Class1 Div2 protection for Nema 4 and Nema 4X environmental protection electrical enclosures used in hazardous conditions
As a systems integrator, it is important that you understand the proper environmental ratings and Enhanced Safety Protection ratings before specifying and ordering your electrical enclosure for use in hazardous conditions. People's safety depends on it. Let Nema Enclosures Mfg help you with your Class I, Div. II or ATEX/IECEx e.
To clarify, Nema Enclosures Manufacture does NOT offer Nema 7 or Explosion Proof enclosures. In an environment where hazardous gases or dusts are always present, a Class 1, Division 1 approval is required in North America and an EX d approval for the rest of the world. Unfortunately, this is not something we manufacture. Explosion-proof enclosures are typically made from cast aluminum and then machined to meet requirements to contain a potential explosion.
We at Nema CabinetsBuild eco-friendly control cabinets exactly to your specifications.
If your electrical cabinet is used in a hazardous location, it is important that flammable substances such as gases, dust or metals do not enter and come into contact with the electrical components inside. In this case, the combustible component inside the box could catch fire or, even worse, explode, further endangering the environment and people. That means security issues, downtime, potential lawsuits, and additional costs.
It is a simple process to specify a safety rated electrical enclosure for use in hazardous locations. Here are the basic steps:
- Determine NEMA Environmental Rating
- Discover NEC's explosion protection rating
- If necessary, determine the type of flushing and pressurization.
- Specify panel type with necessary modifications that meet all of the above criteria
We are occasionally asked to certify an electrical enclosure for use in a specific explosion protection application. Our answer to this is a simple "NO GO" because we are only contributing a part (albeit a critical part) of the entire process of designing and manufacturing a Nema 4 or 4X certified electrical enclosure suitable for use in a class application. dangerous. 1 Div2 is suitable. As we do not know the exact hazardous conditions under which the enclosure will operate, we can only certify the enclosure to the NEMA environmental rating and not the NEC explosion protection rating for the performance of its contents and systems in a hazardous environment.
Nema Enclosures Environmentally Certified NEMA Type 4 and NEMA Type 4X Electrical Enclosures
At NEMA Enclosures, our knowledge and experience in NEMA certified enclosures is so extensive that it's on our behalf. The National Electrical Manufacturers Association (NEMA) uses a standard rating system that defines the types of environments in which an electrical enclosure can be used and generally indicates the ability of a solid enclosure to withstand specific environmental conditions.
We recommend that electrical enclosures meet or exceed NEMA Type 4 or Type 4X ratings for use in Class 1, Div2 hazardous locations when used with appropriate purge systems.
NEMA Type 4 enclosures are designed for indoor and outdoor use primarily to provide some protection against windblown dust and rain, water spray, water jets, and external ice damage.
NEMA Type 4X enclosures are designed for indoor and outdoor use primarily to provide some protection against corrosion, dust and rain, spray and jet water; and damage from external ice.
See our NEMA rating chart belowhttp://www.nemaenclosures.com/media/pdf/NE-NEMA-vs-UL-012314.pdffor complete environmental information about electrical enclosures.
Explosion protection rating system for hazardous locations
The National Electrical Code (NEC) defines hazardous locations as areas where fire or explosion conditions may exist due to the presence of flammable gases or vapors, flammable liquids, combustible dusts, or flammable fibers or missiles in amounts or concentrations sufficient to cause a potential present a risk of explosion.
In North America, a class/division system of electrical codes and standards is used as the basis for classifying hazardous locations. Hazardous areas are divided into three classes and two divisions because the hazards and methods of protecting electrical equipment from these hazards are different for different materials. Classes are separated according to the nature of the hazard and the explosive properties of the material. Classifications are based on the occurrence or risk of fire or explosion presented by the material. Classes, or types of materials, are divided into divisions based on the risk of fire or explosion presented by the material.
Class I locations are those where flammable "gases or vapours" are or may be present in the air in quantities sufficient to produce flammable or explosive mixtures. The terms gases or vapors distinguish between substances that are in a gaseous state under normal atmospheric conditions, such as hydrogen or methane, and a vapor that evaporates from a liquid, such as gasoline, under normal atmospheric conditions.
Classification of Class I locations into "divisions" is based on the likelihood that an explosive gas atmosphere could be present at a location. The frequency of occurrence determines the degree of danger of a location, that is, the longer the material is present, the greater the risk. See diagram below.
Class I locations are divided into groups based on the explosive properties of the materials present, as shown in the following table.
Nema Enclosures manufactures enclosures suitable for use inClass 1 Division II environments when used in conjunction with a purge system appropriate for the gases present and components within the enclosure
At Nema Enclosures, we build electrical enclosures that are Class 1, Division II rated, meaning they can be used in areas where hazardous materials are present only under abnormal conditions (less than 10% of the time). A broken pipeline or leak in a refinery would be considered an abnormal condition. Another abnormal condition would be if an arc/spark device is present and operating in normal mode, such as: B. a contractor mechanic or engine starter. However, we cannot offer third-party certification for the cases we do. Our certification ends with the environmental classification and not with the hazard classification.
Design and construction of electrical enclosure protection for hazardous areas
There are several ways to protect electrical equipment from explosion when used in a flammable gas situation or in the presence of combustible dust or flammable fibers.
For an explosion to occur, three elements must be present: fuel, oxygen, and a source of heat or ignition. Fuel and oxygen must be in the correct mixture: too little fuel (lean mixture) or too much fuel (rich mixture) cannot ignite.
All methods of protection address the fire triangle in some way, either by containing an internal explosion or by removing one or more of the components necessary for an explosion to occur.
Image courtesy of Wikipedia
We recommend flushing and pressurizing your electrical cabinet.
Purging and pressurizing prevents ambient atmosphere from entering an electrical enclosure by maintaining a positive pressure in the enclosure. It does this by using clean air or inert gas to keep the enclosure at a higher pressure than the surrounding atmosphere. In this case, potentially hazardous (explosive) gases could not enter the enclosure due to the seal provided by the gasket and the pressure managed and monitored by the purge control system. To access built-in cabinets, the electrical systems that are part of the cabinet must normally be turned off (via a main circuit breaker). This is done through a blocking system that is part of the download. Typically, the purge system requires a certain amount of air changes after shutdown to ensure no hazardous gas is in the enclosure after sealing. The purge system requires "instrument grade" air from a source (usually a compressor) where there is no risk of hazardous gases being present. The result is that the electrical equipment inside the enclosure is securely connected to a system that circulates clean air inside the unit to remove explosive gases prior to launch.
There are different types of pressurization to suit specific conditions in hazardous areas. The National Fire Protection Association (NFPA) and Instrument Society of America (ISA) define pressurization "types" based on the divisional classification of a hazardous area and the electrical ratings of the protected equipment. General purpose and Division 2 electrical equipment require different protections depending on location.
- Type "X" - Protects general purpose equipment in Division 1 areas - This system reduces the classification within Division 1 protected facilities to non-hazardous. It is necessary to automatically control the power supply of all protected devices.
- Type "Y" - Protects Division 2 rated equipment in Division 1 areas - This system reduces the Division 1 rating to Division 2 inside protected enclosures. All protected equipment must be Division 2 rated. No breakouts require flow control, but visual and/or audible alarms must be triggered if pressure loss occurs.
- Type "Z" - Protects general purpose equipment in Division 2 areas - This system reduces the classification within Division 2 protected facilities to non-classified. Automatic stops of the capacity control are not necessary, but optical and/or acoustic alarms must be activated in case of loss of pressure.
Another safety issue is managing the temperature rise in electrical cabinets.
However, the electrical components inside the case cannot generate enough heat during normal operation to cause an explosion; They may be at risk of heat and could cause an explosion due to an excessively hot electrical cabinet surface. Research shows that for every 18°F (10°C) above normal ambient temperature, 72-75°F (22-24°C) inside the enclosure; the reliability of electronic components is halved. Therefore, it is important to maintain a manageable temperature through proper ventilation and cooling within the enclosure.
Adaptation of an electrical cabinet for safe use in Class 1, Div2 hazardous conditions
We produce a wide range of control panels for use in hazardous areas, which can be customized for various protection methods. Remember that our certification ends with the environmental qualification (4 or 4X in this case) of the case. Final responsibility for electrical enclosure that meets all NEMA Class 1 Div2 environmental hazard rating requirements rests with the system integrator.
With our extensive manufacturing capabilities and access to quality material, our facilities allow us to manufacture custom products to your exact safety and qualification specifications using the correct:
- through the holes
- folding panels
- the door remains
- gland plates
- front bag
- drip protection
- Additional ground screws
- mechanical interlocks
- timer settings
We've only scratched the surface here, giving you a high-level overview of how to specify an electrical enclosure for use in hazardous locations. Keep an eye out for upcoming blog posts for more detailed information on this topic. Speak with one of our project managers as you develop your case. They have the experience and knowledge to help you select the right electrical system for your specific application.
Knowing the proper safety and environmental ratings and protection option for an electrical enclosure and its contents is a safety necessity when an enclosure is used in hazardous conditions. Keep this in mind for your next order. By taking this essential precaution, your electrical equipment and the people who work around you will be safer.