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The CPD, sponsored by Thomas Bell-Wright International Consultants, explains the correct tools for using passive fire protection methods to ensure the fire safety of external wall systems
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Thomas Bell-Wright Laboratory is conducting NFPA 285 testing of the ACP system
With the increase in reports of building cladding fires, the global construction industry has been forced to face the problem of fire test cladding, especially the fatal disaster in Grenfell Tower in West London two years ago. Some people say that the cladding fires that have occurred all over the world in the past decade are the result of the cladding using a new material aluminum composite material being widely used in the cladding as a building finish in high-rise buildings.
The new generation of aluminum composite cladding (ACM) contains flame retardants in the plastic core. However, this increases costs, so fire tests are required to ensure that the correct amount of flame retardant is used. Because the cladding process is so repeated—every detail is copied to every centimeter of the building—it is extremely prone to defects. At the same time, repairing is extremely difficult, expensive and complicated, because it means removing the entire system and replacing it.
For decades, various industries have used tests and test reports to prove the organization's ability to produce products or materials that meet given requirements.
This CPD will study the use of passive fire protection methods to ensure the fire safety of external wall systems.
NFPA 285 testing: before, during and after
The ACM cladding consists of a plastic core sandwiched between two thin (~0.4 mm) aluminum skins, and the resulting board is usually 4 mm or 6 mm thick. The outer skin material is a huge coil with a color coating of the buyer's choice.
A V-shaped groove surrounds the periphery about 2 cm or 3 cm, which will remove all material up to the outer skin. The edges can then be easily folded to make a tray with hard edges without damaging the coating. The steel bars can be fixed with adhesives to support the middle and avoid "oil cans", and rivets are used to fix the clips on the building. It can be architecturally pleasing, inexpensive and easy to work. However, although ACM is not so easy to ignite, once it catches fire, it will burn quickly, and the flame that burns downwards is as violent as it burns upwards.
Fire tests are roughly divided into three groups: Fire tests are applicable to building elements, such as walls or doors, including fire separations between defined compartments in buildings, such as individual offices or hotel rooms. Put the sample into the frame, place it on the open side of the full-scale test furnace, and expose it for a period of time under the standard time/temperature curve. The maximum time reached places the element within a rating range, such as 30 minutes or 60 minutes. The same testing equipment and principles are applicable to the protective coating of structural steel components, and can also be tested under load. These coatings are called intumescent because they expand with heat, increase their volume and decrease their density, and protect the component for a period of time and reach the rated value.
The second set of tests are response tests to fire, mainly for materials rather than systems, and are usually tested in smaller equipment, albeit with a wider range of tests. Typical characteristics that are important to exterior wall engineers who design fire-resistant exterior walls are the conditions under which the material catches fire (called flammability); the heat (energy) released when the material burns or burns (called calorific value or heat release rate); The speed at which the back flame passes through the surface of the material (called flame spread) and the physical reaction to the fire, such as the release of smoke and liquid droplets.
The third set of tests is actually a subset of the reaction to fire, called fire propagation. In these tests, there are several different standards around the world, and a full-size or slightly reduced two-layer sample is erected on the support system. An opening was constructed to represent a window, and a fire was lit on the side of the room with the opening. The test piece includes all materials combined according to the facade design, and if it does not meet any failure criteria, it will pass the test.
A test report is a snapshot of the behavior of a given sample of a material or system. The result is the result of the test sample-if there are no measures to confirm that it is representative, it should not be automatically considered representative.
A valid and usable test report must include the following:
1. The accreditation or authorization of testing by the laboratory. Institutions such as the UK Accreditation Service (UKAS) or the American International Accreditation Service (IAS) provide laboratory accreditation. The laboratory needs to follow a unified quality management system and demonstrate its ability to conduct tests within its scope.
These requirements are contained in the international standard ISO 17025, the general requirements for the competence of testing and calibration laboratories. This is equivalent to the manufacturer's ISO 9001. The certification body is affiliated to umbrella organizations such as the International Laboratory Accreditation Cooperation (ILAC), and its members have a system of mutual recognition.
Therefore, an acceptable accreditation body will be a signatory to its umbrella organization "Mutual Recognition Agreement" (MRA) or "Multilateral Agreement" (MLA). If the laboratory does not test and certify the certification body of the MRA/MLA signatory, the laboratory test report may not be universally accepted.
2. The content of the specific test should be fully described, including the name of the product, the name of the test initiator, and the location of the manufacturing plant. If this information is not recorded, even if the information is provided by the customer and has not been verified, the value of the test report to others will be reduced.
3. The date of the test report and the version of the test standard under which the test was conducted must be stated. Sample reports that were tested a long time ago (for example, several years) or tested according to the old version of the test standard should be handled with caution.
The test report itself does not provide much assurance that the content that arrives at the site is the same as the content of the test-for this, you need "certification", which will be discussed in the later part of this CPD.
ASTM D 1929: The ignition temperature of the front and rear plastics
Some commonly used flammability test methods are:
The chemical composition of the material determines the potential energy of the material. This is different from flammability, which remains the same regardless of the volume or quantity of the material.
ACP system is undergoing BS 8414 testing
Depending on the composition and distribution of the potentially flammable components of the material, the speed at which the flame spreads on its surface and the smoke produced will vary.
So, how can the purchaser or end user of the product or material ensure that what they buy is the same as the one tested? The answer is certification.
Certification relies on a third-party organization, that is, a certification body (CB) that conducts conformity assessment of product, process and service certification bodies through the ISO 17065 standard.
The certification process includes the following steps:
Step 1: The CB auditor visits the manufacturing site and verifies whether the facility has a quality management system, such as ISO 9001. Without the control provided by an appropriate quality management system, the factory cannot be expected to produce a consistent product.
The auditor then witnesses the production process of the product/material to be tested. Processes and raw materials are mapped, and one or more samples of the production line are identified for testing and marked by the auditor. Auditors usually leave many "corrective actions" to manufacturers to implement them in their systems or procedures as a precedent for CB to issue their certification.
Step 2: Transport the labeled samples to the testing laboratory for testing. The test report will be generated and will include the elements discussed earlier.
Step 3: After successfully testing and solving corrective actions, CB issues certification documents, lists the products on its website and authorizes the manufacturer to use the CB mark on the product, its packaging or promotional materials. Typical CB marks include the UL mark on some electronic products and the "Kite Mark" of the British Standards Institution. Any purchaser of a product that claims to be certified should check its certification status on the listing website before proceeding.
Step 4: As part of the certification and continued listing, CB regularly reviews the production and quality control processes at the manufacturing site several times a year. This provides a high level of assurance that products subsequently shipped under certification and listing are manufactured in the same manner and materials as the tested samples.
Once the fire protection properties of the material are determined, the façade engineer will carefully design the cladding system for a given project. Each project has several different details, and one or more may be at risk of fire spreading. These are then simulated and tested according to NFPA 285 or BS 8414-Fire Propagation Test. As mentioned above, for the two standards mentioned, these are full-scale tests, and the height of the sample is between 6m and 8m, respectively. Including every element of the system, such test results validate the design concept and confirm the reduction of fire risk.
BS EN ISO 1182: Non-combustibility test before and after
There is now a certified product with traceability that can be inspected at the construction site, with approved cladding drawings and model test certificates. However, there is a further inspection stage.
Several parts of the cladding system design may be installed incorrectly or the installation method is inconsistent with the test or review method of the sample material. This is where the façade expert engineers regularly conduct on-site inspections of the cladding work. This may be the most onerous part of the entire exercise, but it can be said to be the most critical part.
ASTM E84 for insulating materials: before and after
Professionals who inspect the installation of the external wall system need to be qualified and able to distinguish between errors in drawings and on-site and understand process practices. ISO 17020 is a standard for conformity assessment of the operation of various executive inspection agencies. Certification according to this standard in the field of cladding inspection is essential and mandatory in many places.
The global standards ISO 17020, ISO 17025 and ISO 17065 laid the foundation for independent and reliable third-party testing, inspection and certification agencies. These institutions are concentrated in the testing, inspection and certification (TIC) industry, which is increasingly important in building construction, especially in cladding and curtain walls.
Manufacturers use the services of an accredited independent certification body (through certification marks and lists) to prove and ensure the reliability of their production. This helps to build a high degree of confidence among stakeholders that what is installed is the same as what is tested.
The project manager utilizes the services of an accredited independent inspection agency to ensure that the cladding system and curtain wall are installed in a manner that complies with the test installation.
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