ASME Vertical Tank Head Replacement 1

[Will4431]

Need to replace the head on a vertical tank. Can anyone outline the proper cutting, weld bevel, welding process, and NDE steps required to replace a 2:1 elliptical head (.375” thick) on a 7/16” thick x 3’ dia x 8’ carbon steel (SA-285-C) vertical tank?

 

[Geoff13]

Hire an ASME registered contractor.

 

[Will4431]

Not looking for overly detailed reply as I said, just looking for a general overview of the process for my general understanding in order to make the best engineer / contractor selection decision.

 

[MJCronin]

This sounds a lot like a tiny, commercially available carbon steel tank commonly used as a head tank or Air Receiver

Why do you want to replace the head for this "throw-away" CS tank ? ... How old is this beast ?

Are you replacing just the lower head ? Was there a corrosion failure ?

A new tested, carbon steel tank of this volume should be about $2600 to $4000 plus shipping.

Buy a new carbon steel tank with a premium internal coating and move on ...

Are you sure you want to replace the head ?

Please give us more information including pictures and the reason for head replacement

MJCronin
Sr. Process Engineer

 

[JStephen]

I will point out that the proper cutting, weld bevel, and welding process will depend on who is doing it, and what they routinely use for similar applications; there isn't one right answer.

 

[r6155]

See ASME PCC-2 and API-510.
Are you sure a replacement is necessary?

Regards

 

[FacEngrPE]

Step 1 is to get a price on a replacement tank. If the installed price of a replacement is less do that instead.
Step 2 Determine if your jurisdiction or insurer requires repairs to be made by firm holding an ASME U stamp ASME certificate Search
Step 3 Hire a firm on the list, your contract should require the repair firm to apply his code stamp to the work, and provide the National Board form describing the repair, and NDE.

 

[MJCronin]

FacEngrPE ...

I disagree slightly ....

You state: "Step 1 is to get a price on a replacement tank. If the installed price of a replacement is less do that instead"

It is my opinion that credit must be placed on the company benefit and increased value of a brand-new, pre-tested entire tank, rather than a pieced together Frankenstein. The company benefits from new reliable capital equipment, quicker installation and probably the benefit of modern long-lasting coatings.

Remember, a new tank head must replicate the existing nozzle orientation. There will be some piping impact

Because, of course, we get little or no information about the existing tank, this is all guesswork !!! ... The third world newbies strike again !

I would replace the entire tank even if it cost 50 to 75% more than the head replacement.

Remember, this tiny vertical tank is more akin to an overgrown water heater !!!.... In my town, "Mr. Water Heater" guarantee's a replacement in three hours or less. What is the cost of a halt in the process worth ?

Oh, wait ..... Like all the other questions from the mid-east ....You have given up on this thread and will no longer offer information or participate



MJCronin
Sr. Process Engineer

 

[r6155]

At the moment we do not know the reason for the replacement, therefore I do not know the criterion of (0P).

Regards

 

[thebard3]

The OP's question sounds a little like-
"I want to build a spaceship to fly into a black hole. How do I do that?"

Brad Waybright

The more you know, the more you know you don't know.

 

[Christine74]

Is it the top head? If so you would likely need to build scaffolding. If it's the bottom head and the vessel has leg supports, you'll have problems machining the bevel. If the vessel has a skirt you will have machining/fit-up issues.

Is the vessel 3 ft ID or 3 ft OD? Make sure of that before ordering a replacement head. Also make sure that you request mill certs with the new head.

Is the vessel painted? Depending on the age of the vessel, some primers were lead-based so you made need to do lead abatement.

You would need to find an "R" stamp holder to perform the NBIC Repair. The existing head can be gouged off but you would probably have to use special portable equipment to true-up the cut and machine the bevel.

Due to the confined space issue probably would want to avoid welding from both sides/back-gouging, so after tack-welding the new head in place you might consider purging the vessel with an inert gas such as Argon/Xenon and using GTAW for the root pass at a minimum. All welding would need to be performed by an ASME-qualified welder.

Does the existing head have any nozzles in it? If so, will you be replacing them with new nozzles or salvaging the existing nozzles?

For NDE you would probably have to perform some level radiography (assuming the existing vessel had RT performed) and liquid penetrant examination (PT) or magnetic particle (MT) examination, depending on the criticality of the service. Then your contractor's AI would probably require you to hydrotest the vessel prior to signing off the R-1 form, after which you could touch up the paint.

That having been said, it's probably easier just to replace the vessel. Another option would be to send the vessel to a shop that has an "R" stamp.


-Christine