by Doods A. Amora, PEE
In any facets in life, there is always what we call as “desired condition”. And Performance Standards have always been derived from these “desired conditions”...
Performance Standards of machines as goals in maintenance are often based on the workings of things when they are still brand new. In other words, it is often desired that performance of anything (capacity, process capability, efficiency, throughput, etc) must not degenerate in the entire lifetime of the machine. But reality is that there is always an end to any lifetime and that the likelihood of deterioration increases with age.
MAINTENANCE – ‘A DIFFERENT THING TO DIFFERENT PEOPLE’
Maintenance, per se, did not change much. But approaches to its management had evolved significantly. For instance in today’s management concepts, the philosophy that “maintenance is 50% production job and production is 50% maintenance job” has now brought maintenance as a condition to production while conversely, production a condition to maintenance. Note that in the past, maintenance is merely seen as a “necessary evil service department” – not a condition to production.
Furthermore, implementation of maintenance differs. For instance, the British, Japanese, American, Swedish and Filipino styles of maintenance are not exactly in the same terms. Usually, a manufacturing concern tailor-fits its own maintenance system to the management philosophy of the business, to the culture of the people and the conditions prevailing the business environment. Thus, even in the modern times, according to notable experts, “the function of maintenance still means different things to different people” (John Peter Koss, Beverage World International, Feb. 1999 issue).
A Large Maintenance Shop (picture courtesy of the Internet)A Just-In-Time (JIT) type of maintenance may fit the Japanese environment, but might not be ideal to Philippine conditions. Japanese JIT-practicing companies do not believe in stocking spare parts (cost of space in Japan is very prohibitive) but then, their parts suppliers or manufacturers are just next door. They order now through computer links and the spare parts are there in minutes! In the Philippines, it might take 6 months. JIT means just-in-time in Japan. In the Philippines, it means, “almost late…?"
On the other hand, the concept of Corrective Maintenance was previously defined by practitioners as, emergency maintenance. Arguably, to other practitioners this may not be exactly true today because corrective maintenance can also be planned. Corrective Maintenance covers all maintenance activities carried out to correct or repair a fault in the equipment. The above statement says that as long as the activity needs repair, it is classified as, corrective. A timely changing of car engine oil for having just about losing its correct properties after an inspection is in fact, correcting a fault. But this correction of fault is not an emergency situation because the breakdown has yet to happen. Corrective maintenance therefore can be both preventive and breakdown maintenance.
IMPLEMENTING MAINTENANCE
To implement a maintenance system for a plant, all personnel without exception - from the top managers, production personnel, maintenance practitioners to the last janitor, must speak in the same language. It is therefore necessary to go through how different maintenance practices are defined in any plant context and application.
The term maintenance is defined as:
“Maintenance covers all activities undertaken to keep equipment, machineries & facilities in a desired state or condition to include all other services done to return the equipment or facilities back to that desired condition.”
IEEE on the other hand, defines maintenance as: “The act of preserving or keeping in existence those conditions that are necessary in order for equipment to operate as it was originally intended”.
There are two general classification of maintenance: :
* Breakdown Maintenance (BDM)
* Preventive Maintenance (PM)
BREAKDOWN MAINTENANCE
Breakdown Maintenance (BDM’s) are maintenance services carried out to bring a faulted equipment or machine back to its productive state.
Tell tale signs of breakdown maintenance are the following: a) emergency activity, b) unplanned services, c) production stoppages, d) lost production opportunities, e) large product rejects, f) fighting fires, g) costly.
In this mode, there must be equipment breakdowns to fix - or fires to put out. In other words, breakdowns in a production plant are states of emergencies. And no management wants a series of emergencies in the plant.
PREVENTIVE MAINTENANCE
Maintenance practitioners declare that the best maintenance must be the preventive & proactive one. Breakdown maintenance is fighting fires and therefore not desirable. In agreement, maintenance managers say that “an ounce of prevention is much better than a ton of cure”. Breakdowns are always costly – not only on the physical damage of the machine but on the cost of lost opportunity.
Preventive Maintenance (PM) is defined as maintenance activities that cover all programmed services carried out to control deteriorating conditions that lead to the occurrence of failures. These activities must be performed before these deteriorating conditions develop into a breakdown or disturbance in production. Note that a maintenance activity can only be PM if it is programmed or planned. This means that PM’s are services decided in advance.
The practice of Preventive Maintenance can be further classified as:
1) Time - Based Maintenance (TBM
2) Condition - Based Maintenance (CBM)
3) Improvement Maintenance (IPM)
Time-Based Maintenance (TBM):
* regular, periodic, cyclic as attributes
* having fixed-time frequency (daily, weekly, monthly, yearly …)
* usage-based activities (running hrs, flying hrs, mileage …)
Condition-Based Maintenance (CBM):
* services that follow after tests & measurements
* planned correction of a certain condition
* services resulting from condition monitoring
* planned & programmed
Improvement Maintenance (IPM):
* redesigns to improve equipment performance
* environmental controls & improvements
* systems improvements
In real life, Preventive Maintenance can be a combination of TBM’s, UBM’s CBM’s and IPM’s. In advance countries today, Condition-Based Maintenance (CBM), also called Planned Corrective Maintenance (PCM) is the one identified as the most cost-effective type of maintenance. It becomes too expensive to replace spare parts just because it reaches the scheduled frequency. With condition monitoring activities made regular, “touching a running machine” becomes justifiable only when the condition of the machine is the one calling for it. But effective surveillance to these abnormalities is the key. Abnormalities must be detected before they develop into full-grown failures. Thus, surveillance on the health of the equipment is what we refer to as Condition Monitoring.
Improvement Maintenance (IPM) in Japan is termed as "Maintenance Prevention" or ‘MP’. Some other literatures call it “Design-Out Maintenance”. Modifications into the machine itself or making changes in the system or environment are common scenes in IPM. Enclosing and providing air-conditioning to a high tech control centre full of electronics components to manage environmental conditions as dust intrusion, humidity and temperature inconsistencies are examples of IPM. To operate a control centre heavy in electronics components without environmental control is facing everyday troubles & breakdowns. Providing it with the right environment to free up these pestering troubles is Improvement Maintenance.
CONDITION MONITORING
Condition-Based Maintenance or the so-called Planned Corrective Maintenance can not succeed without Condition Monitoring. Practitioners of modern-day maintenance systems discovered that most machine failures do have the so-called FDT or “Failure Development Time”. If most failures have to undergo FDT’s (as in most mechanical & electrical equipment) before actual seizures, then these failures can be detected in advance through Condition Monitoring. Results of condition monitoring will trigger implementation of Condition-Based Maintenance (CBM's) or Planned Corrective Maintenance (PCM) in the first window of opportunity to do so. With advance diagnostic instruments & testing equipment, other practitioners refer these activities as Predictive Maintenance.
Condition Monitoring leading to Predictive Maintenance services can be done in four (4) different ways:
* Subjective Condition Monitoring
* Objective Condition Monitoring
* Continuous Condition
* Statistical Process Control
Subjective Condition Monitoring are regular surveillance activities on the health of equipment and machines by means of human senses (sight, smell, touch, taste, hearing and “the sixth” sense). Being the first line of defense against deterioration, it is the domain and responsibility of the operators.
This type of condition monitoring is putting great demands on the individuals performing the activity. However, experience of the operators & technicians on the operating behavior of their machines internalized over the years is a wealth of expertise that can not be under-estimated. The Taong-Bahay or the car driver normally knows what’s happening to his ward if there is a shift in performance. The awesome resources of our operators are just there waiting to be tapped. Even in advanced countries, 70% to 80% of condition monitoring is done subjectively.
Objective Condition Monitoring is when the condition of the machine is being determined with the aid of portable diagnostic instruments. State-of-the-art diagnostic instruments may be in the form of photo-thermal, vibration-based, ultrasonic, laser-based, temperature-based, shock pulse, infrared scans, or electronics-processing techniques that could provide timely information on the integrity of the equipment in relation to failure modes. Overheating, leaks, joints & weldment failures, insulation deterioration, moisture intrusion, cracks, excessive vibration, bearing condition, material wear and many more failure modes can be detected in advance while they are still undergoing FDT’s. Again, other practitioners call them, Predictive Maintenance. 
Continuous Condition Monitoring is a form of a self-diagnostic objective condition monitoring, but in this case, instruments are attached permanently in the machine and their sensors imbedded or built-in the machine system. Normally computer-based, the system gives out alarms and automatically prints-out schedule for its maintenance should an operating parameter is nearing to or beyond specified limits. This needs large investments that require a careful study on the benefits of this technique to justify the capital outlay. Even in highly industrialized countries, condition monitoring is 75% subjective, 20% objective and 5% continuous. Unless the equipment in question is very vital, dangerous and exceedingly expensive as in nuclear plants, large turbines or steel mills; “continuous condition monitoring" may not be justifiable. But as technology becoming cheaper, new generation diesel power plants are now sporting this type of condition monitoring and their number is increasing.
Statistical Process Control: The increasing popularity of the practice of Statistical Process Control (SPC) where quality monitoring of the product output of the machine is a built-in process, has paved the way for a more reliable monitoring of the equipment. A variation of the quality of the output product means a questionable process capability of the machine. A questionable process capability means that there’s something wrong in the machine. Any significant variation of product quality therefore means an immediate requirement for maintenance services.
“IF AIN’T BROKE, DON’T FIX IT” 
It is worthwhile to mention that many maintenance practitioners believe that PM is to take out the equipment from operation after a certain time interval for disassembling and replacement of large number of parts, as what old plant engineering handbooks had recommended. Experience showed that when the equipment is re-assembled and brought back to operation, problems oftentimes occur because the repairmen had transferred faults into the equipment. In modern maintenance management, PM is something more than disassembling and changing of parts. MGruppen Consultants of Sweden left us with a saying: “NEVER TOUCH A RUNNING MACHINE”. Same way that Americans say, “IF AIN’T BROKE, DON’T FIX IT”. This means that teardowns could only be done if there’s strong reason to do it. And that strong reason must be established first.
How? Through Condition Monitoring leading to Condition-Based Maintenance services…
DAA: June 2008
(Note: All pictures - courtesy of the Internet)
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