Mnimum Weld toe-to toe distance in API 620

[inammanj123]

In API 620, as per clause 5.14.5, minimum weld toe toe distance is 150 mm for all nozzle. In aramco spec 32-samss-006 it give an additional clause to api 620 which says 50 mm distance,should i follow the stringent which is 150 mm?

quote
5.14.5 Each opening in the walls of a tank shall be located so that the distance between the outer edge of its
reinforcement and any line of significant discontinuity in the curvature of the tank walls (such as the juncture between
two nodes in a noded surface, the juncture between a dished or conical roof or bottom and cylindrical sidewalls, or the
juncture between a roof or bottom and cylindrical sidewalls, or the juncture between a roof or bottom knuckle and
other portions of the tank) is not less than 6 in. or (if this be larger) eight times the nominal thickness (including
corrosion allowance; if any) of the wall plate containing the opening, except as permitted by 5.14.3. The term “edge of
reinforcement” means the edge, or toe, of the outermost weld that attaches the reinforcing pad to the wall of the tank.
unquote

From 32-samss-006:

Nozzles, manways and their reinforcement shall not be located within 50 mm (2 in.) of any weld seam. Where this requirement cannot be met, 100% radiography shall be performed on the encroached weld seam according to API STD 650, paragraph 5.7.3.4.

 

[david339933]

Both...as they are not referring to the same thing. 5.14.5 is not for "all nozzles", it is for nozzles close to significant discontinuities, such as the roof to shell juncture. It is not referring to all weld seams. If there is a nozzle in the shell, it must be 2" from any weld seam.

 

[inammanj123]

david339933

So It mean 150 mm distance is especially important for nozzle located in lower part of shell. In my case i have 8 inch pump suction nozzle, which need to be lower than Low low liquid level.

Due to this i selected low type pad,so to avoid toe to toe requirement form pad edge to shell/bottom joint, because in low type pad case, this 150 mm spacing will be required from nozzle edge to shell/pad/bottom joint

Is my understanding ok?

 

[david339933]

Correct.