“Static pressurization”, a new technique for the protection of portable areas and mobile equipment in hazardous areas

The second edition of EN 50016 ("Pressurized Enclosure") to be published in 1994, will introduce the new technique of "static pressurization" to the range of "Ex" "types of protection" already available to the user and manufacturer. Originally a French proposal, the simple principle specifies a pressurized enclosure which is so leak tight that it will remain pressurized even after the supply has been disconnected. The apparatus may then be taken and used in a Zone 1 or 2 hazardous area without the need for trailing pipes or a constant supply of protective gas. The author describes the technique and relates his practical experience in manufacturing equipment using the requirements of the draft standard. Seven sets of the equipment were put into service at an EC Pharmaceutical plant during the summer of 1993 and have been in satisfactory use ever since