The Fire Solutions Group Newsletter

In this newsletter you will find a short write-up on the development of a NFPA 18/18A wetting agent. These agents are sometimes overlooked but aid in suppressing some of the more difficult fire sources such as deep seated bulk storage,  lithium-ion battery, and three dimensional pressurized fuel fires.

New product news contains information on some of the features of the new FLIR thermal camera models and a portable telescoping waterway. The telescoping waterway with an IFI nozzle can be deployed to create a thermal barrier or for fire suppression. Don't forget to sign up for the newsletter below to receive it via email.

Development of an NFPA 18/18A Wetting Agent for Vapor Mitigation and Fire Control

Introduction

NFPA 18 was officially adopted in 1951 and originally included foam as a wetting agent. In 1959, foam was transferred to a separate committee. It was not until 1998 that major changes occurred to the standard when the NFPA Standards Council approved the formation of the Technical Committee on Water Additives for Fire Control and Vapor Mitigation (NFPA 18A). The committee, as stated in the the standard, was tasked 

"with having primary responsibility for documents on the manufacture, testing, application, and use of water additives for the control and or suppression of fire and flammable vapor mitigation, including water additives used to prevent or reduce the spread of fire and the use of water additives in fixed, semi-fixed, mobile, and portable fire suppression systems."

NFPA defines a wetting agent as a concentrate that when added to water reduces the surface tension and increases the ability to penetrate and spread. NFPA 18A broadens the scope and defines a water additive as an agent that when added to water in proper quantities, suppresses, cools, mitigates fire and/or vapors and/or provides insulating properties for fuel exposed to radiant heat or direct flame impingement.

The purpose of this testing was to evaluate a wetting agent under development and the attributes that make a water additive useful. 

Surface Tension

The most common attribute in the additives tested is the reduction of surface tension. The reduction in surface tension results in smaller droplet formation and increased surface area. Thus, the smaller drops improve the cooling capability of water and suffocate the fire source when converted to steam. From FSG's last newsletter, you may recall that the formation of droplets discharged from a traditional sprinkler head will depend on the instability of the sheet formed by the deflector plate (figure below). The sheet instability is determined by the pressure, friction, surface tension, and viscous forces. This droplet formation holds true for manual operations as well. The second added benefit of reducing the surface tension is the increased penetration capabilities. Reducing the surface tension to create "slippery water", as it is sometimes called, will allow for deeper penetration when combatting deep seated fire sources in bulk or piled storage. Coal bunkers, grain silos, recycling and trash facility fires are good examples of where the reduction in surface tension will expedite the suppression operation. 

To evaluate the reduction in surface tension an unprocessed cotton ball was used (figure below). Cotton is extremely hydrophobic and will float on water as seen on the far left of the image below. Concentrations of 3% (middle) and 6% (right) were used to measure the time it would take for the agent to penetrate the cotton and have it sink to the bottom. The glass on the left was water only and used for comparison. Four different formulations were tested with varying results. As would be expected, the higher 6% concentration always resulted in a faster penetration time. Over the 4 experimental agents tested, times ranged from a few seconds to a few minutes. The cotton ball on the water (left) did not sink during the entire 48 hour period of testing. 

Gels

Water additives also have the capability to thicken water creating a gel. These gels are very useful as a thermal shield and have applications in the wildfire urban interface, welding operations, as well as fire suppression. FSG has tested the FireIce gel on electrical fires and lithium ion battery fires with great success. Several large fire departments are now using the agent for electrical fires such as manhole and pole fires. The formation of a gel allows the agent to coat the fuel surface, removing it as a source for continued fire propagation (figure below). The energy required to separate the water from the binding agent and create steam is also increased, inhibiting flame spread. 

Similar to the gels, a new agent called AVD creates a crust over the fuel surface preventing oxygen from reaching the fuel (figure below). The solution is an Aqueous Vermiculite Dispersion (AVD).  Vermiculite, due to is great thermal absorption properties, is the dominant material in spray-on fire proofing for steal beams. The aqueous solutions cools the fires as the vermiculite form the thermal barrier. AVD has been successfully tested on Lithium Ion battery fires, Class A, and Class D fires. 

Emulsification

One final property of water additives is the ability to emulsify a flammable liquid, or as it is sometimes referred to as encapsulate. An emulsion is defined as a fine dispersion of minute droplets of one liquid in another in which it is not soluble or miscible. Flammable and combustible liquids are immiscible with water and by definition will not form a homogeneous mixture when added together. However, when a emulsifier is added it will promote the formation of a homogeneous solution and in the case of flammable liquids, render them non-combustible. This is not a permanent state but typically will hold long enough to suppress the fire and have surrounding materials cool below the ignition temperature. The figure below shows a flammable liquid and water separating after being mixed (left) and a flammable liquid with water and water additive remaining homogenous after mixing (right). Emulsification is desirable on Class B fires.

There are numerous NFPA 18 / 18A agents out on the market today. Each one differs and has their own qualities. Tests can be done to confirm and compare these agents. The right characteristic has to be present to suppress the desired hazard and it is physically impossible for one agent to possess all the attributes.  Care should be taken when choosing an agent. I suggest to always confirm and compare with testing and do a baseline fire test against water. 

Product News

FLIR Cameras

FLIR redesigned the Exx-Series from the handle up to deliver the best performance, resolution, and sensitivity of any pistol-grip handheld thermal camera. The new Exx-Series cameras are packed with the features you need to find hot spots, detect the early signs of building deficiencies, troubleshoot electrical and mechanical systems, and prevent problems before they cause serious damage.

The FLIR E75 has the sensitivity and resolution needed to diagnose problems and find hidden deficiencies – even from a distance.

The FLIR E85 is packed with high performance features, offers wide temperature ranges, and measures area (m2 or ft2) on-screen.

The FLIR E95 offers the great features of the E75 and E85, plus up to 161,472 points of temperature measurement.

IFI Telescoping Waterway

FSG has developed a telescoping waterway with an IFI nozzle. This portable device can be set up in minutes, attached to a pumper truck or other suitable pump and water supply. When activated, the mast rises from 19 to 42 feet in the air (model dependent). The IFI nozzle can be positioned to create a thermal barrier between two structures, used for gas mitigation, or for fire suppression purposes. 

Kind regards,

James Andy Lynch, Managing Partner

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+1 (312) 351-5919

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