Advances in Explosion Protection: How Advanced Solutions Open New Doors

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Venting Solutions – An Easy Way for Explosion Control

The second protection option is venting, that is, the control of pressure by release of the deflagration through an opening of the appropriate size. The closure, vent panel, door, etc. opens at pressure pre-determined to prevent damage to the enclosure. Venting may well be the first intentional form of explosion protection. Some of the original closures were made of metal sheets, plastic sheets, composites, etc. While able to release the deflagration pressure, they all suffered in not having predictable release pressures (P_stat), good quality control, vacuum resistance, pressure cycle tolerance, low mass, etc. All of these limitations work against being able to accurately predict final enclosure pressure (P_red).

Many also reduced venting efficiency requiring extra area to achieve the required reduced pressure. Now, manufactured vent closures are subject to extensive quality control and have predictable performance. Single panel closures have less weight which improves efficiency; new designs allow high vacuum operating conditions, higher temperature, cycling and pulsing, as well as meet hygienic requirements. For example the prescriptive sections of NFPA 68-2007 include a number of significant advances in the vent area calculation.

Flameless Venting – The Best of both Worlds?

The most notable advance in venting in recent years has been flameless venting. It is well recognized and stipulated in relevant industry standards that indoor venting is discouraged. At the same time, due largely to the new awareness of dust explosion hazards, many existing processes are being reviewed for protection. Many of these are located within buildings which restricts the use of conventional venting. Flameless venting becomes an attractive alternative to suppression. Flameless venting merges the well established technology of venting with flame arresting and controlled particle retention.

The fire ball exiting through the vent opening is required to pass through flame arresting elements and particle retention mesh. The end result is the prevention of flame release and the retention of particles at the expense of efficiency. By using additional vent area, based on large scale testing and agency approvals, indoor venting is a proven, safe alternative. Fig. 5 illustrates the difference between open venting and flameless venting.

While venting is a reliable, cost-effective method of preventing damage from pressure, it does not affect flame. One consequence can be a residual fire in the dust collector, silo, etc. On page 9, present several approaches to this problem ....

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