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DeFelsko manufactures hand-held, non-destructive coating thickness gages that are ideal for measuring the dry film thickness of intumescent fire resistive coatings applied to structural Steel.
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Measurement Challenges
Accurately and non-destructively measure the total dry film thickness of the intumescent fire resistive coating to determine if adequate coverage has been applied to protect the structure for a specified time period during crisis situations. Applied coating thickness may range from 0.5 to 12.5 mm (20 to 500 mils) and is dependent on specifications for the coating being applied, the type of structure being coated, and the applicable building code requirements for the application.
Intumescent fire resistive coatings are either water-based or solvent-based. Water based coatings are typically applied when relative humidity is between 40% and 60%. Solvent-based fireproof coatings are much more job-site friendly and can be applied with relative humidity up to 85%.
Dry Film Thickness Measurement Solution
DeFelsko offers two PosiTector 6000 coating thickness gages that are ideal for measuring the total thickness of the intumescent fire resistive coatings. Selection is dependent on the expected coating thickness. The PosiTector 6000 FT series is ideal for measuring coating thickness up to 6 mm (250 mils). The PosiTector 6000 FKS series which is recommended for thicker applications up to 13 mm (500 mils). The FT provides slightly better accuracy and resolution than the FKS.
PosiTector 6000 Series
Climatic Condition Monitoring Solution
The multi-purpose PosiTector Dew Point Meter (DPM) is ideal for continuous monitoring of air temperature, surface temperature, and percent relative humidity. By placing the instrument in the vicinity of the structure to be coated or lined, the Dew Point Meter has the built-in software capability to calculate the dew point temperature and the difference between the surface and dew point temperatures.
The adjacent figure illustrates a sample LCD display provided by the Dew Point Meter. It shows ambient air temperature (Ta), surface temperature (Ts), relative humidity (RH), dew point temperature (Td), and surface temperature minus dew point temperature. At any time, all five of the climatic conditions being monitored and calculated, plus the date and time, can also be stored in memory with the simple press of a button. The Dew Point Meter also has a unique Auto Logging feature which automatically records datasets containing all 5 climatic conditions at a user selected time interval. This is useful for maintaining a complete record of environmental conditions and trends leading up to, during, and after application of the intumescent coating.
Free Consultation
For current pricing or to order these instruments, please contact us by telephone (315) 393-4450, fax (315) 393-8471, or e-mail techsale@defelsko.com. If you require additional technical information or have questions relating to your particular application, we encourage you to take advantage of our years of experience in recommending the best gage for your application.
What is the Application?
Conventional sprayed fire-resistive materials are covered with construction materials such as wallboard or gypsum board. Thin-film intumescent mastic fire-resistive coatings enable steel structures (I-beams, T-beams, C-channels, Z-beams and pipe / tubular columns) to be exposed to high temperature conditions for extended periods of time with minimal damage to structural integrity. These coatings that resemble painted steel with a gloss finish, provide the fire protection required by building codes, while still providing an attractive finish for exposed structural steel members.
Thin-film intumescent mastic fire-resistive coatings generally consist of a primer for adherence, the intumescent base coat, and some type of decorative topcoat to serve as a protective barrier. When exposed to fire, the intumescent base coat expands, forming a thick layer of foam that protects the steel by thermally insulating it and shielding it from the heat. Intumescent fire resistive coatings are designed to expand up to 15 to 30 times during a UL 263 Fire Tests of Building Construction and Materials (ASTM E119, NFPA 251, and UBC 7-1) fire test. In addition, most intumescent coatings generate an ash-like or char layer during their expansion process. As the fire exposure continues, the ash coating erodes exposing the remaining intumescent coating. Depending upon the coating thickness, this expansion process repeats itself several times. Too much char can result in premature delamination from the structure.
Some common brands of sprayed on intumescent fire resistive coatings include Firefilm (A/D Fire Protection Systems), Nullifire (The Carboline Company), SRAYFILM™,WB 2 and WB 3 (CAFCO® Industries, Inc).
Why measure?
Intumescent fire resistive coatings are designed to provide an insulating barrier between flames and steel and are necessary to ensure the structural performance of the steel members at the temperatures anticipated during a fully developed fire. For coatings to be effective during crisis conditions two unique characteristics are critical, the expansion of the coating, and the retention of the insulating char layer to the structure. Both of these characteristics are highly dependant on the proper thickness (per the coating manufacturer’s specification) of the cured, applied coating. Thickness is so critical that prior to approving intumescent coatings for use, Underwriters Laboratories Inc. (UL) obtains test data from a variety of coated samples to verify the influence of the coating's expansion and the ability of the coating to retain its char layer. Test data is then developed and published based on actual performance results of a known coating thickness. Result are published in a UL Fire Resistance Directory with limits on minimum and maximum thickness for specific intumescent coatings, steel shapes and hourly ratings.
An additional reason for controlling the amount applied is that like most protective coatings, the cost of intumescent fire resistive coating can be quite expensive. Depending on the rating of the material, applied costs for the coating can range from $5 to $18 per square foot.
UL's Fire Resistance Directory may be searched online at UL's home page at www.ul.com/database.
The Association of Wall and Ceiling Industries (AWCI) International technical manual 12-B, “Standard Practice for the Inspection of Field Applied Thin-Film Intumescent Fire-Resistive Material; an Annotated Guide” is available by contacting AWCI: e-mail – info@awci.org
PosiTector 6000 PosiTector DPM
