Purge, Pressurize, Protect: Keeping Your Plant, & Your Product, Safe
Tue, 01/27/2009 - 8:42am
In spite of the hazards associated with working with chemicals, various safety measures have resulted in lower injury and illness rates for some segments of the industry. In 2006, the chemical industry reported 2.9 cases of work-related injury or illness per 100 workers in contrast to an average of six for all manufacturing industries, according to the U.S. Department of Labor.
Per a 2002 U.S. Chemical Safety Board study, equipment maintenance was one of the most frequently reported management deficiencies. And as U.S. chemical companies turn their attention to dedicating more resources to competing in the global market, some of the most commonplace plant equipment—operator interface system enclosures, for example—are likely to be overlooked.
It can be explosive to overlook operator interface systems in areas where combustible liquids, gases or vapors exist. A component failure enclosed in an inadequately equipped or poorly maintained operator interface system can ignite arcs and sparks that cause explosions when they interact with chemical materials.
Proper operator interface system management is relatively simple, however, if you know the facts. It comes down to purging and pressurizing—and knowing your hazardous environment.
Understanding Your Hazardous Environment
Each class is further separated into divisions, which are defined by the level of hazardous substance concentration. Division I classifications apply when hazardous substances are present during normal operation. Division II classification (the most common) pertains to hazardous substances are present only during abnormal conditions, such as leaks.
The following groups further characterize the hazardous substances present in the environment. Class I substances consist of:
- Group A—acetylene.
- Group B—hydrogen.
- Group C—ethylene.
- Group D—methane.
There are three types of purge and pressurization systems:
- Type X, which reduces the enclosure area classification from Division I to a non-hazardous or general-purpose rating.
- Type Y, which reduces the enclosure area classification from Division I to II.
- Type Z, which reduces the area classification from Division II to general purpose.
While purge systems utilize an external airflow source to maintain internal pressure of the enclosure, it is typically insufficient for cooling. However, heat-pipe exchangers can cool the system by circulating cooler external air alongside the hotter interior air without intermingling. External air never enters the enclosure and is circulated by an external fan. Some times external air is supplied via a compressed-air hose, eliminating the need for a fan and possible sparking.
Cleanability is also a concern. Systems intended for chemical environments should feature the fewest possible crevices and ledges to reduce particulate accumulation and permit easy cleaning. They should also meet NEMA 4X standards, which require interior component protection from splashing water, water seepage, hose-directed water, falling water or severe exterior condensation. Ideal for washdown environments, NEMA 4X systems incorporate stainless steel construction for extra corrosion resistance, as well as doors and seals to prevent water from entering the enclosure.
Selecting The Right System
Popular operator interface design options include:
- Vertically adjustable systems to provide up to 30 in. of counterbalanced vertical repositioning with additional rotational articulation.
- Low-height console systems for improved process visibility.
- In-wall stations to fit in the confines of a shallow wall.
- On-wall stations for direct mounting via tabs or holes in the enclosure.
- Mobile systems so that you can bring the operator interface to the process, eliminating the need for multiple fixed stations.
Thanks to a variety of new operator interface system designs, engineers can choose customized solutions that are not only outfitted with UL- or FM-approved technology, but are also designed to meet their specific space requirements. Customization permits you to strategically place an easily accessible operator interface system anywhere in your environment and still meet safety requirements.
By including operator interface systems as part of your overall safety plans, you can ensure that your products, workers and future business plans remain safe—and don’t go up in smoke.
For more information, contact Bill Fleming of STRONGARM Inc. at 215.443.3400 or visit www.strongarm.com.