Preventive Maintenance Strategy
By Terry Harris, CMRP
As I roam the US and the world in teaching people and companies, how to make their equipment last longer. I find that every plant I encounter has some form of preventive maintenance program. I am often confused by the process that is used to develop the program and how so many things done have no value. Is there a strategy for a PM program and how can it be used in every type of operation?
There are many types of Preventive Maintenance Programs:
- Time based (two shots of grease per week)
- Condition based (if it’s squeaking then lets tighten)
- Failure Finding (verify functioning of a high level probe)
- OEM Directed (recommendations in equipment manual)
- ‘Hand me down’ (Experience / “we have always done it that way”)
- Regulatory (EPA, OSHA, Etc)
- Risk (expensive equipment, lets do this task more often)
It is normally one of these methods that determine if a PM task will be assigned and completed. We grease a bearing based on time, two shots per week. We have always completed this task every week for the last 15 years so it must be good. Is there something else we can do to justify what we are doing daily, weekly, and monthly? Are OEM recommended tasks always the right thing to do?
Preventive Maintenance is used in all industrial process plants and this training class will help you determine which tasks add value to your program and extend equipment life. This program covers a variety of PM process such as RCM, PM Optimization, MTBF, and Asset / Equipment Criticality. Attendees will also learn how to use equipment-saving and money-saving tools to help your team make the right decisions. Attend this program and learn how to improve up-time and properly schedule PM tasks wisely.
Stop wasting valuable man hours on tasks that simply do not add value, increase equipment life cycles and add dollars to the bottom line.
If we look at a very common practice in preventive maintenance procedures; “grease the bearing with two shots of grease every week” A common question: does the speed of the bearing require grease every week? What is the speed, load, and temperature condition? Are we using the correct grease? On many occasions I have performed maintenance audits and found companies using cheap grease from automotive stores. The grease has the incorrect viscosity or additives for the industrial application. The act of performing the PM task is actually shorting the life of the bearing.
Preventive Maintenance programs are designed to do the following:
- Reduce equipment failures
- Reduce the magnitude of equipment failure or repair costs
- Reduce the product loss or production downtime due to equipment failure or repair
- Reduce the deterioration in the productive capacity of equipment
If we look at each PM task and ask if we are accomplishing the above items can we justify the task? These are pretty broad based items making it difficult for many of our PM work tasks.
There are some processes that are used in many companies to justify PM work. The first and most effective is the RCM Process. Reliability Centered Maintenance was developed by Nolan and Heap and United Airlines in the late 60’s and early 70’s. The process looks at every component in our process and asks: how can or has this component failed? Once we determine all the ways it can fail we ask the questions: how can we predict, prevent, or eliminate the failure? This process takes some training and understanding of predictive technologies and the overall RCM Process. But through the process, a strategic PM program is developed with all PM tasks adding life and value to the equipment.
A second process, which is less cost but effective is called PM Optimization. PM Optimization looks at all existing PM tasks and asks a series of questions about the task to determine if the task adds value or life to the component. If it does not, the task is eliminated or modified to add value. Simply, a little training on PM Optimization and this process can be very effective.
A third process, used by many reliable processes is called equipment criticality or sometimes asset criticality. This process actually rates each piece of equipment on its criticality or value to the process. It not only looks at the maintenance view point, but looks at how critical is the equipment to areas such as safety, product quality, customer issues, environmental issues, and production. Each piece of equipment has a criticality rating, such as a numeric value of 0-1000. The higher value number indicates equipment with high criticality or high cost if it fails. Maintenance resources and time, (PM tasks) are then assigned based on the equipment criticality rating.
A process used by many plants is “Mean Time Between Failure”, (MTBF). This is used in companies that have well maintained CMMS systems and failure data is very accurate.
Example: If we have MTBF data that says a belt has failed numerous times at approx. 6 months, we change the belt before 6 months, on a scheduled basis, and eliminate the unexpected (emergency) downtime. This is very effective for some equipment and reduces emergency downtime. The biggest mistake made in most plants that use the MTBF method is not determining how to make the equipment last longer on the next cycle. You should always determine why it failed and develop or make changes to extend the life of the component. PM’s can be developed or adjusted to improve life cycles.
Predictive Maintenance (PdM) adds value. My training shows that 90% of all rotating equipment failures can be predicted months before the failure. Use of predictive technologies can improve our PM programs and add life to the equipment.
Example: An OEM directed PM task: A centrifuge OEM states in the manual; “Change the oil in the gearbox every 30 days” or “rebuild the gearbox every year or a specified number of hours of operation”. If we are trained on predictive maintenance techniques, we would change the oil after oil analysis indicates a problem. This keeps the machine operating and producing until the oil needs to be changed. We would also ask why the oil needs changed; can we filter it while it’s operating? On the yearly gearbox rebuild we would use Vibration Analysis, Mechanical Ultrasound, or Wear Particle Analysis to tell us we need the gearbox rebuilt. This is a great strategy for critical equipment and improving operating time.
The two areas of training that are lacking in all operations are Lubrication Excellence and Predictive Maintenance. Understanding how to purchase, store, and transport lubes as well as keep them clean is a key element in lubrication training. The simple act of lubricating a bearing can cause failures if particles are pumped in with the grease. Understanding how Predictive Technologies can predict rotating equipment failure months before they fail is the key to reducing unplanned downtime.
As you can see in this overview article there are strategies to make Preventive Maintenance more effective. We must change our way of thinking about PM programs to PM processes. What is the difference? A program is something that is defined, and we do it the same way every time. A process is continually evolving to meet the needs of the process and equipment.
The key is to invest in training to improve knowledge at all levels of the company. It has been proven for every dollar saved in maintenance on improvements in equipment reliability, there is a 5-10 dollar return to the bottom line. We are living in a time when only the most efficient operations will ultimately survive. Competition is fierce in every industry so we must be the best. Companies moving resources to third world countries to compete are just fooling themselves, and taking what they see as the easy way out. They usually lose on other issues such as production quality.
Improving processes, up-time, quality, and reducing E,H,&S issues is where the true savings are. This can only be accomplished by understanding and moving away from the traditional thought processes of equipment PM’s that have been used since the 50’s.