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specification and grade of material is used. Does this paragraph apply to a single vessel, either from the

aspect of the thickness limitation or the length of welded joints welded by the same procedure?

Reply 2: No.

Interpretation: VIII-77-74

Subject: Section VIII, Division 1; UA-280Date Issued: August 16, 1977

File: BC75-760

Question 1: In UA-280, what is the origin of the 0.7 factor applied to the allowable tensile stress in

the nozzle wall shear calculation?

Reply 1: The 0.7 factor is given in UG-45(b). The derivation of this factor can be found in earlier

Editions of the Code. The allowable stress in shear is taken as 80% of the allowable tensile stress and a

factor of 87.5% is applied for combined end and side loading. Therefore: 0.80 X 0.875 = 0.70

Question 2: In UA-280, in the calculation of (A) fillet weld shear why is (divided by 2 in this

equation? It appears that only 1/2 of the weld circumference is considered.

Reply 2: The example is intended to follow the rules given UG-41(c) and in particular the

sentence: "The strength of the attachment joint shall be considered for its entire length of each side of the

plane of the area of reinforcement defined in UG-40." This length, in Example 1 of UA-280, is "/2 X

nozzle O.D." The basis concept is that the forces in the vessel from one side of the plane must be

transmitted through the attachment joint and back to the vessel on the other side of the plane.

Question 3: In UA-280, in the calculation for (C) groove weld tension, why is tension considered in

the groove weld rather than shear? Unless the vessel is externally pressurized it would appear that the

principal loading of the weld is in the shear.

Reply 3: Conceptually, the vessel shell in the above example is trying to pull away from the

nozzle, thereby placing tension on the groove weld.

Interpretation: VIII-77-75

Subject: Section VIII, Division 1; UG-39, UG-40. Section VIII, Division 2; AD-540.1

Date Issued: August 17, 1977

File: BC77-362

Question 1: In Section VIII, Divisions 1 and 2 what are the applicable paragraphs for the limits of

reinforcement for openings and flat heads?

Reply 1: UG-40 of Section VIII, Division 1 and AD-540 in Section VIII, Division 2 are the

applicable paragraphs for such openings.

Question 2: Under what conditions would a single opening in a Section VIII, Division 1vessel not

require reinforcement?

Reply 2: Refer to UG-36(c)(3) which outlines the conditions under which a single opening in a

vessel not subject to rapid fluctuations in pressure would not require reinforcement.