Crack in square steel tube on below the hook lifting device 3

[AlbertaMecchie]

Hi,
Just wondering if anyone in the group has experience with evaluating cracks in square tubes forming part of structure of a below the hook lifting device.

Are repairs allowed depending on extent of cracking, or take out of service permanently the entire device ? Or replace the affected structural member ?

Terminate crack ends by drilling and weld repair ?

Thanks.

 

[TugboatEng]

Start by contacting the manufacturer. Below the hook lifting devices are typically a minimum 5:1 safety factor. You shouldn't be seeing fatigue failures. Something is wrong, either a defect in manufacture or incorrect use in the field.

 

[desertfox]

Hi AlbertaMecchie

Are these below hook lifting devices made by your company for a specific job or are the purchased from a manufacturer?
If your company manufactured the said devices you might be able to repair them but you would need to consult the lifting standard they were designed and manufactured too.

Also can you post pictures of the cracks you described.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[EdStainless]

We used to make our own spreader bars.
If we saw any distortion or cracking, they came out of use immediately and the entire connecting portion was cut away and re-built.
We designed at 6x and then load tested (with defection measurements) annually at 2x (I think).

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[dvd]

I was involved in investigation of some cracked HSS recently. This is a nice short article discussing cracking and ductile to brittle transition.

HSS cracking in bend zone

Our failure propagated pretty quickly. I would recommend removing from service.

 

[Tmoose]

I'll wait for a half dozen detailed pictures of the device, and the crack(s) before commenting.

 

[rb1957]

my industry's experience with "stop drilling" is that it more like "pause drilling". Sure it "can" work but often doesn't.

if this is steel structure, I'd look to grind out the crack and weld over it. Of course depends on details, and other repair actions probably required.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[drawoh]

AlbertaMecchie,

How catastrophic will it be when this thing fails?

--
JHG

 

[weldstan]

Not enough info as to use when crack discovered and how long in operation. I'm with Ed and dvd. Replace, do not weld repair.

 

[AlbertaMecchie]

Thanks everyone for the replies.
I've passed on my recommendation to not weld repair, and I'm going to review prior inspection history.
I am thinking the best course of action will probably be to buy a new lifting device, with possibly some design improvements.
Possibly this was being overloaded as well.
Cheers !

 

[Tmoose]

"buy a new lifting device"

I gUeSs this was a purchased item, maybe even COTS . OEM warrantee or certified refurbishing options TBD.