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Hazardous Area Electrical Protection


Process and plant considerations will often require the installation of electrical systems and instruments in hazardous atmospheres that pose the potential danger for electrical ignition, resulting in fire or explosion. This concern is particularly common in chemical manufacturing, oil and gas refineries, oilfield equipment and services, and other industries where combustible liquids, gases, or vapors are found. Neal Systems has 25+ years of experience helping plants choose a safe and reliable electrical protection solution for their signals, displays, and panels in hazardous areas.

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See our Top FAQs for Hazardous Area Electrical Protection

Click below to see our Hazardous Area Electrical Protection solutions for your application need:

ANNOUNCEMENTS

Intrinsic Safety Protection

MTL products are used in all types of hazardous locations, from offshore oil and gas platforms, power production plants, and petrochemical installations to pharmaceuticals, telecommunications, and other manufacturing plants. MTL is a recognized world leader in fieldbus power systems and wiring components, intrinsic safety interfaces, and surge protection techniques as well as being a leading authority in industrial Ethernet and HMI / visualization for hazardous locations.

INTRINSIC SAFETY BARRIERS / ISOLATORS

MTL’s barriers passively prevent dangerous electrical signals through the use of a Zener diode to divert excess electrical energy to the ground. Isolators perform a similar function with simplified installation and elimination of ground fluctuation problems.


ALARM BEACONS AND HORNS

MTL offers a range of notification products to keep workers in hazardous areas informed quickly and clearly of any potential hazard. The range includes sounders, beacons, LED clusters, and alarm displays, all certified for use in potentially hazardous areas.

Purge Gas Protection

Purge and pressurization enables you to use any electrical equipment inside an enclosure in a hazardous location. Expo Technologies’ purge systems get your equipment up and running with comparatively quick installation, ready access, and easy maintenance.

Expo

Click here for Expo’s handy guide on hazardous location standards.

PURGE SYSTEMS

Positive pressure is used to prevent a hazardous situation from occurring within electrical component enclosures. Purge systems are a cost effective and practical solution for hazardous area electrical components in most industrial applications.

SmartPurge II

PRESSURIZED ENCLOSURES

Expo offers custom designed pressurized enclosures for classified hazardous areas or general increased safety.

pressurized enclosures

DUST PROTECTION

Purge systems are available for classified hazardous areas involving combustible airborne particulates.

dust protection

HAZARDOUS AREA CERTIFICATION

EXPO can provide assistance in assessment of panels in order to guarantee certification, verification and testing of equipment to ensure conformity, validation to an expected certification body’s testing, and other engineering services.

Top FAQs

Q: How do I determine my area classification?
Summary of Class I, II, III Hazardous Locations
CLASSES GROUPS DIVISIONS
1 2
I Gases, vapors, and liquids
(Art. 501)
A: Acetylene

B: Hydrogen, etc.

C: Ether, etc.

D: Hydrocarbons, fuels, solvents, etc.
Normally explosive and hazardous Not normally present in an explosive concentration (but may accidentally exist)
II Dusts
(Art. 502)
E: Metal dusts (conductive,* and explosive)

F: Carbon dusts (some are conductive,* and all are explosive)

G: Flour, starch, grain, combustible plastic or chemical dust (explosive)
Ignitable quantities of dust normally are or may be in suspension, or conductive dust may be present Dust not normally suspended in an ignitable concentration (but may accidentally exist). Dust layers are present.
III Fibers and flyings
(Art. 503)
Textiles, wood-working, etc. (easily ignitable, but not likely to be explosive) Handled or used in manufacturing Stored or handled in storage (exclusive of manufacturing)
Q: What are the benefits and drawbacks of purge protection?
Purge protection does not require a special enclosure as normally a standard industrial enclosure will work. This protection method also addresses possible internal releases of flammable gas, vapor, or liquid. This is important for analyzers and other equipment that have a flammable liquid or gas pass through them. The only downside is that it requires a supply of protective gas, typically air, to purge the enclosure and keep it pressurized.
Q: What are the benefits and drawbacks of intrinsically safe protection?
Intrinsic safety relies on the equipment supplies being of low voltage and power and suitable for electronic devices. The operating current of the circuitry should be low enough not to be affected by series resistance, which may be required to limit energy. The circuitry should contain low values of inductance and capacitance. Supply values exceeding 30V and 1.3W are possible but will be increasingly more difficult to certify. A detailed analysis of the circuit design will likely be necessary, possibly revealing a need to modify the circuit design in order to obtain certification.
The strength and shape of the enclosure is not as important as full control and knowledge of the circuit design.
Q: Where can I learn about the electrical code definitions and capabilities for the various hazardous area electrical protection methods?

The National Electrical Manufacturers Association (NEMA) has developed a rating system to identify the ability of a device or system to afford protection from the outside environment. Factory Mutual (FM) Global and Underwriters Laboratories (UL) have adopted the NEMA Type designations. These rating systems provide information that assists users in making informed product choices in selecting the proper enclosures for hazardous locations. Check these websites:

To see the scope of FM Global’s hazardous location and protection equipment testing and approvals, go here.

FM Global’s Approval Guide contains tens of thousands of products and services tested and FM approved, as well as essential engineering data and technical information. You must first register for access here.

Visit this site for the scope and purchasing of UL 698A, Industrial Control Panels Relating to Hazardous (Classified) Locations.

View this PDF for NEMA Enclosure Types.

For more detailed and complete information, see NEMA Standards Publication 250-2008, Enclosures for Electrical Equipment (100 Volts Maximum).

Q: What are the differences between continuous flow purge and leakage compensation purge methods?
A continuous flow system will continuously flow air through the control panel. The flow rate depends on which orifice plate you choose. Applications are small enclosures and analyzers. A leakage compensation system first purges the enclosure. It then shuts itself down and just tops off for any leakages the enclosure may have. It will maintain a minimum pressure in the enclosure. Continuous flow is more economical to purchase but requires continuous consumption of the purge medium. Leakage compensation is more costly up front, but these higher costs can be quickly recovered through purge medium savings.
Q: What do the X,Y, and Z purge methods mean?
Purging is used extensively today for electrical / instrument enclosures. A purge and pressurized enclosure allows easy maintenance of the internal equipment, and there is no limit to the power that can be supplied. The purge medium, usually compressed air, is used to keep the enclosure at a higher pressure than the outside of the enclosure, preventing the entry of explosive gas. After closing the enclosure, there must be a purging to dilute any gas that may be present within the enclosure before applying the power, hence the term, “purge and pressurize.” There are three types of purge: X, Y, and Z.
Type X Purge
Type X reduces the area classification within the purged enclosure from Class I, Division 1, to non-classified where general purpose equipment can be fitted within the enclosure. The enclosure must be purged at least four full volume changes, timed automatically before the electrical interlock supplies power to the general purpose equipment. On loss of pressure the power must be disconnected except under special conditions.
Type Y Purge
Type Y purge reduces the area classification within the purged enclosure from a Class I, Division 1, to Class I, Division 2, where nonincendive (Division 2) equipment can be fitted within the enclosure. The requirements for the operation of the Y Purge are the same as the Z Purge. The difference is the application and contents of the purged enclosure.
Type Z Purge
Type Z purge reduces the area classification within the purged enclosure from Class I, Division 2, to non-classified where general purpose equipment can be fitted within the enclosure. The enclosure must be purged at least four full volume changes before the electrical supply can be applied to the general purpose equipment. This is a manual function completed by the plant operator. On loss of pressure, there is no need to disconnect the electrical supply if the Division 2 area is known to be nonhazardous, but there must be a visual or audible alarm.
Q: Which type of hazardous area protection is the most cost effective?
Cost effectiveness depends on the area classification and the availability of compressed air. Y or Z purge is most economical when these methods meet the requirement. Leakage compensation will also achieve cost savings in the long term by saving on the purge medium.
Q: Do barriers or isolators alone make my system safe?
No, the apparatus to be used in the hazardous zone must either be an intrinsically safe apparatus or a simple apparatus.
Q: What is a simple apparatus?
Any device which does not generate or store more than 1.5V, 100mA, and 25mW, including inductance and capacitance.