Pressure Vessel Corrosion Problem 3

[Inchtain]

Hi,

We have a Production Separator with the following data:

Design Code ANCC PNR (Italian Standard)
Position: Horizontal
Stress Relieved: Yes
Radiographed: Whole Joints
Shell—Material Fe E-45-UNI 5869 (Original Thickness 32)
Size—Nominal ID, mm 4154
Length Base Line to Base Line, mm 15000
Design—Pressure, psi 256
Operating Press, psi ±150
Design Temperature, oC 80
Operating Temp, oC ~ 80

Widely Scattered Pitting & Metal Loss found at the Separator Bottom (Minimum Recorded Thickness,
mm 10.36)

Is it better to repair, after Preparing the Surface, by only Weld Filling all Points ≤ 7.64 mm? or shall we line the Whole Affected Area Using Patch Plates? In case we have to weld patch plates, is it mandatory to use the same materials of the separator plates, or we can propose alternatives like ASTM A283 Gr. C?

The original WPS/PQR of the said Separator is missing. So, do you think that we can use an approved 6G-SMAW-Pipe using E7016 & E7018-G and API 5L Gr. X52 pipe WPS/PQR for the qualification of the welders who are going to perform the job?

The last point, I seek your advice concerning the repair welding procedure as long as the plates of the vessel have previously been heat treated.

Thank you for your usual cooperation.

Best regards,

 

[mk3223]

Should understand the root cause of the pitting and corrosion, and then decide the options of in-kind repair vs upgrade replacement.
It seems the weld patch repair is a better option to remove all the corrosion defects. It's a Code repair and the PWHT will be required for the vessel which was previously heat treated.

 

[r6155]

It seems that the inspections were not done for a long time.

Regards

 

[dik]

Are these for the oil and gas industry? What are the contents? Do different materials have different corrosion issues? Have you examined the pitting to determine what type it is?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[Inchtain]

Good morning,

The equipment is a 3-phase separator for an Oil & Gas Plant. It receives the crude oil and separates it to oil, water and gas.

The root cause of the pitting is the stagnated water during some previous prolonged shutdown periods and due to the deterioration of the internal coating.

The pitting are in the forms of Shallow-wide and trough-type.

Which is the best practice to perform the heat treatment for the vessel after repair?, or which are the other better alternative as the heat treatment is quite difficult to perform on-site?

Thanks and best regards,

 

[LittleInch]

What and who are you using to undertake the condition assessment of this vessel?

Most countries require an authorised party to undertake the inspection and repair and an authorised Inspector from the authorities to approve any repair.

I would normally expect any inspector / inspection company to give me a report detailing the condition of the vessel and what I need to do to repair it if indeed that was required.

Now at 10mm thick plate in places compared to 32mm in the original design, I think you have more trouble than a simple patch weld repair myself, but I'm no PV expert.

I strongly suggest you find yourself one.

you may find you don't have a pressure Vessel, you have a lump of scrap metal. Or you need to actually replace the bottom plates completely.

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

 

[weldstan]

Once the internal coating was gone, it is no wonder that corrosion would rapidly occur due to the water composition, most likely containing chlorides, sulfur containing compounds and CO2 and possibly anaerobic bacteria. Whereas you don't define the total area involved or the jurisdictional requirements, it's hard to provide the most cost effective repair.

 

[Inchtain]

Dear weldstan,

We would like to follow API 510 and ASME PCC2 for the repair and the Extent of the repair is nearly 55% of the vessel bottom between 5 o'clock and 7 o'clock.

Thanks for the input

 

[weldstan]

If you can find a vessel shop with a Field R-Stamp, it might be cheapest to have them roll a replacement plate to the appropriate radius, remove the entire corroded section or sections, and replace with the new plate, weld it in and RT the welds. Also the entire internal surface should be recoated.

 

[LittleInch]

See the last line of my previous response....

The scrap metal option looks closer to the truth based on the response above.

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

 

[PMCap]

Restoration by encapsulation without removal of the degraded area is accepted by the National Board Inspection Code (NBIC) as restoration by Alteration. This method of restoration can be very cost effective as the degraded area does not have to be removed thus saving fit-up, welding, and examination installation time and avoiding entry of foreign matter into the vessel. The Encapsulation component attachment weld is typically classified as an ASME Category D weld that would not required volumetric examinations.

I suggest you search the internet using the keywords such as "asme vessel restoration by encapsulation" Let me know if you need any further help on this method of restoration for which I am extremely familiar.

 

[GD2]

Inchtain,
You can certainly follow API 510 and PCC-2 to repair the vessel bottom by encapsulation option as PMCap has suggested. The issue could be if you have nozzles on the repair area. Usually, there will be a set back distance from nozzle weld to the next weld.

Many codes allows alternative to PWHT. Obviously, if the separator handles sour hydrocarbon, you will need to do an engineering assessment or even do a test/mock up welding to make sure that welds are within hardness and toughness limits.


GDD
Canada

 

[LittleInch]

Plus you still need to recoat the internal liner to prevent the original material from eating through to the new plate and starting to corrode that.

A production separator will have at least two nozzles on the bottom for condensate and water and possibly drains or flushing nozzles.

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