Using Unstamped Pressure Vessel. Just How Bad Of Idea? 1

[BenjaminM]

I've got a bit of a problem that I need some serious direction on. I have not been involved directly in the following but it will be falling in my lap very soon and I have several reservation about it.

We have a used rotary vacuum dryer that we intend to use in an upcoming project. It's about 20 ft long and 5 ft in diameter just to give you a scale. Originally rated for 150 PSI on the jacket I believe, FV inside the dryer.

The jacket of the RVD was in very rough shape when we received it. Badly corroded along the bottom half. A welding contractor was brought in and they cut away several of the weak area. Sheets of steel were then rolled and welded on to the old jacket, basically covering the entire bottom half of the dryer.

I'd questioned the powers that be about if the welders were code stamped to do these repairs. To be blunt, the response was "There were patches already on the jacket and no R stamp present, so it doesn't matter. Don't worry, we will only have 15 PSI on it".

I've been asked to hydrotest the jacket, I feel confident I can accomplish this task safetly. They are intending to have an operating pressure of 15 PSIG steam on the jacket. However, since our steam supply is at 100 PSIG, I intend to hydro it upto at least 100 PSIG with the justification that the regulator could fail.

SO.... can you (legally) use a repaired vessel to hold low pressure steam at 15 PSI with out an R-Stamp?

Can you use a vessel completely missing the National Board number to hold steam at 15 PSI?

Can you get a pressure vessel approved by the National Board after the fact or do all repairs have to be done by a coded shop?

I am sorry I am not well versed on ASME codes, but I just feel this is not wise. If you can point me in the direction of some good resources on the subject I would be much appreciative.

Please feel free to be blunt. I am not pleased about the situation, though no one else seems to be too overly concerned.

 

[metengr]

"There were patches already on the jacket and no R stamp present, so it doesn't matter. Don't worry, we will only have 15 PSI on it".

Wrong, it does matter.

SO.... can you (legally) use a repaired vessel to hold low pressure steam at 15 PSI with out an R-Stamp?

Check your local Jurisdictional rules where this will be installed.

Can you use a vessel completely missing the National Board number to hold steam at 15 PSI?

Check with your local Jurisdictional rules where this will be installed.

quote]Can you get a pressure vessel approved by the National Board after the fact or do all repairs have to be done by a coded shop?[/quote]

No. The National Board does not approve anything. Once the vessel is registered with the National Board, all weld repairs to this vessel must be performed by an R-Certificate holder.

 

[moltenmetal]

Put a properly sized relief valve on the line to protect against regulator failure, set no higher than 15 psig, and consider the jacket NON CODE. That's the safest option that doesn't (potentially) require major re-work of the vessel.

Hydrotest to whatever pressure you wish (up to the original hydrotest pressure of the jacket), but you still need the relief valve. The thing IS a vessel if you operate it as a vessel, and operating at 15 psig with relief set at 100 psig is still operating it as a vessel. The proper functional definition of design pressure for a vessel is minimum required MAWP- that is RELIEF pressure, not expected operating pressure.

Obviously you will NOT be able to operate this at 15 psig with a relief valve SET at 15 psig. You'll be limited to perhaps 10-12 psig max.

If you KNOW that the welding work was done incompetently, then calling the thing non-code won't save you. 15 psig steam released instantaneously in large quantity can still hurt people. But just because the welders who did the work didn't posess an R stamp doesn't immediately mean they were incompetent to do the work. It is possible to find competent welders, even ASME IX qualified welders (for piping for instance), whose employers don't posess an R stamp. Better find out what the welders who did the work WERE qualified to, if anything. That won't change the status of the thing now as non-code, though.

 

[BenjaminM]

Thankyou Metengr and Moltenmetal.

The welding contractors are skilled, and I believe they are competent. They have done excellent work on previous jobs. I do believe their work will hold up.

My first concern is always safety of course, but the majority of my current worry is if it is legal to operate a non code vessel.

At the same time we have spent a decient amount of capital having this dryer repaired. Afterward we will invest even more installing this new process line. I just do not want an inspector to show up one day and force us to stop the production because of an uncoded vessel.

Thankyou again!

 

[unclesyd]

We have some twin cone (100" x 100", FV and 15 psig on both shell and tubes} driers that are not code stamped but were designed to code as close as possible. These dryers are heated and cooled with Therminol VP1 and run 24/7/365. The problem with the design is the tubesheet that in no way meets any code.
Though we are not a code state all repairs are cleared through the insurance.s AI. These dryers are constantly under repair due thermal fatigue especially the tube to tubesheet weld. Three of these dryers have had major repairs in that the existing trunnions were failing and had to be replaced by a new design. The repair was sanctioned by the vendor, insurance company, fabricated by our shop, and installation carried out by a code shop.
We have two of these dryers in a code state and as far as I know have no problems with operating as built. They have had few repairs and again no problem with the jurisdiction.

 

[BJaffa]

The legality of use is clearly determined by the local pressure vessel jurisdiction (if any the vessel is operated in. Local laws and conformance to to applicable Codes can be confirmed by your local State Boiler Inspector or your equipment insurer. The plate repairs using flush inserts are permitted by repair Codes.

 

[zdas04]

At the end of the day, the code stamp is insurance to mitigate liability. Knowing that the vessel has not been demonstrated to meet the code pushes your company towards "negligence" or "gross negligence" if someone is ever hurt by this vessel failing.

I live in a "non-code state" in the US, and that distinction only means that the state does not have an official "boiler inspector" position in the state government. If someone is hurt in a vessel failure, the courts immediately go to the boiler code to see if the vessel meets "good engineering practices". Without a "U" and any required "R" stamps it is tough to demonstrate that the vessel meets good engineering practice and civil awards can go way up.

David