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UG-45 Nozzle Thickness on an F&D Head

UG-45 Nozzle Thickness on an F&D Head

UG-45 Nozzle Thickness on an F&D Head


I have a vessel with an F&D head full of nozzles. COMPRESS is requiring a minimum thickness of 0.337" on an 8" nozzle (limited by UG-45, Tb-1). This nozzle is located in the inner 80% of the F&D, therefore, it's in the spherical portion. The fabricator ordered his materials and has specified a SCH40 (0.322"). The fabricator claims that the tb1 value should be that of the hemi-head formula and not the Torishperical.

I've used this exemption in the past for nozzle reinforcements because it specifically allows it in UG-37 for torispherical heads but UG-45 doesn't specifically spell it out.

UG-37 (tr def):
(A)when the opening and its reinforcement are entirely within the spherical portion of a torispherical head , tr is the thickness required by 1-4(d), using M=1.

UG-45 (tb1 def):
tb1 = for vessels under internal pressure , the thickness (plus corrosion allowance) required for pressure (assuming E=1) for the shell or head at the location where the nozzle neck or other connection attaches to the vessel but in no case less than the minimum thickness specified for the material in UG-16(b).

COMPRESS automatically uses the UG-37 exemption for nozzle reinforcements when they land in the spherical portion, but holds to the torispherical formula for the UG-45, tb1 thickness.

Any input is appreciated .

RE: UG-45 Nozzle Thickness on an F&D Head

I just figured it out....COMPRESS had the little note (ASME VIII-1-83-66 Interpretation applied) which states that just because the hemi-head formula is used in the reinforcement calcs (UG-37) doesn't mean it can be used for UG-45. Either UG-32(d) or 1-4 shall be used for the Tb1 on a torispherical head.

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