Timing For Vessel Repair

[NamiW]

Hi All,

I can't seem to find an answer for this but for example lets say I have a vessel with a design pressure of 250 psi. The vessel has some general thinning at a well known rate and upon inspection has shown to be below design tmin. However the vessel operates at 50 psi. How long can the vessel continue to operate before it needs to be repaired? I've looked through PCC-2 but haven't found anything that really answers my question.

 

[Louisiana Inspector]

You need to have a fitness for service evaluation performed using API 579 and have the vessel rerated to continue service.

 

[NamiW]

Hey LI,

Lets say the vessel is going to fail the level 2 FFS since the corroded area is located next to a structural support and will require a level 3. At this point the options would be to repair or rerate, does code specify how long I can operate that vessel before I need to make the repair?

 

[LittleInch]

No code will tell you that as it cannot predict the future.

It can only deal with what you know at the current point in time.

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

 

[Louisiana Inspector]

If the results of the fitness for service require a rerate or repair the vessel should be taken out of service immediately to make the repairs or a rerate should be performed. The point of the evaluation is to determine if the vessel is fit for continued service. Failing to do so would be the owner's decision and not complying with the standards. If something was to happen it would not be a good situation. Your playing with fire.

 

[GD2]

OP,
If the vessel fails at Level 2 Assessment, you can do the following:
1. Go to Level 3 or
2. Rerate the MAWP or
3. take remedial action to repair the damage.

If you need to plan for the repair, run the vessel at the rerated condition (MAWP[sub]R[/sub]). API 579 provides equation for calculating MAWP[sub]R[/sub]


GDD
Canada

 

[TGS4]

Given that the vessel normally operates at 50 psi, you seem to have lots of room to derate the (design pressure of the) vessel. You will need to undergo a complete MOC (Management of Change) process to capture the revised design pressure. During that process, though, you may find out that the design pressure is set for a very specific reason, unrelated to that vessel, but critical to the system in which it operates. At that point, if a derate is not feasible, then you will need to repair at as soon as possible. As others have noted, running a vessel that is no longer fit-for-service at the design conditions puts you and your facility in potentially serious legal problems (depending on your insurance situation and your local jurisdiction having authority).

 

[LittleInch]

"Operates at" and MAWP set at are two different things.

If you have potential to reach 250 and that's what all your relief valve and protections are set at then you're currently not in a good place IMHO. There is no time period where you are permitted to operate something which is not fit for service.

So to continue operating legally you need to de rate the vessel via a proper MOC process and modify all your protective devices as long as the vessel passes A FFP test at or close to your current operating pressure (60 psi?)

You might need new PRVs if you go beyond the range allowed.

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

 

[r6155]

Try acoustic emission test, see ASME V.

Regards