ASME SEC VIII D1 MA APP 28
APPENDIX28
ALTERNATIVE CORNER WELD JOINT DETAIL FOR BOX HEADERS FOR AIR-COOLED HEAT
EXCHANGERS
28-1GENERAL
For box headers for air-cooled heat exchangers using a multipass corner weld joint constructed in accordance with Fig.28-1,the rules of UW-13(e)(4)and Fig.UW-13.2shall be supplemented as described below.
28-2SUPPLEMENTARY
REQUIREMENTS
This Appendix only replaces the requirement,“a+ b not less than2t s”of UW-13(e)(4)and the weld joint geometry of Fig.UW-13.2.All other rules in the Code pertaining to welded joints shall apply.
In addition,the following shall apply.
28-2(a)A sample corner weld joint shall be prepared to qualify the weld procedure;and a sample corner weld joint shall be prepared to qualify each welder or welding operator.The Manufacturer shall prepare the sample corner weld joint with nominal thickness and con?guration matching that to be employed with the following tolerances:
28-2(a)(1)the sample thinner plate shall match the thickness of the production thinner plate within ±1?4in.;
28-2(a)(2)the sample thicker plate shall be at least1.5times the thickness of the sample thinner plate. The sample shall be sectioned,polished,and etched to clearly delineate the line of fusion.Acceptability shall be determined by measurements of the line of fusion for use in the calculations for compliance with Fig.28-1.The sample shall be free from slag,cracks, and lack of fusion.A sample corner weld shall be prepared for each P-Number,except that a sample prepared to qualify a joint made from material with a given value for K[see28-2(d)]may be used to qualify a joint made from material having an equal or higher value for K but not vice versa.
28-2(b)This sample corner weld joint is an addition to the Welding Procedure Speci?cation Quali?cation and the Welder and Welding Operator Performance Quali?cation requirements of Section IX.The following essential variables apply for both the procedure and performance quali?cation,in addition to those of Sec-tion IX:
28-2(b)(1)a change in the nominal size of the electrode or electrodes used and listed in the PQR;
28-2(b)(2)a change in the quali?ed root gap exceeding±1?16in.(±1.6mm);
28-2(b)(3)addition or deletion of nonmetallic re-tainers or nonfusing metal retainers;
28-2(b)(4)a change in the SFA speci?cation?ller metal classi?cation or to a weld metal or?ller metal composition not covered in the speci?cations;
28-2(b)(5)the addition of other welding positions than those quali?ed;
28-2(b)(6)for?ll passes,a change in amperage exceeding25amp,change in voltage exceeding3v;
28-2(b)(7)a change in contact tube to work distance exceeding1?4in.(6mm);
28-2(b)(8)a change from single electrode to multi-ple electrodes,or vice versa;
28-2(b)(9)a change in the electrode spacing;
28-2(b)(10)a change from manual or semiauto-matic to machine or automatic welding or vice versa. 28-2(c)After production welding,the back side of the weld shall be subjected to a visual examination to assure that complete fusion and penetration have been achieved in the root,except where visual examination is locally prevented by an internal member covering the weld.
28-2(d)K,the ratio of through-thickness(Z direction) tensile strength to the speci?ed minimum tensile strength,shall be taken as0.6.Higher values for K, but not higher than 1.0,may be used if through-thickness tensile strength is determined in accordance
0128-2APPENDIX28—MANDATORY28-2 with Speci?cation SA-770.The test results,including
the UTS in addition to the reduction in area,shall be
reported on the Material Test Report,in addition to
the information required by Speci?cation SA-20when
the testing in accordance with Speci?cation SA-770is
performed by the material manufacturer.If the testing
is performed by the vessel Manufacturer,the test result
shall be reported on the Manufacturer’s Data Report.
See UG-93(b)and UG-93(c).
28-2(e)The maximum value of t s(see Fig.28-1)
shall be limited to3in.(76mm).
28-2(f)Both members may be beveled as shown in
Fig.28-1sketch(b).When the bevel angle(?)is large
enough to satisfy the UW-13(e)(4)requirements,the
alternative rules of this Appendix do not apply.When
the bevel angle(?)results in weld fusion dimensions
that do not satisfy the UW-13(e)(4)requirement that
a+b is not less than2t s,the following shall be
satis?ed.
28-2(f)(1)The angle(?)shall be equal to or
greater than15deg.
28-2(f)(2)The dimension a2shall be measured
from the projected surface of the plate being attached
as shown in Fig.28-1sketch(b).
28-2(f)(3)The angle(?)shall be equal to or
greater than15deg.
28-2(f)(4)All other requirements of this Appendix
shall be applied.
28-2(g)When all the requirements of this Division
and the supplemental requirements of this Appendix
have been met,the following notation shall be entered
in the Manufacturer’s Data Report under Remarks,
“Constructed in conformance with Appendix28.”