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WWST

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Reply with quote  #1 
Another small but critical one. We just installed the sensors and the next day the temperature on the gearbox went to 226F/105C. My analysis showed some impacting and looseness. Below are some plots.

image005.png  IR000036.JPG  visual gearbox.jpg 

WWST

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Reply with quote  #2 
Temp and FFT/TWF plots:
2017-05-15_14-39-27.jpg  2017-05-15_15-28-36.jpg  2017-05-15_15-34-31.png 

John from PA

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Reply with quote  #3 
Quote:
Originally Posted by WWST
Another small but critical one. We just installed the sensors and the next day the temperature on the gearbox went to 226F/105C. My analysis showed some impacting and looseness. Below are some plots.


What else has recently been done?  Worm gears and the operating temperature are very susceptible to the proper lubricant.  Has it been changed recently?  What lubricant is being used?  Can you shut down and inspect or drain an oil sample and check for bronze particles?  There is often an inspection port on the casing, something like a 1 inch NPT plus that can be removed allowing visual observation of the teeth.
WWST

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Reply with quote  #4 
This has been in place about 3 years, with only minor maintenance. The gearbox is mounted on it's side, which most likely does not allow the oil to circulate correctly. They pulled it today, based on our recommendation. Pictures below.

image001.png  image004.png 

Ralph Stewart

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This may be a dumb question, but has the oil been checked in the gearbox?

These type gearboxes normally do not show much, IMO, what appears to be gearmesh in the spectrum and waveform.

The impacting in the waveform seems to be at 1x the wormgear speed with somewhere around 16 smaller "impacts" between each rev of the wormgear.

There may be ~ 8 Bronze "teeth" touching the wormgear causing the ~16x "gearmesh" pattern frequency.

Looks like the bronze ring gear may be about to fail.

Strange the temperature went up after installing the sensors??????

Was there anything else done to the gearbox when the sensors were installed, like a routine oil change?

Just my opinion. [smile]

Thanks and Have a Great Day,
Ralph

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Ralph Stewart
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Ralph Stewart

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Well looks like I was 12 minutes late with  my question/reply. [smile]
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John from PA

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Reply with quote  #7 
It would be interesting to know the actual lubricant.  In worm gears using a bronze gear, especially those that operate at elevated temperatures, it is not a good idea to use a lubricant with an EP additive.  Most EP additives are compounds of phosphorous and sulfur. Elevated operating temperatures of a lubricant with EP additives, in the presence of moisture can rapidly break down a typical EP mineral oil creating corrosive acids and other compounds that can cause distress.  In general, review the recommended lubrication or consult the OEM whenever considering an EP lubricant, especially in a machine that might utilize components containing copper.
Ralph Stewart

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In the picture, it looks like it is using grease as a lubricant instead of oil.

Surely not, huh?

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WWST

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Reply with quote  #9 
I'm sure it's oil but it has been highly contaminated. I will find out what kind of oil they use. Thanks for the tip John.
John from PA

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Reply with quote  #10 
Lubricating worm gears can be quite complex and it can be further hindered by not setting up the tooth contact properly.  One of the best write-ups I'm aware of is from Noria and is available at http://www.machinerylubrication.com/Read/30388/lubricate-worm-gears.

The drive graphic originally posted shows what is likely a location for an oil level gauge.  You should check the OEM materials and make sure you are using a gauge and also verify the proper gauge location based on the drive orientation ("... the gearbox is mounted on its side"). 


worm.JPG 

VibGuy~5

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Reply with quote  #11 

Small worm and planetary gearboxes are often filled with grease (known as liquid grease). Basically a low NLGI grease with a small % of thickener. It will be formulated to suit the phosphor bronze worm gear. A quick way to figure out if it’s this type is to look for a fill and drain port (fill close to the top, drain towards the bottom). If they’re not there, then it’s probably liquid grease. From the look of the photo, this one looks like grease (very oxidised at that)

I would more look to the load as an explanation of the elevated temperature. If this was your first time taking an IR image, then it may be that it’s always run at a high temperature and so is a design issue. Worm gear boxes are very susceptible to running hot because of the large gear surface contact area, which will be made worse if it’s under designed. You could suggest using a gearbox with a higher service factor and thermal rating for the design load (if they know it), but that would mean a larger bore and larger gearbox, which means new head pulley with larger shaft and redesigning the support structure for the gearbox, which they may not be willing to do (replace the gearbox once a year instead?) It would be an idea to de-grease the gear surface area and look for wear. You might also find pieces of bronze in the grease as this will often wear away first (being softer)

ukvibes

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Reply with quote  #12 
I've found these worm and wheel gearboxes can run quite hot at 100 C normally. 

Gs pk-pk has been successful trend to monitor as in line with Ralph you've done well to get a GMF, I typically get nothing at GMF and on the occasions I do it's input gear wearing/failing. 

Sometimes oil replacement can bring down levels and keep it going for some time. 
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