The “NFPA 68 Explosion Protection with Deflagration Ventilation” standard, developed by the National Fire Protection Association (NFPA), describes the requirements for the design and use of vents to limit the pressures resulting from the explosion (deflagration) of dust or gases (vapors) in buildings, rooms, warehouses and equipment, and to prevent or reduce structural or mechanical damage.
This standard applies to the design, location, installation, maintenance and use of devices and systems that vent combustion gases and pressures generated by an explosion within an enclosure to minimise structural and mechanical damage.
If there are operations that generate dust or if dust processing equipment is being manufactured, especially if that dust is kept in confined spaces, it is important to understand the explosion risk. Many types of dust, from aluminum to epoxy resin to corn, can explode if the conditions are right.
Vents are one way to protect against damage that could be caused by an explosion. If a business is designing or using equipment that includes vents, it is essential to be familiar with the NFPA 68 standard.
Dust that can explode is called “combustible dust.” Although efforts are made to eliminate dust accumulations, anything that can make dust airborne, and sources of ignition, the risk is always present. Therefore, all equipment that is sensitive to dust explosions must be designed to minimize the damage caused.
The National Fire Protection Association (NFPA) has done a great deal of work on engineering methods for managing combustible dust incidents and these are included in the standard “NFPA 654-2020 Prevention of fires and dust explosions resulting from the manufacture, processing, and handling of combustible particulate solids.” This standard references the NFPA 68 standard for combustible dust environments.
Deflagration is extremely rapid combustion, but the flame front moves slower than the speed of sound. An explosion is a faster and more violent event.
The purpose of the NFPA 68 standard is to assist equipment manufacturers in incorporating vents and related devices into dust collectors, spray dryers, and other devices that have an explosion hazard. Proper vent design and location are relevant to their installation, maintenance, and use.
Some specific aspects of explosion venting that the NFPA 68 standard addresses are:
Deflector plates are used when venting horizontally. These direct a fireball upwards, away from where it could cause injury or damage.
Mass is a concern in explosion vents because the high inertia causes pressure to build up before it is released. NFPA 68 addresses the effects of panel inertia on the size of the panel required. Essentially, a slower-acting panel must be larger to provide the necessary protection.
Ventilation ducts are used to direct a fire ball out of the building. However, they should avoid bends as much as possible and have an appropriate cross-section.
Flame arrestance and particulate arrestance systems are an alternative to ventilation ducts. They may be required if equipment layout makes ventilation to the outside impractical.
Isolation devices such as valves and dampers installed in the ductwork can help prevent an explosion from spreading through the system. These are usually triggered by pressure or temperature sensors that detect an explosion.
The NFPA 68 standard requires businesses operating equipment with flame-exhaust ventilation to keep comprehensive documentation on the devices they own, as well as inspection and maintenance records.
The NFPA 68 standard was first introduced as a guideline and then became a standard. Compliance with this standard is not mandatory. However, if an explosion occurs and a business is later found to be non-compliant with the NFPA 68 standard, the company must suffer the consequences.
The details of the standard are of great importance to businesses that design and manufacture dust processing equipment. Dust collectors, spray dryers, process vessels, ducts and industrial structures all fall under this broad definition.
For users of such equipment, two points stand out:
In order to protect the business from deflation events, an authorized organization must be contacted.
Among the numerous testing, measurement, analysis and evaluation studies that our organization has carried out for businesses in various sectors, it also provides testing services defined in the “NFPA 68 Explosion Protection with Deflagration Ventilation” standard with its trained and expert staff and advanced technological equipment.
To get an appointment, to get more detailed information or to request an evaluation, you can ask us to fill in our form and reach you.
