Attention is increasingly being focussed on structural fire protection. One more reason why it is even more important to be able to rely on the fire protection characteristics of a product. The quality mark "fire-tested pipe supports" was developed to be able to offer certainty to all those involved with a construction – and in particular the planner.
The quality mark "fire-tested pipe supports" is awarded solely to products that have already been awarded the quality mark "pipe supports". Both quality marks are based on a comprehensive technical assessment and monitoring standard. This always involves an impartial, independent assessment of the mechanical characteristics of the product to RAL-GZ 655 as well as an evaluation of fire behaviour tests to RAL-GZ 656.
The following national and international test institutes are approved in accordance with RAL-GZ 656 and able to verify appropriate levels of experience in carrying out initial tests and monitoring inspections.
The technical standard RAL-GZ 656 was drawn up together with the leading test institutes and manufacturers. It is the first comprehensive model to assess the fire behaviour characteristics of pipe supports approved industry-wide by manufacturers and test institutes alike. It contains rules specifying how to carry out and evaluate fire behaviour tests on pipe clamps.
With the aid of these rules it is possible to determine the fire resistance curve and the load-deformation curve of a pipe clamp. This makes it possible to attain a completely new quality of fire protection planning that had never before been available to planners.
Modern buildings are fitted out with an extensive range of building services installations such as for drinking water, waste water, rain water, heating and ventilation systems. In some cases these installations are tightly packed, a point that applies to pipework in particular which is often routed through extremely confined spaces above suspended ceilings.
This has serious consequences in particular in and around building exits and escape routes, because the fire protection qualities of the suspended ceiling must be reliably guaranteed despite the pipework routed above. That is only possible if the fire protection properties of the pipes, and in particular the pipe supports installed, are both known and predictable. Appropriate verification is essential. That is why the technical standard RAL-GZ 656 was drawn up.
Steel does not burn. But it does fail nevertheless.
All steel constructions lose their mechanical stability with increasing temperature. That is directly attributable to the change in the material properties at high temperatures. For instance, at 800 °C (corresponds to approx. 30 minutes fire duration) the strength and elasticity of steel fall to about 10% of their nominal value.
The load-bearing capacity of pipe clamps suffers considerably as the temperature rises. And because steel is a good conductor of heat and pipe clamps are comparatively frail components the component temperature quickly takes on the heat of the surrounding environment.
As a consequence, there is an approved load that the pipe clamp can bear for every temperature. As it is possible to assign a burning time to any temperature via the standard temperature curve (STC) to DIN 4102 or EN 1363, it is possible to directly plot the allowable load for a pipe clamp against the fire duration. This curve is known as the fire resistance curve.
It is possible to read off the allowable load a pipe clamp is able to bear for any preferred fire duration from the fire resistance curve. The allowable load specified in RAL-GZ 655 limits the load-bearing capacity in the lower temperature range. Consequently, determining the mechanical characteristics at room temperature to RAL-GZ 655 is of considerable importance, also to assess the fire behaviour characteristics of a component. The allowable load falls as the temperature rises. That means the fixing centre distances must become progressively smaller as the fire resistance duration progresses.
As the temperature rises the yield strength and the modulus of elasticity (E) of steel fall. Consequently, the pipe clamp will deform elastically and plastically as the temperature rises. Predicting this deformation is not a trivial matter.
For example, if pipes are routed above a suspended ceiling acting as a fire barrier it must not only be guaranteed that the ceiling is not struck by falling components; it must also be guaranteed that the pipework does not drop down so far that it comes into contact with the ceiling. Otherwise the fire protection function of the ceiling can no longer be guaranteed. For that reason, it is very important to be able to predict the deformation behaviour of the pipe clamps in a fire. This deformation behaviour depends on the type of pipe clamp, the load applied and the duration of the fire (temperature).
As the deformation depends on the load, it is possible to reduce the expected amount of deformation by reducing the load. This can prove particularly advantageous in extremely confined installation spaces. It is possible to read off the product data required for an appropriate design from a load-deformation curve. Consequently, it is possible to determine appropriate fixing centres to guarantee the maximum preferred distance the pipes will drop in a fire lasting 30 minutes.Download quality mark RAL-GZ 656
To date it has only been possible to assess the behaviour of pipe supports exposed to fire on the basis of individual assessment procedures. Each manufacturer wishing to determine the behaviour of his products under given circumstances used his own assessment procedure, which differed from manufacturer to manufacturer and test institute to test institute.
Therefore, it was not possible to make a direct comparison. Far more important, most procedures were only of limited suitability to make reliable, comparable predictions regarding the deformation behaviour of pipe clamps. Due to the complex behaviour of assemblies such as a pipe clamp, it is not possible to provide a suitably reliable calculated solution to the problem.
In high-class construction projects in particular, certainty is fundamentally essential to everything a planner does. The reliability and comparability of technical data is particularly important in this field. And the same applies to the certainty of knowing that all details have been determined on the basis of recognised codes of practice.