Hazard Area Classification

Not enough data has been provided to answer this question!

What are the hazardous materials that will be present? What are you doing with them? What type of electrical equipment will be present? Is this zone inside a building or outside? If inside, what is the ventilation system? Where in the world is this located? What code document is in force? And on and on...

A proper answer requires a proper question!

Thanks very much for the information, next I will give you a more detailed descripiton of thre process:

Our plant is a Direct Reduction Plant, located in UAE, we produce sponge iron or also called DRI (Direct Reduced Iron) which is directly fed to the EAF.

The DRP is located in an open area and consiste mainly of two areas, whcih are: Reformed Gas Generation area and Reduction Area.

In the reformer, a mixture of preconditoned natural gas and steam are passed through a nickel based catalyst, where it temeprature is increased from 550 deg C to 820 deg C, giving as result a refromed gas stream with a content of Hydrogen 75%, CO 14, CH4 3%, plus, some CO2, and Nitrogen and water. Next the reformed gas stream is cooled down in order to remove the water content. Reformer is working at a pressure of 8 kg/cm2.

Refromed Gas Reactions

CH4 + H2O → CO + 3H2

CO + H2O → CO + H2

the reformed gas is fed into the reduction area, where its temperature is increased to 930 deg C, in a NG fired heater. Next the gas enters the reactor. The reactor is a vessel with a volume on 740 m3, full pressurized at 5kg/cm2 with the reducing gas. Iron or is fed from the top and flow downwards by gravity, while the reducing gas enters in the middle of the vessel and flows upwards countercurrent to the iron ore.

Reduction Reactions

Fe2O3 + 3H2 → Fe° + 3H2O

Fe2O3 + 3CO → Fe° + 3CO2

Reactor is placed in a 90 meters height tower.

I have been checking in internet about a minimun distance from a pressurized vessel and found nothing, in all plants I worked before, while you are inside the plant it is considered a hazard area, but never heard before about miniumun distance, excuse that our contractor is taking not tu use explosion proof lighitng in the reactor tower.

I appreciate all your comments, and if there is an additional advice I will appreciate very much.

What hazardous area standards are you working to. The standards indicate how to go about zoning specific areas in a hazardous area. It is going to require a professional design by qualified personnel, and it is very important that it is done correctly.

What do you think about fluorescent lighting installed in a Chemical plant handling mainly Hydrogen, CO and Natural Gas?

Possible and commonly done , but ONLY if the lighting is rated for the zone that it is placed in.

More information is required.

When I was an emergency management volunteer, I received a copy of the Emergency Response Guidebook for hazardous materials. It had information on safe distances for staging, decontamination, etc. The link I gave says you can print out the pages for the materials you are interested in.

You might also want to check with your local emergency management agency (still called civil defense in some areas), and/or your local fire department. In some areas, the fire department has emergency management authority and responsibilities if the local government has not set up a separate agency. Either way, the fire department will be the ones responding if something breaks, blows up, or leaks out at the factory, so you definitely want to be in communication with them.

First you identify the hazard

Then you determine the risk

Risk depends upon the hazard, size of hazard, exposure conditions and time of exposure.

In the case of gases such as quotes they are all extremely hazardous & in fact in the case of hydrogen - explosive. CO is also toxic & so is double barrelled!.

All electrical fittings in the proximity should be flameproof. Other fire precautions should also be observed.

To ascertain the actual level then a explosimeter should be used - otherwise fail safe and assume a full hazard.

Not sure about the minimum distance, but it is on the order of tens of feet I believe. In a normal H2 plant, we were considered class 1 div 2 group B throughout and the lighting had to meet that classification. There are several gases that are in Group B and hydrogen is one of them.

As others have pointed out, the nature of the hazard, the material that makes it hazardous, and other factors are essential to provide even a rudimentary answer. The suggestion to contact the local first responders is an excellent one. Most Fire Departments have people (or a person) whose main job is fire prevention, and this is the sort of info they would be able to provide on a site-specific basis.

Explosion proof flourescent lights are available for any hazardous environment including Class I, Div 1 (suitable for use in areas where explosive vapors are present at all times). You purchase explosion proof lights accourding the hazard rating of each area. The price for electrical devices rated Class I, Div 1 is much higher than the price for devices rated Class I, Div 2, so doing your homework will save you thousands of dollars per area.

Your plant's electrical engineer should know the explosive hazard ratings for each area in your plant. If not, then you will need to hire a consultant to classify the areas for you.

Here is a link to a distributor of explosion proof flourescent lights:

http://www.magnalight.com/c-183-explosion-proof-fluorescent-lights.aspx

Hazard location identification:

A demarcation line shall be provided on the drawing to show the equipment in the hazardous location and the nonhazardous location.
The Class, Division, and Group of the hazardous location should be identified and sometimes even using the temperature CLASS DIVISION GROUP TEMPERATURE

ALSO – Hazardous areas in North America are classified by class, division, and group.

CLASS:
The Class defines the general nature of the hazardous material in the surrounding atmosphere.

Class I—Locations in which flammable gases or vapors are, or may be, present in the air in quantities sufficient to produce explosive or ignitable mixtures.

Class II—Locations that are hazardous because of the presence of combustible dusts.

Class III—Locations in which easily ignitable fibers or flying may be present but not likely to be in suspension in sufficient quantities to product ignitable mixtures.

DIVISION:
The Division defines the probability of hazardous material being present in an ignitable concentration in the surrounding atmosphere.

Division 1: Locations in which the probability of the atmosphere being hazardous is high due to flammable

material being present continuously, intermittently, or periodically.

Division 2: Locations that are presumed to be hazardous only in an abnormal situation.

GROUP:
The Group defines the hazardous material in the surrounding atmosphere.

The specific hazardous materials within each group and their automatic ignition temperatures can

be found in Article 500 of the NEC and in NFPA 497M. Groups A, B, C and D apply to Class I, and Groups E, F and G apply to Class II locations.

The following definitions are from the NEC.

Group A: Atmospheres containing acetylene.

Group B: Atmospheres containing hydrogen, fuel and combustible process gases containing more

than 30 percent hydrogen by volume, or gases or vapors of equivalent hazard such as butadiene, ethylene oxide, propylene oxide, and acrolein.

Group C: Atmospheres such as ethyl ether, ethylene, or gases or vapors of equivalent hazard.

Group D: Atmospheres such as acetone, ammonia, benzene, butane, cyclopropane, ethanol, gasoline,
hex naphtha, propane, or gases or vapors of equivalent hazard.

Group E: Atmospheres containing combustible metal dusts, including aluminum, magnesium, and their commercial alloy, or other combustible dusts whose particle size, abrasiveness, and conductivity present similar hazards in the use of electrical equipment.

Group F: Atmospheres containing combustible carbonaceous dusts, including carbon black, charcoal, coal,

or dusts that have been sensitized by other materials so that they present an explosion hazard.

Group G: Atmospheres containing combustible dusts not included in Group E or F, including flour, grain,

wood, plastic, and chemicals.

TEMPERATURE CODE:

A mixture of hazardous gases and air may be ignited by coming into contact with a hot surface. The conditions under which a hot surface will ignite a gas depend on surface area, temperature,

and the concentration of the gas.

The approval agencies test and establish maximum temperature ratings for the different equipment submitted for approval. Equipment that has been tested receives a temperature code that indicates the maximum surface temperature attained by the equipment. The following is a list of the different

temperature codes:

North American Temperature Codes

TEMPERATURE CODE MAXIMUM SURFACE TEMPERATURE

C F

T1 450 842

T2 300 572

T2A 280 536

T2B 260 500

T2C 230 446

T2D 215 419

T3 200 392

T3A 180 356

T3B 165 329

T3C 160 320

T4 135 275

T4A 120 248

T5 100 212

T6 85 185

The NEC states that any equipment that does not exceed a maximum surfacetemperature of 100 _C (212 _F) [based on 40 _C (104 _F) ambienttemperature] is not required to be marked with the temperature code.Therefore, when a temperature code is not specified on the approved apparatus, it is assumed to be T5.

thanks

Thanks very much for the information, next I will give you a more detailed descripiton of thre process:

Our plant is a Direct Reduction Plant, located in UAE, we produce sponge iron or also called DRI (Direct Reduced Iron) which is directly fed to the EAF.

The DRP is located in an open area and consiste mainly of two areas, whcih are: Reformed Gas Generation area and Reduction Area.

In the reformer, a mixture of preconditoned natural gas and steam are passed through a nickel based catalyst, where it temeprature is increased from 550 deg C to 820 deg C, giving as result a refromed gas stream with a content of Hydrogen 75%, CO 14, CH4 3%, plus, some CO2, and Nitrogen and water. Next the reformed gas stream is cooled down in order to remove the water content. Reformer is working at a pressure of 8 kg/cm2.

Refromed Gas Reactions

CH4 + H2O → CO + 3H2

CO + H2O → CO + H2

the reformed gas is fed into the reduction area, where its temperature is increased to 930 deg C, in a NG fired heater. Next the gas enters the reactor. The reactor is a vessel with a volume on 740 m3, full pressurized at 5kg/cm2 with the reducing gas. Iron or is fed from the top and flow downwards by gravity, while the reducing gas enters in the middle of the vessel and flows upwards countercurrent to the iron ore.

Reduction Reactions

Fe2O3 + 3H2 → Fe° + 3H2O

Fe2O3 + 3CO → Fe° + 3CO2

Reactor is placed in a 90 meters height tower.

I have been checking in internet about a minimun distance from a pressurized vessel and found nothing, in all plants I worked before, while you are inside the plant it is considered a hazard area, but never heard before about miniumun distance, excuse that our contractor is taking not tu use explosion proof lighitng in the reactor tower.

I appreciate all your comments, and if there is an additional advice I will appreciate very much.

The only way to settle this is to use an explosimeter and establish where you are in relation to the explosion level and find out at what distance you are above the UEL. Generally speaking exposed area are not a problem but better safe than sorry.

That's right - nothing's more useful than the facts in a case like this!

There is not such a thing as minimum safe distance from the hazardous area. Refer to your national electrical code (NEC in USA-CEC in Canada) for rules governing hazardous area classification. This is a very specialized topic and can not be dealt with online.

Hydrogen and natural gas are extremely explosive if dispersed around any electrical equipment, including fluorescent lights. You must talk to a professional engineer or local electrical inspector to help you IMMEDIATELY!