Prove the value of predictive maintenance (PdM) to senior management

Allied’s Trulli argues not to rely exclusively on predictive technologies. “Studies have proven that the most cost-effective maintenance programs include a combination of precision maintenance practices, predictive maintenance, preventive maintenance and run-to-failure maintenance strategies,” he explains. “That said, where failure mode-based maintenance strategies overlap, PdM or condition monitoring should be preferred over the other applications. PdM technologies should be developed and applied based on asset criticality with ever-increasing coverage levels applied as the organization’s work management systems and maturity levels evolve. The key is to feed the work execution process with work identified by condition monitoring and preventive action activities. As the organization realizes the benefits from these activities with a less reactive culture and reduced unplanned down time, resources can be redirected to supporting additional maintenance and reliability initiatives.”

Figure 2. This version of the P-F curve assigns maintenance priorities and suggested maintenance strategies for the various stages of degradation. (Green Energy Engineering Services, Inc.)

Another key to establishing the intensity of an application lies in historical records. “The source information is typically in the form of CMMS work orders, reflecting equipment maintenance history,” says Paul Lachance, chief technology officer at Smartware Group (smartwaregroup.com). “Work orders show the real-life needs during equipment failures. It’s helpful to compare corrective maintenance with preventive maintenance, as well. Meter readings also can be used for PdM analysis. If you can retrieve this data in an automated way, you’ll get more data points on the asset while eliminating human error doing data entry, thus giving better, more accurate and timely analysis.”

Dean Wallace, president of Applied Facility Solutions, Inc., in Jeffersonville, Pa, agrees that equipment history is another factor and suggests results from the PdM program be reviewed to determine if the frequency needs to be adjusted.

“If by intensity you mean frequency, then equipment criticality, shaft speed, typical repair costs and lost production factor into monitoring intensity,” says EMP’s Smithman. “However, intensity often can mean more than frequency. It also can mean the types of monitoring performed. Is oil sampling appropriate? How about a megger test versus a full electrical analysis? Do we monitor vibration on each bearing or simply on the entire component?”

Truthful numbers

To gain any traction for a PdM program at the management level, the cash saved because a breakdown didn’t occur need to be quantified. “We use cost avoidance,” says Therma-Tru’s Neubauer, “which is a total of parts, labor and the cost of the asset being unavailable.” Downtime should be looked at as parts and resources are available, or if they aren’t, he adds.

“This is an area where condition monitoring aficionados tend to oversell themselves,” says EMP’s Smithman. “If the lost opportunity cost is $35,000/hr, a lost week is 7 times 24 times $35,000, or almost $6 million, right? Of course not. Any effective plant finds ways to reduce the hemorrhaging once the corrective measures begin. The hourly cost will drop off, usually by quite a bit. Likewise, citing the full savings over every bearing identified is dishonest. People identified worn bearings by sound and temperature and overloads long before anybody thought of using spectral analysis. Lose sight of that fact or your numbers, and you can lose credibility.”

Each time you find a problem, make sure you publicize the catch and what would have happened if it hadn’t been caught, explains Machinery Management’s Taylor. “You want to build a subconscious belief in PdM’s effectiveness,” he says. “Then, for at least the major finds, do a repair work order estimate as if the failure had occurred, but don’t overdo it with cascading and secondary failures. Be conservative. Then compare that to the cost of the PdM program. I’d strongly advise having someone from the treasurer’s or comptroller’s staff on the team putting together the cost avoidance. When that cost/benefit study gets to the plant manager or higher, you want the comptroller to be able to say, ‘Those are good numbers; my staff helped put them together.’ One other thing, I’d advise reaching agreement a priori on the cost of lost availability. Direct costs are not too controversial, but lost production or sales cost can be.”

How to quantify the benefit of PdM is often asked and frequently left unanswered, says Allied’s Trulli. “The obvious answer is a cost-avoidance figure, an arbitrary or subjective number assigned to an event illustrating a what-if scenario based on an identified defect, the maintenance costs and production loss,” he says. “The trouble with this approach is that when you present the cost-avoidance figure to justify programs or request additional funding, even though the estimations might be accurate, the typical response is that cost avoidance is a fictional calculation. The best way to quantify your program’s effectiveness is to capture metrics specific to the application and effectiveness of the maintenance and reliability initiatives. For example, you can track emergency downtime, maintenance costs as a percent of replacement asset value, overtime costs, parts, PdM and PM compliance, and mean time to implement condition entries.”