Modification for hazardous class

[picasa]

I am looking at a quote for a rotary screw air compressor. I find that it takes quite a bit of money for 'Modifications for hazardous class 1 division 2 group D'. Can some one please explain to me as to what is involved in this modification? Why is it so expensive? Also please tell me where I can read about these classes 1,2 etc. divisions and groups for hazardous class.

 

[IASMike]

The reason it is so expensive is that special precautions and special equipment have to be used. You can read about the requirements in the National Electrical Code.

Mike McCowan
Automation Specialist
Industrial Automated Systems
mvmccowan@iasengineering.com

 

[TMD]

Most likely, the electric motor will need to be explosion-proof or flameproof and the controls explosion/flame-proof or increased safety.

The NEC will give you the rules, but won't tell you anything about equipment deisgn. Google these key words: "explosion-proof", "flameproof", "Exd", "Exe", "Class1 hazardous area". Most suppliers (Crouse-Hinds, Killark, Hawke (Hubbell)) and certification agencies (CSA, UL, FM, SIRA, BASEEFA, Nemko, Demko...) have good sections on hazardous areas.

 

[badasselectric]

class 1 div. 1 or 2 = money, money, money. anything with this rating is expensive.there are some nfpa publications that clarify requirments. not for compressors but for motors, switches, etc.

 

[brinkmann27]

Sounds like an environmental remediation project. Remember the compressor also requires air for compression and cooling of the unit. You would be money ahead to put the compressor in a non hazardous area or zone.

 

[dgallagher]

Here is a link to definitions for Hazardous Area Classes and Zones:

http://www.hazardousareadirect.com/ClassificationInfo/Definitions.htm

 

[mc5w]

You also need have the air intake for the compressor pump located in an area that has a nonhazardous atomosphere. Concentrations of flammable vapors that are no burning at atmospheric pressure can become explosive at elevated pressure. Some flammable vapors can condense out at elevated pressure and contaminate the heck out of the compressor oil.

Water vapor going into a rotary screw air compressor will also mess up the oil. An air compressor essentially triples the relative humidity of air. In a rotary screw compressor the oil is used partially to cool the air as it compresses. If the intake aire is over about 33% humidity you will have water condensing onto the oil in a high speed mortar and pestle. What comes out is salad dressing of much larger volume than the original oil and this then overflows into the air lines and gums up your equipment.

Now imagine doing this with gasoline vapor and you can see what kind of mess you can get. If you do this with propane vapor I can guaranteed that your system will blow up.