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Posted By dave burrage
Does anybody have any definitive guidance or reference on the use of petrol vehicles in refineries? I thought this was pretty much discouraged in favour of diesel drive, but cant find anything 'official' giving definitive answer. If anybody can help it would be appreciated.
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Posted By Ian Waldram
You are crrect about it being discouraged. However, from a hazard/risk perspective there are at least 3 illogicalities in that.
1) The refinery layout will typically ensure that all normal access roads are beyond the hazardous ('classified') areas;
2) Most diesel vehicles will have associated electrics which are not Ex-rated (e.g cranes, emergency vehicles, which are normally allowed in);
3) Even a diesel engine can be a source of ignition for a large gas cloud, unless protected by an air-inlet closure and overspeed protection system.
What is clearly unacceptable practice is leaving any unattended vehicle with engine running in or near a classified area, unless it has such protection. Apparently that was normal practice at BP Texas City, as was a likely source of the ignition (not sure what type of engine).
So vehicle controls are certainly needed, but saying petrol is banned and diesel is OK is too simplistic!
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Posted By Pete48
Dave, you will find such matters in documents such as the IP codes of practice for Refining and or Marketing Codes.
I have a few moth-eared and much loved copies from way back in the late 70's and early 80's.
Basically both types of engines are sources of ignition and must be controlled in accordance with current codes. But as ever, there are things that can be done with design controls and/or under permit controls dependant upon zoning arrangements.
Standard road vehicles or hired in kit with diesel engines do not usually conform to any of the required design codes that allow entry to zoned areas.
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Posted By dave burrage
Thanks, much appreciated, the presence of electric circuits, (lights, horns, engine and fuel systems etc etc etc) in both types of vehicles clearly prohibits entry into any 'hazardous area' except under permit conditions for spark potential or in some cases, hot work. What i was trying to locate was something from API or similar which might give some guidance on the petrol/diesel question. Thanks again.
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Posted By Peter Leese
This isn't my field but....
Isn't any vehicle with an exhaust an ignition source - isn't that just as (or more) important as the type of engine?
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Posted By allan wood
I did some work on the esso fuel terminals across the U.K. a few years ago,and the following applied;
you could only take diesel fuelled vehicles on site;
you had to have permission from the plant manager for the vehicle to be on site;
the keys had to be left in the ignition at all times so that the vehicle could be moved in the case of an emergency.
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Posted By Pete48
Peter L, yes and no.
Sorry I couldnt resist on the cusp of Friday:)
There are at least two pages of closely typed guidance on this one aspect of controls in the IP codes, enough said really.
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Posted By Peter Leese
OK let's try again. Why is a petrol engine running more dangerous than a hot exhaust?
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Posted By Ian Waldram
Because the generator, points and HT leads are all likely direct sources of ignition. The more modern designs of engine with alternator are less of a hazard, but this type of 'ban' on petrol began many years ago when all petrol engines had open electrical sparks, so would be very reliable sources of ignition if enveloped in a gas cloud. The lack of any engine electrics on diesels made them apparently safer - but see my posting above for all the other electrical systems (lower voltage, but still possible ignition sources) which are usually present on vehicles.
Exhaust temperature isn't a problem until it reaches auto-ignition, which is quite high for the hydrocarbons typically present in a refinery, which is where this thread started. Obviously that can be a different issue for other gases with much lower auto-ignition temperatures.
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Posted By Peter Leese
Many thanks Ian, that aspect has always puzzled me before.
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