Roots 33 Blower Failure

Thought I'd show you guys the inner workings of a Roots blower.
This is from our sewage treatment plant. Probably the original blower from 1975 since this model was discontinued in the '80's. This thing has been running 45 minute on/off cycles for 47 years.

 

What's the bet that with a little maintenance like new bearings occasionally, it would still be working today?.

 

It did get a pump of grease into the bearings every couple of months.

 

I just binned a very similar fuel drum pump as the powdered metal gears had corroded back into powder again: you could see how the very fine clearances rely on the rotors being synchronized by the gears and any wear would be catastrophic.

 

I guess that old pump doesn’t owe anyone anything.

Pete

 

That blows. Or blew. Plenty.

What form will it take for its next life?

 

Here's the rest of the story.
By the serial # it's a '73 model. I was told their usual life was 20 years.

 

They probably want it back to make sure that never happens again

 

Replace the gears or braze on some new teeth and you'll be set for another 45+ years.

 

I wonder which side gave up first. He surviving gear teeth look like they’re in pretty good shape.

 

My guess on this...the lobes probably started rubbing on each other causing excess heat which caused them to expand. Then the vibrations finally caused one lobe to break and when it locked up the gear teeth sheared. A Myth Buster's plausible?
Damn, two beautiful, not a cloud in the sky days. The replacement blower is due in today and it's raining and the temp is dropping.
I'll be out there standing over the shit pools installing the blower. Don't drop your tools because you'll never see them again!

 

One of the sewage farm dwellers and staff:

 

SOB!
I ordered a replacement blower from Grainger last year, it's their Speedair brand...don't know who actually made it. Came with a 12 month warranty. The sucker failed yesterday, 14 months of use. Talked to Grainger, sorry, we can give you the number of a rebuild shop or order you another.
Yeah right, kiss off.
Ordered a Sutorbuilt Legend today.
Popped the cover off the gear side, broken tooth locked it up tight, shaft sprung.
There's wear on the driven side gears, you would think the drive side would wear faster.

 

Just by looking down the intake hole, I don't see any damage.

 

Is the newer unit made from aluminium instead of iron?. It's be interesting to contrast the differences in construction like shaft diameter, gears made from softer material or not as thick as the original that contribute to earlier failure.

 

The housing is cast iron, the rotors look aluminium.
I was at the plant the day of the failure. I thought there was bearing noise so I got my stethoscope out and listened to the motor and the blower. The driven gear side had that noise when bearings lose their chrome coating, kind of a slight crunchy sound. I put a couple pumps of grease in and nothing changed. It failed around 3am popping the overload on the motor.

On a lighter note, I was on the back deck and heard a commotion. Out around the garage came a fox squirrel with a mockingbird hot on his tail. That bird chased him around the house actually hitting him in the ass a couple times. Made me chuckle.