Passive Fire Protection

Fire Testing, New Technologies and the Shop-Applied Trend in Product Application

Passive fire protection (PFP) systems should be "install and forget" solutions performing to the specified standard throughout the complete lifecycle of the structure, with minimal operational maintenance. This is as opposed to active fire protection systems, such as sprinklers and alarms.

PFP enables owners to safeguard the structural strength of steelwork, the integrity of divisions and protect personnel and equipment for the duration of the fire or during escape. The specification of a suitable PFP product for a project is usually based on a number of factors including fire type, duration, substrate material (usually steel), substrate type and environmental location. Fire test approval is also one of the most important factors in assisting correct specification.

Following the recommendations of the NIST (National Institute of Standards and Technology) report after the collapse of the World Trade Center Twin Towers in New York City, there is a growing trend for Passive Fire Protection (PFP) to be shop applied (offsite). This market development is resulting in new technologies to meet the changing needs of owners and contractors. The introduction of these unique products is bringing new efficiencies to owners, contractors and applicators and, combined with improved aesthetics, is opening up new possibilities for specifiers, project designers and architects.

Figure 1. Click image for larger view.

Fire Types

PFP products fall under specific performance categories, usually determined by the type of fire they are designed to withstand. Types of fire, often called fire loads, have a distinctive time/temperature relationship (except jet fires, which have a specified fuel load) that is used to categorize the level of severity:

Cellulosic - intended to simulate natural carbonaceous-type materials such as wood and paper, these fires have relatively slow heat rise and peak temperatures of 950 °C.

Hydrocarbon - intended to represent fires fuelled by oil spills or gas clouds, characterized by higher heat fluxes and faster time to a maximum temperature of 1100 °C. After the Piper Alpha Platform fire in 1988, protection against hydrocarbon-fuelled fires has become the norm for the offshore industry.

Jet Fires - a unique type of hydrocarbon fire caused by pressurized gases or fuels that are released through an orifice and then ignited. These produce even higher heat fluxes: peak temperatures can exceed 1200 °C and generate highly erosive forces.

Rapid Rise Fires - these occur when fires are in a confined space and/or the fuel is highly flammable, as in tunnel or nuclear fires.

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Products

There are a wide range of PFP products available, including intumescent coatings and cement- and fiber-based products, in both sprays and boards. To combat these different fire loads, PFP products can be split into two categories:

Category 1- Cellulosic fire protection developed for use on civil construction and infrastructure projects. Intumescent coatings for this category are generally known as "thin film," with application thicknesses typically up to about 1 mm. The material swells rapidly (intumesces) to up to 60 times the original thickness when exposed to fire.

Category 2 - Hydrocarbon, Jet and Rapid Rise fire protection developed for high-risk environments such as oil rigs and refineries. Intumescent coatings for this category are often labeled "thick film," with their thickness measured in millimetres rather than microns. The required coating can be anything from 3 to 20 mm thick, depending on the desired level of fire resistance.

Table 3. Click image for larger view.

Shop-Applied Trend for Cellulosic PFP

The application of intumescent coatings has become a major issue recently following the NIST report into the collapse of the World Trade Centre Twin Towers. Traditionally, intumescents have been applied on site, but more recently, products have been developed that allow the application to be taken off site or in the shop.

NIST recommends the development of criteria, test methods and standards: (1) for the in-service performance of sprayed fire-resistive material used to protect structural components and (2) to ensure that these materials, as installed, conform to conditions in tests used to establish the fire resistance rating of components, assemblies and systems. Consequently, offsite application ensures consistent and to-specification application.

The main advantage of applying PFP offsite is that structural steel arrives to the site already fire protected. Should there be any fires on site before erection is fully complete, the steel will be fully protected. In many cases when using a single coatings supplier, the steel should also arrive at the site fully protected with a high-performance PFP and paint system.

The application of PFP offsite also greatly reduces complexity across the project by decreasing the number of trades present on site, thus helping with scheduling. Other advantages are:

Reduced cost

Steel is protected by companies operating in the most cost-effective locations rather than locations dictated by the site.

Easy access and large application areas lead to increased efficiency.

Reduced equipment and scaffold requirements on site.

No need to seal off areas during application or mask sensitive equipment.

Improved quality control

Controlled application conditions and auditable quality control procedures ensure the correct thickness of PFP is applied.

Greater control over application techniques.

No access issues.

Environmental and Health & Safety impact reduced

Less trades involved on the construction site reduces the chances of accidents and by eliminating the intumescent paint system on site there is a reduced chance of spills and fire.

Again, steel is at ground level so no access issues.

International Protective Coatings has responded to the industry's evaluation of PFP materials with a cutting-edge solution. Interchar® 212 is an advanced PFP material that delivers both the specified fire protection and anti-corrosive performance deemed necessary to safeguard our high-rise and public infrastructure buildings to the highest standards.

Interchar 212 provides anti-corrosive and extreme-heat fire protection that has never before been available in the building industry. As a thin-film intumescent epoxy material, Interchar 212 delivers up to three hours of fire protection (where the typical fire resistance for currently available offsite applied PFP is 1 hour) and also provides the aesthetic versatility architects want for exposed steel designs. With the ability to be applied over freshly blasted steel, as a solventless technology, and with faster cure times, Interchar 212 is ideally suited for offsite application in fabrication shops.

Table 4. Click image for larger view.

Testing PFP Products

In each country, rules, regulations and building codes prescriptively specify the level of fire protection that is required for different structures: for example "60 minutes fire protection." However, there is a trend towards providing a level of protection commensurate with the risk and hazard - a "Fire Engineering" approach.

The performance properties of a PFP product normally have to be proven by a fire test, which is necessary for certification. Such tests are defined by specific national and international standards, providing a methodology for proving compliance with the fire resistance levels set for different fire types. Although fire test standards can be complex because of the sheer number available, more established ones like British Standards (BS), ASTM International, Underwriters Laboratories (UL) and the EN13381 European Standard are widely used outside national boundaries.

Whether the fire resistance is defined by prescriptive regulation or by risk/hazard assessment, the level of fire resistance for structural steel will be defined as follows:

Fire type: cellulosic, hydrocarbon or jet fire
Fire duration: minutes or hours
Critical core temperature: typically between 400 °C and 600 °C for structural steel members
Unexposed (non-fire side) temperature: for divisions: typically 140 °C

Specifiers and contractors should use products from manufacturers that are independently tested to those standards mentioned above. Of course, as with any certified product, the specifier should seek further details on the level of certification or additional certification that would be of use to architects or designers such as UL263 exterior listing, approval for use in ISO 12944 environments or explosion testing to 4 bar overpressure. Another trend for PFP use in buildings is for the product to have some level of hydrocarbon fire resistance (UL1709 Design XR627).

PFP Follow-Up Services

Passive Fire Protection manufacturers have to carry out extensive testing to demonstrate their products' ability, ensuring the PFP coatings are correctly evaluated and meaningful performance data established. Fire testing is essential for ensuring that any PFP material specified, or used, meets the required performance standards for the structure set by national or international legislation.

In addition to fire resistance, products are tested for suitability in different environments and to demonstrate that their performance does not deteriorate over time. To make sure the product sold matches the performance of the original fire-tested product, recognized test establishments offer follow-up services to monitor factory quality control and undertake random product sampling and verification.

By policing any changes to products that may contradict their original certification, these ensure that PFP product performance claims continue to match actual performance in the field. However, it is worth noting that not all manufacturers subscribe to this service. A high-quality PFP manufacturer will provide the user or specifier with:

The right PFP product
For the right fire type scenario
With recognized approvals
And an approved follow-up service

International Protective Coatings is a world leader in intumescent fire protection. Our Chartek® and Interchar® brands deliver cutting-edge technology for both the hydrocarbon and cellulosic fireproofing markets. The long-established Chartek products have an unrivalled track record in the hydrocarbon fireproofing market, and the technology and expertise have been used to develop the new Interchar product range, which is specifically designed and tested for the cellulosic fireproofing market.

Product development is carried out in our state-of-the-art fire test laboratory, capable of replicating any international fire test standards. Chartek and Interchar are then also tested and certified by recognized independent test laboratories. International Protective Coatings subscribes to the Underwriters Laboratories (UL) follow-up service for both product ranges.

For more information, contact Ginny McEvoy at ginny.mcevoy@internationalpaint.com.