Re: [PipingDesign] Category M Service

From: <bbullough@foth.com>
Date: Fri Oct 23 2009 - 12:11:00 EDT

>According to B31.1 Categpry M service applies with fluids (gases,
too) which cause damage to human tissue. Caustics and acids come to mind, but extreme carcinogens and blistering agents might be included. Figure M300 is a flow chart for classifying service.

I've never known caustics to be included, and very few acids, although, since it is up to the owner to specify, they could be. The only mineral acids I've known of (mineral acids are those that are usually the most nasty) are fuming nitric, nitrous (such a beautiful sky blue and so unstable!), and sulfuric (oleum), and the concentrated forms of simple halogen acids (HF, HCl, HBr). Chemistry can be such fun! They are so nasty in so many ways that Cat M is often seen as inadequate. A lot of concentrated volatile fluoro-chemicals, some chloro- and bromo-chemicals, phosgene, hydrogen selenide, and similars more or less fall into the same group. Never known any carcinogens or mutagens to - although the really bad ones are used and produced in such small quantities that B31.3 doesn't usually come into play.

... Bruce D. Bullough ...
Sr. Technical Consultant
Foth Companies
8550 Hudson Boulevard North, Suite 100
Lake Elmo, MN 55042
Phone: (651) 288-8598 Fax: (651) 288-8551 cell: (651) 269-1514 http://www.foth.com

[Non-text portions of this message have been removed] Received on Fri Oct 23 12:11:00 2009

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