inspection of (possible) weld damage to sign post

[HouseBoy]

I have a sign pole (welded to a base plate) that was hit by a car. It "looks" OK but is visual examination adequate to determine if it is structurally sound?

I am expecting that it is not enough.

What level of examination is generally enough? Are non-destructive tests required?

The local building dept wants and engineer's opinion but I don't want to just look at it and say something and I don't know how much testing $ to authorize.

Any thoughts?

 

[swall]

I assume you are concerned about cracks. You could have a penetrant inspection performed if the post is non ferrous.If ferrous, you could have magnetic particle inspection performed.

 

[dik]

You might call a testing agency... they might use a dye penetrant or a magnetic particle test. You could also call a mobile welding outfit and just reweld. Depending on the local, the latter may be less costly.

 

[evelrod]

Dye penetrant is cheap, indeed, it's a 'do it yourself' deal, not definitive for anything but large surface defects, IMO.

Zyglo, for non ferrous and, Magnaflux for ferrous is acceptable for surface crack testing and is usually definitive for that purpose.

X-ray or Ultrasonic testing is what you need to detect anything other than surface cracks. Takes a little longer, requires a professional operator and, is not always cheapest method, but---it is definitive for nearly all defects.

Rod

 

[dik]

Thanks evelrod... I thought that the outer surface of the weld would be most likely compromised from the collision. It should have received the greatest deformation... with the interface between the base metal and the weld maybe being the most 'brittle'; the x-ray or ultrasonic would catch that. Re-welding would likely be less costly than x-ray or ultrasonic. I thought that the dye penetrant would catch larger cracking and that magntic might be more sensitive for smaller ones.

 

[gtaw]

I would suggest an ultrasonic examination for the complete joint penetration groove welds (should there be any). The crash could have initiated cracks in the area of the root. Neither penetrant or magnetic particle examination would definitively find the cracks unless they are surface breaking.

Granted, magnetic particle examination can detect discontinuities such as cracks, incomplete fusion, etc. that are slightly subsurface, but the depth of detection will be a function of the size of the discontinuity and the depth of the discontinuity. I typically tell my clients that MT with an AC/DC yoke is limited to about 1/16 inch or less if small discontinuities are a concern. Very small discontinuities, such as fatigue cracks must be surface breaking and require wet fluorescent magnetic particles or fluorescent dye penetrant to be detected in their early stages of formation.

Check the qualifications and certifications of the individual that is performing the NDT to verify they were trained, have adequate experience, and took both written examinations and performance examinations as part of the qualification process. They should also provide you with a copy of their Written Practice and NDT procedure.

Best regards - Al

 

[HgTX]

How would one go about UT or RT of the structure in question? I assume we're talking about small fillet welds connecting a small pipe to a base plate.

Hg

Eng-Tips policies: faq731-376

 

[evelrod]

Hi HG. I think we are assuming a commercial type sign post here and not something like 1.5" pipe stopsign (I can see no logical reason to UT something like that...it can be done, but why bother? Just cut it off and re weld). We have had a rash of sign post failures along the very windy I-15 corridor below the Cajon Pass here in Socal. One ended in a fatality.

Re reading my post, I realized that I have personally supervised some pretty stupid NDT on Gov't. jobs in the past...Taxpayer's money at work.

Rod

 

[gtaw]

Based on the limited information included in the post, I assume we're not talking about a stop sign at an intersection. The post says that there is no apparent damage after the crash. I assume we're talking about a substantial structure that includes complete joint penetration groove welds securing the vertical member (tubular possibly) to a heavy base plate. Those welds would be candidates for UT. Fillet welds would be candidates for MT.

A case like this is when a Level III earns his money by recommending the appropriate NDT method. The Level III should visit the site and review the drawings with an engineer to determine the best approach to evaluating the welds.


Best regards - Al

 

[HgTX]

Sorry; guess the word "pole" threw me. I should have figured a stop sign would have done what it was supposed to do and just broken off...

Hg

Eng-Tips policies: faq731-376

 

[KENAT]

How big/heavy is the sign.

Would a proof test be easier than NDT and be adequate?

If you could estimate the maximum load likely to be endured and proof test it to slightly above that, without damaging it, perhaps it's an easier way.

I've never dealt with building codes etc and doubt my idea would be acceptable but I have used proof test instead of NDT of weld before when it made functional and economic sense.