For the refractometer I just use a Brix scale and calibrate it by mixing up the solution I should have and comparing it to the solution I do have. Accuracy of the scale then is irrelevant.
On Tue, Nov 16, 2010 at 12:28 PM, Chris Cahill <[email protected]> wrote: > If you are trying to prevent the pipe from breaking there is some safety in > the difference between freeze point and break point of the AF. We usually > speak in terms of freeze point but the breaking point is much lower. > Between the two points my limited kitchen research shows a milkshake > consistency. If you use the ASHRAE data you are probably fine with no SD. > Our friend Scott F. believes we should be using the coldest ever recorded > for that area. ASHRAE, coldest ever or some SD plus or not a further safety > (8) all have merit but I don't think there is any specific guidance. I > thought I read ASHRAE once but have been unable to find a reference. There > is also some safety potentially in the location of the piping, in how long > it is exposed to a specific cold temp and the time it takes to cool the pipe > to ambient. Think in an residential attic, the outside ambient a few > degrees below the temp it's rated for and a couple hours vs. an exterior > canopy on the north side, exposed piping, a windy day and 20 degrees below > the rated point for 8 hours. > > The 40 IMHO may be related to the fact to keep something at 40 the HVAC > units will be putting out something less than 40 and could cause a local > problem. Yeah it doesn't explain an outside reasoning. > > If you are interested in the ability of cold AF to fight a fire I think > there is a gaping hole in the information available. I know 13 went all DW > on us for bigger systems but that was a knee-jerk reaction not unlike IMHO > the current TIA. And DW doesn't tell us anything about the character of the > spray of AF at cold temps or how long it takes the AF to clear. Something > needs to be done but we don't really know what yet. In theory we might want > to walk a closer line on the rated temp vs. potential ambient to preserve > some more firefighting ability or maybe not depending on the flow > characteristics, size of the flow path and increased fire contribution of > the AF. > > Pocket refractometers - I have my doubts especially when used in the field > after bouncing around a truck for years. > > I doubt many use pre-mix. At best a few do for the original installation > but not on annuals if it needs a little touching up. > > Chris Cahill > > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of David de > Vries > Sent: Tuesday, November 16, 2010 1:35 PM > To: AFSA SprinklerForum > Subject: Anti-Freeze Solution Freeze Point > > Is there any guidance on how much of a safety factor an anti-freeze solution > should have? I cannot find any such in 13, but of course 13 requires an 8 > degree F cushion for wet systems (maintain at or above 40 F). > > Looking at the ASHRAE Handbook there is weather data which shows the mean > coldest temp and a standard deviation for locations throughout the USA and > Canada. Using that data, what should be the design basis, i.e. how many > standard deviations below the mean coldest temp? > > Does it make sense for a locale with a reported mean coldest temp of -10 and > 5.8 standard deviation to design for 2 standard deviations below and a > safety factor? So, freeze point of anti-freeze solution = -10 - 2(5.8) -8 = > -30 F or lower? > > How accurate are the pocket refractometers used in the field? > > Do most contractors use pre-mixed anti-freeze solutions? > > As always, the Forum's insights are welcome. > > Dave > > David A. de Vries, P.E., CSP > Firetech Engineering Incorporated > > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum > > For Technical Assistance, send an email to: [email protected] > > To Unsubscribe, send an email to:[email protected] > (Put the word unsubscribe in the subject field) > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum > > For Technical Assistance, send an email to: [email protected] > > To Unsubscribe, send an email to:[email protected] > (Put the word unsubscribe in the subject field) > -- Ron Greenman Instructor Fire Protection Engineering Technology Bates Technical College 1101 So. Yakima Ave. Tacoma, WA 98405 [email protected] http://www.bates.ctc.edu/fireprotection/ 253.680.7346 253.576.9700 (cell) Member: AFSA, SFPE, ASCET, NFPA, NFSA, AFAA, ASEE, NIBS, WSAFM, WFC They are happy men whose natures sort with their vocations. -Francis Bacon, essayist, philosopher, and statesman (1561-1626) _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field)
