Failure of steel channel at Travel Screen

[patelam]

Working on the traveling screen installed at the water gate where the water from sea comes inside the plant. The traveling screen has a rotating gear(called sprocket) which moves the connected screens as it spins. The gear wheel sits on channel beam at its mid span. The channel has failed as the support for rotor, at the mid span. You can see the loss of metal near weld which is possibly due to bacterial attack. However, I am not able to figure out the failure of the channel in the rest of area. It seems like the brittle failure with no sign of stress deformation.

The screen is installed in sea water; however the failed channel is not submerged in the sea water. But it is exposed to the sprays of sea water.

Please provide your suggestions on what would have caused the failure outside local area near weld?

Steel channel is SS 316

I can only post on image with my post. Will have subsequent post for other images.

 

[patelam]

Image attached

 

[patelam]

Image attached

 

[dvd]

Do you have three pillow (plummer) block bearings supporting a single shaft? You may have an induced heavy load at the middle bearing due to misalignment of the bearings. What does the chain/screen path look like? Can you provide a section view through the frame - I don't really understand what I am looking at? Is the chain/screen wrapping around the center-mounted drive sprocket system, or is it a single-tooth drive? You definitely have the most load on the middle bearing.

 

[patelam]

@dvd The channel is under the sprocket as shown in the attached image. The damage is at the middle of channel where the sprocket bearing sits. The sprocket gear that rotates the sprocket is attached to the side, as shown in section BB.

The additional details of travel screen are shown here -

https://hydrolox.com/solutions?solution=fish-recovery-and-return

https://www.youtube.com/watch?v=1u_G8AOE4yQ

- Watch this video from 1:15

 

[dvd]

I can't really get a feel for the failure based on the information/pics provided. If I were investigating this, I would want to determine -

What does the manufacturer have to say about this failure?
Is this very thick plate, it looks like it from the picture?
Is the failure in a bend?
What was the bend radius?
Has there been maintenance or repairs performed at other areas of this unit?
Was the unit functioning normally other than the crack?
Motor amps within normal range?
Chain and pin wear not accelerated?
Was screen tensioner functioning properly?
Were bearings aligned properly?