1998 Section VIII hydrotest pressure 1

[akdale]

Is the hydrotest pressure for a Section VIII Div. 1 pressure vessel built in 1998 still 1.5 times the MAWP as opposed to the current 1.3 times MAWP?

 

[lostsailor]

akdale,
UG-99(b) of the 1998 Edition with 1999 Addenda states 1.3 multiplied by stress/temperature correction ratio.
Regards,
Ron

 

[jte]

akdale-

Yes, the proper code minimum hydro for a vessel built in 1998 (to the 1998 Code or 1995 A97 - what does the U form say?) would be 1.5*MAWP. In many cases the shop hydro would be higher (often 1.5*MAP) based on client standards.

Since you are asking the question roughly six years after the vessel was built, I presume that a repair or alteration is involved. The AI involved would specify the hydrotest pressure which need not be higher than 1.5*MAWP. I've seen AI's specify hydros at lower pressures at their discretion or waive the hydro altogether depending on the type of work and NDE performed.

jt

 

[akdale]

I spoke with the owner's AI and we agreed that 1.3 times MAWP would be acceptable. We are doing an Alteration on a gray water tanker that is not registered with the National Board (no U1-A form) but our program is designed to treat non-registered vessels/tankers the same as registered ones. Only difference is that we will not send the R2 to the National Board.
The question came up as to which year the 1.5 times MAWP hydro requirement was reduced to 1.3 times MAWP. I'm thinking it went into effect in 1999 but I'm not sure now and unfortunately all my old copies of Sec. VIII Div. 1 have disappeared.
Thanks to everyone for your replys.
Dale

 

[jte]

akdale-

The 1.5x hydro was changed to 1.3x with the increased allowable stresses introduced with the 1999 Addenda. Simply put, the stress during the hydrotest remains basically the same: The allowable stresses (those which were limited by ulitmate strength) increased from Sut/4 to Sut/3.5 and correspondingly the hydrotest was changed by the same ratio. 1.5*[3.5/4]=1.3. For example, a vessel built of SA516-70 (at 500°F or lower) material would have its circ stress brought up to about 1.5*17.5 = 26.25 ksi during the hydrotest. A vessel built to the 1999 or later addenda would have its circ stress brought up to about 1.3*20 = 26 ksi.

The post-construction hydrotesting requirement is, as I mentioned, up to the AI who may request a lower than VIII-1 hydro. In theory though, a 1.3xMAWP hydro would not meet VIII-1 for a vessel built to the 1998 or earlier addenda. It would not result in the stress in the vessel which it would have seen during the shop hydro. In this case, for the example in the above paragraph, the hydrotest circ stress would be only 1.3*17.5 = 22.75 ksi.

jt

 

[deanc]

If you need to comply with the NBIC rules see RC-3031.