Slow movement toward predictive maintenance seen in Tennessee study

Production throughput and being cost competitive are as important as ever. Understanding what is attainable and implementing reliability and maintenance best practices can provide that opportunity. This benchmarking study is a repeat of a similar effort performed in 1991. It will be published in two parts.


Production throughput and being cost competitive are as important as ever. Understanding what is attainable and implementing reliability and maintenance best practices can provide that opportunity. This benchmarking study is a repeat of a similar effort performed in 1991. It will be published in two parts. Part one will be a comparison of 1991 versus 2008 results and some additional findings. Part two will be an analysis of trends, impacts of variables (such as size of company and operator involvement), most important maintenance metrics used and a summary of anticipated changes in reliability and maintainability over the next 10 years, and more.

Predictive maintenance refers to compiling and analyzing machine condition data to warn of impending failure and identify defective parts (examples include vibration and motor current analysis, infrared thermography and oil analysis).

Preventive maintenance uses scheduled routine inspections and improvements to intercept failure (examples are time-based adjustments, replacements, lubrication and refurbishments).

Reactive maintenance refers to emergency breakdowns and related repairs.

Responses were compiled from 217 companies across North America. About 70% of the responses were from manufacturing companies, with the remainder being almost equally split between the remaining categories. The responses were categorized into five areas. Below are examples of the types of companies included in each category.

Manufacturing %%MDASSML%% automotive stampings (small & large), plastic parts, locomotive parts, machinery, sound systems, conveyor systems, fasteners, ceiling tile, air tools, aircraft, batteries, signs, transmission components, truck accessories and shipping racks.

Assembly %%MDASSML%% small instruments/equipment, CMM machines, tools, sunroofs, electrical products, automation equipment, automobiles, welding & assembly equipment and automotive components.

Process %%MDASSML%% steel, chemicals, precious metals and mining.

Distribution %%MDASSML%% safety products, pumps, instruments, valves, tapes/adhesives, hardware parts and metal products.

Consultants/others %%MDASSML%% consultants, hydraulic component repair, tool and die, construction, filtration services, equipment repair services and research and development facilities.

The intent was to collect current actual and perceived world class data, two ratios expressed as a percent (maintenance expenditure to original investment in machinery and equipment, and maintenance expenditure to sales volume in dollars), and several other R&M questions.

There was significant improvement made by North American companies. Reactive maintenance declined from 54.6% to 34.1% and maintenance expenditure as a percentage of machinery and equipment investment went from 15.5% to 9.7%. Maintenance expenditure as a percentage of sales improved from 5.9% to 4.4%.

For North American companies the largest opportunity to improve R&M is in “more designed-in reliability” and “more involvement by operators.” Breaking out manufacturing companies by themselves paralleled North America. Assembly companies show the same two opportunities, with “more involvement by operators” having even a larger potential for improvement.

It's noteworthy that the companies with the best performance selected “more reliable machinery and equipment” as having the greatest positive impact in the last five years. They also selected “more designed-in maintainability” and “more involvement by operators” as having the largest opportunity for improvement.

From 1991 to 2008, reactive maintenance decreased and proactive maintenance (predictive + preventive) increased. It appears that predictive maintenance remained at about 13%, while preventive maintenance increased from 32.5% to 52.8%. Note that in 2008, perceived world class maintenance for reactive was 12.3%, predictive was 26.3% and preventive was 61.5%. Perceived world class maintenance values from 1991 to 2008 decreased for reactive (17.6% to 12.3%) and predictive (35.2% to 26.3%), while preventive increased (from 47.4% to 61.5%).

The Actual and Perceived Maintenance Percents from the North American average were compared to the top 20 percent of performing companies (based on maintenance expenditure/investment in machinery and equipment).

It's good to see that maintenance practices are improving. However, where I feel that most companies need to focus more on is in establishing a robust reliability process. Reliability will be further analyzed and discussed in part two in the July issue of Plant Engineering.


For more information on the study, go to

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