Explosion vents and explosion doors are often the most cost-effective solutions to mitigate combustible dust propagation. Both types of solutions are designed to effectively open at predetermined pressures, relieving pressure and deflagration.
The primary difference between the two is their reusability: explosion doors can be used indefinitely while explosion vents are one-time use. Both come with their advantages and disadvantages.
Which solution is better for the application?
Explosion Door
An Explosion Door is a hinged door mounted vertically or horizontally on the process component to be protected. The door is designed to close once the explosion has been released.
The primary benefit of explosion doors is that they don’t need to be replaced after activation
Advantages
The primary benefit of explosion doors is that they don’t need to be replaced after activation. Also, downtime is often minimal after an explosion event, as explosion doors usually close automatically.
Disadvantages- Inertia for activation
The first disadvantage of explosion doors is their dependence on inertia for activation. Generally, explosion doors have greater inertia than an explosion vent panel, reducing their efficiency. This reduced efficiency can result in the need for larger doors to achieve the same reduced pressure as a smaller, more cost-effective explosion vent.
For example, if the volume of the vessel is small, the doors may not open fast enough since their weight is not countered sufficiently by the inertia of the explosion. In this case, the explosion is not released and can damage the equipment.
The position of the doors on the vessel plays an important factor here too.
Disadvantages- Doors attached to hinges
The hinges are attached to the equipment, so all parts must be able to withstand the inertia of the door The second main disadvantage is that doors are attached to hinges. These moving parts can be damaged through use or simply by the weather. The hinges are also attached to the equipment, so all parts must be able to withstand the inertia of the door opening during an explosion.
Other disadvantages of explosion doors, and why not all explosion protection providers (like Fike) offer them, include:
- Weighing over 5 lbs. per square foot can reduce the efficiency of the much heavier explosion doors. Additional relief area must be used (increasing the costs) or the resulting reduced pressure will be greater which can also increase costs of process equipment that must now be made to withstand the higher pressure.
- Because explosion doors are hinged, a closing door may create a vacuum in the protected vessel, (resulting from cooling of the hot combustion gases) causing the vessel to collapse or implode. The poor sealing capability of explosion doors may require the use of vacuum breakers.
- Explosion doors come in limited sizes and shapes.
- Explosion doors are not suitable for all processes or materials.
- Vulnerability to natural forces (such as rust) and tampering may inhibit explosion door performance.
- Operation and opening pressure must be checked at intervals, requiring additional time and the ability to easily access the door. Explosion doors may fragment during the opening, creating a safety concern.
Explosion Vent
An explosion vent is a non-reusable safety device designed to burst at a set pressure along a specific rupture line, relieving pressure and providing a pathway for deflagration hazards to safely escape.
Vents can open with almost no inertia, so they are suitable for all sizes of vessel and all positions
Advantages
Vents can open with almost no inertia, so they are suitable for all sizes of vessel and for all positions on that vessel.
They also are free of moving parts. They are far less affected by the weather or other wear and tear found in explosion doors, and they require minimal maintenance.
Disadvantages
Vents require replacement once they have opened. However, since they are a very simple solution, replacement is easy and cost-effective, since they are cheaper to install than doors.
Explosion pressure relief can be best achieved through the use of relief devices that cannot be tampered with and which offer the highest venting efficiency. Due to the inherent weight and constructional restraints, explosion doors should be selected with the necessary caution, whereas the process compatibility and ease of installation and maintenance often lead to prefer to use explosion vents.