Resources‎ > ‎Engineering‎ > ‎

Lethal Service

Figure UW-3

Note: This reference information is provided for your convenience only. You are responsible for complying with all ASME Section VIII, Division 1 & 2 lethal service requirements. We are not offering engineering advise nor engineering services here and accept no liability whatsoever for use of this information.

Definition of Lethal Service / Substance: Poisonous gases (or vapors of liquids, or vapors mixed with air) which are dangerous to life when inhaled in small quantities.

Lethal Vessels: Includes vessels under mechanical pressure and closed vessels which generate vapor pressure due to heating.

Responsibility: ASME requires the end user or designated agent (not the contractor or fabricator) to specify when lethal service is required.

U-2(a)(2): The end user or designated agent (not the contractor or fabricator) must specify when lethal service is required.

UG-16(b)(5)(a): Air cooled and cooling tower heat exchanger tube walls must be 1/16" minimum thickness.

UG-24(a)(6): Casting requirements.

     UCI-2, UCD-2: Castings of cast iron and cast ductile iron are not allowed.

          Appendix 7-1: Examinations per Appendix 7 is mandatory for steel castings.

UG-25(e): Telltale holes not allowed on pressure boundary parts (shells, heads, nozzle necks, etc.)

     Interpretation VIII-1-16-42: UG-37(g) telltale holes are required in (outside) reinforcement plates and nozzle saddles.

     ULW-76: Telltale hole required for layered vessels.

          ULW-1: Lethal requirements apply to the inner shell and heads only.

UG-99(g): Hydrostatic test visual leak inspection is mandatory.

UG-99(k): Painting and lining prior to hydrostatic test are not allowed.

UG-116(c): Stamp "L" on nameplate.

UG-120(d)(1): Add "Lethal Service" to the ASME data report.

UW-2(a): We recommend reading this entire section carefully. Summary:

     All butt weld joints require full length radiography. [Also UW-11(a)(1), Interpretation VIII-82-65]

     ERW pipe and tube are not allowed for shells or nozzles unless the longitudinal seams are fully radiographed per UW-11(a)(1).

          Interpretations VIII-1-01-118 and VIII-1-83-77R.

          Braun Note: We recommend using seamless pipe & tube.

     Post weld heat treatment (PWHT) is mandatory for carbon and low alloy steels.

     Lap joint stub ends. UW-2(a)(1)(c), Figure UW-13.5, Interpretation VIII-80-111.

     Category A weld seams must be Table UW-12 Type No. 1 only. UW-2(a)(1)(a).

     Category B & C weld seams must be Table UW-12 Type No. 1 or Type No. 2 only. UW-2(a)(1)(b), Interpretation VIII-1-92-211.

     Category D weld seams must be full penetration. UW-2(a)(1)(d), Interpretation VIII-1-98-23.

     Slip-on flanges and Figure UW-13.2 details are not allowed. UW-2(a)(1)(b), Interpretation VIII-1-92-211.

     Heat exchanger tubes. Lethal stamping only one exchanger side. UW-2(a)(2), UW-2(a)(3).

UB-3(a): Brazed construction is not allowed.

UCS-6(b)(1): SA-36, SA/CSA-G40.21 38W, and SA-283-A,B,C,D are not allowed.

UCS-79(d)(1): Heat treatment is mandatory if extreme fiber elongation exceeds 5%.

UHX-19.1(b): Required nameplate markings.

Appendix 9-8(c): If only inner vessel is lethal service, jackets are exempt from lethal service requirements.

Appendix 17-2(a): Dimpled or embossed assemblies are not allowed in lethal service.

Appendix 35-3(c): Mass production. Inspections per UG-90(c)(1) are mandatory.

Appendix 35-7(d): Mass production hydrotest rule.