Z-Direction Testing of Steel Plate

[kander]

We have a steel structure that we need to attach some lifting padeyes. Where these padeyes will be attached is loading the steel in it's non prefered direction (Z-direction pull). The material certification doesn't cover Z-direction tensile testing. The remainder of the structure has been checked and is suitable for the lift.

What is the procedure to test materials for Z-direction properties? I've heard this can be determined by ultrasonic testing?

 

[johnp]

Hi kander,

The problem with plate steel is that inclusions can be rolled into the plate causing laminations. It you attach to one surface then there might be a plane of weakness deeper within the plate. That is always a risk when welding to the surface of plate. Any test that will give you a better understanding of sub-surface inclusions is valuable. You may need to talk to a specialist steel consultant on that one.

Regards - Sgt John.Rz

http://www.latviantourists.com.au

Johnp.Rz

http://www.mets.net.au

 

[IRstuff]

Why can't you bolt through the entire plate? That's what's normally done, isn't it?

TTFN

FAQ731-376

 

[JStephen]

The normal concern would be plate bending around the attachment point, not a base metal failure due to tension. If calculated tension under the attachment point is really that high, increase the size of the attachment.

 

[kander]

The concern is de-lamination of the plate in this undefined direction. This seems unlikely I know and I have never came across it, but mill certs for steel plate only give X & Y direction properties (Length & Width on the mill), but not Z direction (Thickness). Apparently steel with impurities can split similar to timber. Again, unlikely I know.

For Z-direction rated steel the mill will normally take standard stock and do a tensile test of a sample in the Z direction, however our structure has been manufactured from non Z-rated steel stock.

The question, is there a procedure or device that can be attached to non Z-rated steel to define the properties in this direction?

As for bolted connections, yes this can be done, however the structure will be in a marine environment with perhaps a 20-year life. Working in Oil & Gas bolted lift points are never really used due to the uncertainty of the bolts corroding, slackening off, being swapped for something weaker, etc. Unfotunately these connections will have to be welded.

Regards, Kev

 

[unclesyd]

No much practical help, maybe some leads.

I've seen papers from both the API and NBS on Laminar Tearing from problems encountered in existing structures of the same nature as yours.
I believe that any new book on structural steel should cover the topic, especially one that covers work on existing structures.

There was also a paper form (AWS) about problems encountered with tearing in existing structures located in Seismic zones.

We had a problem in early on when it came to lifting some very heavy reactors. The problem at the time wasn't well publicized and it required the services of a consultant. As I recall there were a lot of UT work in the area of lifting lugs and numerous drillings for Sulphur analysis.

 

[unclesyd]

Change the word laminar to Lamellar Tearing in my previous post.

Thinking one thing and writing another.

 

[metengr]

I would suggest performing ultrasonic examination of the through thickness to check for plate laminations. If none are found, you should be good to go for lifting.