Pepperl+Fuchs Blog

Could Hazardous Gas Be Trapped Inside My Industrial Cabinet?

Posted by Zach Lohr on Thu, Jan 24, 2013

Q. We have an industrial cabinet (1.2 m x 0.8 m x 2 m) that is segregated into two halves with a door on the front and back. We want to properly configure a Type X purge system for this enclosure. Air has the ability to freely flow between the two compartments. Our concern is related to this segregation/separation of the two compartments. We believe there might still be hazardous gas trapped inside after the purging process is complete.

Hazardous gas in industrial cabinet

To eliminate this problem, we are thinking of splitting the air tubing and routing these tubes to each compartment. We believe this method ensures adequate air is delivered to each compartment. Given this scenario, is it necessary to install two vents, one for each compartment to ensure proper purging? Are there any other options?

A. You have definitely thought through some of the concerns associated with the enclosure configuration you are trying to solve. In the end, the key is to ensure an adequate amount of clean air is exchanged within the compartments and that the individual components within the compartments are also purged. Always remember that it is equally important to verify the individual items mounted inside the industrial cabinet are purged with clean air. Often, purging is possible only with modifications to the item to make sure air is delivered to internal cavities and voids.

Going back to the original question of the separate compartments, there are two methods for properly purging an enclosure such as this:

  1. You could treat these enclosures as a “series” application. Meaning, you would purge the two enclosures from smallest to largest. Think of it like this—the purge controller is installed on the smaller enclosure with the vent being installed on the largest. This setup allows air to be fed from the first enclosure (smaller) into the second enclosure (larger) with the clean air exiting out the vent. This way, the small enclosure will be properly purged. And because the enclosure reference pressure is being monitored from the vent mounted on the larger enclosure, you can ensure a proper flow of air through the larger enclosure.
  2. You could treat the entire enclosure as two separate, smaller enclosures being fed with two separate air tubes as described above in the initial question. However, you would need to block the interconnection between the two enclosures so they are completely separated. In this case, you would use two separate vents (EPV-6000-AA-01 and EPV-6000-AA-02), one on each enclosure. Additionally, the Type X purge controller (6000 Series) would need to be programmed in as “Least Flow Mode.” This setting guarantees the purge time is properly calculated by the controller and the hazardous gases are thoroughly purged from each enclosure.
Questions about Purge Systems? Get the Engineer's Guide

Topics: Purge/ Pressurization Systems, Ask an Expert, Hazardous Area Enclosures/ Equipment

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