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Re: American "Imperialism"

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On Nov 22, 2004, at 2:09 AM, G Vishwanath wrote:

In India, we don't have a system that requires a PE to stamp the designs. We don't have debates on the legality or ethics of some one doing the design and another vetting or approving it, either in the same office or remotely.
We don't split hairs on what "direct supervision" means.
Those of us who work to American specifications, are
compelled to put up with your infernal imperial units.
Perhaps inadvertently, you've made the point that design codes are a helluva lot more than just a bunch of formulas for plugging and chugging. I think there are lot of people world-wide who think that engineering is all formulas and calculation: make the numbers and that's the end of it. I see this in pressure vessel and piping work and I also see it in FEA use. Go check the Usenet sometime if you need proof that there are more than a few people who think all safe design is only a matter of asking a stranger for an equation or a software download. Attitudes like this kill people, just as surely as an AK-47 fired thoughtlessly into the air.

US codes are as good as they are and as workable as they are because our manufacturing and professional standards have kept pace. We've learned the hard way, over the past 100 years that you can't pluck a formula out of a book and expect that the resulting structure will perform if the fabrication is slipshod or the engineer hasn't learned about engineering judgement from experienced peers. There are even a few of us who don't believe that CAD or FEA software can do our thinking.

Some years ago there was a rash of US pressure vessel and piping failures resulting from poorly manufactured components obtained offshore. Flanges which were supposed to be one piece forgings were in fact made up from poorly welded (the welds were slugged) cast pieces and marked as conforming to ANSI standards. I ran into a brittle fracture in steel plate which was certified as conforming to ASTM A-212, but was in fact poorly rolled and had non-compliant chemistry. In both of these cases the design codes were used properly, but the materials of construction were so poor that the actual parts were garbage. No need to presume malicious intent for those failures, just the inability of people to appreciate everything that goes into a Code compliant structure.

In the particular case of field welding it is a fact that welds made under controlled conditions out of the wind and rain with such amenities as electrode holding ovens and QA supervision are generally better welds. US practice is to limit field welding as practical, if for no other reason than to avoid putting engineering decisions into the hands of someone who may not understand why weld procedures matter.

The issue of professional certification and accountability is equally as important as reliable fabrication and materials. The number of posts on this list about sub-standard construction by people who fancy themselves as 'practical engineers' is enormous. I can't tell you (for liability reasons ;->) how much crap I've pawed over, cobbled together and sold by some well-meaning blacksmith who really had no idea about the basics of safe design. And I've had a few sessions with academics who could argue endlessly about second order equations but couldn't construct a free-body diagram or had never been into a weld shop. Debate over drawing approval address standard of care issues, which are just as important as the availability of equations. Engineers need to be accountable and the existence of an agreed-to standards of conduct are part of that accountability.

Those of us who work to American specifications, are
compelled to put up with your infernal imperial units.
I'm inclined to say tough beans--write your own standards, then. In fact the real issue is engineering standards, like beam sections or screw threads not units of measure. As far as units of measure go I don't see any practical difference between a system based on the length of Henry Beauclerc's arm or another based on some long dead Frenchman's guess at the length of the meridian through Paris. When you're talking about infernal section moduli or infernal pipe wall thickness or infernal sheet metal gauges, it's an infernal 3 place decimal in any case, so being able to change scale by powers of 10 is an infernal non-issue.

Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw(--nospam--at)skypoint.com    | this distance" (last words of Gen.
...................................| John Sedgwick, Spotsylvania 1864)
http://www.skypoint.com/~chrisw/


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