This document provides an overview of the ASME VIII Div. 1 code requirements for vessels in lethal service. It defines lethal service and lists the key sections of the code that apply, including UW-2 which has most of the lethal service requirements. Some of the major requirements mentioned are 100% radiography of all butt welds, restrictions on materials and joints allowed, and special marking and documentation. It also lists some relevant code cases and interpretations that relate to lethal service requirements.

1. ASME VIII Div.1
Ing. José Juan Jiménez Alejandro: jjjimeneza@gmail.com
Lethal Service - Quick GuideServicios de
Soldadura
Industrial

2. Introductions
Requirements for lethal service are scattered through
VIII-1, the code cases and the interpretations. ASME VIII-
1 section UW-2 has most of the requirements for lethal
service. Two definitions of lethal service are provided in
UW-2. The second definition is also duplicated in the end
notes:
[A] vessel is to contain fluids of such a nature that a very
small amount mixed or unmixed with air is dangerous to
life when inhaled[.]

3. Introductions
By "lethal substances" are meant poisonous gases or liquids
of such a nature that a very small amount of the gas or of
the vapour of the liquid mixed or unmixed with air is
dangerous to-life when inhaled. For purposes of this
Division, this class includes substances of this nature which
are stored under pressure or may generate a pressure if
stored in a closed vessel.
It is up to the user to determine if a service is lethal. We at
Pressure Vessel Engineering do not determine if the
vessel service is lethal (but we might have opinions
based on previous jobs).

4. ASME VIII-1 Lethal Service Code References
UW-2 Service Restrictions is a very important section for
lethal service vessels and must be read in its entirety. A few
brief points from UW-2:
UW-2(a) and UW-11(a)(1) - All butt welds shall be
100% radiographed
UW-2(a) - ERW pipe (like some grades of SA-53) is not
permitted but interpretation VIII-1-01-118 says it is
acceptable if the long seam is fully radiographed
UW-2(a) - Post weld heat treatment is required for CS
and Low Alloy
UW-2(a)(1)(a) - Category A welds shall be type 1 only
(butt welded with no permanent backing strip)

5. ASME VIII-1 Lethal Service Code References
UW-2(a)(1)(b&c) &Interpretation VIII-1 92-211 -
Category B & C welds shall be type 1 or 2 only (butt
welded). No slip on flanges! No Figure UW-13.2 Flange or
Head to Shell attachments
Interpretation VIII-I-98-23 - Category D welds
(typically nozzles) shall be full penetration.
UW-2(a)(1)(c) - Category C joints for stub ends have a
long list of requirements
UW-2(a)(2 and 3) - Heat exchangers have a long list of
requirements
Read all of UW-2 for more restrictions...

6. ASME VIII-1 Lethal Service Code References
When it has been determined that a vessel is in Lethal
Service, some of the following code sections will apply. Other
code sections might also be required. (List last updated June
16 2015 based on the ASME 2013 VIII-1 code edition.)
U-2(a)(2) - The user determines if the service is lethal.
UG-16(5)(a) - Air cooled and cooling tower heat
exchanger tube walls to be 1/16" min.
UG-24(6) - Casting RT requirements.
UG-25(e) - No telltale holes.
UG-99(g),(k) - Hydro test visual leak inspection cannot be
waived. Do not paint prior to the hydro test.

7. ASME VIII-1 Lethal Service Code References
UG-100(d)(4) - Pneumatic tests cannot be used for
lethal service vessels, but also see code cases 2046-2,
2055-2, 2407 regarding pneumatic instead of hydrostatic
testing
UG-116(c) - "L" stamping must be added to the
nameplate.
UG-120(d)(1) - "lethal service" is added to the data
report
UW-2 - Service Restrictions - main source of info on
Lethal Service (see lots more from UW-2 below)
UW-11(a)(1) - All shell and head butt welds to be
100% RT

8. ASME VIII-1 Lethal Service Code References
Fig UW-13.5 - One possible lap joint stub end
configuration - see also interpretation BC-79-680 / VIII-
80-111
UB-3 - Brazed vessels shall not be used
UCS-6 - Do not use SA-36, 38W or SA-283
UCS-79 - PWHT and extreme fiber elongation - read for
rules when heat treatment is required
UCI-2, UCD-2 Cast iron and ductile cast iron vessels are
not allowed.

9. ASME VIII-1 Lethal Service Code References
UIG-2(c) - Metal parts for graphite vessels are to be
designed to UIG requirements
UIG-23(b) - Factor of safety for lethal service
UIG-60 - Lethal service
UIG-99 - Lethal service pressure tests
ULW-1 & ULW-26(b)(4) - Layered vessels lethal
restrictions apply to the inner shell and heads only

10. ASME VIII-1 Lethal Service Code References
UHX-19.1(b) - Heat exchanger markings
Appendix 2-5(d) & 2-6 - Maximum Flange Bolt Spacing
Appendix 2-14(a) - Mandatory flange flexibility
Appendix 7-1, 7-5 - Steel casting examination for 100%
quality factor
Appendix 9-8 - if the jacket does not carry lethal
substances, lethal service restrictions do not apply to it

11. ASME VIII-1 Lethal Service Code References
Appendix 17-2(a) - Dimple jackets will not contain lethal
substances
Appendix 35-3(c) & 35-7(d) - Mass production rules
Appendix W Table W-3 - Filing out the U forms
Appendix KK (note 12) - Filling out User Design
Requirements forms
Appendix NN Table NN-6-5 - User or designated again
determines if the contents are lethal
End notes 65 - Definition of lethal service

12. Weld restrictions by category

13. Special lap joint stub end for
lethal service - see also Fig UW-
13.3 and Fig 2-4(5) and (6)

14. All partial penetration nozzles are prohibited

15. All figure UW-13.2 corner welds are prohibited

16. No slip on flanges

17. Code Cases
The following Code Cases refer to lethal service for VIII-1
vessels (2013 edition)
1750-20(g) - A126 not to be used for prvs, or rupture
disks.
2249 - Furnace Brazing
2318 - slip on flanges in lethal service
2321-1 PWHT of P4 and P5A materials
2324 - Ultrasonic inspection
2334 - single fillet lap joint tubesheet to shell connection
2346-1 & 2537 - Alternative rules for SE and F&D head
to shell attachment

18. Code Cases
2369 - Testing of covers separate from vessels
2377 - RT of SA-612 steel
2421 - Single fillet joints in Heat exchanger tubes
2437 - Diffusion bonded heat exchangers
2527 – Pneumatic testing of UM vessels
2537 – alternative F&D and SE head to shell
attachment is not for lethal service
2621 – Diffusion bonding
2751 – alternative spherical head to shell attachment
is not for lethal service

19. Interpretations
With interpretations now available on line at
cstools.asme.org/Interpretation/SearchInterpretation.cfm it is
now easier to find relevant and up to date interpretations. A
search for "BPV Section VIII Div 1" keyword: "lethal" returns
44 records. The comments on the most interesting lethal
service interpretations are listed below. Refer to the actual
interpretations for the actual text.
VIII-1-01-118 and VIII-1-83-77R - ERW pipe may only
be used if the long seam is radiographed
VIII-82-65 - volumetric examination of category D joints
is not always required

20. Interpretations
VIII-1-01-42 and VIII-1-04-48 - cone >30° and and
corner joints not permitted
VIII-1-86-84 and VIII-1-95-138 - prohibited flange
attachments - Fig UW-13.2(m) and Fig 2-4 sketches (7),
(8), (8a), (8b), and (9)
VIII-1-92-112 - full radiography of category C and D
butt welds is required except for UW-11(a)(4)
VIII-1-92-194 - full penetration angle joints are not
permitted
VIII-1-92-211 - Fig UW-13.2 attachments are not
permissible

21. Interpretations
 VIII-1-98-113 - permissible repad and flange pad
arrangements
VIII-1-98-23 - Fig UW-16.1 (a) and (c) are permissible
nozzle attachments, others are not discussed
VIII-77-62 - "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)."

22. Interpretations
VIII-80-02 - do not use corner joints from Fig UW-
13.2 - redesign to create butt joints that can be
radiographed
VIII-80-111 - acceptable lap joint flanges include
Fig. 2-4(1) and Fig. UW-13.3 and Fig. 2-4(5) and (6)
Disclaimer: This material is provided for educational uses
only. Only ASME can make code interpretations.
http://www.pveng.com/ASME/ASMEComment/LethalService/LethalService.php