Cement Manufacturers Association (CMA)

Page 46 Good explosion door designs therefore will comprise spring-loaded inwardly opening equation for the dimensioning of vacuum breakers. The need for explosion isolation in the in-feed of the silo when the in-feed is by means of a mechanical conveying system has already been discussed. See DC-to-pump pre-hopper transfer or DC-to-PF silo transfer. Should the in-feed be by means of pneumatic conveying (usually positive pressure), no cyclone should be used. Silo and cyclone then would constitute interconnected vessels, which would make constructional explosion protection complicated. Should a cyclone have been installed, the explosion protection of the silo usually is incorrect. The fan has to have the necessary EPSR. EPSR for unmitigated explosion pressure or to be equipped with explosion venting Here explosion Isolation has to be in place. PF silo This is a complicated way to install the PF silo’s explosion isolation, explosion de-coupling, CO monitoring and a connection with the emergency explosion vents and EPSR. same EPSR as the PF silo in which it is integrated. The explosion pressure in it is the same as the venting-mitigated explosion pressure in the silo. The main reason for negative pressure in the silo is that a part of the original air volume above the column of coal under atmospheric pressure was pressed (vented) out of the silo as the result of its heat-induced expansion. Example: The explosion pressure was mitigated by the explosion venting but still reached 1 bar g, meaning that the volume of the air above the column of coal doubled. After the vent(s) has(ve) closed, roughly 50 % of the expanded hot air will have been vented. The remaining 50 % will cool down rapidly and shrink. Ergo: Negative pressure in the silo, for which the silo needs to be Here explosion de-coupling has to be in place.