Cement Manufacturers Association (CMA)

Monitoring of the clean air’s cleanliness is necessary to know about bag damage and to be able to do what is needed then. And that has to be done then! Most coal grinding systems have a remote-control valve in DC-to-main fan clean duct. Damper is an often-used name for this valve, but using the word damper is not very well suiting. This valve plays a role in the emergency inerting concept for the system inhibiting dissipation of CO or N into the clean air duct, where the gas would be useless. This role of the valve has to be understood well by the process controllers and the controls that would enable the valve to play its role have to be in place. - DC-to-pump pre-hopper transfer or DC-to-PF silo transfer It is normal for pump pre-hoppers to have no explosion protection. Some are, as they should be, EPSR for unmitigated explosion pressure, that is good for 9 or 10 bar g. Often pumps with a pre-hopper without EPSR can be found, which is wrong. Due to the possibility that a dust explosion is ignited in a pump pre-hopper, it is necessary pre-hopper. The maximum explosion pressure in the DC depends on the DC’s EPSR (good for a pred value) and explosion venting concept. The highest value for P red of a rectangular DC geometry designed by a serious manufacturer will be 0.4 bar g. For most DCs the value for pred will be considerably lower, if known at all. This means that the explosion isolation between the DC and the pump pre-hopper needs above and for 9 or 10 bar g from the pump pre-hopper below. Page 42