Technology and Expertise

[Warning!  Technical post following!  Be prepared for acronyms and unexplained manufacturing processes!  Hang in there... it’s worth it.]

I was relatively new in my first maintenance job when we began to make use of accelerometers and vibration-monitoring software to keep an eye on our most crucial large rotating equipment.  Our new NDT group collected data with a hand-held device and did the analysis using software on a PC.  I’ll admit, it was long enough ago that PCs in the plant were still pretty novel.

This was about the time one of my graveyard shift mill mechanics encouraged me to stick a long-bladed screwdriver in my ear.  It’s not what you think, and I’ll come back to this later.

I was (and still am) a true believer in the value of predictive maintenance, and for our processes – rolling mills – being able to plan ahead for major downtime tasks was exceptionally valuable.

The first instance we had of predicting a bearing failure was met with skepticism by our old school production manager.  Fortunately, he was an open-minded old school production manager, and we negotiated a couple days of downtime.  When the time came, and we began to open the rewind mandrel gearbox with the failing bearing, there he was, wanting to see the proof with his own eyes.  And, there it was, where we had identified it, a large crack (almost a complete fracture) of the outer race of the inboard bearing.  Run to failure would have ruined the gearbox and caused more than a wee bit of downtime, which was a very precious commodity to us.  As it was, caught early, we had a fairly easy time changing the bearing, and we were back up and running early.

Independent of, and actually prior to, being informed of the impending bearing failure by the NDT folks, one of my graveyard mechanics waved me over one night when I was in visiting the folks on that shift.

He pulled a long-bladed screwdriver out of his toolbox on the back of his industrial-sized tricycle (it was a big plant, and that’s how the mechanics got around).  I followed him over to the rewind mandrel gearbox of the Tandem Mill, which was ticking over.

He jammed the blade between the inboard bearing carrier and the housing, bent over, and placed an ear firmly against the handle of the screwdriver.  He listened, nodded, then stood up and gestured to me.  I put my ear on the end of the screwdriver handle, and conducted through the blade and handle to my ear was the fast gearbox hum as it turned an empty spool in the beltwrapper.  The noise level in the plant was high, but using the screwdriver that way I could clearly hear the gears.

“I don’t hear anything but the gears.” I told him.

“Exactly,” he said.

About that time, we heard the coolant sprays go on, the bang of a coil hitting the first stand, and in a few seconds the sheet came out of stand two and flapped and crashed into the beltwrapper.  After about five turns on the spool, the beltwrapper pulled away and the mill ramped up to speed.  After watching the sheet wind up on the spool for a few seconds (it’s actually pretty mesmerizing), I looked back and he was listening to the gearbox again.

“Now try it,” he said.

I did.  This time I heard a distinct high speed click.  I stood up and we backed away to a safer distance from the edge of the sheet.

He said, “It’s been getting worse – and you only hear it under load.  Better get ready to replace that bearing.”

I asked him if he listened to all the mill gearboxes.  He looked mildly insulted and said, “Of course I do.”

I believed him.  I also believed in and respected what he knew, and what he would do to take best care of his equipment (for he considered it “his” mill).  I thanked him, and assured him we would plan a bearing change.

A few days later, the NDT folks told me the same thing, but with different details, and we made plans with our production manager for the downtime to change the bearing

The point of this is that there is a definite place for technology in maintenance – vibration monitoring works, and it should be an important technological part of many maintenance programs.  Having the NDT prints of changes over time in amplitude of the bearing crack frequency made it easier to persuade our production manager to agree to the downtime.

A greater point, however, is that dedicated and expert craftspeople are a crucial part of any maintenance program, for their impact is not limited to one small aspect of maintenance.

Are your maintenance people experts on your equipment?  If not, we can help you get them there.  Contact us.

 

photo credit: www.industrialbicycles.com – mover-trike