SAFETY IN THE PLANT
RECONSIDERING
Today’s single-sheet, compound dome alternatives provide greater stability and reliability for explosion venting
such as food, grain and feed. In response to this hazard, in 1945 the USA’s National Fire Protection Association (NFPA) initiated a tentative standard, NFPA 68 titled ‘Standard on Explosion Protection by Defl agration Venting’, updated in 2007 to a Standard. It is currently in its 2018 revision, which provides specifi c direction to mitigate the risk through the use of venting. Today, explosion venting is the most commonly used method of mitigating the pressure eff ects of a defl agration. Designed to open rapidly at a predetermined
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burst pressure, explosion vents allow the combustion process to escape to the atmosphere, while limiting the pressure generated inside the process equipment to calulated safe limits.
herever combustible dusts can accumulate, the risk of an explosive event is present. T is poses a considerable risk to industries
COMPOSITE VENTS
Installed VSP single piece domed vent
Vent panel with compound dome 42
www.engineerlive.com
T is type of vent is installed on dust collections, conveyors, bucket elevators, dryers/ovens, bins, and silos. For more than 50 years, traditional composite vents comprised of plastic fi lm sandwiched between two stainless steel sheets have been utilised for this purpose. However, this design approach has largely fallen out of favour in all but a few niche applications due to signifi cant disadvantages, including the risk that dust and process debris can accumulate such that it aff ects the speed and reliability of the vent opening. “Over time there can be an evolving risk with composite vents that leakage will occur, or that dust or process materials will accumulate within the layers and the vent will become very heavy and won’t function as it should,” says Geof Brazier, president of BS&B Pressure Safety Management, a manufacturer of a range of dust explosion prevention and protection technologies. T is has some facility personnel taking a closer look at more advanced single
sheet vent alternatives that weigh less and include design features that make them more durable, even in the presence of light vacuum conditions or vibration. T ese modern options also reduce installation costs while increasing service longevity.
VENT INSPECTION NFPA 68-2018 Standard on Explosion Protection by Defl agration Venting establishes requirements for the design, location, installation, maintenance, and use of devices and systems that vent the combustion gases and pressures resulting from a defl agration within an enclosure so that structural and mechanical damage is minimised. Within the standard is the requirement that installed explosion vents in service “shall be inspected” to ensure their integrity as they perform a critical safety function. However, in practice, many view explosion vents as ‘set it and forget it’ safety devices, and often fail to complete periodic inspections.
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