Cement Manufacturers Association (CMA)

Page 47 Often it is not understood that if the the installation constitutes interconnected and very often 3 connections that need special protection: - the silo needs at least explosion de-coupling. - into the silo needs explosion isolation. - If the fan has no EPSR, the connection between the bag chamber and the fan needs at least explosion de-coupling, since an explosion in the bag chamber is possible. needs EPSR, since the silo has explosion be connected with other equipment, which often is the case, additional explosion isolation or at least explosion de-coupling is necessary. this kind practically never are designed correctly. remote control valve that enables isolation of the silo from the atmosphere, in order to inhibit the loss of inerting gas (CO or N ). During CO or N inundation some pressure will build up. This has to be limited to a value below the value at which the explosion doors would open. For this, the needs to be controlled by a pressure transducer, which causes the valve to be open as long as a certain pressure value in the silo is exceeded. The control function shall only become active during emergency inerting. Something else that often goes wrong is negative pressure in the silo that the explosion doors’ vacuum breakers are continuously open. Very often the fan’s capacity and its power consumption needlessly are way too high. - Instrumentation and emergency explosion protection Apart from metal detectors and metal separation mechanisms on the raw coal extinguishing on top of conveyor belts is in place. Smoke detectors in belt transition point Nothing can be said against having a sprinkler system installed and keeping it on top of a raw coal conveyor belt, coal already have been dropped in a raw coal silo, meaning that something that should not go wrong has gone wrong. The silo’s CO monitoring and emergency inerting of the displaced air that has to exit the silo during in-feed. Small quantities of displaced air in case of in-feed by means of mechanical conveying. Larger quantities in case of in-feed by means of positive pressure pneumatic conveying.