The quality mark "fire-tested pipe supports"

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.

How is the fire behaviour of pipe supports assessed?

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.