Precision Maintenance Drives Uptime
Klaus M. Blache | July 20, 2020
By Dr. Klaus M. Blache, Univ. of Tennessee Reliability and Maintainability Center (RMC) and Tim Dunton, Reliability Solutions
Q: How important are essential craft skills and precision maintenance?
A: Because of his extensive applied experience in improving machinery/plant performance, I asked Tim Dunton, Director of Product Development, Reliability Solutions, Walnut Hill, FL (reliabilitysolutions.net), a UT-RMC training partner, to discuss why learning essential craft skills and using them to perform precision maintenance is so important. Here is his answer to this month’s question.
In the past few decades, much has changed in the world of asset reliability. Obviously, the tools and technologies available today offer unprecedented ability to monitor and measure the performance of our equipment in significant detail. These technologies can, if used properly, provide deep insights into how and why things fail, thus providing an opportunity to prevent or control those failures. Remember, it’s not the data that is important. It’s how we utilize the data that counts. It’s easy to get wrapped up in the mountains of information the technology provides and lose sight of the real goal.
If we truly want to improve asset reliability and performance, we have to change our approach. Most important, we must recognize that reliability is everyone’s responsibility. While this article focuses on maintenance activities, without the involvement of everyone in your organization, results will be mediocre at best. In many maintenance organizations today, emphasis is often placed on changing parts as quickly and efficiently as possible. If you want to improve machine performance and reliability, you must assemble and install parts such that they extend machine life.
Precision maintenance is an approach that aims to place the machine in an improved or precise state. It is executed with discipline, precision, and control, and audited for reliability. As part of a broader reliability process, the proper assembly and installation of machinery is where an immediate impact can be realized.
The techniques required are not complex or technically difficult and include activities such as eliminating unbalance, misalignment, and assembly errors. Simple errors such as incorrect key length, excessive run-out, improper tightening of fasteners, and soft foot, individually can shorten machine life, but collectively can contribute significantly to reliability problems.
Documented results indicate that when taking a machine in poor condition, typically with vibration levels exceeding 0.3 ips (pk) (7.5 mm/sec. (pk)) to a precise state, the machine life is doubled, at minimum. For example, we have data from 336 machines from several manufacturers, of various styles and types, with a wide range of horsepower ratings, to which our Reliable Manufacturing (essential craft skills and precision maintenance) techniques and principles were applied. The mean time between repairs (MTBR) was somewhere between 2.8 and 3.2 yr., before the improvements. After our techniques were applied, the MTBR on the same machines improved to 6.8 to 7.2 yr.
Of note here is that the mean time to repair (MTTR) does not necessarily increase with the application of precision maintenance, because the techniques are applied in a disciplined and controlled manner in which technicians understand what they’re doing and why they’re doing it. The extra time needed to execute and document the work is more than offset by eliminating generally inefficient existing work processes.
In terms of the cost of maintenance (parts and labor), reducing the vibration levels by 50% will typically result in a cost reduction of 30%. We’ve also seen notable process improvement. At one company, we were able to improve OEE (overall equipment effectiveness) from a peak of 67% to 75% during 25 years of operation to a sustained 91% today.
Average electrical consumption changes as we reduce the various frictional loads. The savings are typically at least 20%. Documenting electrical savings demonstrates immediate return, which is important as it bridges the gap before longer term results are realized. As for reliability performance (When I push the button it does what I want it to do for as long as I want it to do it and when I shut it off and start it again, performance will repeat.), we have seen three to-eight times improvements.
A simple formula is used to generate these statistics. Load life for most mechanical parts is equal to the inverse of load to the third power. On a practical level, this means that if you remove 20% of a frictional load that is caused mostly by the way an asset is assembled and installed on the floor, then you double the life of the machine.
To improve reliability, we must understand the failures we wish to control, eliminate them by using precision-maintenance techniques applied in a systematic and disciplined manner, document the work accomplished, and broadly communicate those results. Operational excellence is accomplished one machine at a time. EP
Based in Knoxville, Klaus M. Blache is director of the Reliability & Maintainability Center at the Univ. of Tennessee, and a research professor in the College of Engineering. Contact him at firstname.lastname@example.org.
Tim Dunton is Director of Product Development for Reliability Solutions, Walnut Hill, FL (reliabilitysolutions.net), a UT-RMC training partner. He has more than 40 years of experience in vibration analysis and technical training related to the reliability of rotating machinery. Dunton also has extensive experience in workforce development, curriculum development, instructional design, and reliable-manufacturing practices. He holds DTI Class 1 Certification and CMRP and CMRT Certifications,