Cement Manufacturers Association (CMA)

Page 45 What this means for the necessary explosion isolation in the transport connection between the DC and the PF with pump pre-hoppers with 9 or 10 bar g EPSR, the explosion isolation system in the connection with the PF silo has to be between 0.1 and 0.4 bar g from above and 2 bar g from below. Another incorrect design is given when one or more PF silos are interconnected via an air duct. See the illustration above. - Sampling Facilities Often it is overlooked that sampling facilities will be exposed to explosion pressure. In case of an explosion in the through them, and parts of them may turn facilities systems and their position in the system have to ensure safety. - PF silo or PF silos First of all, PF silos should never be installed inside a building or a partially enclosed structure. There is no need for that. A good design with good rain drainage of the roof even not from very hard rain. Since PF silos normally have constructional explosion protection in form of explosion venting installed and since the direction of the venting blast normally is upwards, the location of silos inside buildings or partially enclosed structures demands a change of direction of the venting blast that ensures or structure without causing hazards or damage. Although there are possibilities to design to safely exit, multiple possibilities to get that wrong exist. Unfortunately, things are going wrong often, as can be seen in the industry. vents for silos were for silos for coal and rupture disks or panels, explosion doors, when correctly designed and positioned, will re-close. Their venting element is a hinged lid that will fall back into its closed position by gravity Unfortunately, a multitude of wrong explosion door designs exist and numerous dangerous designs can be found in the industry. It was understood early that silos, after a venting occurrence, have to be closed again. After an explosion venting supported by the O of the ambient air Should CO or N be applied for emergency inerting, the gas should not be lost to the atmosphere. The self-re-closing explosion vents require a feature that prevents the protected silo from taking damage as result of negative pressure after the explosion venting has taken place and the vent(s) has(ve) reclosed. In case of DC-to- PF silo screw conveyor silos normally are equipped with explosion vents and designed for the resulting worst case mitigated explosion pressure P red . According to EN 14491 the highest acceptable value for pred is 2 bar g. NFPA 68 has stopped to give a limit for pred some years ago, but the limit set by EN 14491 (2 bar g) is suitable for cylindrical PF silo designs.