How to Justify Electrical Eqpm Area Classification Inside Gas Turbine Compressor

I'd look for a new job, if I were you.

Now!

The only entity who MIGHT save you is your customer.

If they are willing to relax the specification to accommodate the non-compliant equipment.

Good luck with your job search.

Sorry?

is my discussion not relevant to the forum?

No, go right ahead with your discussion.

Relevance will be determined as the discussion progresses.

Despite your description there are a few pieces of the puzzle still mising.

1. "...inside a gas turbine compressor..." Is this electrical equipment inside the actual compressor (ignitors, metering, etc.) or inside an enclosure or building that houses a GT driven compressor?

2. Fuel type(s)?

3. Gas(es) being compressed?

4. Nature of the classified electrical equipment?

5. Your relationship to the project; consultant, client, the guy who ordered the equipment, or the guy who has to correct the problem?

Based upon your analysis and without those answers I'm guessing that your company provided the equipment in question, and you're tasked with getting the customer to agree that it's "OK". If that's the case then all can offer is a "good luck to you" because the client's insurance underwriters will never buy your argument.

Somebody screwed up/cheapened out and tried to save a few pennies and got caught. It is unlikely that you can convince the ultimate owners that something won't break, that a valve won't operate properly, that the LEL won't be reached, that under maintenance conditions nothing will be released, etc., etc., and your enclosure won't be subject to trapping an explosive mixture of gases despite it's ventilation interlocks.

You can save a lot of time and money by bringing everything up to the area classification and subsequent code requirements. It will be much cheaper than the ensuing lawsuits that will result, even if an accident has absolutely nothing to do with the electrical equipment in question.

Dear Sir,

1. the electrical equipment inside a skid that house the gas turbine compressor or "gas turbine enclosure skid"

2&3. fuel type = the compressed gas = hydrocarbon gas (mostly methane, ethane)

4. they are lube oil pump, fan ventilation, lighting, starter motor, space heater

5. the second one (unfortunately )

so, it is best to upgrade the equipment classification to the level they should be (Class 1 Div 1)...

Yup... and before the equipment is placed in service. If it is in service... shut it down!

Before you shut down ask the supplier of the equipment (in writing) what classification it has. It is not necessary, but it never hurts to lift it to a higher requirement.

If this "electrical equipment" is inside the skid I would place it at a different spot. You do not want to create an explosive environment in case of defects or leaks.

There are much better ways to ensure working under LEL or a percentage of it. (see the fire triangle)

Or you come up with a complete file and still ask a authorized body in your area to have ammo or you just don't listen to any of us. First because no one has seen it all.

I guess pictures and plans will show us the reality about the electric equipment.

Dear Sir,

this unit is a new one, not yet installed. anyway but it is already FAT.

the vendor is giving us the reference list of the same unit had already installed with the same classification area. i wonder how it can be...is it because the other client has less stringent specification than my company has?

is it possible to change all the electrical equipment inside the skid on the field without break out the warranty from the vendor?

You need to get the info on what it was that your company ordered from the vendor. If the vendor did not supply you with what you ordered, get them to supply you with what they were supposed to sell you.

If your company did not specify what type of equipment must be supplied with this skid mounted unit and you do in fact want it to be good for Class 1 Div 1, talk to the vendor about making these changes.

Making changes to this packaged equipment without the approval and support of the vendor will... more than likely kill your warranty and cause the equipment to no longer be considered as being certified.

Either way... you need to talk to the vendor about this.

Who ever owns or paid for the design of this facility brought in a professional engineer to classify the various pieces of equipment meant for this facility. If the inside of the compressor requires gear classified as being Class 1 Div 1, installing anything less than that will expose those who installed it to huge liability.

No amount of engineering controls will get around that reality. I doubt you will get any other advice here other than to "install the proper equipment".

waw, what happen on that? something related to the classification also?

This is what can happen when unqualified people try to justify the use of non-compliant equipment in hazardous environments.

Don't.

It is sometimes possible to justify in your head how and why you can get away using kit of a lower spec. Some clever people have classified the area you are working in. Your insurers are very interested in this. If the area classification gives a value do not deviate from it - your insurers won't!

RS-2013,

1. Your post is worded in a way that suggests you are considering ventilation and other changes that would allow the skid to be reclassified as Cl-1 Div-2. This appears to fall within the NEC 500.5(B)(2)(2) wording "In which ignitible concentrations of flammable gases...are normally prevented by positive mechanical ventilation and which might become hazardous through failure or abnormal operation of the ventilating equipment..." To do this, I would expect an professional engineer to review the proposed changes and how the ventilating equipment would work, and have this person sign-off on the changed classification.
2. A common misconception is that "explosion proof" equipment will not allow any explosion to occur. In fact, an explosive atmosphere can build-up within such equipment. Then when (not IF) this contained atmosphere does explode, the equipment is supposed to have been installed with the proper seal-offs and ground joints so that any combustion products that vent to the larger area are cooled as they escape so the explosion does not propagate to this larger area.
3. You have two possible ways to cause an explosion in your skid--sources of sparks and surface heat of equipment. Both must be controlled, which is all covered in Art. 501. However, there is an alternative method of classification which is less well-known in the USA. This is Class and Zone (see NEC art.505). The two methods cannot be mixed--either all one or all the other for any single hazardous area. The Class/Zone approach may give you options not readily obvious in the Class/Division approach.
4. No matter how you proceed, remember the KISS principle, and remember that someone will have to work on this equipment later.

--John M.

Dear Sir,

1. i get your point, so it is advised that the authority having jurisdiction who should judge that the location would become hazardous only in case of an accident or os some unsual operating condition.

2. noted, your advised is to make sure the integrity of explosion proof equipment

3. noted, there are items to control:

- source of sparks (by make sure by the explosion proof equipment),

- surface heat (by means of cooling, inside skid, there is main and backup ventilation fan that function as the cooling tool), also

- presence of flammable vapor or gas (by ventilation fan)

4. got it, keep it simple stupid principle...

5. If refer to API 500 section 6.3 stated that "the decison to classify a location as Div 1, Div 2 or unclassified depends in part on the degree of ventilation of the location"

in section 6.3.2 written about Adequate Ventilation i.e the ventilation required to prevent flammable gas/vapour concentration >25% LFL, and the methods of achieving it (natural/artificial ventilation, minimum 6 air changes per hour, one cfm per square foot, fugitive emission).

How is your opinion on it?

RS-2013,

Re-1: The AHJ usually will make a conservative call, because it is better to err on the side of safety than to have a chance for a mistake. That is why I recommended the use of an engineer to study your system and make/approve recommendations on what to do to meet the Cl.-1/Div.-2 requirements. The engineer's report should give you this margin of safety, so the AHJ has this additional cushion in making a decision.

Re-3: Choose components that are inherently unable to achieve a surface temperature high enough to cause ignition. That is the KISS principle in practice. Don't rely on ventilation to cool them down to such a temperature. Also, have a method of proving that the ventilation is occurring at a level higher than required for the <25% LEL requirement.

Re-3: Look again at the Class/Zone rules--but be prepared to read the text at least 3-5 times in order to understand it (perhaps trying to explain it to someone else will help to get it understood by yourself, because I have always found that teaching a topic really helps me in learning it).

Re-5: I am unfamiliar with the API texts, but what you quote seems to follow a basic principle in engineering--to have a substantial margin of safety.

--John M.

Dear John,

appreciate your opinion in this discussion.

1. well, i would suggest to my supervisor to start search for appropriate AHJ.

is it common to have written mutual agreement between engineering, operation, safety and any stakeholder to understand the impact on the deviation and prepare to the worst risk scenario? or do you have another method or experience before for such condition?

3. ok, i try to check the temperature rating of the components. currently the vendor is not submitted the calculation method of the ventilation. they only give the result number in scfm.

4. sure...yes it helps explaining other to make you even understand and memorize longer.

5. ok

thanks.

RS-2013,

North of 60 makes a very good point. The AHJ is the "authority having jurisdiction", or in other words, the inspector. His/Her job is to compare the installed work with the requirements of the code. The code is not a design guide, but a specification of standards or conditions which the completed installation must fulfill. One of these specifications is that everything must be installed in accordance with the manufacturer's and testing agency's instructions. Any time you deviate from these instructions you are probably violating the code. I don't know of any AHJ's who will tell you how to do the work; they will only tell you what portion of the work does not meet which portion of the code rules.

When I say to contact a competent professional engineer, I am meaning a consultant who you would hire to independently evaluate the equipment and environment and then in his/her professional capacity this person/firm would tell you what needs to be done to meet the requirements of the code(s)---to be safe. At the same time you may want to be working with the AHJ to see if they will allow such a consultant's work to be used for achieving you change in environment classification.

--JMM

I am an AHJ, and I must say that under no circumstances would I (or any other AHJ that I interact with) would offer comments on how the areas or equipment in question is to be classified.

That is not our role. The designers of the equipment and of the facility own that responsibility. Our role is to enforce the requirement of the classification after it has been set by the engineerring resources involved in the design.

There is no doubt that the codes in question offer clear guidelines as to requirements for specific types of equipment, the types of equipment are very limited. Outside of what the codes speak to is not, IMHO, up to an AHJ to decide upon.