Electronics design for explosive environment - Page 1
Forum section: electronics / general

author: Aleksandar B.
author_rank: Contributor
timestamp: December 20, 2014, 06:54:07 pm
content: Hey guys, I got a new project where I am supposed to design some hardware that is going to be used in an explosive environment. I tried to find some information about the subject on the internet , but couldn't find much useful information (maybe I am using the wrong keywords..), besides that you should limit current surges, but I couldn't find information about how this is usually done.I know that different countries use different standards and regulations, but I am looking for a reference book (preferably a free e-book), or application note where I can find useful generic information on the subject.I would be very grateful if someone could recommend a good reference book, or any advice (besides the obvious "prevent sparking") that could help me out.Regards,Aleksandar

author: 8086
author_rank: Super Contributor
timestamp: December 20, 2014, 06:59:55 pm
content: This may be of some use:http://www.mtl-inst.com//images/uploads/datasheets/App_Notes/AN9003.pdfI suggest seeing if you can find some of the actual regulations and read them. Then you will see what you have to comply with at least.Looking for info about "intrinsically safe systems" will likely get you some useful results.

author: IanB
author_rank: Super Contributor
timestamp: December 20, 2014, 07:11:32 pm
content: As 8086 says, you will need to find the applicable laws and regulations for the location and protection category where the hardware will be installed.The most generic information is that for a device to be intrinsically safe there is not enough energy in the system to ignite surrounding combustible gases. This is more subtle than preventing sparks, since where there is electricity there can be sparks. The critical factor is that if a spark should happen, it will be too weak to cause ignition.

author: PChi
author_rank: Frequent Contributor
timestamp: December 20, 2014, 07:14:48 pm
content: I am assuming that Europe is the intended market then IEC 60079-0 is the place to start. I recommend buying the standards. If the company are serious then the cost is trivial compared to the cost of getting a product approved. Beware the standards are vague so a lot is in the interpretation so it is worth talking to one of the outfits that do approvals. A search should find the culprits like Sira, Baseefa and Intertek.Linear Technology athttp://cds.linear.com/docs/en/lt-journal/LTMag-V19N3-03-LT4356-MurphyPickard_HachCo.pdfhave some information about one way of passing the approvals.I have come across a couple of book titles but they don't look too useful.The approvals process is going to look at possible thermal ignition sources and spark sources. If the project is low power, say less than 1.3 W, and low voltage, say less than 10 V, then it shouldn't be too difficult. Encapsulation can be useful along with keeping capacitance and inductance low.http://www.technetea.com/eng_domaines.html#id_atexis useful if you take the 'Intrinsic Safety' approach.

author: nctnico
author_rank: Super Contributor
timestamp: December 20, 2014, 07:29:12 pm
content: I'd talk to a test house which has to test the equipment. They often can give more detailed information than the standards provide.

author: tggzzz
author_rank: Super Contributor
timestamp: December 20, 2014, 07:41:46 pm
content: It sounds like people's lives are at risk. If you don't know what you are doing you are riskingtheirlives.Consider thatyour equipment could kill peopleeven if it performs correctly as intended.Apart from that, I do hope you have the appropriate liability insurance, and that it will cover such activities.Such considerations would make me decline such work, unless I was in a professional environment where I would be taught the necessary and sufficient precautions.

author: Zero999
author_rank: Super Contributor
timestamp: December 20, 2014, 08:05:39 pm
content: I agree with the above.I suspect it depends on the device. If it's something which is low power and is completely hermetically sealed then it's going to be less of an issue than a device with capacitors in free air that could blow.

author: KJDS
author_rank: Super Contributor
timestamp: December 20, 2014, 08:15:18 pm
content: The interweb is not the place to ask about how not to accidentally kill people.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 20, 2014, 09:09:17 pm
content: This is an area where you definitely need to talk to someone with experience. The standards (once you figure out which apply) themselves are barely comprehensible until you know more about the context - at first reading you will wonder how it is possible to design anything at all to meet them.There are several means to achieve safety - probably the most common is intrinsic safety (IS), where power levels and stored energy (caps, inductors) are limited to levels below what can cause ignition by sparks or hot surfaces, even under certain fault conditions. The energy levels depend on the environment it is to be approved for.The number of faults that must be considered depends on the required approval level (e.g. gear to be used in places where gas is normally present has to be safer than that for where it is only present rarely or in unusual circumstances)IS must be considered at every stage of design, and except in the case of some very low power systems, cannot be "added later".In some cases there will be design decisions that are taken for no other reason than to make it easier to approve 7 demonstrate safety in fault conditions - e.g. adding resistors and/or zener barriers between modules to guarantee that even under worst-case conditions, any fault in one module cannot affect safety of another.There are other techniques, which in the more niche areas where where they can be used, can be a lot simpler electrically. e.g. a flameproof enclosure, the idea being that if gas can get in, any explosion will be contained inside and prevent external ignition - generally this involves cast+machined enclosures with long, close-fitting flange joints. Electrically it's often little more than making sure all big caps have discharge resistors so it's safe if opened after being powered down.It's many years since I did any of this stuff - more modern low-power, low-voltage parts will have made some aspects much easier than in the past.One thing that is not of concern is software - systems must be safe regardless what the software does

author: G7PSK
author_rank: Super Contributor
timestamp: December 20, 2014, 09:40:46 pm
content: It also depends on what the explosive environment is going to be. Is it oil vapours,gases or air born powders or explosives and detonators. Some of the requirements are quite frankly nuts as well, I personally did some works in a chemical factory requiring the use of a portable welder, I was not allowed to use a petrol or gas powered plant but diesel driven with a spark arrester on the exhaust system was OK, not one mention was made of the dirty great spark that was going to be made at the end of the leads though.

author: hamdi.tn
author_rank: Frequent Contributor
timestamp: December 20, 2014, 10:35:32 pm
content: Quote from: mikeselectricstuff on December 20, 2014, 09:09:17 pmam not sure if software it self is not a concern, recently someone talked to me about a potential project that i may have to do and it's about gas boiler and central heating , well the software should be written in a called "class B" structure , don't know what that as is but as i understand it's basically to similar process that run either under the same processor or in two different processors that compare each other progress, if any difference between the process execution detected by one or both , immediately kill the flame and signal failure or run a fail-safe mode or whatever. So even with the right hardware , the software have to follow some kind of regulation.There even a class C, no idea what it's about, maybe for military application.

author: IanB
author_rank: Super Contributor
timestamp: December 20, 2014, 10:39:39 pm
content: Quote from: hamdi.tn on December 20, 2014, 10:35:32 pmhttp://blog.cm-dm.com/post/2012/04/14/Is-my-software-in-class-A,-B-or-C

author: hamdi.tn
author_rank: Frequent Contributor
timestamp: December 20, 2014, 10:54:43 pm
content: thanks IanB for the linkClass B: Non-SERIOUS INJURY is possible , with all stupid unexpected death we saw on the news , no damn way to be so sure

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: December 20, 2014, 11:27:41 pm
content: I majored in control systems with specialization in chemical industry. To make it short - in chemical industry Control Systems usually called "Process Control" and Control Systems Engineering is called Process Control Engineering respectfully. If you search information on Process Control and standards you perhaps will find more of what you are looking for. In chemical industry everything you deal with is explosive, corrosive and poisonous and there are no "special" design rules on top of what already used in Process Control in general. Electronics probably lesser concern in that environment comparable to more powerful stuff like motors. If you are trying to control reaction in a column that requires an agitator driven by 16KW motor then sparks that can come from that motor are more of the concern than your standard 24V control gear. Your customer may not actually care what you do - they will put it into their own sealed enclosure, so I would actually make sure it is not the case to avoid wasting time and money.I remember testing equipment in a lab at university - you place a box with electronics inside a box that have gaps in a seal (lets say 0.5 mm gap). Then you put this box into a Plexiglas chamber and fill it with gas mix (propane/air). When you short something inside the box and you get sparking (inside a box). Depending on the gap size mix in a chamber explodes (shooting the stopper to the ceiling) or not. Those gaps are one of most important requirements for equipment such as electrical motors and actuators placed in explosive environments. Then there is external wiring and other rues of course, but for electrical equipment it is those gaps that are important.No if you want to control somethingSuper Explosivethen use pneumatic control system. Every single discrete component like integrator, differentiator, adder, AND, OR, NAND gates available as pneumatic components. Pneumatic PID controller works as well as electronic one. No electric components, no electrical problems - you kill all rabbits in one shot.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 20, 2014, 11:43:57 pm
content: Quote from: hamdi.tn on December 20, 2014, 10:35:32 pmThat's a completely different area.Intrinsic safety & other hazardous area design techniques etc. is about a piece of equipment not being a hazard when used in potentially flammable or explosive atmospheres. It has nothing to do with product performance or reliability - the standards don't care if something works or not, just that it doesn't cause an explosion under normal or plausible fault conditions.What you are referring to is functional safety, where a system can create a hazardous situation by itself, or is relied on to maintain safety, protection, life support etc.There may of course be some situations where both are applicable.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 20, 2014, 11:52:31 pm
content: Quote..but just remember that flowing air can cause static charges to build up in some cases..!BTW Intrinsic safety also covers things like using antistatic case materials, ann impact testing to ensure case integrity if products are dropped etc. (as this could introduce unpredictable fault conditions)QuoteThis is the "Flameproof" stuff I referred to.Here are some examples :http://www.e2s.com/products/hazardous-area-signalling/explosion-flame-proof/visualhttp://www.e2s.com/product/13117-gnexs1-alarm-horn-sounder-117db-aThe speaker uses a small sintered metal disc between the horn and the driver to allow the sound out while providing a large surface area -to- distance ratio to cool any hot gas or flame from inside.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 20, 2014, 11:56:58 pm
content: there are no "special" design rules on top of what already used in Process Control in general.Quote

author: tggzzz
author_rank: Super Contributor
timestamp: December 20, 2014, 11:58:28 pm
content: Quote from: Alexei.Polkhanov on December 20, 2014, 11:27:41 pmVery true.Thirty years ago I did a study of how microprocessors could be used on unmanned offshore oil rigs, to control oil/gas flow. The existing equipment used pneumatic logic at 2000psi.Naturally I included many "bells and whistles" (e.g remote monitoring/control) that could be done by micros. But the main conclusion was that it would be difficult to improve the basic functions - and that it would be such a major undertaking to ensure safety that it was questionable whether it was worth proceeding.They took my advice, as far as I know

author: IanB
author_rank: Super Contributor
timestamp: December 21, 2014, 12:36:38 am
content: Quote from: tggzzz on December 20, 2014, 11:58:28 pmPossibly it was the valve actuators that needed 2000 psi? Pneumatic control and logic devices would work at more moderate pressures around 100 psi. The low pressure logic signals would operate a valve to allow high pressure air through, which in turn would move a piston to operate big and heavy items. In some cases the big and heavy items are operated hydraulically rather than pneumatically.

author: SeanB
author_rank: Super Contributor
timestamp: December 21, 2014, 07:49:12 am
content: 2000PSI might be used to operate actuators at the bottom of the ocean, but the controls would likely be running at4 bar or so pressure, provided by a filter regulator ( or if you only have the 2000PSI by a cascade of regulators) and most likely it will be oil free as well. If you are doing fully pneumatic you can get step controllers, and even crude PLC like functions in ladder logic to run quite well, and even have analogue systems using a 0-4bar air pressure to drive proportional controllers and operate throttling valves. I did repair those and set them up during training, but have rarely used them in plant. But I have done controls that use pressure control to make variable speed actuators that have different rates on close and open. If I installed the pneumatic reed switches ( yes you do get cylinder switches in pneumatic versions ) I would have done dual speed operation on each stroke, but running slower was simpler than the extra cost of the logic, and it was not much speed difference in any case. All off the shelf cheap ( in industrial terms cheap, not that it is actually cheap)parts available from in most cases multiple vendors. Festo has a large range, and some pretty interesting stuff in there as well.

author: Stonent
author_rank: Super Contributor
timestamp: December 21, 2014, 07:50:17 am
content: Where I work we have a paint storage and mixing room that has a blast reflective wall. If something blows up, everyone in the room will probably perish but nobody outside the room will be injured.There is an Ex rated analog phone box in the room and a computer console that is sealed with the actual computer in a room above.I once looked up how the phone was wired and the guts of the phone exist outside the room on the other side of the wall. I think the specs showed isolation transformers and 1M Ohm resistors on all the phone wiring that goes into the room.All of the paint cans have ground terminals on them and are clamped with large alligator clips when not being moved around.There are lots of small diameter stainless steel air lines going all over the place to all the equipment, which may be part of some pneumatic logic control, I'm not really sure.

author: tggzzz
author_rank: Super Contributor
timestamp: December 21, 2014, 09:27:42 am
content: Quote from: IanB on December 21, 2014, 12:36:38 amPossibly, but my recollection was 2000psi.Other information is that there was no electricity on the platform, all air pressure being derived from the well itself. The tubes were maybe 3mm external diameter, and the gates the size of matchboxes.Given that it was controlling the flow, which seems pretty big and heavy to a neophyte like myself, maybe it was hydraulic rather than pneumatic logic. Could I finesse the point by calling it fluidic logic ?

author: German_EE
author_rank: Super Contributor
timestamp: December 21, 2014, 09:47:57 am
content: Years ago I helped with the installation of an elevator system that was used in an area where there could be explosive vapours. Almost everything had to be custom made and there were multiple layers of safety features to the point of things getting crazy. How crazy?Electronics sealed inside boxes even though nothing inside the box could generate a sparkCopper nuts and bolts used throughout (and we had to use brass tools provided by them) all to prevent sparks.Pneumatic buttons on the elevator panel rather than the conventional electric variety.At one point I had to resolder a connection and whilst doing the job I had two men with fire extinguishers for company and part of the plant was shut down, all because my soldering iron was not intrinsically safe. My suggestion of using a butane soldering iron that was not mains powered was politely refused

author: tggzzz
author_rank: Super Contributor
timestamp: December 21, 2014, 10:33:05 am
content: Quote from: Aleksandar B. on December 20, 2014, 06:54:07 pmI can't help remembering the distinguished professor (Eric Laithwaite, an early proponent of MagLev trains and Linear Motors)...On principle in the final year exams he set for undergraduates, he would include three questons:one question could be answered by everyone that had attended and understood his lecturesone could be answered by people that had explored beyond his course materialone couldn't be answered in the time availableand he expected that anengineercould determine which was which and avoid the impossible question. If you couldn't distinguish what should be avoided, then you deserved to get poor marks.

author: IanB
author_rank: Super Contributor
timestamp: December 21, 2014, 04:40:01 pm
content: Quote from: tggzzz on December 21, 2014, 09:27:42 amOn the subject of oil and gas, I once built an operator training simulator for an offshore platform (it was Statoil's Sleipner A platform in the North Sea, a large manned platform). Due to the size and weight constraints on such a platform the process plant was highly integrated (meaning tightly connected and interdependent). When starting the process plant up from cold this led to a situation where you couldn't completely start item "A" without starting item "B" first. But conversely, you couldn't start item "B" without starting item "A" first. This produced a situation where you had to start items "A" and "B" simultaneously and bring them both up together in stages. But the same situation applied to other items too. To complete a successful start-up you had to be all hands and eyes, jumping from screen to screen and keeping a close eye on everything that was going on. Which is why computer training simulators are so valuable. You can learn on the simulator before you try to "fly" the real thing. I really liked that simulator. I called it the world's most challenging video game. It even had a "Game Over" feature. If you exceeded one of the safety trip thresholds you would get an automatic Process Shutdown on the alarm panel and the whole wall would light up with red flashing lights.

author: SeanB
author_rank: Super Contributor
timestamp: December 21, 2014, 04:58:53 pm
content: In real life you got Deepwater Horizon.........http://en.wikipedia.org/wiki/Deepwater_Horizon_oil_spill

author: MickF
author_rank: Newbie
timestamp: December 22, 2014, 04:46:12 am
content: Quote from: Aleksandar B. on December 20, 2014, 06:54:07 pmSent from my iPad using Tapatalk

author: MickF
author_rank: Newbie
timestamp: December 22, 2014, 04:48:13 am
content: Checkout hazardous area, devices known as barriers are usedSent from my iPad using Tapatalk

author: crusader66
author_rank: Contributor
timestamp: December 22, 2014, 08:16:52 pm
content: Alexsandar, you will find the following book helpful as a place to start.http://www.amazon.com/Electrical-Instruments-Hazardous-Locations-Magison/dp/097923431XDesign for hazardous locations can be complicated and difficult. I work for an analytical instrument company that designs instruments for hazardous locations in Petrochem Industry and I can tell you that, while this is not always difficult, it is a tedious and time consuming task. There really is no "self-certification". The current fad is ATEX but because of its many and various interpretations of that set of standards the IEC EX standards are rolling out and are basically, ATEX without the interpretations.Depending on the product and where the product will be sold/installed, you might be able to avoid IEC EX. For example, if Canada, then CSA standards will dominate the design. As you dig into this, you will find that many of the standards are the same but the interpretation and semantic games played by the various organizations will make your head spin. Ultimately, you or someone will need to obtain a certificate and this will require a certifying agency to review your design which might or might not involve tests. You or someone will need to maintain that document set and if changes are ever made after certification, you might have to recertify.To begin with, your design will need to consider the set of standards to which your product must conform. Your electronics will have spacing requirements, maybe need to be intrinsically safe, possibly need to be conformal coated or have a cover that prevents accidental contact with field wiring (or both). Sometimes putting it in an ex proof box and potting will make life easier but the electronic spacing requirements will still need to be applied. I don't envy you. I don't know where I or any of us here would start if we didn't have a set of engineers and designers that were around as these standards were growing. (Just realized that if it is mining industry there are probably standards that are similar to petrochem but have a different slants and variations.) Other than the link to book, I doubt much of what I have said is helpful but I know from experience that each design is not easy. As you do more and more, it gets easier but is always somewhat of a pain.

author: retrolefty
author_rank: Super Contributor
timestamp: December 22, 2014, 10:08:08 pm
content: I worked extensively in this field at a large oil refinery before retirement 7 years ago. Basically there are two ways to gain permission to utilize electrical equipment in hazardous atmosphere locations.If the equipment is low power instrumentation type equipment (process transmitters in the jargon) then it's possible to obtain intrinsically safe components that work with intrinsically safe barriers between the remote source of electrical power (typically from a control house) and the field mounted sensor. These are typically 24vdc 'current loops' where the amount of power will not be able to create an initiating spark strong enough to create an external explosion. Such equipment is not required to be mounted in 'explosion proof' housings, indeed one can even open it up, disconnect, reconnect loop wires, measure loop current, calibrate, etc. So while I.S. rated equipment and infrastructure is expensive it does allow maintenance activities without special safety procedures.The second method is for higher power equipment such as large 440vac 3 phase motors where the electrical energy would always be enough to initiate explosive sparking. Such equipment has to me mounted and installed with 'explosion proof' enclosure. To work on such equipment in a hazardous location one has to implement special safety procedures such as actual and active testing of the local atmosphere, standby safety operators, etc.Most of the standards and reference information we used to guide us for new installations came from the N.E.C. (national electric code) and FM (Factory Mutual) and yes it can be quite complex and frustrating at times.On the subject of offshore oil platforms, while I never worked on one I did work with some that had. One stated he served on used extensive pneumatic for the process control sensors and control valves and one platform even used the natural gas produced (after conditioning) by the platform for the pressure medium rather then normal compressed air. Saved money I guess but I would sure not feel safe as most pneumatic equipment vents a small amount of pressure at all times through various 'flapper/nozzle' assemblies. Safe to say that smoking would be a very risky proposition for such a installation.Seasons Greetings to all

author: tggzzz
author_rank: Super Contributor
timestamp: December 22, 2014, 10:29:49 pm
content: Quote from: retrolefty on December 22, 2014, 10:08:08 pmInteresting. I am under the impression that is what was used on the platforms for which I did the study. But I could easily be wrong, partly because it was so long ago (early 80s), partly because I know less than a complete neophyte about this subject.

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: December 22, 2014, 10:39:36 pm
content: Quote from: tggzzz on December 22, 2014, 10:29:49 pmIt must be because they don't want to run filter/dehumidifier for air if conditioned gas already available. Dust and water are two major pains for pneumatics. There could be other, less obvious, reasons.

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: December 22, 2014, 10:41:58 pm
content: Quote from: crusader66 on December 22, 2014, 08:16:52 pmDo you think that there is a shortage of "certified" control gear in industry? I am thinking one can create business by retrofitting off-the shelf equipment into certified versions? I found that with most of these certifications - once you go through the process once, second, third and every time after will be far less painful.There must be some firms that do just that already.

author: crusader66
author_rank: Contributor
timestamp: December 22, 2014, 11:25:17 pm
content: Quote from: Alexei.Polkhanov on December 22, 2014, 10:41:58 pmI am trying to answer this and find myself retyping and retyping as it is a complicated world in petrochemical applications.I don't think it is a shortage of gear as much as it is a large task to implement a project from the control room out to the sensors and deal with the varying levels of hazardous areas. You would think that the second or third or fourth time of doing this would get easier but when interpretations change or the designs change due to parts becoming obsolete then the cost of development goes up. There are many companies that make the pieces and then there are the large system integrators that put them all together. That to me is the attraction of the energy industry. You can work on the sensors, the control equipment, the small systems in a box all the way to the large systems that tie all of this together at a site.I think that in the energy industry there is always room for the small guy to build his business into a successful venture. I see that quite often from the oilfield to the refinery and out to the point of sale to the public. I think the same applies for the entire energy industry; not just petrochem. You just have to be willing to live in the world of NFPA/NEC, ATEX, CSA, FM, UL, Cenelec, EU, IEC EX....... Having said that, I have seen/heard of many cases in the upstream oilfield that would blow your mind when it comes to the lack of safety or understanding of any standards.This seems to be drifting off topic though. I'll stop there. I think the original question was about designing parts for hazardous locations and my best advice was to start with that book by Magison.

author: PChi
author_rank: Frequent Contributor
timestamp: December 23, 2014, 07:12:45 pm
content: I think that the statement on the Technetea web site of 'An equipment which is not designed from the beginning for a use in potentially explosive atmospheres,has thereafter very little chance to be able to be adapted for a use in this context.' (hopefully they wont mind me quoting) is correct.So any adaption of any equipment could be extensive. Also the cost of the approval process is high. Equipment designed for use in Explosive Atmospheres is expensive for a reason. It has taken much time and money to approve it.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 23, 2014, 08:28:49 pm
content: Quote from: PChi on December 23, 2014, 07:12:45 pmIn the case of IS, definitely. for flameproof, it can be as "simple" as adding discharge resistors across any big caps, putting it in appropriate enclosure, using the correct type of cable glands or line bushings, though this is to some extent trading off an electrical problem for a mechanical one, and is limited to nailed-down equipment.

author: PChi
author_rank: Frequent Contributor
timestamp: December 23, 2014, 09:58:58 pm
content: Dave has done a tear done of a tear down of 'Intrinsically Safe' electronics in episode #603.Also Sira have a 'Hazardous Area' Wallchart athttp://www.siracertification.com/resources.aspx?page=129.

author: HP-ILnerd
author_rank: Frequent Contributor
timestamp: December 24, 2014, 07:08:00 pm
content: That is crazy cool, Mike! No pun intended!

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 24, 2014, 07:31:33 pm
content: Quote from: HP-ILnerd on December 24, 2014, 07:08:00 pmOops - wrong video!Should be :

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: December 24, 2014, 09:23:20 pm
content: Back in 1995-96 walking around large chemical plants as intern, especially those that deal with petrochemical stuff, I noticed that they have plenty of small pilot burners everywhere. They suppose to ignite large flame (also called "Flares" I believe) in case of leak. These are located almost everywhere near any potential leakage points. If anything happens such as, for example, excessive pressure causing relief valve to dump some crap into atmosphere - that flare will immediately ignite and burn it. Some of them supplied with large gas canisters because leaking gas may not support the flame by itself. It appears to be very popular safety measure. When pilot burner shuts off it is immediately detected by control system and everything shuts off - it is much easier to ensure safety this way than to monitor atmosphere for flammable gases.I have feeling that often "flame resistant" is misinterpreted as "preventing flames" when in reality it means opposite - "works even when Flare is burning nearby". Some of these were turning into large fires pretty often and nobody seemed to care at all, some engineers just say something like "holy molly!" and carry on.Looking at incident reports like this:http://cchealth.org/hazmat/accident-history.php. you can see that "smoky flare" is frequent problem.

author: retrolefty
author_rank: Super Contributor
timestamp: December 25, 2014, 12:26:57 pm
content: QuoteWhat do you base your opinion on? Having worked at a major refinery for 27 years I can state my experience that safety and the prevention of incidents was the #1 concern at our refinery. Our yearly OSHA incident rate had drastically decreased over my 27 years there. We even 'earned' year end cash bonus (a couple thousand $ in some years) if ever increasing safety goals were met. Plant shutdowns, automatically tripped or manually by plant operators could cost a $1 million a day in lost production. There is direct positive correlation between refinery profitability and reduced safety incidents. It was every employees job and responsibility to obey and report any safety violation or incidents. Virtually every employee had the 'power' to stop any on going activity for questions of safety.Management took the stand and policy that every safety incident is preventable. That sounded to me at first pretty much like a useless slogan in my opinion (shit happens) when first implemented, but I had to admit that over the years that it did cause a change of culture that did result in steady reduction in safety incidents. Make no mistake, a large petrochemical plant has the capability of tremendous damage and health and safety concerns.Over my tenure there was lots of money and time invested in control technology with most plants 'armed' with automatic plant shutdown systems which help a lot. Of course this brought cases of automatic plant shutdowns based on 'false positive' sensor readings. Helping in the design, installation, and maintenance of such safety shutdown systems was one major part of my specific job. It could be very stressful work at times but I considered it a very rewarding career both for pay/benefits and making a positive contribution over the years.PS: My refinery was one of those listed in that accident history link you posted!

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: December 26, 2014, 05:27:17 am
content: Quote from: retrolefty on December 25, 2014, 12:26:57 pmPerhaps I did not make it clear why I linked that incident reportI gave an example of incident report to illustrate fact that Flares used extensively as safety mechanism. Report I linked confirms that Flares are in fact used a lot. I am referring to_Flares_(see Wikipediahttp://en.wikipedia.org/wiki/Gas_flare) NOT random fires that appear from cracks in rusted pipes.I was not trying to say anything about reasons of accidents or my opinion about them. Accidents themselves are awesome thing from statistical point of view - they are recorded more accurately since it is required by law. So If I get stats from let's say car sellers telling me what types and what colors of cars people own in Canada I would not trust it much. If I get same information by mining insurance claims with fatal injuries I would be more confident in data I have obtained as result because I assume that since car model and color is recorded as part of accident investigation it is more likely to be correct. When I noticed that Flares often mentioned in accident report I concluded that they are used. I hope I explained it well.

author: retrolefty
author_rank: Super Contributor
timestamp: December 26, 2014, 01:56:21 pm
content: Ok, if flaring during plant emergencies is your main topic or concern, then what is your question or point? Flares are an essential safety component in most any petrochemical plant. Think of flares like emergency air bags deploying during a auto collision, their purpose is to burn off gases in a controlled manner rather then allow unburned hydrocarbon gases to be released to the atmosphere directly because of some plant upset.When you see a flare flaring it's because it's actively performing a safety function to allow the protected plant to depressurize as quickly as possible to limit damage and health and safety risks.