be asking themselves questions like, “Why do we perform this maintenance task on a quarterly basis?  What was the basis for establishing the task interval?  How much could we save if this task were done on a six-month basis?  Could it become a yearly task?”

 Let’s examine annualized costs associated with maintenance.  In the table below, the cost associated with a simple .5 hour task has been shown based on differing intervals.   


Frequency

Hours Per Task

Intervals

(Instances Per Year)

Annualized Hours

Burdened Hourly Rate ($18 *1.22)

Total Cost

Bi-Annual

0.5

2

1

21.96

$21.96

Quarter

0.5

4

2

21.96

$43.92

Bi-Monthly

0.5

6

3

21.96

$65.88

Monthly

0.5

12

6

21.96

$131.76

Bi-Weekly

0.5

24

12

21.96

$263.52

Weekly

0.5

52

26

21.96

$570.96


It’s easy to see that if the number of instances per year is not appropriate for the equipment being maintained, the costs can very quickly get out of control.  If you multiply the above figures times the potential hundreds of assets in the average facility the costs quickly add up.

Rate your equipment before you adjust anything.

Before you begin any adjustments to your maintenance frequencies, review the need for the asset.  Has the criticality of the asset been rated?  I like to rank criticality using the following logic:

1.     Is this asset directly required to generate revenue for your company?  If you answer yes, this is most likely a critical asset.  

2.     If the asset is required to generate revenue, do you have another means to substitute its use (spare equipment on the shelf, just in time overnight delivery, a separate train or process within the operation to keep the production going, etc.)?  If the answer is no, this might be a critical asset.  

3.     Do you have reserve capacity?  Can a short period of time without the asset be sacrificed due to a substantial amount of product inventory?  If you do not have reserve capacity and you require the asset to maintain production levels, this is most likely a critical asset. 

If you have deemed an asset as critical, you should not adjust your PM intervals without studying the situation carefully.  I have seen instances where adding an additional pump was a less expensive alternative than the costs associated with aggressive maintenance.  Many times excessive maintenance on a critical task is nothing other than a knee-jerk reaction to continue a high “awareness level” such that all members of management and maintenance understand the operation will cease to function without the piece of equipment.  Generally, when assets fail, they don’t fail according to your schedule.  Typically, it will be in the wee hours of the night when a skeleton maintenance staff is available.

What is the cost of “too little” maintenance on a critical asset?

A basic worst case scenario for any facility can be the failure of a key asset; particularly, if the asset disables production at the facility.  The chart below shows typical production costs for different periods of downtime.  As you can see, an operation that has a $20,000 per hour production cost expends $100,000 in just five hours of downtime.  In most cases, $100,000 can fund a generous amount of redundancy at any facility.


Operation Cost Per Hour

Total Costs for Downtime Per Hour

 

1

2

3

4

5

6

7

8

9

$5,000

$5,000

$10,000

$15,000

$20,000

$25,000

$30,000

$35,000

$40,000

$45,000

$10,000

$10,000

$20,000

$30,000

$40,000

$50,000

$60,000

$70,000

$80,000

$90,000

$15,000

$15,000

$30,000

$45,000

$60,000

$75,000

$90,000

$105,000

$120,000

$135,000

$20,000

$20,000

$40,000

$60,000

$80,000

$100,000

$120,000

$140,000

$160,000

$180,000

$25,000

$25,000

$50,000

$75,000

$100,000

$125,000

$150,000

$175,000

$200,000

$225,000

$30,000

$30,000

$60,000

$90,000

$120,000

$150,000

$180,000

$210,000

$240,000

$270,000


Unfortunately, not all operations have taken the time to identify their absolute “drop dead” must-have assets.  This, in my opinion is the most important exercise that management at any facility can undertake.  In fact, this should be done every year because operation philosophies change.  What was deemed critical last year may not be the case this year.

Once the critical components have been identified, it can be easy to review where and how maintenance dollars can be substantially reduced.  Usually, facilities that have not segregated their critical assets from non-critical assets find they are performing high priority maintenance on low priority assets.  Parking lot striping is not what one should deem critical.  Air handler filters, although not normally deemed as critical, can be considered critical; particularly, in the healthcare environment.

Personally, I never feel comfortable discussing maintenance intervals on critical equipment without obtaining the full background of the asset.  I have made it a point in my observations of work histories to study the total number of corrective (reactive) work orders where extensive preventive maintenance (PM) tasks have been ongoing.  If there very are few corrective work orders, this is an indication their maintenance plan is working.  

I make an effort to study in detail comments on the historical preventive tasks to see if the mechanic has made any notations that point to problems or requests for additional work.  In many cases, I can take a couple years’ worth of weekly PMs and see absolutely no comments or any corrective maintenance tasks being required for the assets.  Personally, when I observe this situation, I immediately advise my customer to consider cutting the frequency of the maintenance interval.  As an example, if the task is currently being addressed on a weekly basis, I might suggest to them a monthly interval.  

Conclusion  

Ask yourself this one question.  “What are the factors that have been utilized to determine task intervals at our facility?”  In many cases the answer is simple, “That’s the interval we’ve always used; they were set up years ago.  I have no idea why.”  If this is your particular answer, in a short amount of time there is a good chance you can make your company’s bottom line for maintenance improve by leaps and bounds.  Redundant or unnecessary maintenance may be the low hanging fruit -- ripe for the picking in your company that can give your maintenance operation a banner harvest.  

On the other hand, if you feel as though your operation doesn’t need any adjustments to your maintenance intervals, I extend my congratulations.  Keep up the good work!  

Roger D. Evans, is the Owner and General Manager of CT, Inc.  CTI, makers of the maintenance software Mechanic’s Mate, offers consulting and maintenance implementation services. 

gear imagePrivacy Policy | Contact Us