My company utilizes vibration analysis to monitor most of our electric motors, and also a good number of pumps and fans. We also have an IR camera for electrical fault analysis, but have yet to figure out any significant uses for it concerning machinery monitoring. I was wondering if anyone uses IR cameras to monitor their gearboxes. Currently, our in-house vibration analyst doesn't monitor gearboxes ( I don't know if it has to do with lack or experience or difficulty or what..) so we just use a reactive maintenance approach when it comes to all our gearboxes. Any suggestions or info?

You don't share enough information to well answer the question. However, thermography can be useful with gearing. Many years ago I used a technique of shooting across the face of open gearing (spur) to adjust the tooth contact. Uniform temperature indicated proper load sharing. It was surprising the temperature differential when the gearing wasn't properly set.

To use thermography effectively you would need to know the characterisctics of the gearing. Single helical gearing for instance is hotter at one end of the teeth as compared to the other end. This can affect alignment in certain designs.

John

I'm with you Jeff. We rely on vibe readings for most of our gearboxes. The majority of our gearboxes are split case Dodge TXT reducers used on conveyor belts, so there's no way to "open them up" and watch the gear mesh. (In fact, the way the case halves are pinned, there isn't much we can do to change the gear mesh anyway.)

In my opinion and experience we haven't been able to determine anything useful, using the IR camera on a gearbox. I do occasionally check things out if I'm in the area. The one interesting thing I have noticed is on our horizontal conveyor belts, the gearboxes seem to run hotter when they are NOT loaded, as opposed to when they are loaded. I'm assuming this is from the backlash? All the rest of our conveyor belts are inclined, and therefore have some amount of load continuosly, and run a continuos temperature, regardless of their load.

Thanks for the responses. I wish I knew all the minute details of our gearboxes, but I'm still 'green' in that area.
We have mainly planetary reducers and dodge reducers scattered throughout the plant. Like Bill, we can't open up gearboxes to have a look at meshing. Also like Bill, I've noticed several gearboxes that run hotter that their identical neighbors - and they happen to be under decreased or less consistant loading. Don't know why that results in hotter operation...
I was already under the impression that we couldn't get much useful info from an IR scan of gearbox housings, but I was wondering if there were any exceptions out there.

Jeff Brunet
Reliability 'Engineer'
OSB Plant - Lemoyen

When looking at gearboxes with thermography, you are typically looking for the level in the gearbox as seen in the difference between the airspace and the oil, or for localized heating typically at the bearings. For a good running gearbox, typically most of the heat is generated by the churning of the oil, which mostly happens as the gear dips down into the oil. The temperature can be very dependent on the oil level, and optimal level for splash lubricated gears is so that the lowest gear tooth is covered by oil. Other, usually larger, gearboxes can have pumped oil (forced lubrication) or can have a slinger ring or disk to carry oil to smaller gears or to bearings. So it is important to note oil level when performing IR inspections to verify that temperature changes are not due to improper level. In fact, when oil level is too low, the gears may not pick up the oil at their low point of travel, or not pick up enough. Initially, this can actually cause the gearbox to run cooler than normal, until the lack of lubrication results in severe wear, and friction takes over and is seen at the bearing locations as hotspots.

You can also compare bearing temperatures, and in most gearboxes they should be about the same, and should not be significantly hotter than the gearbox oil.

In addition to vibration and IR, oil analysis can be a very effective tool for gearbox monitoring, and can often pick up problems in the very early stages.

Rich Wurzbach
Maintenance Reliability Group

Jeffro,

At our facility we are doing Vibration analysis on Motors, Pumps and Gearboxes. We use Thermograghy on some of our small C face gearbox and motor combinations where we seem to be losing seals do to heat in the summer time. Vibration analysis is your best bet for gearboxes.