ON THE EFFECT OF VENTING LARGE VESSELS WITH MASS INERT PANELS

A numerical analysis indicated that in some situations venting by rath er heavy venting devices such as panels or explosion doors will lead t o substantial increase of the peak pressure in the considered enclosur e compared to venting with burst disks or membranes of negligible mass . Vent sizing guidelines like the VDI 3673 consider a vent capability of explosion doors which has to be tested prior to their use. To study the effect of mass inertia of explosion doors or panels moved by tran slation, a set of experiments was carried out in a 50 m(3) silo with a height to diameter ratio H/D = 4. The experiments showed, however, pa rtially unexpected results. The peak pressure p(red) increased when ch anging membranes with inert devices (turbulent mixtures). When the mas s of the devices was varied, no variation of p(red) was detected, thou gh it could be demonstrated that the time necessary for full opening o f the vent increased with higher mass. When venting with inert devices (quiescent gas mixtures at the instant of ignition), there are even s ituations which led to lower explosion pressures compared with membran e venting. Panels moved by translation are faster than explosion doors , but the flow through the vent seems to be less disturbed during vent ing in the case of explosion doors. The effect of pressure generation and flame front propagation during a vented explosion is dominated by conditions other than the mass of the devices, especially with the tur bulence level of the mixture at the instant of ignition. (C) 1998 Else vier Science Ltd. All rights reserved.