The Devil is in the Details (Again)
July 18, 2008

Some things are best restored, especially good things that are sound and have worked well.  Maybe restored is a poor choice of words but I don’t care for the word “rebuilt”.  How do you “rebuild” something anyway or re-manufacture something for that matter?  I can get my hands on “restoration” I suppose it’s a point of view or matter-of-fact wording.
 

Some time ago we retired our Gardner Denver 50 HP screw compressor.  It had provided many hours of reliable service but was beginning to show signs of wear especially during the hot Georgia summers.  The old green machine was moved to the back lot and unceremoniously adorned with a tarp, the vision sadly similar to covering up a dead body.
 

The usefulness of the old beast was debated for awhile.  Of course it got in the way even though for the most part it was out of sight out of mind.  We knew it was there and had every intention of resurrecting it someday.  That’s the problem with “someday” we solve a problem, buy new stuff, cover up the old stuff and tend to forget about it.  Other projects take precedence, bigger fires are burning, other issues take over and as long as the air is still flowing resurrecting an old piece of equipment is not that important.  Still the old green beast sat out there under its tarp just waiting to shine once again.
 
Compressed air is one of those “infrastructural commodities” that is often taken for granted.  That is until it is not available then everyone begins to have a coronary!  The decision to purchase a new compressor was relatively easy considering Metcam’s substantial growth and increasing need for clean dry pressurized air.  After researching the various systems we determined that not only did we need a new unit we needed redundancy.  The retired GD would be the redundancy!  Great plan!
 
As I stated earlier we always have good intentions but the noisy wheel gets the grease and a redundant air supply was not loud enough, that is until we began to experience trouble with the new unit.  But that’s another blog topic, I digress.
 
What does this have to do with details?  It has much to do with details.  Eventually we did resurrect the beast but not without some pain.  Different folks had begun disassembling the unit over a year ago and yes you guessed it, the key word being “year” many of the parts had been misplaced.  We didn’t realize this until we purchased a “remanufactured” air end.  After some head scratching we decided it would be best to send it away to a qualified GD shop.
 
The unit came back looking like new.  Everything was cleaned and painted a nice white.  Power was put on the unit and it worked well.  The shop had done an excellent job of putting everything back together and we felt confident the unit was as good as new.  Stop! Don’t mistake confidence with assumption!
 
After operating the machine we began to experience problems such as over temperature, belts breaking different things and of course we thought the compressor shop might have messed this one up.  Our maintenance guys did an excellent job at diagnosing and repairing but in the end some things are best left to the proper surgeon.
 
The technician that came out definitely knew his stuff.  Within minutes he had discovered two items that needed to be replaced.  (We did not have the compressor shop replace anything that was not missing or damaged.)  Ultimately the compressor had to run for awhile before these items failed and most likely it was due to sitting up for so long without operating.
 
Once the technician replaced the necessary components we still were having problems with belts breaking.  I was afraid we had a faulty air end but after some discussion with our quality manager and the compressor shop we determined that if the bearings were the problem the whole air end unit would be scrap considering the tolerances utilized in it’s construction.

 
The source of the problem was worn and misaligned pulleys.  Consider the physics of 50 horsepower of work being transmitted through (3) belts that is a ton of work and things better be in order!  After inspecting the pulleys it was determined that the V-grooves were excessively worn resulting in belt fatigue.  The belts would run fine for a little while but ultimately would break.  As the belts ran in the contorted grooves they heated up of course with heat comes expansion as the belts expanded they slipped.  Once the belts begin to slip they began to heat up even more to the point of failure.

The detail? It’s not the air end!

Posted by on July 18, 2008 | Comments (0)