Electrical Classification for Nat Gas compressor and cooler 2

[dbarker72]

I have a client that has decided the outdoor gas compressor oil/gas cooler he listed in his RFP needs to go inside. I am trying to convince him that this would require making the room explosion proof (in addition to all the air I will now need to suck out of the building to remove the heat). However, he is stating that installing more gas detectors can eliminate this problem.

I am looking for any definitive resource I can use to help decide this issue.

The compressor (95 to 240 psi) installation is not in an explosion proof room, the skid mounted equipment is XP, but there is a gas detector installed, so that is the client's basis for the cooler not needing to be explosion proof.

Some research shows me that AGA XF0277 - Classification of Gas Utility Areas for Electrical Installations, but I have not picked it up yet.

Any suggestions, other than forcing the explosion proof requirement since it will be the safest?

Thanks.

dbarker72

 

[BigInch]

What country are you in? Check your hazardous area definition code.

Gas detectors are nice, but perform no function in electrical protection. They will detect gas only if they are still functioning after the explosion.

The U.S. National Electric Code classifies specific hazardous locations by use in Articles 511 through 517. Article 500 is also loaded with Fine Print Notes. While not Code requirements [90.5(C]), they are immensely helpful in making a hazardous location safe.

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ABSOLUTE MINIMUM IS CLASS I, DIV 2
[/color]

Class I, Division 1. Ignitible concentrations of flammable gases or vapors may exist in the course of normal operations [500.5(B)(1)].

Class I, Division 2. Volatile flammable gases or vapors would become hazardous only in case of an accident or some unusual operating condition — or under certain conditions [500.5(B)(2)]:


Where volatile flammable liquids or gases are handled, processed, or used, but are normally confined within closed containers and the gases would escape only in the case of accidental rupture or breakdown — or by abnormal operation of equipment.

Where ignitible concentrations of flammable gases or vapors are normally prevented by positive mechanical ventilation, but might become hazardous through abnormal operation of ventilating equipment.

Areas adjacent to a Class I, Division 1 location where flammable gases or vapors might occasionally be present unless prevented by adequate positive-pressure ventilation with effective safeguards against ventilation failure.

Protection. You must protect electrical equipment and wiring within hazardous locations [500.7].

Use any of the following:

Explosionproof enclosures (Class I locations)
These withstand and contain the force of an internal explosion — the hot gases within the enclosure cool as they escape [500.2].

Dust-ignitionproof enclosures (Class II locations)
These exclude dusts. They will not permit arcs, sparks, or heat within the enclosure to cause ignition of exterior dust [500.2].

Dusttight enclosures (Class II, Division 2 and Class III locations)
These prevent the entrance of dust or flyings. They have no openings to allow electrical sparks or burning material to escape [500.2 and 502.115(B)].

Purged and pressurized systems
For Class I Locations (containing flammable gases or vapors), these permit general-purpose enclosures [500.2]. For Class II Locations (contains combustible dust), these supply positive pressure to general-purpose enclosures [500.2].

Intrinsically safe systems (all locations)
These are incapable of releasing sufficient electrical or thermal energy to cause ignition of flammable gases or vapors [500.2]. None of the requirements in Articles 501 through 503, or 510 through 516 apply to intrinsically safe system installations, except as required by Article 504.

Nonincendive circuits (Class I, Division 2; Class II, Division 2; or Class III, locations)
These are incapable of releasing sufficient electrical or thermal energy to cause ignition of flammable gases, vapors, or dust [500.2].

Oil-immersed make-and-break contacts (Class I, Division 2)
You can install these in a general-purpose enclosure in an area that doesn't contain explosive or ignitible mixtures under normal conditions [500.2].

Hermetically sealed contacts (Class I, Division 2; Class II, Division 2; or Class III, Division 1 and 2 locations)
You can install these in a general-purpose enclosure in an area that doesn't contain explosive or ignitible mixtures under normal conditions [500.2].



Going the Big Inch!

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[BigInch]

P.S.
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Only a registered professional engineer with experience in the application of the NEC [/color] can make the determination if any given area is subject to a particular class and what kind of class, ... or not.


Going the Big Inch!

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[Zapster]

Only a registered professional engineer with experience in the application of the NEC can make the determination if any given area is subject to a particular class and what kind of class, ... or not.

BigInch, who is the global authority that is going to enforce the above statement you made? I believe that it is just as important to understand the process, locations of hazardous areas, etc., and the requirements of the regulatory authority, if any.

dbarker72 , I would recommend you review, “API Recommended Practice 500” (Recommended Practice for Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class I, Division 1 and Division 2. API RP 500 gives a detailed explanation of electrical classifications that includes a discussion of NEC requirements.

 

[BigInch]

Zapster, What is your point? Do you object to PE's making the hazardous area determination, or do you object to my reference to the NEC? I mentioned the PE bit, simply because the OP's client seems to be objecting, so its a perfect excuse to negate the objection, if the OP is not registered.

I am well aware that there is no international authority that will enforce the NEC (why do you make that statement?), nor do I think there should be one. That's why I asked where the OP lives. In fact nobody cares what the NEC says where I myself live. What do you want? Are you suggesting we use API instead of NEC? Now, I suggest you take a look at YOUR local code. I believe you will find that NEC is the legal requirement in your local area, not API 500, or API XXX. Who will enforce NEC? In the US, local building code officials enforce the NEC, BOCA, UBC and many others. As far as I know, there is no legal authority that can legally enforce any API anywhere in the world.

You say, "I believe that it is just as important to understand the process, locations of hazardous areas, etc., and the requirements of the regulatory authority, if any." To which I say, good! So do I. Check yours. What's your point with this?

Now, specifically looking at API 500, do you notice the "Recommended Practice" part of the title? API doesn't even think it carries legal weight. Law? Not even. Its a "recommended practice". I don't know of a single instance where any API is law, nor even used as a reference by a law, regulation or code, but I'm no lawyer either, so please let me know if you understand differently.

So is the main point that you are telling dbarker to use API 500 instead of NEC? What's your legal basis for that?

Going the Big Inch!

http://virtualpipeline.spaces.msn.com

 

[zdas04]

In the US more and more states are adopting the NEC as law, much like many of them have adopted the ASME Boiler & Pressure Vessel Code as law. In those cases API RP 500 can give you some insite into how the NEC can be intrepreted for an Oil & Gas installation, but the NEC is the law.

BigInch, that was a good review for sites that are already designed, but for a new site you went pretty light on options to help avoid creating a hazardous situation.

For a fully-enclosed building, if you are using natural gas for instrument gas then you have the choices of making everything Class 1 Div 1, adding adequate forced ventilation to provide 6 air changes per hour, replacing the instrument gas with instrument air, or removing 50% of the wall surface and opening vents in the ceiling. In RP500 they suggest that you can provide a natural ventilation route that will allow natural ventilation to give you 6 air changes per hour, but that option is missing from the current NEC.

A lot of people have felt that fire eyes and gas detectors (usually set at 20% of LEL) mitigate the requirements of the NEC, but neither do a darn thing (as BigInch said above) for prevention--think about it, by the time you are at 20% LEL at the roof line a bunch of the building is over 100% LEL and at risk. By the time a fire eye trips an ESD you already have a fire and it has all the fuel between the ESD's to do its damage.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The harder I work, the luckier I seem

 

[BigInch]

Two reasons for that; He's got an existing building and I'm not an electrical professional engineer. I just wanted to get the OP thinking in the right direction and to take his client with him.

Going the Big Inch!

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[BigInch]

And since this IS the gas compression forum, I might as well mention the same provision applies for US regulated pipeline installations; Yes there are ASME B31.8 for gas pipelines or B31.4 for liquid pielines, but the Federal legal requirements are specified by Code of Federal Regulations Title 49 Part 192 for gas pipelines or Part 195 for liquid pipelines. Some individual states and some specific municipalities may also have additional local regulations that may apply. It is not safe to assume that if you follow the B's alone, you're home free.

Going the Big Inch!

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[dcasto]

I think you need to ask why you need the gas/oil cooler inside a building. The idea is to reject heat. Even in artic climates, the cooler is outside the building on packaged units. One can even draw air from inside the building to outside in the summer or outside to inside in the winter. The cooler fan will replace the air more than 6 times per hour in either direction if installed correctly.

Now, the industry defacto, generally accepted practice, and defendable standards are: API 500 for oil and gas equipment and NFPA 38 for ignition systems on gas engines. These recommended practices interpt the NEC because the NEC is generic and does not take into account risks with every industry.