If a defect is identified, a new work request to make the repair is written by the PdM technician. On the work request, it is important for the PdM technician to identify the cause of the potential failure. Many times the cause will be "human-induced failures," due either to current maintenance technicians not having effective procedures with accurate specifications, or to a rebuild vendor not having or following procedures and specifications. Identifying the cause of the potential failure is critical to the continuous improvement of the maintenance processes and establishing buy-in of the PdM program.
When repairing, replacing, or installing anything on a critical or important asset, it is imperative that the PdM technician conduct a baseline survey and communicate to management whether or not the equipment is free of defects after the work is completed.
Planned and Scheduled Work:
The PdM technician has a planned and scheduled route to conduct his/her inspections and to conduct baseline readings on repaired or replaced equipment during the day. This is a busy job when done correctly.
From a PdM technician's standpoint, his/her time needs to be scheduled to validate that a defect has been eliminated and establish a baseline anytime a repair is made. If you do not conduct this validation, expect that unexpected failures will occur, which will result in people believing PdM is not effective.
The table on the left shows an example of a daily schedule for a proactive PdM technician.
Key Learning Point: If your maintenance process is reactive, then your PdM Technicians will be reacting to urgent and emergency work and their true value will be diminished.
Common Questions a PdM Technician Will Be Asked:
Q: What value does a PdM technician provide to a proactive organization?
A: The ability to identify a defect or unacceptable condition that will lead to equipment failure and unexpected downtime.
The purpose of early defect identification is that work can be planned, scheduled, and executed without getting close to a failure on critical assets. The PF curve on the next page clearly demonstrates this value.
Early defect identification affords the ability to schedule maintenance work during the windows of opportunity that operations/productions offers us, therefore creating the ability to run as much production as possible without an upset.
Q: What is a PdM technician unable to provide to a proactive organization?
A: A PdM technician is unable to estimate when the failure will occur.
The focus of a PdM technician is detection of defects that are random in nature. To attempt to trend the propagation of a defect and forecast the actual time of functional failure is a difficult proposition, as well as a very poor use of the technician's time. The defect will never be cheaper to address than directly before failure, and the PdM work execution processes must be utilized to address the timing of repairs as opposed to the PdM team. This one issue causes more pain to an organization than any other. Management always wants to know: "How much longer will it run?" To this question, the only appropriate answer is: "How much risk are you willing to accept?"
Sometimes, people lose confidence in PdM technologies. Listed below are some common arguments:
"Predictive maintenance is not a true term."
This has some truth to it. Condition monitoring is the true definition of PdM, because we are measuring the condition of specific failure modes at a specified time. It may be 30-90 days before a reading is taken again.
"If you really want to know what the most effective method for addressing failure modes is, you must begin by determining what the most dominant failure pattern is at your organization."
Less than 2% of organizations can identify a failure pattern statistically, because they do not have the data from their maintenance software to support a decision. As it turns out, identifying the dominant failure pattern is useless anyway. A study conducted in the 1960s by Nowlan and Heap proved that the majority of failures are random.
Q: From where does proactive work come?
A: Here is how PM and PdM work should break out:
PM Execution: 15% of Work
Results from PM: 15% of Work
Condition Monitoring Execution: 15% of Work
Results from Condition Monitoring: 35% of Work (planned and scheduled work; emergencies not included)
Q: Does a PdM technician focus on the present or the future?
A: A PdM technician's focus is on the future, not today's problems.
A potential failure (low defect severity - time to plan and schedule proactive work) is an identifiable physical condition that indicates a functional failure is imminent and is usually identified by a maintenance technician using PdM or quantitative PM.
As a PdM Technician, You Know You Are Still In Reactive Maintenance Mode When:
- An organization is using only vibration analysis and infrared technologies, so technicians can identify potential failures only on specific failure modes addressed by the two technologies. What about the failure modes that can be addressed only by ultrasound, UT, MCA, etc.?
- A technician makes a repair after a defect, but the equipment is not inspected to ensure it is free of defects after the repair. For example, if a loose electrical connection was repaired after an outage, and infrared is not employed to confirm the defect has been fixed, how do you know that the repair has been made properly?
- Ultrasound is used only for compressed air leaks.
- PdM technicians do not know each other and never work together as a unit.
- The PdM program is not focused on specific failure modes, which causes "too much PM" to be conducted.
- Infrared technology is not employed for low-voltage applications and is instead used only for high-voltage applications.
- Maintenance technicians do not use repeatable, effective work procedures.
- Your main source of failure mode identification is when something fails.
A PdM technician performs a vital role in making sure that a company's needed repairs are identified, made, and done correctly. A PdM functions best and is of the most value when allowed to take a proactive role in identifying and solving problems rather than being left to respond to emergencies. A proactive PdM technician can be an invaluable asset.
Ricky Smith, CMRP, CPMM, is the Senior Technical Advisor for Allied Reliability. Ricky has over 30 years in maintenance as a maintenance manager, maintenance supervisor, maintenance engineer, maintenance training specialist, and maintenance consultant and is a well-known published author. www.gpallied.com
Carey Repasz, CMRP, has spent the last fifteen years in maintenance. Today, he serves as the Program Manager for Cargill Corn Milling in Eddyville, Iowa. He is one of Allied's Senior Instructors for the PM/PdM Best Practices Training & Tools Series. www.alliedreliability.com