Pressurised enclosures are protected by a slight overpressure inside them. This completely prevents the ingress and ignition of potentially flammable atmospheres. In other words, Ex p enclosures provide a safe system with fewer material expenditures and less engineering effort.
By atmospherically isolating the equipment, the pressurised enclosure method according to the Ex p type of protection takes a different approach to pressurised enclosures according to Ex d. In the latter, explosions inside the panels are essentially possible and permissible; an event of this nature does, of course, require all installed devices to be fully replaced. To prevent this situation from arising in the first place, pressurised enclosures in accordance with the Ex p type of protection use compressed air or pressurised inert gases to prevent an explosive atmosphere from entering the inside of the panels.
Depending on the application, there are three possible ways to maintain the overpressure. For smaller installation volumes, hermetically sealed enclosures with a static overpressure, which require no air or gas supply, are recommended. For the other variants, either a controlled supply of compressed air or gas can be used to evenly compensate for leakage losses, or continuous purging with compressed air can be used – this is the simplest solution in terms of control technology. The advantages of using the pressurised enclosure method for control panels or boxes according to the Ex p type of protection are clear:
- By ensuring that the atmosphere in the installation space is non-explosive, standard industry technology can be used throughout.
- Since the use of specially protected assemblies is no longer necessary, there is predominantly no need to take any energy demand limits into account or to make particularly efficient use of the installation space.
- Cooling equipment of all kinds can be installed relatively easily using this type of ignition protection. This means that the integrated standard industry technology can be operated within its permissible temperature range despite high ambient temperatures.
- Furthermore, pressurising panels also enables even larger windows to be integrated without any issues, offering a good overview of device displays within the panels.