Ignition Tests with Cooling Tower Packing Made of PVC and PP with Integrated Fire Protection Agents
Project Number 335
So far, rare cooling tower fires always resulted in complete destruction. In particular for larger buildings, such loss is always followed by a longer plant shutdown. Cooling towers with a concrete shell should be so impaired in their stability that repair will not be an option.
Fire hazards in cooling towers mostly occur during maintenance and repair works owing to forbidden smoking as well as during works were hot particles leave the working area uncontrolled (i. e. cutting and welding works with spark emission).
Today, cooling tower packings consists by far predominantly of highly combustible plastic material like PE, PP or PVC. In mostly all cases, surfaces are covered with moss/lichens, which in dry condition have firing characteristics similar to those of nitro-cellulose. Due to this covering by biologic material, partly already in the original condition, cooling tower packing cannot be moistened with extinguishing water. Due to the cooling tower thermal conditions the fire is fanned so strong that already in the early stages of its development it cannot be fought. The extremely fast heat production corresponding to the fast fire development leads to high heat stress, considerably impairing the strength of the concrete building.
As the result of the precedent tests carried out in the scope of VGB Project 289 it turned out that there is no realistic possibility of fire fighting in case of the ignition of cooling towers. Therefore, it is necessary to develop strategies to exclude an ignition of the plastic materials.
As an edifice, cooling towers must be produced from materials and components, which meet the B2-test according to DIN 4102-1 and/or EN 13501 1 or more. Even if materials are used in cooling towers, which meet this qualification in general, it is very difficult to meet the related requirements because of the profiling of the packing. Therefore, it is essential to develop an extended test method for the determination of the ignitability.
Further ignition tests have to be carried out with cooling tower packing made of PVC (new/old) and PP (old, with and without biofouling) with integrated fire protection agents.
The project shall be carried out with the aim to determine
- the efficiency of integrated fire protection agents after several years of operation,
- if biological fouling suspends integrated fire protection,
- if the chlorine content of PVC sufficiently works as integrated fire protection,
- if the common B2-test according to DIN 4102-1 and/or EN 13501-1 is a sufficient quality standard.
The project is being carried out 2010/2011 by Project manager Tim Matausch, Centre for Fire and Explosion Protection DMT GmbH & Co. KG (Dortmund,Germany).
The knowledge to be gained from this project will be integrated in revisions of the VGB Standards "Fire Protection in Power Plants" (R108) and "Einsatzmöglichkeiten von Kunststoffen in Kühltürmen" (M621).