Safety Zone Magazine January 2018 - Page 28

will open slowly and less efficiently, and ultimately the pressure in the equipment will be higher than expect- ed which is a safety concern,” explains Brazier. In 1990, BS&B Systems patented the first single-sec- tion explosion vent, comprised of a solitary sheet of stainless steel in a domed configuration. Perforations around the perimeter to aid opening at the desired low set pressure are protected with gasket materials. The single-section domed design produces a vent that is more robust, lighter in weight and also largely eliminates the potential for build-up or contamination. In 2010, the company improved on the design by sure Safety Management provide a flameless system designed with the vent installed inside the flame arrestor. In doing so, the heavier flame arrestor is mechanically mounted directly to the equipment, reducing the weight load transmitted through the more sensitive vent and eliminating the risk of damag- ing the vent. It also serves the dual purpose of allowing for easy inspection of the vent and arrestor while installed. NFPA Standards require periodic inspection of explo- sion safety equipment. Suppression Equipment altering the shape of the dome to a unique compound For processes where an explosion would ideally be Despite its popularity, explosion vents will not work Explosion suppression equipment detects a dust geometry that delivers even greater rigidity for high vacuum or vibration applications. for every application. With venting, the combustion process will release a large ball of flame into the atmosphere that might be 10 times the size of the protected equipment for a few milliseconds. While this might be an acceptable consequence for equipment that is outdoors at a remote location, for applications within a plant compound or inside a building it could endanger personnel or equipment, and even lead to a secondary explosion external to the protected equipment. In cases where a flameball must be avoided, flame arrestors can be deployed. These devices are designed to absorb the pressure wave, flame and at least some of the dust that would normally be ejected by a vented explosion. The 3 dimensional flame arrestors applied down- stream of explosion vents are heavy and when in- stalled directly on top of a vent damage can result. To address this concern, companies like BS&B Pres- 26 Safety Zone Magazine • January ‘18 prevented altogether, suppression systems are the best alternative. explosion in the first milliseconds of the event and then signals extinguishing modules to release a flame quenching medium into the process equipment. This effectively stops the explosion in its infancy and only low pressure is produced that is safe for the protected equipment. “Suppression can be preferable for indoor equipment, simply because the explosion doesn’t really propagate; it starts, but it never evolves into a full blown event,” says Brazier. For a 24/7 process, a suppression system can be very desirable, because the speed of clean up and refit allows for a quick return to production. “If you use venting or flameless venting, you are allowing the explosion to fully develop in process equipment, so you have cleanup to deal with, you may have fire-related damages and other consequences that take time to get the process back into operation,” adds Brazier.