Photos courtesy of Rembe.
Most production processes in mills, mixed feed plants, breweries, power stations and the like start with the unloading of “raw material.” After its delivery by road or rail, the material is often poured into conveying equipment. Organizational precautions can be taken such as allowing the truck to cool down for at least 15 minutes before starting the unloading process, said Charlotte, North Carolina, U.S.-based REMBE, Inc. This substantially reduces the potential for ignition hazards from hot brakes, hot exhaust pipes or catalytic converters.
As an additional preventative measure, grounding can also offer protection against spark discharge. If movable vehicles are involved, such as trucks and rail cars, it is vital to proceed with great caution and regular staff training should be provided, REMBE said. To continue the typical scenario, the raw material is taken downstream via elevator or conveying line.
Open conveyor belts are considered to be the least hazard-prone, since the conveyed material does not typically create a dust cloud and is not in direct contact with hot surfaces – unlike chain conveyors and screw conveyors, which operate differently.
Explosion venting devices such as REMBE explosion vents or REMBE flameless venting systems will likely be necessary, depending on a number of variables, including:
• Material characteristics: fineness, moisture level, dusting propensity
• Conveying type and speed
• Interconnected plant equipment
• Ignition risk assessment
REMBE explosion vents will rupture at a defined pressure, protecting the conveyor by reducing the overpressure within it and releasing the explosion into the surrounding area. For inside installations, REMBE flameless venting systems incorporate this same explosion panel or disc, but the pressure and flame will be contained within the metal mesh body of the flameless vent. The metal mesh extinguishes flames through heat dissipation and reduces pressure/noise to negligible levels.
In addition to venting, isolation systems are mandatory to prevent explosion propagation through interconnected plant processes/equipment. The general standard is to install ATEX-approved quench valves or quick-closing valves such as the REMBE EXKOP System, passive isolation devices such as the REMBE Q-Flap, chemical barriers or rotary valves.
The situation is different with a trough auger, where the upper cross section is not filled with product. In these applications, REMBE flameless vents or chemical barriers are necessary. Chemical barriers are controlled by pressure detectors or infrared sensors, which identify flames and explosions. This triggers the release of an extinguishing agent within a few milliseconds, thus extinguishing the explosion.
Outdoors, on the other hand, it may be wiser and more cost-effective to use approved pressure venting devices such as REMBE explosion vent panels or REMBE flameless venting devices.