Certify an old pressure vessel 1

[azeotrope1]

Hello all,

I have an old carbon steel horizontal tank that needs to be used as a pressure vessel (100 psi)

The tank has no stamp or plate. API 510 has provisions for getting a stamp for tanks with minimal information but I am having trouble finding out what needs to be done and what it would cost.

I have spoken to tank inspectors and their opinion is it would cost so much it is better to replace it because samples of the tank would have to be taken to determine the alloy, weld inspections etc.

The tank is large at 16000 gallons and NDT has shows that it is a minimum of 1 in thick. This is an OSHA PSM project if it makes a difference.

Can anyone give me advice on how to proceed?

Thanks,

Tom Jones

 

[NBrink]

The very first thing I'd do is contact your jurisdiction and see about their requirements for certifying a non-code pressure vessel (sometimes called a "state special") requirements will vary significantly across different jurisdictions. You may find what you're looking to do is pretty simple, or pretty near impossible depending on how much information you have available to you. Could very well be cheaper to build a new vessel.

 

[metengr]

There is no easy route for this type of activity. Locations which regulate pressure vessels in the USA, use a "state special" category to allow for a vessel to be used in pressure vessel service. They have rules surrounding this type of activity. I know of no Codes that allow a vessel to be used as a pressure vessel because typically one cannot stamp a vessel as being compliant with a construction code, after the fact.

 

[LittleInch]

"I have an old carbon steel horizontal tank that needs to be used some cheapskate would like to use as a pressure vessel (100 psi)"

Big difference. This has been discussed many times on this forum and the answer is always the same - no stamp / plate / paperwork = no pressure vessel = lump of scrap metal.

I don't know what it is you were thinking of storing in it, but that's a big volume at a decent pressure if e.g. the end fell off.

It kind of scares me a little that anyone is actually trying to do this.


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[azeotrope1]

Editorials aside, the tank has actually been in service as a pressure vessel for about 20 years. It was certainly designed as a pressure vessel and state inspectors had OK'd its use given NDT and PVELite type calculations. The Feds are in disagreement with that opinion however.

I think replacement is the best option but the bosses (and yes they could be characterized as cheap) want to know what would be involved to code the tank and compare that to replacement costs.

 

[MJCronin]

Bravo, Littleinch Bravo !!! I strongly agree with the statements above,

Either a new or perhaps used, but certified, pressure vessel may be best (and cheapest in the long run)

Cheapskate indeed .... all MBAs seem to put their staff through this useless "make-it-a-pressure-vessel" exercise

Ohh ... Has your boss yet told you that the project cost estimate does not include the cost of a replacement vessel ???

Azeo, please keep us informed about the final decision and the reasons for it.

You should be able to find prices for a used ~ 16000 gallon, carbon steel vessel on the internet ....

MJCronin
Sr. Process Engineer

 

[JStephen]

My state has a boiler law, but does not regulate pressure vessels. So there are some non-code vessels around. Many of the rural hydropneumatic tanks are non-coded tanks, capacity and pressure similar to that described. So it's not an unknown item. I don't know what all the differences are, but the one I can see when driving down the highway is that the tanks have a fairly small knuckle radius rather than the 6% minimum.

Anyway, if it's an inch thick, it wasn't built as a "tank", it was built for some kind of pressure service. But without any papers or knowing the construction details and past history, I would not be inclined to put it back into pressure service.

 

[SnTMan]

azeotrope1, I'd also recommend you get your insurance carrier involved early.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[LittleInch]

Ok, a bit of a low blow and you didn't say in your OP what you subsequently said about the current / past use. "Tank" is not normally seen as a "pressure vessel", hence my somewhat snappy reply.

However presumably something is changing if you're going from what the local inspectors signed off and now. So what are the changes ( pressure, contents, location, regulation??).

Let us know how it goes.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[loilfan]

You can use Positive Material Identification (PMI) to identify the material type (I would suggest doing hardness testing too to verify UTS), Ultrasonics to determine the thicknesses, RT to determine joint efficiency, MT to check for cracking, and visual inspection to determine the known condition and flanges.

You will need to determine the year of construction to determine the allowable stresses since the Safety Factor in ASME changed from 4 to 3.5 about 20 years ago.

You will need to check the PWHT requirements of the original Code of Construction to determine if it is exempt or not. Although it's probably not since it's less than 1.5". Note that the service may make PWHT a requirement as per UW-2. If PWHT is a requirement and you have no proof that it was done, you should do it again but be careful since the UTS drops with every PWHT performed.

You also have no proof that the welding was done by an ASME shop with an acceptable WPS, so this can never be fully compliant to the ASME Code and will never get a U-stamp or Manufacturer's Data Report.

This is a fair amount of work to not become fully compliant to the Code. I also suggest looking at replacement over backwards engineering it.

 

[chicopee]

A minimum 1" steel thickness to me would imply a pressure vessel. Are there any manhole or handhole in your tank? About the quality of the welds, do they appear to be uniform and full penetration indicating good quality work? Sometimes it will be difficult to find the plate stamping, so carefully look around the shell to head seams or right on the tank heads for such stamp; may have to peel some paint to find the stamping.

 

[chicopee]

And if you do find some form of stamping, be careful as it could just be a heat number assigned at the foundry.

 

[weldstan]

Is there any Manufacturer information on the vessel or in (previous?) Operator document/drawing files? Do try to find a paper trail to determine material. Do check with your Insurer and the Jurisdiction as previously mentioned.