20:26 Dec 16, 2011 

if it's not a typo that should read sur les tracés HF, i.e. on the HF lines/routes. Do you have traceur and/or tracé anywhere else in your doc?

14:11 Dec 16, 2011 

I believe all chemical symbolic names have been standardised, so H20 is H2O even in China, ditto HCl, HF, HBr, etc.

14:02 Dec 16, 2011 

that HF is indeed hydrogen fluoride (normally FH in French, no?) or something else. What is it used for?

13:34 Dec 16, 2011 

Assuming "traceurs H/F" doesn't mean M/F draughtspersons, your HF must refer to hydrogen fluoride tracers. HF is an exceptionally nasty substance used among other things, for etching glass. You would want to make sure any pipework didn't leak, maybe by using a pipe within a pipe system.