SAFETY IN THE PLANT
heat into the fl ame quenching element. T e large wire surface area of the mesh allows for effi cient heat absorption. T e absorbed heat is dissipated throughout the mesh, eff ectively cooling it down below the ignition temperature. By keeping the temperature of the mesh below the ignition point, the fl ame cannot propagate through the mesh.
KNOW WHAT YOU ARE WORKING WITH If you are considering fl ameless venting devices or any other explosion protection device in general, you must know your dust, your material and its explosion characteristics. T at is the alfa and omega to any well-designed explosion protection. For the successful application of fl ameless venting, the heat of combustion of the material is an important parameter because it determines the amount of heat produced during the combustion of that material. T ere is a diff erence between heat from organic dusts and metal. If the heat of combustion is too high, the amount of heat transferred will not be suffi cient to provide fl ameless venting, and fl ame extinguishment will not be successful. When fl ameless venting is applied to dusts with relatively low melting points, such as resins, for instance, the powder can melt at defl agration temperatures, and on cooling, the solidifi ed product blocks the mesh of the fl ameless device. In an extreme case, this would prevent eff ective venting. Examples of such dusts are
Experts can assist in selecting the
right devices for the environment
plastics, resins and some types of coal. Very similar phenomena can also be observed with coarse and fi brous dusts, where their particles are diff erent in size. T e size of particles and their type (organic, metal, fi brous, coarse) plays a crucial role when choosing proper explosion protection. And it all comes down to the effi ciency of a fl ameless venting device. Dust characteristic is not the only one you need to focus on. T e volume of the protected vessel is another important parameter to consider, but not only volume itself but also the shape. T is may present a challenge to many customers as they need to be able to evaluate if a recommended device is truly the best option for them.
RSBP devices are installed at sites around the world
THE IMPORTANCE OF KST One way to see if a fl ameless venting device suits your production process is to know which Kst has your material. Kst value is one of the most used parameters in dust explosion protection. It has three main categories, which are called ST classes. We have ST1, ST2, ST3 classes, which help us categorise the eff ects of an explosion. Other parameters, such as MIE and MIT (minimum ignition energy and temperature) are often mentioned in regard to explosion protection. T e lower the MIE, the higher the risk of explosion, as a minimal amount of energy input can trigger a dust cloud explosion. MIT, on the other hand, is the lowest temperature of a hot surface that will cause ignition of a dust cloud and propagate fl ame. Explosions become more dangerous and violent with each ST class. Major explosion protection manufacturers have their devices categorised according to these three ST classes. If you are considering fl ameless venting for your facility, always check to which Kst is the off ered product suitable and that it has valid certifi cation according to the proper standard. Flameless venting devices are more complex devices requiring much more information for correct assessment and effi ciency.
Tomáš Wyka is technical director of RSBP.
www.rsbp.cz
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