Venting Is Important For Explosion-Proof Dust Collectors
Many industrial production processes produce combustible and explosive dusts that need to be extracted to keep employees safe. Explosion proof dust collectors are a necessary investment to reduce risk in the workplace.
However, the closed nature of dust collectors makes them a prime location for explosions. Several factors contribute to this risk including static discharge, confined clouds of dust and ledges in the collector.
Venting
If your operations generate dust that can explode, you have to take every precaution possible to prevent an accident. Those precautions include explosion-proof equipment to handle the dust. But even with the best dust collection equipment, there’s always a risk of an incident. And that’s why venting is an important part of your safety system.
Explosion vents work by giving flames and gases a way to escape the dust collector in an explosion. When internal pressure in the device reaches a certain point, the vent opens and releases pressure and flames into a safe zone. Venting is designed to minimize damage to the dust collector and avoid employee injury. It’s one of several strategies that can be used to protect against combustible dust explosions, and NFPA 68 offers specific formulas for calculating the size of an explosion vent in a given application.
When a vent opens as a result of an explosion, the fireball it produces can be extremely hot and dangerous. It’s also likely to travel a considerable distance, especially if it occurs inside a building. A properly sized vent should mitigate the force of an explosion, but it’s important to remember that no protection system is perfect.
If a dust collector doesn’t have enough room to house an explosion vent, you can install a flameless vent. This type of vent explosion-proof dustremoval equipment works on the same principle as an explosion vent, but with a mechanical back draft damper. When the explosion wave enters, it slams into the damper which is held open by the process air pressure. This slam stops the flow of flame and allows the explosion to escape, preventing it from reaching employees or damaging the collector.
Suppression
Almost all industrial manufacturing, processing or packaging operations produce combustible and explosive dusts. The risk of these dust explosions can be significantly reduced by extracting the particles from the plant environment. However, unless the extraction system is safe it will just move the danger elsewhere. Choosing the right machine is critical and it’s important to understand your needs before you buy.
An unprotected explosion in a dust collector can send heat, flames and dangerous projectiles throughout the facility. This can seriously injure people and damage equipment and buildings. Fortunately, there are passive systems and active systems to protect the collection system from an explosion.
The most common protection method is through a suppression system for the dust collector. Explosion pressure detectors mounted on the collection vessel detect the initial pressure excursion from an incipient explosion and transmit a signal to a control panel, which initiates high rate discharge of nitrogen and suppressant. This suppressant rapidly quenches the fireball and prevents the buildup of destructive pressures within the vessel. An isolation extinguisher mounted on the inlet duct prevents flashback upstream to interconnected process equipment.
This type of system is also common for double leg bucket elevators used in grain explosion-proof dustremoval equipment handling. It combines explosion protection of the elevator head and boot section with isolation and suppression of the legs, feed and discharge points and dust extraction points.
Chemical Isolation
Many types of industrial machinery and commercial manufacturing processes create harmful combustible dust that must be extracted from the air. Putting this dust into the wrong type of air cleaning machine can cause an explosion. Explosion-proof dust collection equipment is the safest way to extract combustible and explosive dust from your shop.
Regular inspections of the dust collector, explosion venting system, duct work and safety systems are required by NFPA standards to ensure the equipment is operating correctly. These inspections must be conducted by a trained, certified and competent person, and should include removing any debris or dust build-up on the equipment and all ducting within the safety zone.
Several methods of chemical isolation are available to prevent a deflagration from propagating from one piece of equipment into interconnected equipment, ducting or other connections. Explosion isolation systems inject an agent into ducting or piping to interrupt the transport of the burning material and quench the flame front. Typical agents used in chemical isolation include nitrogen, inert gas, sodium bicarbonate and water.
Besides isolation, other control measures to prevent combustible dust explosions include house-keeping, improved equipment design, venting systems that comply with NFPA standards and central vacuum system designs that have attachments made of static dissipative materials. Also, it is important to follow all NFPA and ATEX standards for electrical motors and use explosion-proof electric motors when handling hazardous dusts.
Flameless Vent
Venting is an important part of explosion protection for dust collectors. It allows the pressure wave from an explosion to escape – rather than destroying equipment or harming people. However, this must be done safely. A standard way of allowing this to happen is to connect the vent to a duct that takes it outside. This method also needs to be designed and tested to ensure that the duct does not become a free projectile in an explosion.
Another option for safely escaping the pressure wave from an explosion is to install a flame quench, also known as a flame arrestor. This is a large device that covers the flame vent to stop the spread of flames, preventing the fireball from damaging equipment. However, this type of device requires maintenance to ensure that the stainless steel grid and filters do not get clogged over time.
REMBE is the inventor of flameless venting and offers three different variations of the device, including the Q-Rohr, Q-Box and the Q-Ball. Each variation has a unique design that helps it handle various types of applications and products. The Q-Rohr is able to handle explosions with Kst values up to 400 bar x m/s and can be used on equipment such as dust collection, silos, conveyors and storage vessels. The Q-Box and the Q-Ball are ideal for less complex processes or products that require a lower explosion Kst value.