welding near fuel tanks 2

[tristrium1]

Hi all.

I am managing the construction of an above ground storage tank facility as the client. Does anyone know were I can find guidelines relating to min welding distances from above ground storage tanks containing diesel and jet A1.

Thanks

 

[CRG]

You could start by evaluating the electrical area classification for the facility.

 

[BigInch]

Minimum code distance will be about 10 ft from a vent, but 50 ft is a typical company standard, without making a big deal out of it.

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus

 

[racookpe1978]

The threat is real - but your response (the stand-off distance involved) needs to be based on sampled permitted explosion limits for the explosive odors actually present. Welding and cutting/plasma/gouging are the most visible, but lots of activities on a construction site create sparks that can ignite fumes.

Heat (more vapors at higher ground and fuel temperatures), wind direction and the direction between the welding/construction zone and the filled tanks and empty (non-purged) tanks nearby, humidity, wind strength, etc.

On a calm day (near dawn ?) sample PEL exposure data for the tanks. Most air samplers report this as ppm. Take data again at different distances to get your info about dilution ratios. Repeat for a modestly windy day (7-8 knots).

 

[MJCronin]

tristrium1,

You have put your finger on a real significant hazard that is, IMHO, virtually ignored by OSHA/NFPA/CSB and others.

There have been many deadly accidents caused bt welding/hotwork at the tops of tanks storing flammable substances.

In the same way OSHA has prohibited ditch digging without cave-in prevention walls; in the same way that fall protection harnesses are mandated; in the same way hearing protection is mandated....

WARNING SIGNAGE SHOULD BE REQUIRED ON THE ENTRYWAYS AND AT ALL TANK VENTS OF ALL STORARGE TANKS !!!!!

I suggest: " DANGER EXPLOSION HAZARD - NO HOT WORK WITHIN 25 FEET"

Well..... this matter has been under government consideration for the past several years....

I don't understand the delay....

I don't understand the downside.....

 

[BigInch]

Delay? After being president of a 150 unit condo complex for the past year, I am pretty sure that there is probably a committee involved in making the decision.

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus

 

[chicopee]

You can always erect a fire resistive wall such as steel plates.

 

[GregLamberson]

For fire you need 3 things, oxygen, a spark and a combustible. Near a tank filled with diesel or jet fuel you have 2 of 3 - add welding and bingo. You need to use gas detectors to assure the level of vapors are suffeciently low prior to welding and continually monitor it during welding.

A protective wall is a good idea for sparks from grinding, but will not protect against the vapors. If you can't get the gas vapors down to acceptable levels then you need to start looking for alternatives in getting rid of the fuel/vapors.

Proceed very, very carefully. I would suggest getting some expertise in the area of fire prevention prior to starting any hot work.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[Duwe6]

Distance is somewhat of importance, but wind direction and windspeed, and tank activity are the major factors in how much vapor will be present at the work location.

Since wind changes w/o notice, keep a LEL monitor at the Hot Work, on the tank side. Lock out the tank fill line, so there will be no vapor pushed out the vent(s) due to filling.

Not a bad idea to have a small firehose [not garden hose] at the work site, and wet the area prior to starting work. Sparks quench instantly when they hit a wet surface. The person on the hose must be trained and experienced, prefferably a fireman. If something bad happens, they are your last line of protection.

 

[BigInch]

If you have an explosive atmosphere 50 feet from a diesel or jet A1 tank, you first better be looking for sawdust, sponges and a snorkle.

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus

 

[GregLamberson]

tristrium1

This is nothing to fool around with. Suggest you take a look at API 2207 which is written for preparing tank bottoms for hot work. Not exactly what you are doing, but it has some very prudent precautions you need to take.

I would also suggest, if you don't already have it in place is a prescriptive permit to work system and a specific permit for hot work. Your hot work permit should include all of the mitigations that should be in place. I would also do a Job Safety Analysis or Job Hazard Analysis (different people use different terminology) - it's like a task specific risk assessment. In looking at all of the hazards you could face before the work starts, you can put the proper measures in place to avoid ending up on CNN.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[davefitz]

Here's a link to some OSHA examples of failures associated with welding close to fuel tank vents:

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http://www.epa.gov/oem/docs/chem/cat-tnks.pdf>

It would help to have flame arrestors in all vents. Worst case is the bottom weld seam weakened by corrosion and the roof seam being too strong .