How thousands of dollars were saved by using ultrasound to test ballscrews and gearboxes
By Deborah Hays, Dmax, Ltd.
Predictive maintenance is never an easy task, but when a company such as Dmax–which makes the Duramax diesel engine used in General Motors-brand (GM) heavy-duty trucks—has only two technicians (me and one other)to do the work, the job is even tougher. The plant that houses Dmax, a joint venture between General Motors and Isuzu– has around 1,500 pieces of rotating equipment on the machining side of the plant, while there are another 50 pieces on the assembly side. With only two technicians, relying mainly on vibration analysis, inspecting the route as often as it should have been inspected was close to impossible.
The plant was having a particularly difficult time ensuring the health of its more than 500 ballscrews. Two of the plant’s machines–CB-10 ST12 and CB10 ST15–had ballscrews that were failing yearly and gearboxes that were failing approximately every six months. With the ballscrews costing approximately $14,000 to $18,000 each, and gearboxes ranging from $5,000 to $7,000, losses were adding up, and quick. If a ballscrew went bad, the gearbox went bad; if a gearbox went bad, then the whole machine went bad. How to stop the losses? The solution came, in part, through recognizing that ultrasound technology, which the plant had already been using as a leak detector, could be applied in a more thorough, systematic way.
As mentioned, Dmax began using ultrasound technology in a very familiar way: as a leak detector. We found a major leak (65 gallons) on a hydraulic head line, and, as a result, saved tens of thousands of dollars. In learning more about how ultrasound could be applied beyond “simple” leak detection, we decided to add ultrasound to our toolkit and began a predictive maintenance program. (Previously, monitoring had been a 24/7, not a predictive, process.)
While vibration analysis is a wonderful and reliable tool, it is impossible for only two technicians to take care of such a vast inventory of rotating equipment using it alone. Because of the compromises imposed on us by workforce and technology capabilities, we were having more failures than were acceptable.
A few years ago, we decided to use ultrasound to analyze the ballscrews and gearboxes. As a result, we were able to accomplish two things that vibration analysis could not:
1.) We were able to run the route much more quickly;
2.) We were able to run the route much more often.
Since we were able to run the route more often, we were able to catch more problems before they became critical. By using the transducer on the Ultraprobe 10,000, we were able to hear trouble in the ballscrews before (or as) the troubles began to manifest. We were able to trend this information, before and after intervention, which was critical in helping us to determine how to proceed with repairs and replacements.
Often, the problem with the ballscrews was something as simple as contamination (e.g., mud, debris, etc.) or a lack of lubrication. Vibration analysis, infrared, or MCA may have picked this sort of issue up, but it probably would have picked it up too late. Through ultrasound, we were able to catch it early.
This has a number of benefits. Repairs could be made during third shift, when the machines were not running, which prevented unscheduled downtime. Also, by analyzing trends, we could more accurately predict when a piece of machinery would need to be replaced. This enabled us to save on “rush” shipping costs and further downtime. Getting new machinery in could be a long, arduous process at best, and when one has to rush it, the costs really add up (especially considering that much of our equipment is shipped from Japan).
Ultrasound did not replace vibration analysis; it simply let us know that something was wrong, and in a more timely fashion than vibration analysis could. Following detection of a problem through ultrasound, vibration analysis came next, followed by corrective action.
Again, all of this information is stored and trended. As with all condition monitoring programs, trending is key. It’s like our “crystal ball.”
To say ultrasound saved Dmax money is an understatement. During the four years that it was used as leak detection alone, ultrasound saved Dmax around $40,000 to $50,000. In 2008, the first year that ultrasound was used predictively, it saved Dmax around 20 million dollars.
Through analysis, we found that ultrasonic monitoring was finding potential failures around 6 months before other methods would have. And the technology really did pay for itself—many times over. Not only was it quick and easy to use (we received the equipment on a Thursday and were using it on a Saturday); it was effective.
Trending has been the key ingredient in this successful recipe. By finding failures before they are critical, we not only save money by not having collateral damage; were able to plan jobs in advance, so downtime is minimal.
The ultrasound program, in addition to saving Dmax considerable money, also brought prestige to the company. The program won Uptime Magazine’s 2009 Ultrasonic Program of the Year, as well as numerous additional invited presentations and published case studies in noted industry magazines. It truly has been a “sound” choice.