Spark extinguishing system

The system of the spark extinguishing system is used for preventive fire protection . With a spark extinguishing system it is possible to detect and eliminate ignition sources before a fire or a dust explosion occurs. Above all, systems for grinding / comminution, drying, cooling and pressing with their pneumatic or mechanical transport routes and suction systems, and systems for separation or storage such as filters, cyclones , silos and bunkers are at risk. 

In industrial production, raw materials are severely crushed; therefore pneumatic or mechanical conveying paths are a main component of production facilities. However, not only the “scheduled” dusts and bulk goods are transported via this connection. In processing machines or dryers , sparks or smoldering parts can also arise and thus represent a considerable risk of fire and explosion for downstream system components such as filters and silos.  

A fire or a dust explosion always occurs when three conditions are met at the same place at the same time: combustible dusts, air ( oxygen ) and an effective ignition source . If these requirements are met, an explosion can occur. Since the combustible dusts cannot be eliminated, the option of using inert gases or preventing sources of ignition remains . 

Spark extinguishing systems have established themselves as a preventive fire and explosion protection system in industry and trade . Many branches of industry could no longer be operated economically today without spark extinguishing systems. Spark extinguishing systems are the only preventive technical fire protection. Measures such as explosion suppression or sprinkler systems are reactive measures.  

Creation of sparks and fires

A fire or a dust explosion can occur whenever combustible material, such as B. strongly shredded raw materials, and oxygen (ambient air) are present and at the same time an ignition source reaches the minimum ignition energy . Due to the calming of the air and the material density in filters and silos and the associated material-oxygen ratios, these areas are extremely endangered. This represents a potential hazard for almost all production systems.

The requirements for fires and dust explosions are usually not met in the pneumatic conveying routes themselves. It is therefore possible to equip these systems with spark extinguishing systems as a preventive fire and dust explosion protection system.

With the help of a spark extinguishing system, ignition initials are already detected in the conveying path and mostly eliminated without interrupting production.

Structure and functionality of a spark extinguishing system

Functional principle of a spark extinguishing system

The spark extinguishing system essentially consists of three elements: the spark alarm center, the spark detectors and the automatic extinguishing system.

The spark alarm center forms the center of a spark extinguishing system. This is where the signals from the individual spark detectors from the various areas of the system converge and are evaluated. The connected deletions or alarm outputs of the corresponding areas are activated without delay.

Spark detectors are used to detect ignition initials. They record the thermal radiation emitted by sparks or smoldering particles, sometimes even through layers of dust or the conveyed goods. If sparks are detected in the system, the spark detectors report alarm signals to a spark detection center, which evaluates these signals and automatically initiates targeted countermeasures . Different spark detectors are available depending on the location or application. There are spark detectors for use at very high product temperatures or for spark detection under the influence of daylight .

In most cases, water is used to extinguish the fire . The automatic extinguishing system is installed in the direction of the flow behind the spark detectors. In order to ensure that recognized ignition initials are reliably extinguished, the spark detector and extinguishing device must be at a certain distance from one another. This distance is called the spark extinguishing gap and is calculated from the transport speed of the material and the system-related delay time. The automatic extinguishing system briefly generates a water mist in the pipe section into which the sparks fly. If no more spark is detected, the injection is automatically terminated and production can continue unhindered. The extinguishing agent used is mainly water, as it has an excellent extinguishing effect due to its very high heat capacity . The hot part is cooled down by removing heat. An optimal extinguishing effect is created by keeping the specific surface of the water as large as possible. This is achieved by a very fine atomization of the water. The degree of atomization is achieved through a special nozzle and sufficient operating water pressure. In addition, the amount of extinguishing water can be minimized due to the high atomization. By adding relaxants, hydrophobic substances such as rubber or plastic can also be deleted or the amount of water minimized.

In some cases water is not a suitable extinguishing agent (e.g. light metals cannot be extinguished with water), or the process is disrupted (e.g. sticking in the sugar industry ). In such systems, therefore, switches are used to divert or slides and flaps to shut off the flow. The reaction times of these mechanical systems are as short as the water extinguishing.

How a spark extinguishing system works in a pneumatic delivery line

The pneumatic conveying line is equipped with spark detectors to detect sparks and hot or glowing parts. A subsequent, automatically triggered extinguishing device, usually without interrupting the product, extinguishes the recognized ignition initials with water at lightning speed. The response time is only approx. 100-300 milliseconds .

The extinguishing agent water is given priority over possible alternatives, as it works quickly and is unsurpassed for this special application due to the rapid cooling effect.

How a spark extinguishing system works in a mechanical conveying path

Mechanical conveying paths are preferably used at the material transfer points, e.g. B. on fall shafts, provided with spark detectors. Because of the loosened product flow, spark or glow nest detection can be implemented very well. Using an automatic water extinguishing system, the sparks or glowing nests, as in pneumatic conveying lines, are immediately extinguished.

The creation of the spark extinguishing system 

The history of the spark extinguishing system goes back to the early 1970s. The new Federal Immission Control Act (BImSchG ), which came into force in 1974, required the use of extraction and dedusting systems in the wood-based materials industry . These operators were obliged from particleboard and fibreboard plants, guidelines of the regulations TA Luft to meet TA noise and odor emissions.

Foreign bodies or defective machine parts caused dangerous flying sparks in the extraction and dedusting systems, which posed a danger to the downstream filter systems. This made it necessary to develop a new fire protection solution to avoid the risk of severe fires and explosions.

This new technology made it possible to detect ignition sources and to extinguish them within fractions of a second during operation. 

Areas of application of the spark extinguishing system

Wherever flammable material is processed, transported, filtered or dried, there is a risk of fire or explosion from sparks or hot particles. A spark extinguishing system can prevent fires and dust explosions here. Originally for the timber industry developed safety concept is nearly to transfer all manufacturing industries today. The spark extinguishing system is used in:

• Pellet industry
• Recycling economy
• food industry
• Chemical industry
• Textile industry
• Metal industry
• Furniture industry
• Power plants
• Paper industry
• Feed industry
• Tobacco industry
• Hygiene industry
• Automotive industry
• Mills
• MDF production
• Chipboard production
• OSB production
• Plywood production
• Tire recycling plants
• Flour production
• Sugar industry
• Coffee industry
• Cocoa industry

Individual evidence

1. ↑ • VdS 2106: Guideline on requirements, recommendations for planning and installing spark extinguishing systems. (No longer available online.) In: VdS 2106. 2012, archived from the original on April 12, 2016 ; Retrieved October 25, 2016 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  
2. ↑ VdS 2029. In: 2029 - wood processing companies. VdS, accessed on October 26, 2016 . 
3. ↑ Preventive fire protection. In: BGI 560. Berufsgenossenschaft Holz und Metall, accessed on October 25, 2016 . 
4. ↑ VDI dust fires. In: VDI 2263. VDI - Association of German Engineers, accessed on October 26, 2016 . 
5. ↑ • 654, 2006: NFPA 654-2006 AMD 2010 Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids. National Fire Protection Association, accessed October 25, 2016 . 
6. ↑ 2012: NFPA 664-2012 Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities. National Fire Protection Association, 2012, accessed October 25, 2016 . 
7. ↑ Wood dust - occupational health and safety when collecting, vacuuming and storing. (No longer available online.) In: BGI 739. Holz-Berufsgenossenschaft, 2002, archived from the original on February 21, 2016 ; Retrieved October 25, 2016 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.