What kind of defects are these? 3

[Inspector89]

Hi all,

Can you please help me identify the defects on shell of a crude oil tank.

https://files.engineering.com/getfi...8fb8-4d1a-ab46-64690e2ddcb9&file=IMG_9874.JPG

https://files.engineering.com/getfi...2d77-49f6-a56b-49f480aab8af&file=IMG_0613.JPG

 

[mk3223]

IMO, possibly the machining tool marks?
Any history about this oil tank could be shared?

 

[Inspector89]

This tank was manufactured in 1966 and now taken out of service for inspection and maintenance. This was last inspected 20 years back. We do not have the last inspection report. Lots of tack weld and grinding marks are there.

 

[weldstan]

Corrosion at welds, possibly tack welds not fully removed, one of which may not have had full fusion.

 

[JR97]

I agree. Sites of temporary attachments. Temp attachment welds not fully removed. Second one shows undercut or gas cut gouge where temporary attachment was removed.

 

[weldstan]

Corrosion appears to located near the tank bottom where water would accumulate and the area adjacent appears to have suffered mild general corrosion. A single pass tack weld could readily produce martensite in the HAZ which could induce galvanic corrosion in the HAZ.

 

The three marks in one picture have nearly identical shape, so they could not have spontaneously occurred. Looks like one tool made three indents.

No idea what caused the mess in the other picture.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[InspectorClouseau]

Classic dog marks. I'd say they would be near a weld seam and were used to bring the plates flush before welding. Guessing I'd say a cellulose electrode given the pen and if you look at the cap locally you can see the classic course ripples of a cellulose electrode used to make the main event.
Are you going to fix them or leave them...?

 

[matschka]

IMO: In the 1st set of pictures the two areas of concern look to be where an angle or fit-up attachment was welded and then removed by hammering causing the base material to be 'ripped' out.
We have welding standards now that prohibit this type of removal because you will cause a 'pull out' of the base material and then you have a base metal repair to contend with. Thinning the tack weld down and then hammering usually works without a 'pull out' of the base metal.
The 2nd picture shows the same base metal 'pull outs', however; the last one looks like they
ground the tack weld somewhat but left considerable undercut from welding. Many years ago I worked on tanks and remember this happening when one just took an 8lb. sledge and hammered the attachment off.If their was a 'base metal tear' we would circle the area with soap stone for weld repair.