In any type of production facility, fire control encompasses a wide range of equipment or systems from building sprinklers to plant site fire departments. A spark detection/extinguishing system must be thought of as part of a plant’s overall security and safety network. Just as a residential alarm system provides protection to a homeowner, a spark detection system provides preventive protection against potential loss of human life, production facilities, equipment and costly downtime. selfstoragefirst.com
Where do Spark Streams appear?
Spark streams in dust collection systems are a very common danger. They are not easily detected and this means that they may exist but are not known! Consequently, attention is paid to a spark stream only when it is too late, namely when there has been an explosion or a fire.
When working with industrial machinery, sparks are created very quickly. A blunt tool, a damaged bearing in the fan, an overheated motor or foreign body within the material can be the cause.
Sparks are a constant danger in those factories where combustible materials are being worked, exhausted, transported, filtered or dried.
The damage statistics provided by the insurance companies point out that filters, dust collection bins, silos and even complete production lines are the areas of a plant at greatest risk. Foreign bodies in the conveyed material, defective parts of the production machinery, friction processes as well as electrical sparks are all identified as fire generating. Here are the main danger areas known:
Fiber and Particle Board Industry: The fiber and particle board processing as well as the further processing of the panels by sawing and sanding
Wood-Working Factories: Working of materials by means of saws, planers, mortisers, hoggers, sanders and other wood working machines
Chemical Industry: Pneumatic conveyors of dusts and powders
Foodstuff Industry: e.g. Coffee roasting, tobacco processing and pneumatic conveying of powders
Why is it so Dangerous?
The spark itself is not dangerous. Here’s why: For the creation of fires or explosions there must be three elements that are combined simultaneously: a combustible material, oxygen and an ignition source. Removal of one of the elements will prevent a fire or explosion.
In today’s production plants, we have to cope with all elements that can lead to fire damage or cause an explosion. Extraction systems and pneumatic conveyors increase the danger of fire. Once sparks and glowing embers are created, the pneumatic extraction system conveys this danger very quickly to other subsequent areas of the plant. The danger is when two of the three elements necessary for the creation of fires and explosions are transported, namely: air and ignition sources (sparks).
When this conveyed danger meets combustible materials (filter cloth, deposited and combustible dust in a separator or silo) it becomes more and more likely that a reaction will happen.
Environmental protection measures regarding dust emissions and tightened regulations for air pollution led to an increased use of filter systems, but the danger of dust explosions has not been reduced. In the process of drying, the dryer capacities have been steadily increased so that prevention of fires in these systems has become more important than ever.
What happens after a filter fire? Environmental regulations prohibit plant operation without the filter system. The plant will not only have the cost of repairing the damaged filter system caused by fire but also absorb the extremely high loss of a production shutdown.
According to individual reports, these production losses can exceed the damage costs many times over.
The risk of fire can be efficiently reduced or eliminated by means of modern spark detection and extinguishment systems.
Returned air to the plant also requires spark detection and extinguishment systems. Due to the high amount of material now collected in the dust filter systems, in certain circumstances clean air is allowed to be returned to the production buildings. Enormous savings in heating energy are achieved in this way. A filter fire, however, could quickly be transferred to the production area with devastating consequences.
To protect such a system, all extraction ducts as well as the conveying duct to the material storage should be equipped with spark detection and extinguishment systems.
How can you take Preventive Measures?
Protection can be achieved by installing a modern spark detection and extinguishment system. The sensors detect sparks and glowing embers immediately after their creation. Upon detection and evaluation, countermeasures are induced immediately in order to eliminate the causes of a fire or an explosion.
Let’s compare fire extinguishment systems with spark detection and extinguishment systems. Fire extinguishing systems combat fire after it has come to life, consuming material and air thus producing smoke and damage. A spark detection and extinguishment system eliminates one of the three elements (the ignition source) before it becomes a fire. In this way there is no fire, no smoke, and no damage.
Spark detection and extinguishment systems are able to detect even the smallest of sparks or hot particles in extraction ducts, drop chutes or mechanical conveyors, and to instantly trigger countermeasures. Countermeasures can be: activation of an extinguishing system, diverting the transport path or interrupting the production. All these measures are taken within a split second.
Detection of the ignition source is made by means of spark sensors recognizing the infrared radiation of sparks and glowing particles. These sensitive spark sensors are even capable of detecting sparks through layers of dust or through the conveyed dense material flow. The sensors give alarm signals to the control console, which processes the signals and activates the appropriate countermeasures automatically. Normally an extinguishing device is triggered, which is installed downstream from the spark detectors. This device releases a mist of water in the duct section where the sparks are transported. When no additional sparks are detected, the extinguishment spray is automatically stopped. While the extinguishment takes place, the production process can continue unless otherwise desired. Due to this special operation principle, spark detection and extinguishment systems are classified differently than sprinkler systems, deluge systems, or even explosion suppression systems.
The Control Console
The centerpiece of a spark extinguishing system is the control console.
All signals given by the spark sensors installed in different plant areas are being accumulated and processed by a microprocessor. The extinguishing devices of the affected areas are activated without any delay.
A practical fire protection concept also considers the demand for an almost uninterrupted production. The use of microprocessor technique including the corresponding software results in new possibilities to react on sparks. Integrated counters and time recording systems allow an exact assessment of the spark stream. A graded use of the existing countermeasures is then possible.
For example, single sparks are only extinguished, but for heavy flow of sparks or when single ignition sources are detected over a longer period, further measures like machine shut down of the affected plant sections have to be taken. Diversion of the material transport is also possible using fast-acting abort gates.