Area Classification 1

[avvo0523]

I am a recent graduate and was asked to develope an area classification drawing for a grass-root refinery project. This is a first time for me. Any directions/suggestions or name of books to read would be greatly appreciated.

 

[davidbeach]

Where are you? That will make a significant difference.

 

[avvo0523]

The project is located in WA, USA. Thanks

 

[davidbeach]

The first place to start then would be Chapter 5 of the NEC.

 

[dpc]

Best thing to get is an example of what your boss is looking for, preferably for a similar facility. Then start reading the NEC and Googling.

New refinery in WA state - that's interesting.

 

[rcw retired EE]

If you are not a member of IEEE, join it or find someone who is. Join the Industrial Applications Society and do a search for Area Classification on their "Transactions on Industrial Applications". There have been several tutorial style articles on Area Classification in the last 20 years. These periodicals are carried at most universities with an Engineering school. (U of Washington and Washington State both have them.)

Get a copy of API RP500 Recommended Practice for Classification of Locations for Electrical Installations at Petroleum Facilities." Read it a few times.

Read NFPA 49 A & M.

Look for a company guideline, most engineering companies have one on Area Classification or maybe the eventual Owner of the facility has a guideline you need to follow.

This is just a start. But it should work for a preliminary project.

Good Luck.

 

[cherry2000]

First of all it will depend on the type of plant that u have which will determine whether you will use the Area Classification figures on NFPA 497 or API RP 500.

Again as you may be aware, there are two broad categories of Area Classification : Division method which is the traditional method in US or the Zone method which is the method in Europe & rest of the world.

NFPA 497 has figures for both Div & Zone methods. API RP 500 is only for Division method whereas API RP 505 is for Zone method.

Area Classification methodology widely varies based on type of Plant. If it is a small plant with very less number of hazardous constituents, you can adopt the point method of classfication. Here you will have to locate each and every source along the pipeline, vessels, valves, flanges etc and draw the radius as per the figures. For this you will need P&IDs as well as the Piping model with all equipment.

However if it is a large plant with lot of constituents, then you will need to tabulate all the equipment (which behave as source 0 facility wise and then mention the Hazardous constituent along with the properties of the Gas ( Gas Group, Temp Class, specific gravity etc ). Once the tabulation is done, you will have to select the Legend in the dwg based on the various constituents. Finally, you need to take the envelope of each equipment and draw the radii and develop area classfication.

But as I said before, first step is to find what the Client wants : Div or Zones; NFPA or API.

I have a ppt presentation which I may share with you if you want, which gives the broad framework of Area Classification. Safest bet for a beginner will be to study Area Classification dwgs done for previous projects in your firm ( sometimes these are hard to locate !!! )

 

[avvo0523]

Cherry2000

Your advice help me tremendously. Thanks so much.

It's an Ethanol Plant and Client wants NFPA, I've looked in NEC and it's Class 1 Div. 2 Group D.

I'll use the point method of classification as you had mentioned.

Please send me the PPT Presentation.

 

[tincherb]

Can someone please tell me if Area Classification drawings require a PE seal?

 

[rcw retired EE]

In my expereience, most jurisdictions require a PE Seal on Area Classificaiton Drawings.

 

[controlnovice]

Avvo,

Be careful. You state that the entire plant is Class I, Div 2, Group D. I doubt very much that it is.

Before there is Div 2, there has to be a Div 1 in most cases. This can be inside the vessel, but many times is also outside the vessel. This greatly affects the area classification.

Being fresh out of school, I do not recommend you do this by yourself. You will need input and training from someone who has done this before. As many know, codes can be interpretted differently by everyone. Your plant's/companies standards should also be followed. Even then, they are open for interpretation. Standards can not cover everything.

I highly recommend trying to find someone internal to your company that has done this before and work on this project with them. If there is no one internally, find someone external.

If your boss is asking you to develop these drawings, and you are fresh out of school, you need to be cautious. A wrong interpretation, design and installation can be deadly.

I know this puts you in a difficult situation, but your boss is asking too much (in my mind) without realizing the consequences.

Reading the NFPA and/or API is not enough. You need an experienced engineer's input.

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This is normally the space where people post something insightful.

 

[rcw retired EE]

I have to agree with ContolNovice's points. Area Classification takes some time to learn. (I have been doing it for 33 yearas and still am learning a lot.)

Reading the guidelines might get you enough information to do a preliminary Area Classification document which could be used to estimate the project. But a thorough review by an expereiced PE would be necessary to actually perform the final layout, build the plant, or purchase equipment based on the Classification drawings.