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Up Topic Welding Industry / Technical Discussions / Welding Inside Propane tanks??
- - By awspartb (***) Date 10-03-2008 20:41
This is crazy but here's the situation.  We have an old propane tank that they want to modify and put new fittings on.  It's been drained and the manway is open but it still stinks like propane.  The tank is around 45 feet long and about 8 feet diameter.  They want us to vent it and cut into it for the new fittings then go inside and backweld them.  Our safety dept has serious concerns about this as do we.  We all refuse to do it.  Is there still a risk of explosion due to the propane seeping into the metal?  The tank is over 50 years old and the shell is 1" thick.  Can someone point to a safety procedure for this?  Thanks
Parent - - By ctacker (****) Date 10-03-2008 21:38
who is "they"? ask them to go inside with a torch and make sure its safe!
all kidding aside, fill it with an inert gas or water. if it smells as you say, you'd want fresh air delivered for breathing, so an air tank (as a scuba tank) would work in either case!
Parent - - By awspartb (***) Date 10-03-2008 22:17 Edited 10-03-2008 22:26
"They" would be the office idiots who bid this job.  I'm not sure this thing is legal to even be in NY State because of code regulations.  It was purchased from out of state and brought here for modification.  This tank is a monster, 18,000 gallon capacity.  I'm under the impression that the old rust inside the tank acts like a sponge and holds propane gas .  Even after venting, it can still explode.  Purging is the way to weld on the outside but how about inside??  Not worth my life.  It's only a job.  There are very few places that will do this work due to the explosion hazards.

From what I've been reading, it should be steam cleaned first followed by venting for several days and then inert gas purging for the initial torch cut.   It's the "get inside and backweld it" that we have a problem with as propane has a way of coming back alive by seeping out of the pores of the metal and internal rust.  This thing is 60 years old and was pressurized at 200 PSI when operating.  Am I being over cautious or should I be very afraid?  Any offcial procedures for doing this?  I can find nothing on the internet other than horror stories about working on these.  Thanks.
Parent - - By ctacker (****) Date 10-03-2008 22:26
I found this.
I emailed them awhile back and had a response in a couple days!

IF YOU HAVE WORKPLACE SAFETY AND HEALTH RELATED QUESTIONS:

[By Phone]:
1-800-321-OSHA (6742) {Toll Free U.S.}

[Write To: (required for an Official Agency Response*)]
[DOMESTIC ONLY]
U.S. Department of Labor
Occupational Safety & Health Administration
200 Constitution Avenue
Washington, D.C. 20210

[INTERNATIONAL]:
U.S. Department of Labor
OSHA Coordinator for International Affairs
Occupational Safety & Health Administration - Room N3641
200 Constitution Avenue
Washington, D.C. 20210
[Email (By Electronic Mail Form*)]:
You may complete an online electronic submission form:
* Responses to the Electronic Mail Forms are for informational purposes only, and do not constitute an official communication of the U.S. Department of Labor or OSHA. For an official response, please send your inquiry in writing to the one of the above.
To submit an information inquiry by Electronic Mail Form.
Parent - By awspartb (***) Date 10-03-2008 22:49
Thanks.  Email sent.  I'll be having bad dreams bout this job over the weekend.
Parent - - By dbigkahunna (****) Date 10-03-2008 23:15
[deleted]
Parent - - By awspartb (***) Date 10-03-2008 23:25
Thanks for the info.  The tank only has one manway.  Here's a photo of it.  I'm working for another company that was hired to retrofit this tank, not the company in the link.  They buy up old tanks and then sell them.  My outfit is the ASME company that was hired to weld the new fittings.

http://www.totalenergy.com/Tank%20Inventory/Location%20By%20State/New%20York/LewistonNY/Lewiston.htm
Parent - - By dbigkahunna (****) Date 10-04-2008 23:08
[deleted]
Parent - - By awspartb (***) Date 10-04-2008 23:14
It's 18,000 gallons.  Can propane leech into the steel over time?  The thing is 60 years old and it stinks.  It's not where it is in the photos.  It's laying in the mud up here.    It has very few fittings, all of them very small other than the 20" manway.  We will be adding several more fittings.   
Parent - By Joseph P. Kane (****) Date 10-05-2008 00:56
If the tank is open and removed from the piping and laying in the mud, the smell you detect is very likely the residue of odorizing agent.  (Mercaptan, the smelliest substance on earth.)

There still should be a "Gas Freeing" Engineers Certificate, and a confined space procedure, and the appropriate confined space equipment before any welding is done, or anyone goes into the tank.  A "Hot Work Permit" is usually not required for work done in your company's yard, as long as there are no other fire and explosion dangers in the yard.
Parent - By jetfuelbob (*) Date 10-06-2008 02:26
We hot tap and weld on fuel tanks all the time. What you are smelling is not propane but the mercapten (hope I spelled this right) its
what gives propane its smell and is required when being sold. Natural gas distribution systems also use this same chemical. My best advice
would be to hire a contractor that performs this type of work. This is also a ASME code constructed vessel that will require proper welding procedures and post welding tests along with a new certification data plate.
Parent - - By jrw159 (*****) Date 10-04-2008 23:35
BigK,
I hope this question will benifit awspartb, and is in line with topic.

After cleaning and venting as described, would this still qualify as a confined space?

jrw159
Parent - - By ctacker (****) Date 10-04-2008 23:40
yes
Parent - - By jrw159 (*****) Date 10-04-2008 23:41
thanks
Parent - - By ctacker (****) Date 10-05-2008 00:30
I would think a permit would be required also!
http://www.osha.gov/SLTC/confinedspaces/index.html
Parent - - By awspartb (***) Date 10-05-2008 02:27 Edited 10-05-2008 02:33
Can anyone point to a procedure for welding on and especially INSIDE propane tanks?  I can't find anything.  OSHA?  Refinery or Propane Association safety procedures?  Anything?  I've been told there are specific safety requirments for working on and inside propane tanks that go above and beyond normal confined space procedures due to explosive hazards even after a tank is cleaned and vented but I can't find them.  There has to be something out there on this.  any help appreciated.
Parent - By 803056 (*****) Date 10-05-2008 03:34
Joe is probably right about the smell being Mercaptan, but I think dbigkahunna may be on to something if there is any corrosion on the inside of the tank.

I doubt the gas permeated the steel. The hydrocarbon gas molecules are much larger than the atomic spacing of the steel atoms in the atomic lattice of the crystalline structure of the steel.

As for welding on the inside of the tank: it is definitely a confined space and what are the financial consequences if something was to happen while workers were in the tank?

I have a friend that works in the shipyards in Portland, Oregon. They repair all types of ships, including oil tankers. They weld on steel that still has a paraffin deposit on it that sometimes flares as they weld. Sorry, you wouldn't get me to weld in those tanks for love or money. Call me "Chicken", but I don't like crispy fried chicken skin and I'll be darn if I want my skin in that condition either!

I like the suggestion that the office people that accepted the job should be in the tank with the welder as their helper when the tank is being worked on. They might think twice if they are part of the crew that does the actual work.

Best regards - Al
Parent - - By dbigkahunna (****) Date 10-05-2008 03:44 Edited 10-05-2008 03:58
There is no special procedure for welding inside a propane tank vs repairing a tray on a depropanizer tower. If the space is a permit required confined space, then welding would not be allowed. After the tank is gas free and clean the space may/may not be classified as a permit required or a non permit confined space.
Yes there is a difference. All confined spaces are permit required until the entry supervisor determines the condition of the confined space.
Once the space has been determined not to be a permit required confined space then a hot work permit would be required. The LEL's would have to be 0% and the oxygen between 19.5 and 23% and no other hazards.
All of this should be covered in YOUR company confined space permit procedure and Hot Work procedures. This is done all the time you just need to have the proper safety procedures in place. If there is proper permitting procedures in place, the inside of the tank is gas free, properly clean and there is proper and continuous monitoring of the space there is nothing special about what you would be doing.
Welding on a propane tank with product in it, then you are talking another animal.
You may want to check out API 2015 and 2016 for cleaning of tanks and vessels for inspection and repair. Also
http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=standards&p_id=9797
Parent - By RANDER (***) Date 10-05-2008 03:50
Thats your answer right there awspartB
Parent - By ctacker (****) Date 10-05-2008 20:09
Good answer!
Parent - By jetfuelbob (*) Date 10-06-2008 02:27
Go to API & ASME.
Parent - - By dbigkahunna (****) Date 10-05-2008 03:48 Edited 10-05-2008 03:57
[deleted]
Parent - - By awspartb (***) Date 10-05-2008 11:20
I can't thank you guys enough. 
Parent - By 803056 (*****) Date 10-05-2008 22:40
Good show dbigkahunna!

Best regards - Al
Parent - - By jetfuelbob (*) Date 10-06-2008 02:42
This vessel after being cleaned is still a permit required confined space. The difference after cleaning is that it can become a non-hazardous
confined space, but still a permit required. And remember if torches are being used inside the vessel, remove the torch and hoses as soon as the cutting procedure or pre-heat is done. Leaking torches inside of tanks has caused problems on more than one occasion. And if
personel leave the tank for a break assume that the conditions inside have changed before getting back in!

No internal combustion engine equipment running near the tank, carbon monoxide gas, no painting or solvent operations taking place near
by. There was a crew working for Mobil years ago on a tank, they were using a lamb air mover and and some how another contractors
backhoe working to close sucked in gas vapors into the diesel engine. The engine went into over speed caused a backfire and flashed
back to the tank being service and killed the two workers.

This type of work is for experienced workers only!!!!!
Parent - - By dbigkahunna (****) Date 10-06-2008 12:01
[deleted]
Parent - - By Boilermaker395 Date 10-16-2008 23:05
Welding your new fittings in should not be a problem.  If the proper precautions are taken.  I just welded in two fittings on a propane tank of similar size about a month ago.  That tank was originally built in 1938.

We used full penetration weld procedure so we did not have to go inside and back weld it.  The tank was emptied and ventilated for a few days prior, then we used nitrogen to completely purge the tank.  I would recommend not torch cutting anything.  We used another contractor to come in and bore and bevel the required holes (2.5" and 3" if I remember right).  After that we did a full penetration root with 5P+ (6010+), and then filled and capped with 7018.  Tig welding the root is also a good option.

You will need to verify the material used in the original construction as to use the proper material and filler metal for you modification. 

The nitrogen purge was done continuously as was an air monitor in at all times showing a 0% LEL and around 4-7% oxygen.  After the welding was done a sheer (sp) test was performed to ensure the quality of the welds.

As others have stated the smell will never go away.
Parent - - By awspartb (***) Date 10-16-2008 23:51
Thanks for the reply Boilermaker395.  I really have no desire to go inside this thing and judging by the three coats of paint on the manway bolts...........well you get the picture.  Nobody has been in this thing since JFK was President.  Lead paint.  Another issue.  Office people need to talk to the field people before bidding on a job.  Thank God I'm working Union and have the proper procedures to challenge unsafe work procedures other than calling OSHA and getting fired. 
Parent - By js55 (*****) Date 10-17-2008 16:05
If this thing has a code plate and you plan on continuing the code plate you need to develop and inspection plan. Section VIII though it can be used, is not really suited to repairs, alterations, or rerating of PV's that have been in service. As Kahunna said API 510 is the best reference, with 572 as an addenda. Develope your inspection plan, if necessary consult an engineer or a corrosion specialist based upon what you find. Follow the plan. If you need to perform a fitness for service assessment then API 579 is the reference and is meant to be a continuance of 510 and 572.
I would not do something of this nature without the proper references and procedures in place.
Parent - By vagabond (***) Date 10-17-2008 16:28
I worked as a welder on both butane and propane tank repairs a few years back.  They were steamed and cleaned very thoroughly to start with,  and than vented with fans.  They were always treated as permit required confined spaces.  We always had the area "sniffed" prior to starting work and monitored thru-out the shift. Other than those caveats we proceeded as usual and never had a problem.  I would make sure your safety people are checking everything when they sniff not just oxygen content.  In other words make sure there are no concentrations or pockets of gas in low lying areas etc.  I would get my own info as far as PPM etc. for the product in tank so I could cross-ref. that with the safety guys info.  And I would probably require some 5 min escape packs to be present inside just in case.  An ounce of prevention is worth a pound of cure.  But this is a pretty routine procedure in the refinery sector,  the cleaning usually takes the longest of anything if memory serves correctly.
Up Topic Welding Industry / Technical Discussions / Welding Inside Propane tanks??

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