Passive fire protection systems should be solutions of the type "install and forget them", that should behave in compliance with a specified standard over the lifetime of the structure they were applied to, with minimum operational maintenance. From this point of view, they are opposite to active protection systems, such as sprinklers and alarms.
Passive fire protection systems allow owners to protect the integrity of the steel structure, compartments, staff and equipment during fire and evacuation. The specification of the products used in the passive fire protection depends usually on a number of factors including the type of fire, the duration, the material from which the substrate is made of (usually steel), the type of substrate and its location. The approval of the test fire is one of the most important factors when making the right specifications.
According to the provisions of the NIST (National Institute of Standards and Technology) report, that was prepared following the destruction of World Trade Centre twin towers in New York, there is an increasing tendency to apply passive fire protection at workshops (offsite). This trend leads to the emergence of new technologies, which are in accordance with the requirements of the owners and contractors. The introduction of these new unique products increases the efficiency of the owners, contractors and applicators and, together with improved aesthetics, offers new possibilities for provisions authors, designers and architects.
Types of fires
The products used for passive fire protection fall into different performance categories, usually determined by the type of fire they have to deal with. Fire types have a distinct relationship between time / temperature (with the exception of jet fires - which have a specific value of the fuel flow) used to assess the critical level.
- Cellulosic Fire – Designed to simulate natural carbon materials such as wood and paper, these fires are generally characterized by slow temperature rise and maximum temperatures of 950°C;
- Hydrocarbon pool fire – fires fuelled by oil spills and gas vapors, they are characterized by high heat flux and rapid temperature rise up to 1100°C. After the Piper Alpha platform fire in 1988, protection against these types of fires became a standard for offshore industry;
- Hydrocarbon jet fire – a unique type of hydrocarbon fire caused by pressurized gases or pressurized fuels that are released through an orifice and then ignited. These fires produce even more heat: maximum temperatures can exceed 1200°C and generate highly erosive forces;
- Cryogenic spill jet fire – occur in enclosed spaces and/or when the fuel is highly flammable, such as fires produced in tunnels or nuclear fires.
Passive fire protection products
There is a wide range of products, including intumescent products or cast concrete / fiber products, available both in the form of sprayable liquid and in the form of sheets. To deal with different types of fire, the products can be divided into two categories.
- Protection against cellulosic fires, which is used in construction and infrastructure projects. Intumescent products in this category are generally known to be thin coat applied, with a thickness up to 1 mm. The material expand into an insulating char up to 60 times of the initial thickness when exposed to a fire.
- Protection against hydrocarbon fire, jet fire or cryogenic spill jet fire for high-risk environments such as oil platforms and refineries. The intumescent products in this category are often defined as having a thick layer, their thickness being measured in mm and not in microns. The coating may have thicknesses between 3 and 20 mm, depending on the required fire resistance.
The tendency of applying passive protection to fire in workshops
The application of intumescent protection has become a major concern following the NIST report on the destruction of the World Trade Center twin towers. Traditionally, such protections are applied on site, but lately, products that can be applied in workshops have been developed.
NIST recommends the preparation of specific provisions, test methods and standards 1) for the efficiency during operation of fire resistant materials intended for the protection of structural components and 2) to ensure that, after application, these materials are in accordance with the tests used to establish resistance to fire of components, assemblies and systems. Consequently, offsite application guarantees consistency and compliance with specifications.
The main advantage of applying offsite passive protection is the fact that the steel for the structures is already protected when reaches the site. In the event of fire occurring before construction is completed, the steel is protected. When using a single supplier, it is advisable to protect steel from fire and to paint it.
Applying offsite fire protection also reduces the complexity of the project by reducing the number of people involved at the site, which helps to meet the deadlines. Other advantages include:
- Steel is protected by the companies that operate in the most profitable locations, not the companies referred by the site;
- Easy access and large application areas increase efficiency;
- Minimum equipment and requirements related to scaffolding on site;
- There is no need to seal areas or mask sensitive equipment.
Quality control is improved
- Controlling the conditions when coatings are applied and auditing quality control procedures ensures that the thickness of the layer is correct;
- Greater control over application techniques;
- There are no access problems.
The impact on health, safety and the environment is low
- The presence of a smaller number of site workers leads to a decrease in the likelihood of accidents. Removing intumescent systems on the site leads to a low risk of substance spills and fires;
- The steel is at ground level, so there are no access problems.
International Protective Coatings has responded to the assessment of fire protection materials with an innovative solution. Interchar® 212 is an advanced material that offers fire protection and an efficient anti-corrosive protection which are both required for the highest level of protection of buildings and infrastructure.
Interchar® 212 comes with some unprecedented features in the industry, offering anti-corrosion protection to extreme temperature fires. Being an intumescent epoxy material thin coat applied, Interchar® 212 offers up to 3 hours of fire protection (while other similar offsite applicable products offer only 1 hour), as well as the aesthetic versatility that architects require for the visible parts of the steel structures. Allowing application immediately after the blasting process, as solvent-free and low-strength technology, Interchar® 212 is ideal for offsite application in dyeing workshops.
Testing of fire protection products
In each country, the rules, regulations and codes applicable in constructions prescribe the level of fire protection required for different structures: e.g.: "fire protection for 60 minutes". However, there is a tendency to provide a risk-proportionate level of protection.
The performance of a fire protection product should normally be proven by a fire resistance test required for certification. Such tests are defined by national and international standards, providing a methodology for meeting the fire resistance levels set for different types of fires. Although standards may be complex because of the large number available, the most common (such as British Standards (BS), ASTM International, Underwriters Laboratories (UL) and ISO 834) are widely used worldwide.
Regardless of how fire resistance is defined (by prescriptive regulations or by risk assessment), the fire resistance of structural steel will be defined as follows:
- Type of fire: cellulosic, hydrocarbon or jet;
- Fire duration: minutes or hours;
- Critical temperature: typically between 400°C and 600°C for structural steel elements;
- Maximum allowed temperature on the non-exposed face: for compartments, and firewalls, usually 140°C;
- Thermal flow.
Authors of specifications and contractors must use independently tested products beyond the standards mentioned above. Of course, as with any certified product, the author of the specification needs to provide more details about the level of certification or additional certifications that might be useful to architects or designers, such as: UL263 listing, the possibility to use the products in environments referred to in ISO 12944 or explosion test with overpressure not exceeding 4 bar. Another tendency related to the use of passive fire protection for buildings is that the product should have a certain level of resistance to hydrocarbon fire (UL 1709 Design XR627).
Passive fire protection tracking services
Manufacturers of passive fire protection systems need to conduct thorough testing to demonstrate the features of their products, ensuring they are correctly evaluated and that performance information is accurate. Testing is essential to ensure that the specified or used material meets the performance standards required by national and international legislation.
In addition to fire resistance, products are tested in different environments and they must demonstrate that their efficiency does not degrade over time. To ensure that the sold product has the same performance as the original, accredited testing centers offer quality monitoring, random sampling and verification services. By controlling any changes that might occur from the original certification, these organizations ensure that the product's performance will be the real one in the field. However, it is good to note that not all manufacturers offer this kind of service. A renowned and high-quality manufacturer will provide the user / author with the following information:
- A complying product;
- Appropriate for a certain type of fire;
- With acknowledged approvals;
- An approved verification service.
International Protective Coatings is a world leader in fire protection. Chartek® and Interchar® products encompass the latest technology for fire protection, both for hydrocarbon and cellulosic fires. Chartek® products have no match on hydrocarbon fire protection, while their technology and expertise in the field were also used to produce the Interchar® series of products specifically designed and tested to provide protection in the case of cellulosic fires.
Product development is conducted in latest technology test laboratories that are able to reproduce any international standard of fire testing. Chartek® and Interchar® are also tested and certified by independent test laboratories. International Protective Coatings uses the services of Underwrites laboratories for both product ranges.