Shear shafting?

[slip knot]

inclined screw conveyor at a WWTP. Collects trash off a barscreen washes it and transports it to a rolloff dumpster. @25 ft . Pretty simple device.... unless it freezes.

[digger doug]

Did it fail when powered and frozen ?

Is there a groove worn from a seal or bearing failure ?

You would be surprised how the charpy numbers of some steel
drops off at 20f.

[slip knot]

we assume it failed when running. The wash water failed early on but the unit showed operational. I assume the ice was formed by the nature of the debris and the dewatering that the conveyor naturally does due to the incline. The run indicator gets signal from the starter so we dont know exactly when it failed.

13f was way cold for this area. I've only seen this temperature back in the late 80s. it was 9f then.

The maintenance supervisor and myself will have to figure out whats the best way to keep this from happening again and write that into our emergency operations plan. other than busted piping this appears to be our worst mechanical damage.

[greywynd]

Originally Posted by slip knot

we assume it failed when running. The wash water failed early on but the unit showed operational. I assume the ice was formed by the nature of the debris and the dewatering that the conveyor naturally does due to the incline. The run indicator gets signal from the starter so we dont know exactly when it failed.

13f was way cold for this area. I've only seen this temperature back in the late 80s. it was 9f then.

The maintenance supervisor and myself will have to figure out whats the best way to keep this from happening again and write that into our emergency operations plan. other than busted piping this appears to be our worst mechanical damage.

Most plants here have all the ‘water’ components double jacketed, then insulated. The outer jacket is heated with steam or hot water, and through valves and controls the temperatures can be regulated for use.

Maybe in your case a double jacket for air that can have a salamander or something installed for cold weather would work?


Sent from my iPhone using Tapatalk

[460 Delta]

Is this a flat top auger? If so the shaft stubs are often hardened to be used in the chilled iron hanger bearings.

[Ironman]

Originally Posted by slip knot

13f was way cold for this area. I've only seen this temperature back in the late 80s. it was 9f then.

As long as the left cries about global warming, this is going to be a shock to all. The world is getting colder. I spent 10 hours at -35 wind chill yesterday. Was it fun? no, but not unusual. But I am surprised that with oil present, they don't have thermal generator backup.

I have seen the "shear shaft" and so have most of you. Next time you unbolt a hydraulic pump, look at the necked down shaft area next to the seal. If the pump seizes up the shaft twists off there, and does not destroy the drive gears.
Even Roosamaster injection pumps have this feature internally before the high pressure pump section.

In this case I am sure the shaft was ready to fail and the cold snap just made it earlier. On a gear reducer, as digr said, never heard of such a thing.

[digger doug]

Originally Posted by slip knot

13f was way cold for this area. I've only seen this temperature back in the late 80s. it was 9f then.

I like this part....The global warming nutz keep thinking we are progressing to hell.

Looks like only 13f this time, 9f late 1980's.

Sad to say, it looks like we are improving....but don't want to let that out eh ?

[slip knot]

Local guy called me yesterday morning. Shaft is done. <$500. Got it back in service today. Can’t complain.
I asked them if it was still set up as the shear component. I got the look

[JBFab]

I used to build large screw conveyors for a previous employer. Sounds like a similar setup to what you have. We used Dodge gear reducers exclusively. The output shaft was nothing special, but it did come with the reducer. Cut to length, chamfered, with 2 holes 90° from each other about 2" apart (+/- depending on size of shaft). The bolts would typically be the shear point. I believe they came with Gr. 5 bolts. Occasionally you would see a shaft shear, but this usually happened after many years when the shaft would seize in the bore. A little kroil, some times heat, rarely a press was needed to knock them out. Maybe you had ice form in between the bore and the shaft causing it to seize even if temporarily. We opted to replace the shaft with a direct replacement from Dodge, but I'm sure we had pretty decent buying power through them. That said, I don't think you made the wrong call.