Of all the protection methods available for the installation of electrical or electronic equipment in hazardous locations, purge and pressurization has proven to be a reliable, cost-effective, and easy-to-implement method.
The need to place general-purpose equipment in hazardous (classified) locations is not new, yet in the last three decades the need has intensified dramatically. This is primarily due to the following reasons:
- Process control, measuring, and recording equipment that was once primarily pneumatic is now primarily general-purpose electronic equipment.
- Motors and switchgears now use electronic accessories to satisfy the needs for position, speed or process control, and energy efficiency. The use of these accessories often renders the equipment unsuitable for use in hazardous locations.
- Newly developed equipment, such as robotic manipulators, CNCs, batch weigh/count and filling systems, analyzers, programmable controllers, and visualization systems are rapidly becoming more prevalent in the industrial work environment.
While the demand for these new devices continues to grow, most of them cannot be economically installed in a hazardous location by using explosion-proof enclosures or intrinsic safety barriers alone. Most modern electronic equipment is expensive and delicate. For this reason, it requires environmental protection that cannot be provided by explosion-proof enclosures or intrinsic safety barriers.
When deciding how you want to protect your process, it is important that you have an accurate guide that leads to the most effective method for your application. When utilizing purge and pressurization systems, some of the things you need to know are:
- Area classification—Gas, Dust, Division 1 or Division 2, a particular Zone?
- The often confused or overlooked gas group and temperature class.
- Equipment ratings inside the enclosure.—is there a containment system within the enclosure that houses a hazardous gas or liquid, for instance a gas analyzer?
- Enclosure type and any specifics regarding doors, windows, and any accessories.
- Power requirement to the equipment inside the enclosure.
It is important that the guide you use is accurate and precise. The defining document is NFPA 496. You can read that and interpret the spirit of the NFPA document, or you can talk to experts in purge and pressurization systems.
A great starting place is our “Interesting Facts About Purge and Pressurization” eBook. It can help you identify pitfalls in your process as well as help with pros and cons of different protection methods and things to consider when building your purged enclosure. The eBook simplifies each step in choosing the right system for your application.