Lethal Service Interpretations

Commonly referenced interpretations are listed below for your convenience. Key words and phrases are highlighted in red. For a full list of interpretations we recommend using keyword "lethal" on the ASME search tool page linked above.

VIII-1-01-42: Question: May Fig. UW-13.3 sketches (a) or (b) be used for the construction of noncircular vessels requiring the use of Type No. (1) or (2) butt                                   welds for the Category C joints [for example, to satisfy lethal service requirements of UW-2(a)(1)(b)]?

                     Reply: Yes, see U-2(g).

VIII-1-01-118: Question: May SA-312 Type 304 welded pipe be used for the shell of or for nozzles in pressure vessels constructed according to the rules of                               Section VIII, Division 1 and designated for Lethal Service if the requirements of UW-2 are met?

                     Reply: Yes, provided that the longitudinal seams are fully radiographed per UW-11(a)(1). See also UG-8(a).

VIII-1-04-43: Question (1): With reference to Interpretation VIII-1-95-128, are the welds used to attach heater elements to flat covers in flanged immersion heaters                         classified by UW-3 as a Category A, B, C, or D joint?

                     Reply (1): No.

                     Question (2): If the answer to Question (1) is no, then may a fillet weld be used to attach a heater element to a flat cover in a flanged immersion heater                       intended for lethal service as defined in UW-2(a)?

                     Reply (2): Yes.

VIII-1-04-48: Background: Consider a vessel, constructed according to the rules of Section VIII, Division 1, containing a cone with a half-apex angle exceeding 30                         deg. The cone is attached to a cylindrical shell at its large end and a nozzle at its small end. Both ends are full penetration welds and neither contain                           knuckle transitions.

                     Question: Is it permitted for these joints to be used in a vessel which has been designated for lethal service as per UW-2(a)?

                     Reply: No.

VIII-1-07-60: Question: May an expansion joint, meeting the requirements of Appendix 26 in Section VIII, Division 1, and attached to weld ends in accordance with                         Fig. 26-13, be used in a vessel designed to UW -2(a)?

                     Reply: Yes.

VIII-1-16-39: Question: For a dished cover that is welded to a bolting flange similar to Figure 1-6(d), shall the weld joining the dished cover to the bolting flange be                         considered as a Category C weld joint that would be subjected to the service restrictions found in paragraph UW-2?

                     Reply: Yes.

VIII-1-16-42: Question: For lethal service, Paragraph UG-25(e) prohibits the use of telltale holes that are intended to provide some positive indication when the thickness has been reduced to a dangerous degree due to corrosion. Doe`s the same lethal service restriction apply to the telltale holes required by paragraph UG-37(g)?

                    Reply: No.

VIII-1-16-72: Question: A vessel is constructed using Type No. 3 joints, as described in Table UW-12. All welds noted in UW-11(a) are fully radiographed. Does this                       vessel meet the requirements of RT 4 as described in UG-116(e)(4)?

                     Reply: Yes.

VIII-1-17-11: Question: Do the rules of UG-82(b) prohibit attachments from extending over pressure retaining welds for vessels in lethal service and subject to                                 inspection after hydrotest per UG-99(g)?

                     Reply: No.

VIII-1-83-10: The questions apply to welded tube-to-tubesheet joints where one or both sides of a heat exchanger are in lethal service as defined in UW-2(a) and                           are as follows:

                     Question (1): Do such joints fall under any of the joint categories of UW-3?

                     Reply (1): No.

                     Question (2): Is radiographic examination required?

                     Reply (2): No.

                     Question (3): Other than visual, is any nondestructive examination required?

                     Reply (3): Not unless the requirements of UHA-34 or UHT-57 are applicable.

                     Question (4): For welding processes permitted by UW-27, are there any special requirements concerning the use or absence of filler metal?

                     Reply (4): No.

                     Question (5): Are welded or seal welded joints required? Reply (5): No.

                     Question (6): Must the provisions of Nonmandatory Appendix A concerning tube-to-tubesheet joints be satisfied?

                     Reply (6): No, but they are acceptable where applicable. The details of the joint are the responsibility of the vessel manufacturer, after consideration of                       the service information furnished to him by the user. See UW-2(a).

VIII-1-83-77R: Question: May electric resistance welded (ERW) pipe be used for the shell of a pressure vessel designed for lethal service under UW-2(a) in                            Section VIII, Division 1 whether or not radiographic examination is performed on the ERW welded seam?

                      Reply: No. See UW-2(a). The provisions of UW-2(a)(2) and (3) do not apply.

VIII-1-83-365 : VIII-2-83-46: Question: Do the rules of Section VIII, Division 1 or Division 2, prohibit the use of packed joints in vessels constructed to lethal service                        requirements [for example, UW-2(a)]?

                    Reply: No; however, consideration of the appropriateness of such connections in a particular installation is the responsibility of the user or his                                      designated agent [for example, U-2(a)].

                    Braun Note: We do not recommend packed joints for lethal service vessels.

VIII-1-92-24: Question (1): In a lethal service application a seamless 2:1 ellipsoidal head is welded by a Category B weld to a forged ring to form a quick-opening                          closure. The Category B joint is Type No. (1), and the full radiography requirements of UW-11(a)(1) are thereby met for the vessel part being                                      manufactured. Is it required to also meet the spot radiographic provisions of UW-11(a)(5)(b) in Section VIII, Division 1?

                    Reply (1): No.

                    Question (2): If "Full" is noted in Section 9 of Form U-2A, must it also be noted in Section 14 (Remarks) that the weld meets the requirements of UW-                          11(a)(5)(b)?

                    Reply (2): No.

                    Question (3): Is it required to note the crown radius and knuckle radius in addition to the elliptical ratio in Section 10 of Form U-2A for the head used in                        Question (1)?

                    Reply (3): No.

VIII-1-92-92: Question: A vessel is constructed of 316L SS and is designated for lethal service. One end closure is a carbon steel (SA-105) blind flange to which a                        316L stainless steel liner covering the entire raised-face area has been attached by welding. Does the blind flange require PWHT as noted in UW-2(a)                        of Section VIII, Division 1?

                    Reply: Yes.

VIII-1-92-112: Question: Are Category C and D butt welds required to be fully radiographed when the vessel is to be stamped for lethal service?

                     Reply: Yes, except for those Category C butt welds exempted under UW-11(a)(4).

VIII-1-92-194: Question (1): A heat exchanger consisting of rectangular header boxes is designed in accordance with Appendix 13 of Section VIII, Division 1. Each                         header has full penetration angle joints located at the four corners. The end plates are attached by a single sided full penetration angle joint. Do these                       types of joints meet the requirements of UW-2(a)(1)(b) for lethal service when interpretable radiographs can be produced for the full length of the                                 welds?

                     Reply (1): No.

                     Question (2): Do these types of joints satisfy UW-2(a)(1)(b) if interpretable radiographs cannot be obtained, but ultrasonic examination is performed for                       the full length of the welds?

                     Reply (2): No.

VIII-1-92-211: Question: May any of the attachment details shown in Figure UW-13.2 of Section VIII, Division 1 be used for lethal service?

                     Reply: No, see UW-2(a)(1)(b).

VIII-1-95-08: Question: Can Category C welds shown in Fig. UW-13.2 sketches (b) and (c) of Section VIII, Division 1 be used in lethal service if Code Case 2023 is                       used along with the requirements of UG-93(d)(3) and the welded joint is ultrasonically examined in addition to being fully radiographed?

                     Reply: No.

VIII-1-95-137: Question (1): Are the requirements in UW-2(a) of Section VIII, Division 1 for performing full radiography and postweld heat treatment on vessels

                     which are to contain lethal substances applicable regardless of the calculated pressure and thickness for the vessel?

                     Reply (1): Yes.

                     Question (2): Are the requirements of UW-2(a) superseded by the provisions of UCL-34 and UCL-35?

                     Reply (2): No.

VIII-1-98-23: Question: May the attachment details shown in Figure UW-16.1 sketch (a) or (c) be used on a vessel intended for use in lethal service?

                     Reply: Yes.

VIII-1-98-91: Question: All P-No. 1 materials are used to construct a Type 2 jacketed glass-lined vessel under Appendix 27 of Section VIII, Division 1. The internal                         chamber will contain a lethal substance and has successfully passed examination in accordance with UW-11(a) and UW-51. The internal chamber will                       be subjected to multiple temperature cycles in accordance with 27-4(a)(3) for completion of the glassing operation. May these multiple elevated                                   temperature cycles be substituted for the heat treatment and documentation requirements of UW-2(a) and UCS-56?

                     Reply: Yes.

VIII-1-98-108: Question (1): A pressure vessel is constructed of P-No. 1 and P-No. 8 materials, and is intended for lethal service. The vessel is PWHT. After PWHT,                       but before performing the hydrotest, the interior of the vessel has a stainless steel lining applied using plug welds. Does Note (2)(c)(5) of Table                                   UCS-56 in Section VIII, Division 1 permit the liner to be applied after the vessel has been PWHT without the need to perform any additional heat                                 treatment?

                     Reply (1): Yes, provided that the preheat requirements are met.

                     Question (2): Does UCL-51 permit the liner to be repaired by welding to the P-No. 1 base material after the vessel has been PWHT without the need                         to perform any additional heat treatment?

                     Reply (2): Yes, with the acceptance of the Authorized Inspector.

VIII-1-98-113: Question (1): May reinforced pads attached with fillet welds as shown in Fig. UW-16.1 sketches (a-2) or (h) of Section VIII, Division 1, be used on vessels designed for lethal service per UW-2(a)(1)(d)?

                     Reply (1): Yes.

                     Question (2): Are the welds attaching pad type reinforcement to the vessel as shown in Fig. UG-40 sketches (a-1) through (a-4), with or without a                               nozzle neck, classified as part of the Category D joint?

                     Reply (2): Yes.

                     Question (3): If the reply to Question (2) is yes, do the Category D joints shown in Fig. UG-40 sketches (a-l) through (a-4) meet the requirements of                             UW-2(a)(1)(d)?

                     Reply (3): Of the four sketches cited, only sketch (a-2) meets the requirements of UW-2(a)(1)(d).

VIII-2-13-01: Questions: Does ASME Section VIII, Division 2 include a fluid service category that has been defined as "lethal"?

                     Reply: No, see 2.2.2.

VIII-77-30:    Question 1: Do the service restrictions of UW-2(a) for lethal substances and UW-2(c) for unfired steam boilers with design pressures exceeding 50 psi                       permit the use of partial radiography under UW-11(a)(5)(b)?

                     Reply 1: For lethal substances, all butt welds in vessels are required to be examined radiographically for their full length as prescribed in UW-11(a)(1)                         except as provided in UW-11(a)(4) which permits no radiography for Categories B and C butt welds in nozzles and communicating chambers that                               neither exceed 10 in. nominal pipe size nor 1-1/8 in. wall thickness.

VIII-77-62:    Question: Do the provisions of UW-11(a)(4) override the requirements of UW-2(a) for the exemption of certain butt welds in nozzles where a vessel is                         in lethal service?

                     Reply: It is the intent of Section VIII, Division 1 that Category B and C butt welds in nozzles and communicating chambers that neither exceed 10 in.                           nominal pipe size or 1-1/8 wall thickness are excluded from the provisions of radiography, even though the vessel is in lethal service. This overrides                           the provisions of UW-2(a).

VIII-77-104:  Question: Under the rules of Section VIII, Division 1, may pock-marks, pits, or tears produced on the surface of a carbon or low alloy steel vessel by                           the improper removal of a thermocouple or other attachment subsequent to postweld heat treatment be repaired by welding without subsequent                                 postweld heat treatment after the completion of the repair if the vessel is in lethal service?

                     Reply: Yes, provided this complies with the Notes to Table UCS-56 for the P-Number material.

VIII-79-66:    Question: In vessels manufactured for lethal service may enclosures be fabricated of forged material in accordance with the details shown in Figure                           UW-13.3, sketch (a) or (b) of Section VIII, Division 1?

                     Reply: Yes, provided the welded joint is made a Type 1 or 2 joint of Table UW-12.

VIII-79-70:    Question: Is the joint configuration illustrated in Fig. UW-13.2 sketches (b) and (c) of Section VIII, Division 1 acceptable when used to join side plates                         in a box header designed for lethal service?

                     Reply: No. The last sentence of the first paragraph of UW-2(a) lists the types of joints which may be used with various categories of welded joints. The                       three categories of joints which are used to join the sides of a box header in lethal service and the type of joint are: Category A (Longitudinal welded                           joint) must be Type 1 (butt) Category B (Circumferential welded joint) must be Type 1 or Type 2 (butt) Category C - same as Category B Since the joint                       must be a butt joint, the types shown in Fig. UW-13.2 sketches (b) and (c) are not permitted for lethal service.

VIII-80-02:    Question: Is the joint configuration illustrated in Figure UW-13.2, sketches (b) and (c) of Section VIII Division 1 acceptable when used to join side                               plates in a box header designed for lethal service?

                     Reply: No. The last sentence of the first paragraph of UW-2(a) lists the types of joints which may be used with various categories of welded joints. The                       three categories of joints which are used to join the sides of a box header in lethal service and the type of joint are: Category A (longitudinal welded                           joint) must be Type 1 (butt); Category B (circumferential welded joint) must be Type 1 or Type 2 (butt); Category C - same as Category B. Since the                           joint must be a butt joint, the types shown in Fig. UW-13.2, sketches (b) and (c) are not permitted for lethal service.

VIII-80-111:  Question (1): Is a lap joint stub end as illustrated in Fig. 2-4 sketch (1) the only acceptable flanged connection under the requirements of UW-2(a)?

                     Reply (1): No. Other acceptable connections would include those of Fig. UW-13.3 and Fig. 2-4 sketches (5) and (6).

                          The following Questions apply to stub ends for lap joint flanges.

                     Question (2): Is the weld joining a lap joint stub end to a nozzle neck or shell a Category B or C joint?

                     Reply (2): Category C. See UW-3(a)(3).

                     Question (3): Must the joint described in Question (2) always be fully radiographed?

                     Reply (3): No. See the diameter and thickness exceptions of UW-11(a)(4).

                     Question (4): Are the types of flanges described in 2-4(a)(1), i.e., sketches (1), (1a), (2), (3), and (4) of Fig. 2-4, acceptable for lethal service?

                     Reply (4): (a) The lap joint stub end illustrated by sketch (1) would normally be connected by a butt weld which is not illustrated. If so, it would be                                 acceptable provided all other applicable requirements were satisfied. (b) Sketches (1a), (3), and (4) are not acceptable since they do not satisfy the                           requirement of UW-2(a)(1)(b) that Category C joints be butt welds of Type No. (1) or (2). (c) Use of the screwed flange of sketch (4) is not prohibited.

                     Question (5): UW-3(a)(3) addresses itself to Category C welds attaching "Van Stone laps" to nozzles. Does this mean the lap itself or is the intent that                         this be a lap joint stub end?

                     Reply (5): Any welded joint connecting a flange to a nozzle neck is a Category C joint. See the Replies to Questions (2) and (4) above. Also see                                 Interpretations No. 3, VIII-78-08, which discusses this overall subject in more detail.

VIII-82-65:   Question (1): Is the weld detail shown in Fig. UW-16.1, sketch (b) a butt weld?

                    Reply (1): No.

                    Question (2): In Section VIII - Division 1 construction, is volumetric examination required for Category D welds in lethal service?

                    Reply (2): No, unless nozzle designs of the types shown in Fig. UW-16.1, sketches (f-1) through (f-4) are incorporated into the design (see UW-11).

Record 14-1910: Question: For a P No. 1 material, does General Note (b)(3)(e) of Table UCS-56-1 provide an exemption to PWHT of the weld overlay cladding                             applied to a carbon steel vessel that is designated to be in lethal service?

                     Reply: Yes.

Record 15-634: Background: A vessel categorized as being in lethal service per UW-2(a) is constructed of SA-516 Gr.70 plate clad with 410 stainless. Welds in the                       cladding are deposited using 309/309L stainless filler metal. Para. UW-2(a), requires a lethal service vessel constructed of carbon steel to be PWHT.

                     Question 1: Are welds in carbon steel vessel which are integrally clad, have corrosion resistant weld metal overlay, or have applied corrosion resistant                       linings attached by welding exempt from the PWHT requirements of UW-2(a) for carbon steel vessels in lethal service under the provisions of Table                           UCS-56-1, General Note (b)(3)(e)?

                     Reply 1: No.

                     Question 2: Are corrosion resistant weld metal overlay welds or welds attaching corrosion resistant applied linings on carbon steel vessels in lethal                             service exempt from the PWHT when applied following the provisions of Table UCS-56-1, General Note (b)(3)(e)?

                     Reply 2: Yes.

Record 15-1154: Question: Is it the intent of paragraph UW-2(a) in Section VIII, Division 1 that butt welds in stiffening rings which are designed per UG-29 and are                         attached to lethal service vessels shall be fully radiographed?

                     Reply: No.

Record 15-1215: Question: Does paragraph UW-2(a) prohibit the use of ultrasonic examination in lieu of radiography when the qualifying conditions of paragraph                         UW-51(a)(4) are met?

                     Reply: No.

Record 15-1264: Question (1): Is the weld that attaches a flat plate end closure to a non-circular pressure vessel categorized as Category C in accordance with                             UW-3?

                     Reply (1): Yes.

                     Question (2): If the vessel is designated as being in lethal service, are all the requirements of UW-2(a) applicable to the weld that attaches a flat plate                         end closure to a non-circular vessel?

                     Reply (2): Yes.

Record: 15-1288: Question: A floating head heat exchanger with TEMA rear end head type "S" has the tube side fluid specified as lethal service but the shell side                         fluid is not. The shell cover of the floating end is not directly exposed to the tubeside "lethal" fluid. Is it required that the Category A, B, C and D welds                         in shell cover satisfy the requirements of UW-2(a) if the provisions of UW-2(a)(3) are satisfied?

                     Reply: No.