Cement Manufacturers Association (CMA)

- For HBM systems only: the riser duct The separator constitutes an extra interconnected vessel, when comparing Since a dust explosion can happen in the separator (running in from below, running in from above, as well as initiated inside) both upward (to the DC) and downward (to the Due to the volume of the separator (several m3), the explosion in the separator can become a major contributor to the violence of the overall explosion scenario and this has to be included in both the system’s and the separator’s protection design. Under the header VRM-to-DC or need to install an explosion vent cum diverter close to the mill outlet has been explained. For exactly the same reasons such a vent cum diverter has to be installed close to the separator’s air-ground fuel outlet. This explosion vent also has the function of mitigating the explosion pressure in the separator. mill outlet and at the separator outlet also have to mitigate pressure build-up in the riser duct sections above and below the in the opposite direction take place Often, the recoil force that is caused by explosion venting is not included in the design strength of the supporting structure. this section of the riser duct also has the tendency to accelerate, but the violence of his scenario will be considerably less than in the scenario in which the initial explosion Reason: The relatively low explosion pressure in the rectangular (weak) DC construction, about which more can be read further down. and the separator outlet have to be pressure that come from below. This means that their geometry will not be optimal for the opposite (downward) direction. With the lower violence that comes with front propagation occurs at all being so much lower, the mitigation that is achieved by the non-optimal geometry of the explosion vents cum diverter Here the description of needs that need to be taken-into account in case of typical Downstream of (above) the points X in the illustration above the needs for protection In many coal grinding systems, the explosion vents cum diverters described above are not installed. If they are, they are often not correctly positioned and correctly designed. Without the correctly designed and installed explosion vents/diverters described above the protection of the people and the possibility of un-necessary damage is real. Unfortunately, it is normal that people believe their system to be protected when they see explosion vents in it. This belief is safety. - mill-to-DC riser duct Downstream of (above) the explosion vent cum diverter at the outlet of the VRM and respectively, the conditions under which are similar. Page 39