Passive fire protection of electrical cable penetrations
Technical penetrations can spread gas and flames, either through cracks around the cables or the space left free by the combustion of the coating.
The European reference standard for safety, EN 1366-3, sets the test criteria for fire protection systems that this type of penetrations must meet. As with other plant penetrations, the critical performances monitored in the tests are the following:
- system tightness against combustion fumes and gases;
- ability to restore thermal insulation at a level of the penetrated structure.
There is no one fire solution.
The choice depends on the installation environment and application requirements.
Here we will look at the different sealing systems and analyse them according to their technical features and advantages in application and maintenance.
The most flexible solutions consist of systems that can be easily removed and replaced directly on site, such as intumescent bags (e.g. AF Bags).
Installation is simple, and if necessary, bags can be removed or slightly compressed to allow new cables to be pulled out or inserted.
This type of solution is ideal for small openings or construction sites.
At the end of the work or for large openings, semi-rigid systems such as low-density mineral wool panels (e.g. AF Panel) which offer greater application efficiency for experienced installers, are preferred. However, this is at the expense of ease of re-working.
Another main parameter, besides flexibility, that differentiates cable penetration protection systems is the sealing depth. The solutions offered on the market range from 120 mm to more than 300 mm.
For certification, it is preferable to test a smaller sealing depth to reduce the insulation thickness exceeding that of the substrate in which it is inserted. This will significantly reduce the overall work cost.
To combine the advantages of the different systems, we would like to focus on a new solution that has become increasingly a standard for these penetrations – products based on two-component thermo-expansive foam.
Available in the classic foam version (e.g. AF Graphit Foam) and preformed version of intumescent bricks (e.g. AF Brick with a sealing depth of only 150 mm), these products guarantee integrity even with combustible elements. These are a synthesis combining the advantages of flexible and rigid solutions.
AF Brick received its first ETA (European Technical Approval) certification in November 2021. Like more rigid solutions, these systems have an extremely compact finish and, by compressing them, provide an excellent seal against cold smoke even without additional products.
Their simple installation method makes them ideal for maintenance purposes, with easy re-application.