MECHANICAL CONTRACTING
Antifreeze in wet fire sprinkler systems 74 BY GEORGE RUDOLPH
have been a period of anticipation and uncertainty for engineers, manufacturers and contractors alike. Following a temporary ban on the use of antifreeze, coupled with proposed legislation mandating fire sprinklers in new residential construction, there was plenty to talk about in the industry. As I write this article, there have been two fatal fires in the last 24 hours in my community, resulting in the loss of three lives. While the results of these tragic incidents cannot be reversed, they reinforce the critical role that fire sprinkler systems play in protecting lives. Following a well-publicized fire
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incident involving a fire sprinkler system with a very high concentration of antifreeze, the NFPA began independent testing to determine the risk of combustion posed by antifreeze in residential fire sprinkler systems. The testing centered on the two most common types of antifreeze used in wet systems, glycerine and propylene glycol. Other solutions are less frequently used and are now prohibited, due to toxicity concerns. While antifreeze has been used in fire sprinkler systems for decades, the testing established safe levels which, under fire conditions, do not contribute to an increase in heat or
hen it comes to antifreeze for fire sprinkler systems, the past twelve months
fire intensity, but rather perform similar to water. In March, the NFPA issued a new
set of TIAs (Tentative Interim Amendments) which establish new approaches to the use of antifreeze in both new and existing residential occupancies, as well as in non- residential occupancies. These TIAs also introduce new requirements for the testing, maintaining and tagging of such systems. I have received hundreds of calls and emails regarding the use of antifreeze, and it is apparent that there is a broad range of understanding of the issue amongst fellow industry colleagues. So let’s take a look at the specifics and identify the changes that will affect design and maintenance going forward.
Maximum allowable concentrations Effective March 21, 2011, NFPA
limits the use of antifreeze in wet fire sprinkler systems to either glycerine or glycol. Ethylene glycol and other antifreeze fluids that are toxic are no longer permitted. In the past, field mixing was permitted to desirable freeze protection levels; however, the new standards limit solutions to factory pre-mixes only (no concentrates allowed), with a maximum concentration by volume of 38% propylene glycol or 48% glycerine in new systems. (It should be noted that existing systems are
allowed a concentration of up to 40% propylene glycol or 50% glycerine). For the vast majority of the United States, these concentrations provide sufficient freeze protection levels. However, contractors in regions subjected to extended periods of sub-zero temperatures will need to consider additional freeze protection methods in conjunction with antifreeze. Limiting the use of antifreeze to
factory pre-mix solutions will eliminate the inconsistencies found with field mixing techniques. Glycerine is a particularly difficult solution to mix in the field, as it begins to thicken in concentrate when temperatures drop to just 62 degrees Fahrenheit. Field mixing methods employed in the past ranged from manual agitation to mixing with a wooden paddle to simply pouring concentrate into a system and adding water. Usually, the end result was a piping system with varying degrees of antifreeze concentration. There is no viable field mixing method that provides a consistent and homogenous formulation like that of a factory pre-mixed solution.
Testing and maintenance: changes and challenges With new guidelines having been
established, the next few months will see an enormous increase in system
e Continued on p 76
phc may 2011
www.phcnews.com
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