Improving reliability, you have the data, do the math

Years ago, while practicing the trade, knowing the OEM SME’s was not only a crucial factor in determining root cause of failures, but also to add value in considering corrective solutions.

It wasn’t at all uncommon to hire an OEM expert to oversee and guide such projects as a turbine-generator or drive turbine overhaul, specialty pump and mixer reinstallations, electrical drive rehabs and tune-ups or bearing mounting and dismounting of specialty equipment.

Even with moving around the country within the industry the first person contacted when trouble arose that was beyond our technical capability was the OEM subject matter expert. It’s what they do. They generally had first-hand practical experience with the equipment being refurbished.

These experts kept records of their experiences when assigned to a site, which they shared with the client.

Today, of course, these records, with valuable data and information, are generally kept in-house, and the OEM experts also continue to keep their own data and continue to share the data with the client.

As an example of the value of this data, according to data of large size bearings in use in the pulp and paper manufacturing industry collected by bearing OEM experts examining bearings at various equipment rebuild shop locations, over time, 54% are reused with cleaning.

The bearings examined represent those with inner race bores exceeding 180 mm diameter, so, large size bearings (LSB) which, accordingly, also represent costlier and likely, long delivery replacement bearings.

28% of the bearings examined by OEM experts on site[1] are determined to be non-reusable and therefore scrapped, while 18% are deemed remanufacturing candidates.

This chart identifies the sites of the examination, e.g., number coded for various repair/rebuild/recover shops.

Of particular interest is the ‘Other’ location.

Generally, ‘other’ is the end user’s internal shop which are regularly visited by OEM bearing experts specifically to examine bearings that have been removed from service due to ‘conditions’, e.g., perhaps a roll or gearbox changeout, or they can be bearings pulled from service and set aside waiting for explicit examination to help determine disposition and as evidence to assist with understanding failure modes and causes.

Bearings examined at these end user locations account for just 7% of the total bearings examined from this data set by the OEM experts, which means, typically, that a decision for reuse, disposal or remanufacturing of all the other bearings mounted on rotating assets removed from service in these internal shops is made without advice from the bearing OEM expert, meaning certainly more than 7% of the total bearings removed.

Further analysis reveals that of the total bearings deemed non-reusable, e.g., scrapped, by all examination locations, ‘Other’ accounts for some 19% of the total scrapped population.

And even more revealing, in the chart below, is that of those bearings examined and recommended for scrapping, the highest percentage by location is from the ‘Other’ location category, e.g., 73% of the bearings examined at the ‘Other’ location are scrapped (of total inspected by the OEM experts at the ‘Other’ location).

So, what can be the possible explanation of this information based upon the data collected?

Why are more bearings scrapped (%) in the internal shops (Other) than in the outside vendor shops?

Most bearings examined at the external locations identified by number are repair/rebuild/recover shops performing general services on the equipment they have received from end users, e.g., roll shops that are grinding, recovering, reconditioning rolls and the asset, e.g., rolls in this example, were not sent to the shop specifically for bearing examination.

This bearing exam at these outside locations is a service provided by bearing OEMs to the end user and the rebuild shop as a precautionary action while these still ‘working’, temporarily out-of-service, bearings were available for inspection.

On the other hand, most of the inspections performed at ‘Other’ (the customer’s internal shops), are inspections of known suspected defective bearings removed in the end user’s shops, e.g., machine shop, pump shop, motor shop and roll shop awaiting the OEM’s expert inspection, or just scrapped without OEM examination.

This would not include, as mentioned, those bearings not examined by OEM specialists between regularly scheduled visits. A number which likely is much larger.

These bearings could be found on fans, in gearboxes, pumps, mixers, motors or rolls (rotating assets) that had to be replaced on site during a shutdown, planned or unplanned.

Another factor in this decision process, e.g., whether to reuse, scrap or remanufacture, is the turnaround time of the equipment while out-of-service.

Usually when the bearing, or pump, or motor, etc. is examined in the end user’s shop the solution must include a quick turnaround.

Often, remanufacturing of a bearing, in this example, will take too much time versus replacement with a new bearing from the local bearing distributor.

This eliminates many ‘borderline’ bearings that might otherwise be candidates for remanufacturing, depending upon outcome after further inspection and recommended actions at the bearing OEM’s remanufacturing facility. 

What then is the potential financial benefit if this remanufacturing process can be improved by failure forewarning, bearing replacement pre-stocking, rapid turnaround of remanufacturing?

How many bearings that could be remanufactured are tossed due to untimely return-to-service issues with the asset?

Or how many reusable/remanufacturable bearings are simply tossed because the site is amid a shutdown and no one is thinking of saving bearings for determination of reuse by remanufacturing and restocking?

Experiencing first-hand the scrapping of all bearings regardless of condition annually removed from shaker screens at a site’s woodyard because the established preventive maintenance practice is to replace all bearings is testament to the lack of cost improvement consideration as standard best practice.

Consider this, using the average price per bearing for LSBs, even if the cost of remanufacturing a reusable bearing is 50% of the original price for a new bearing, the potential cost savings are substantial.

For example, what if the decision is made to replace a critical bearing, based upon good condition monitoring practices, before it is subjected to additional potential damage by extending its service life. The bearing then is highly likely to be a candidate for remanufacturing at half or less the cost versus scrapping with zero value.

Ask your condition monitoring crew if they have ‘spotted’ bearings well before failure, only to have the bearings continue to run to near failure and be scrapped.

Or, in the case observed above, what if all the bearings were removed and replaced, but the removed bearings, instead of being scrapped, were examined and those deemed reusable, many perhaps with some level of remanufacturing action required, are then returned to stores for use during the next annual replacement?

In this era of ‘lean’ manufacturing, how many LSB bearings, in this example, are scrapped in your facility without consideration for remanufacturing, or even reused with minor cleaning?

how many LSB bearings are scrapped in your facility without consideration for remanufacturing, or even reused with minor cleaning?

How many failing bearings are ‘run just one more day’ before replacement, that could otherwise be saved and reused after a planned outage?

What if, instead of 54% of bearings taken out of service are reused, as shown above, the number is improved to 60%, or 65%?

How much value is lost?

You have the data, do the math.

Cost savings and cost avoidance is what improving reliability is all about.

[1] The site can be a vendor roll repair shop, a roll recovering and grinding shop., a repair shop for other equipment, such as, motors, drives, mixers, pumps, or the client’s own internal repair/overhaul shop