4 replies to this topic

[farid.k]

Dear All,

 

Based on my local authorities, when I do modification on a pressure vessel (adding one nozzle),

Hydrotest must be done. Just wonder how about other local authorities? Why do we need to re-do the hydrotest after modification of the pressure vessel? What if I avoid the re-do the hydrotest?

[AZIZ_MN]

Hi, Farid,

   i think its legal requirement,if same modified nozzle welding gets failure while normal operation(with normal operating pressure) of pressure vessel and due to that if other plants equipment or structure gets damage or life lost, how you will convience legal authorities,safety and insurance auditors?,is there any other certification method that certified that nozzle welding are not leak,may be simple penitration test or Radiography will work? i'm curious also to know that

best regards

azzu

Edited by azzu, 25 February 2015 - 03:42 AM.

[Zauberberg]

Whether one can use other methods (NDT) instead of pressure test, it is up to local legislation and codes which are mandatory to be followed. This provision may or may not exist, depending on these two factors.

 

Also refer to API 510 "Pressure Vessel Inspection Code" extract, attached.

 

Attached Files

•  Pages from api.510.2006.pdf   459.59KB   18 downloads

[MTumack]

I would not skip the hydrotest. I am not entirely certain (would have to dig out the code), but I believe ASME VIII requires a retest after any modifications. If this is the case, any legal vessel with a current Stamp that needs a modifications would be fraudulent if it were to not be retested.

 

The amount of liability there is not worth any price tag. Even if something were not to happen, I think the ability to sleep at night is worth the hassle. Hydrotesting is not a "you should do it so it looks good" or a "you should do it so the equipment can function" requirement, its a "you should do it to preserve human life" requirement.

 

Even if it was legally acceptable, ethically I think that would be very wrong. You wear a ring to remind you not to cut ethical corners, don't cut this one.

[Zauberberg]

Different codes prescribe different requirements for different types of modifications on different types of vessels. Having defined all four elements of the previous sentence, defines the inspection and testing requirements for a given application.

 

I remember discussing a similar subject recently with one of the certified inspectors, and the subject was revamp of stripping trays in the main CDU column which involved welding of new support rings for the new stripping trays section, some 10 years ago. Whilst - at that time and at that place - we were forced to hydrotest the tower after the welding and installation works were completed, due to local legislation requirements, he was showing me an extract from one of the inspection codes (unfortunately I do not remember the title) where NDT would be sufficient to fully confirm integrity of the vessel, for this kind of modification. It all depends.