Pipe Column Measurement 1

[msquared48]

Is there an instrument available that can measwure the wall thickness of a sealed pipe column in the field? If so, how accurate are they?

I have a tower where some of the leg thicknesses given in the field survey do not correspond to anything in the AISC steel book or other tower manufacturer I am familiar with. I am wondering how he got the measurements he did - no holes to directly micrometer are available.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[JedClampett]

How far off are they?
There's round sections that are not pipe (HSS). See:

http://www.aisc.org/DynamicTaxonomyFAQs.aspx?id=1526

If they're really close, but all a little short, the hollow section manufacturer's have got so good at hitting their thicknesses that they can consistently make the thicknesses the thinnest sectiona allowable by the governing ASTM.

 

[msquared48]

Thanks Jed. I'll check it out.

Some thicknesses are off by a tenth or so.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[Ingenuity]

Check out PROCEQ and the Zonotip test instrument:

http://www.proceq.com/en/non-destructive-test-equipment/metal-testing/thickness-gauge/zonotip.html

 

[dhengr]

Mike:
Regular UT equipment and a good operator would probably solve this problem for you.

 

[JStephen]

Ultrasonic thickness-testers are commonly used to measure the remaining thickness of corroded tanks, vessels, etc., and presumably could be used in your case.

Some of the pipe specifications allow up to a 12.5% undertolerance on the thickness. (I think this actually amounts to the hole being off-center relative to the outside, but it is just given as a thickness tolerance.)

The AISC books just show Standard Weight, Extra-Strong, etc., but actual pipe is available in thicknesses other than Std, X-Str, XX-Strong, including some that are lighter-walled than Std Weight.

If a structure is a one-off item, it's most likely made from whatever types of pipe or tubing are commonly available. If it's one of a large number of similar items, the supplier may have had pipe custom-made with a particular wall thickness. On occasion, "surplus" pipe will be available with odd wall thicknesses as well, leftovers from a pipeline project, for example.

 

[msquared48]

I'm going to be conservative and go with the actual measured thicknesses with an Fy of 35. I fully expect it to fail, but I refuse to buy the tower. I understand the flange connecting plates are also kind of thin, so that is another problem to look into. Thanks for the info.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com