Alteration or Major Repair ??? 3

[Joss10]

Dear mates,
Are adding new nozzles 24" and 12" to existing PV, it is not affecting the pressure-containing capability informed in the original data report.
Is it Alteration or Major Repair.
Any input will be highly appreciated.

 

[mechanical2014]

Hi Evaristo,

In my opinion, it is a major repair and qualifies to be given R stamp.

 

[Joss10]

Hi mate,
Find here below definitions on API 510 (2014):
3.1.1
alteration
A physical change in any component that has design implications that affect the pressure-containing capability of a
pressure vessel beyond the scope described in existing data reports. The following should not be considered
alterations: any comparable or duplicate replacement, the addition of any reinforced nozzle less than or equal to the
size of existing reinforced nozzles, and the addition of nozzles not requiring reinforcement.
3.1.41
major repair
Any work not considered an alteration that removes and replaces a major part of the pressure boundary other than a
nozzle (e.g. replacing part of the shell or replacing a vessel head). If any of the restorative work results in a change to
the design temperature, minimum allowable temperature (MAT), or maximum allowable working pressure (MAWP),
the work shall be considered an alteration and the requirements for rerating shall be satisfied.

 

[metengr]

Adding new nozzles, specifically where you have increased the size of the nozzle from those that were originally installed and requires reinforcement per the original code of construction is an alteration, in accordance with the NBIC, Part 3. IF the pressure vessel has existing nozzles of the same size and you were adding more of them, this would most likely be a repair.

 

[jte]

One criteria that I teach when people ask me the Repair or Alteration question is simple. [But first, recognize that vast generalizations have vast room for error!] If you put pencil to paper (ok, or use a computer) to run a calculation, it is probably an alteration.

As metenger point out above, if you are adding a 24" nozzle which has identical or reduced loads as an existing one (e.g. the new nozzle has less liquid head at its elevation and is in the same thickness of shell), then you can simply copy the design of the existing one. I would run calc's anyway just to verify the design, but technically I do not have to. This would push you towards "Repair."

If, on the other hand, no previous 24" nozzles exist, or you are adding one to a shell section which has a different loading or thickness, then you must run calculations to verify the design. This would push you towards "Alteration".

 

[Joss10]

Dear mates,
Just to summarize.
New 24" nozzle, has simmilar loading and thickness as the PV has, also more bigger nozzles are already installed onto the PV from the original design, but is increasing 10% production of the PV, this production increment is a "design implication" but not affecting any pressure-containing capability.
Then, this new one as per the definition in API 510 (2014) is to be considered as an alteration??

 

[racookpe1978]

But, if the new nozzles in the new nozzle locations increase ANY local stress risers in the PV shell, it doesn't matter WHAT you "call it" in the regulations ... The stress risers have occurred (will occur!) and need to be calculated against the ultimate strength and long term performance of the PV.

 

[david339933]

As Metengr and Jte stated quite well, NBIC Part 3 - Section 3.3.3 states examples of repairs.

3.3.3 (j) - "The addition of a nozzle where reinforcement is a consideration may be considered to be a repair, provided the nozzle is identical to one in the original design, located in a similar part of the vessel, and not closer than three times its diameter from another nozzle."

 

[racookpe1978]

And that "limit" in the clause you quote of 3x diameter to the nearest nozzle seems to be how they attempt to avoid such stress risers.