Passive fire proteccion panels PANACOR PANEL ROCK

PANACOR PANEL ROCK. SOUND ABSORBING PASSIVE FIRE PROTECTION PANELS FOR TUNNELS

The concern about the consequences of the fires in the tunnels, of which we have witnessed as a result of those that occurred in Mont Blanc, Saint Gotthard, Tauern and Ka-prun, with 221 fatalities, to which are added others such as the Canal, which, without causing deaths, causes great losses (in this tunnel alone they were 211 million euros, counting both repairs and loss of operating time), is leading an unstoppable search for fire safety ( SCI) in said constructions. For this reason, smoke extraction and emergency exits, the protection of electrical installations and, very importantly, the concrete structure of the tunnel itself are being studied more and more. This is why passive fire protection solutions have a very positive impact on improving the fire resistance of tunnels.

The main objective of fire safety in tunnels must be the safety of users, providing them with time and safe evacuation routes. In addition, objectives considered secondary, such as structural protection, must also be a priority, since they entail providing more time and more chances of salvation to users involved in the fire and more time for the arrival of firefighters, in addition to preventing, due to its collapse, the magnitude of the tragedy increases by affecting other facilities. Other protections must also be considered highly important in this regard, such as ventilation, smoke evacuation, etc.

The different European regulations on fires in tunnels agree that the evolution of temperature over time in a fire that occurs inside a tunnel differs significantly from that which can occur in a building above ground. In the latter case, temperature evolution studies have led to the international implementation of a mathematical model that can be reproduced in the laboratory in which a cellulosic fuel fire is represented and a temperature of 1000º C is reached in 90 minutes. This model, called "Standard Fire Curve", is defined by the international standard ISO 834 and is also included in the Spanish UNE 23.093. It is applicable in the fire resistance tests that are carried out in our country in accordance with the requirements established by the NBE-CPI/96, as well as in the future European tests developed by CEN in accordance with what is specified in the Directive. European 89/106/CEE on Construction Products.

Studies carried out in Germany establish, however, that in a fire inside a tunnel temperatures rise much more quickly, reaching up to 1200º C in the first 5-10 minutes, and even this rise could reach 1300º C, considering a fire of confined hydrocarbons, according to Dutch studies. In France these fire development criteria are also accepted. We must clarify that these studies refer mainly to road tunnels. However, the experience of fires in railway tunnels (Channel Tunnel) also makes it possible to adopt these fire development criteria in this type of tunnel.

A fire scenario must contemplate:

  • The rate of heating (rate of temperature increase).
  • The maximum expected temperature.
  • The duration of the fire.
  • The subsequent cooling period.

All these aspects have a great influence on the effect of fire on the various elements that make up the tunnel itself, as well as on its behavior. Given that in passive protection it is of great importance to know the degree of protection of a certain constructive solution in its aspect of fire resistance (time in minutes that it is capable of fulfilling its function when subjected to the action of a "standardized fire"), specific test standards must be established to guarantee that the tunnel components will comply with the safety requirements established by the corresponding regulations.

Based on this premise, a test curve model has been developed in Germany, called ZTV-RABT, which reaches 1200º C in five minutes and maintains this temperature for periods that can vary from 30 to 120 minutes, followed by another cooling period, controlled for 110 minutes. Similarly, in the Netherlands, the Rijswaterstaat has developed a specific curve for tunnels, in which up to 1,350º C is reached with an initial heating period of up to 1,200º C in a few minutes, and which represents the fire that combustion in a tunnel entails. uncontrolled fire of a tanker loaded with 50,000 liters of burning oil for 120 minutes. In France, a more severe modified hydrocarbon curve than the normal hydrocarbon curve has been adopted, used for testing systems intended for petrochemical plants. Figure 1 shows a comparison of the different curves mentioned.

Figure 1

Faced with such thermal actions, it is evident that the materials will behave differently from the fire represented by the Standard Curve, which has been verified both in laboratory studies and in the reality of the fires that occurred.

Reinforced concrete, in several of its compositions, is the main constituent element of many tunnels and cut-and-cover tunnels, both road and rail. This material can be greatly affected by fire, especially due to the rate of heating and the maximum temperatures reached.

The effect of temperature on the loss of resistance capacity of both the reinforcement and the concrete itself can be seen in figure 2.

Figure 2

The physical and chemical transformations that take place in the concrete, including its melting at 1200º C, inevitably lead to its collapse and destruction, making it unrecoverable at the end of the incident, so it must be replaced. In any case, it is considered that when it reaches 300 ºC, the concrete loses a significant part of its resistant capacity and must be replaced after suffering the effects of a fire.

Another very important consequence is the spalling effect. The extraordinary rapidity with which the concrete is heated generates the passage of the water contained in the mass into steam with explosive speed. As the concrete used generally has a small pore, this vapor cannot be properly released, which produces a pressure capable of destroying the outermost layers of concrete, exposing the reinforcement and increasing the risk of the tunnel collapsing. The moments in which spalling occurs are in the initial 20-30 minutes of the fire, the most important causes of this effect being the heating rate (especially when it exceeds 2-3º C/minute), the permeability of the material and the pore saturation level (especially above 2-3% by weight of concrete moisture content); This has the result that high-performance, low-permeability concretes are the most vulnerable to this effect.

Spalling has been studied in some laboratories, such as the test carried out by the Norwegian SINTEF in December 1988, in which this effect is verified with thermal actions of hydrocarbon fire, observing an almost total decrease when the concrete receives adequate protection.

Several systems have been proposed to minimize the effects of the action of fire on concrete, but the one that has proven to be the most effective is the thermal barrier. The function of this barrier, as is obvious, is to protect the substrate from the direct action of fire, limiting the flow of heat through it and, therefore, reducing the speed of heating and the time in which the maximum temperature allowed is reached.

The most used barriers are those formed by cement mortars with mesh or by special plates mechanically fixed to the substrate. These systems with mechanical anchors eliminate adherence problems, have no spalling effect and are not sensitive to humidity. This type of product has been extensively tested in the most important laboratories in Europe –TNO (Holland), MPA Braunschweig (Germany), CSTB (France), etc., with results that confirm that the required degrees of protection have been obtained.

The planned protections (and their fastening systems) must have proven characteristics of behavior in case of fire, as well as others that allow them to resist the actions of their situation and normal use of the tunnel, such as pressure variations due to the passage of vehicles, at high speed, which can reach ±800 Pa in road tunnels, ±1,100 Pa in transport railway tunnels and up to ±5,000 Pa in high-speed railway tunnels.

These demonstrated characteristics must be proven by corresponding test reports. In the case of fire resistance, this type of test consists of preparing a concrete sample and its protection as close as possible to how it will actually be installed, with sizes of 4x3 m. Sample is submitted to a suitable installation (oven), to the action of a normalized thermal program such as those previously exposed, measuring during the whole process the deformations of the concrete, the appearance of the spalling phenomenon and the temperature gradients on the underside of the material and in the reinforcement. The information is collected by a certain number of control thermocouples suitably located in the concrete mass.

The requirements that the protection system must meet depend on the type of tunnel, the use and the legislation in this regard in each country. Here are some of the most common encountered recently in our involvement on various projects:

German ZTV requirements:

  • Maximum temperature on the underside of the concrete < 300º C when subjected to the RABT curve.
  • Permanence of protection during the test period.
  • Minimal and shallow spalling effect.
  • Temperature in the sealing of the expansion joint between 60º C and 150º C depending on the material.

Dutch RWS requirements:

  • Resist the effects of the RWS Curve for at least two hours in two different tests.
  • Maximum allowable temperature on the underside of the concrete < 380º C, complemented by a maximum temperature of 250º C on the reinforcing bars, with a 25 mm concrete cover.
  • Temperature in the expansion joints below 60º C.

The issuance of a test report by the laboratory classifies and endorses the tested solution for its use in tunnel protection and can be complemented by other types of tests, such as freeze-thaw cycles, resistance to gases from exhaust pipes and abrasion tests (Taber Test). In addition, we have to consider high speed passages of vehicles that create some dynamic stress. In road tunnels is considered up to ±800, while in the case of railways it can have variations from ±1100 Pa for rail traffic for local transport and up to ±5,000 Pa for high-speed trains, in cycles that can vary depending on the type of tunnel considered and its volume of traffic.

Other critical elements in which the action of passive protection can be decisive is ventilation and smoke control. The main problem with each fire is that of smoke extraction, given the problems they cause. All firefighters know that to successfully attack an underground fire it is of paramount importance to obtain good heat and smoke extraction, which are the direct causes of most personal misfortunes in this type of accident. For this reason, the proper design and installation of extraction ducts that resist the effects of fire and maintain their function for a certain period of time is essential. The foregoing is also valid when we talk about ventilation systems, especially in security areas, with which the execution of fire-resistant ducts must also be considered.

In the cases in which the pipes are integrated into the tunnel structure, the separation elements are made of concrete and everything previously mentioned in the previous section applies to them. Thermal barrier protections (with plates, for example) are used to prevent damage to these separations, which would compromise their conduction function. Smoke extraction can also be carried out through independent ducts made of fire-resistant materials, which allow it to maintain its correct operation and stability for a certain period. Of course, these construction systems must also pass the corresponding tests in accordance with the specific standard for ducts.

The conclusion that we can draw from the above is that passive protection should undoubtedly be taken into account when designing tunnels to make them safer.

And with this objective in mind, PANACOR has developed, through a long R&D&i process, a protection system based on a coating using metal acoustic panels that not only manages to provide a minimum of 2 hours of fire resistance following the hydrocarbon curve, but also which also manages to attenuate the noise generated by road traffic, avoiding the inconvenience of traffic to residents. In the following video you can see the 2 hours that the fast-motion rehearsal lasted:

Benefits of PANACOR PANEL ROCK passive fire protection system
  • Fireproof: withstand 1100 ° C for 2 hours.
  • Weather resistant: impervious to frost and rain.
  • Excellent acoustic performance - Tested to BS EN 354:2003 under typical tunnel lining conditions.
  • Produced in a range of colors to match almost any RAL color.
  • Can be made in custom sizes.
  • Panels can be flexible to allow mounting with curvatures.
  • Can be cleaned without the need for detergents.
  • Environmentally friendly.
PANACOR PANEL ROCK IN PASEO DEL BAJO IN BUENOS AIRES. FIRE PROTECTION PANELS AND HIGH ACOUSTIC ABSORPTION AGAINST NOISE

After extensive development, PANACOR was awarded the contract to line the tunnel with acoustically absorbent panels on a custom-made mounting frame. A panel for the wall and for the ceiling of the upper steps.

The system provides high broadband sound absorption, with high fire safety, stone-like durability, and a range of colors to add an aesthetic bonus to the installation.

PANACOR PANEL ROCK panels eliminate reverberation. This substantially improves the efficiency of the tunnel shape, reducing noise in the open part of the tunnel to protect local residents.

Due to the high low-frequency performance, our panel also reduces potential modal resonances.

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Technical information

Physical properties: Standard size: L x 1000 mm x 100 mm (other sizes used to suit services), with a maximum length of 11 meters. Weight: 22.5kg/m2.

Fire resistance: Tested by APPLUS for fire safety in tunnels. Tested following the procedure indicated in the EN 1364-1:2015 standard and exposed to the hydrocarbon curve indicated in the UNE EN 1363-2:2000 standard. The test involves exposing a complete wall construction to 1200°C for 2 hours to observe its fire behavior in terms of thermal insulation and integrity. The temperature of the thermocouples is in all cases below the limits that can cause the spalling effect.

Impact resistance: EN 1794-1 'Road traffic noise reduction devices - non-acoustic performance - stone impact': "The elements comply with the requirements indicated in the standard".

Acoustic absorption: EN ISO 354 and EN 1793-1.

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Colors

Any color from the RAL chart is possible:

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Fit in an urban environment

As you can see in the images below, the highway crosses a fully urbanized area. Argentina is beginning to have a high demand for noise barriers, as it is often difficult to build new roads in areas where the environment provides natural noise reduction.

In this case, the road was initially buried to allow goods to leave the port without crossing the city of Buenos Aires, increasing traffic, but also to break the direct propagation of highway traffic noise towards residents without the need for use large acoustic screens that can obstruct views.

However, unlike light, sound energy can diffract around objects, so by reducing noise reverberation, our panels make design much more efficient.

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Manufacturing

A project of this scale and importance has required the ability to produce quickly and with scrupulous quality control. This has meant developing an optimized production process in the factory so that we now have the infrastructure to handle projects of almost any scale.

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Installation

Fixings for wall mounted panels include bespoke horizontal omega sections for quick fixing of panels. These sections also include anchors of these omega profiles to the tunnel walls. The panels are fixed mechanically, using self-drilling screws. Other installation method can be promoted if construction site have specifical issues.

Figure 19: The roof uses a very similar system, the panels have more fixing points

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