ASME lethal condition

The lethal working condition in ASME is equivalent to the extremely highly hazardous medium in the national standard. When it is a lethal working condition, there should be more stringent requirements for the equipment. These requirements are scattered in ASME VIII-I, code cases and interpretations. This article tries to summarize some provisions on death. If there is anything wrong or missing, you can reply at the end of the article.

What is lethal condition

First, let’s understand what is lethal working condition. There are two definitions in ASME VIII-I. In ASME VIII-1 endnotes 65, lethal substances are defined.

First, in UW-2, there is also a description of death.

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Who will decide whether to die

So who will specify whether the equipment needs to be designed according to lethal working conditions? According to UW-2 of ASME VIII-1, the user (owner) of the equipment or its agent (Engineering Company) is responsible for determining whether it is a lethal condition.
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Generally, the manufacturer cannot decide what medium is the lethal working condition.

What are the requirements for lethal working conditions

1. UW-2 has most requirements for lethal working conditions:
UW-2 (a): resistance welded pipe or heat exchange pipe (such as SA-53) is not allowed. (however, it is stated in interpretation viii-1-01-118 that it can also be used if the longitudinal weld is 100% RT.)
UW-2 (a): carbon steel or low alloy steel shall be subject to post weld heat treatment.
UW-2 (a) (1) (a): only table uw-12 type No.1 structure (butt welding without backing plate) can be used for class a joints

UW-2 (a) (1) (B & C) & interpretation VIII-1 92-211: type B & C welded joints can only use the structure of table UW-12 type No.1 or 2 (butt welding). It is not allowed to use SO flange, flange in figure UW-13.2 or structure welded between flat head and cylinder.

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W-2 (a) (1) (d) & interpretation viii-i-98-23: Class D welds require full penetration.
UW-2 (a) (1) (c): Class C welded flanged joint:

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And other UW-2 requirements.
2. Other requirements for lethal working conditions:
In addition to uw-2, there are also some requirements for lethal working conditions in other parts of the specification:

  • UG-16 (b) (5) (a): the minimum wall thickness of heat exchange tube of air cooler and cooling tower heat exchanger is 1/16″.
  • UG-24 (6): Casting 100% RT.
  • UG-25 (E): leakage indication hole is not allowed.
  • UG-99 (g), (k): visual inspection of hydrostatic test cannot be exempted, and paint or lining is not allowed before hydrostatic test.
  • UG-100 (d) (4): Wood inspection of pneumatic test cannot be exempted.
  • UG-100 (E) (3): paint or lining is not allowed before pneumatic test.
  • UG-116 (c): mark “L” on the nameplate.
  • UG-120 (d) (1): “lethal service” needs to be filled in the data report.
  • Uw-11 (a) (1): 100% RT is required for all barrel head butt welds.

Fig UW-13.5:

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  • UB-3: brazing is not allowed.
  • UCS-6: materials of SA-36, SA/CSA-g40.21 38W, or SA-283 ABCD cannot be used for pressure containing parts.
  • UCS-79: cold formed parts require heat treatment.
  • Appendix 2-5 (d) & 2-6 – the maximum bolt hole spacing cannot exceed bsmax. And when calculating the bolt load, it needs to be multiplied by BSC.
  • Appendix 2-14 (a) – flange stiffness must be checked under lethal conditions, which cannot be exempted
  • Appendix 9-8 – for the lethal working condition of the inner cylinder, the requirements of UW-2 shall only apply to the welds of the inner cylinder and the welds welding the jacket to the inner cylinder. RT is not required for the welds on the jacket including the inner cylinder, and fillet welds can be used.
  • Appendix 17-2 (a) – honeycomb jacketed layers cannot be used for lethal media.
  • Appendix 27-4 glass lined containers under lethal conditions shall be coated or glass lined after pressure test.
  • Appendix 35-3 (c) & 35-7 (d) – the lethal working condition equipment for mass production shall comply with the rules of UG-90 (c) (1).

Diagram of lethal working condition requirements

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Standard interpretation on the official website

On the official website of ASME, there is the interpretation of various ASME standards, which is similar to some users who have questions about the understanding of the standards, submit the questions to the ASME Committee, and then the committee will reply to the questions. Its website is as follows:

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Search the website for “lethal”.

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You can see a lot of standard definitions and Q & A.
Open a Q & A to see:

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The buyer asked: the fillet joint is used for the welding between the tube plate of class C joint and the cylinder or tube box. Can RT or PT be omitted.
The Committee replied: if it is not a lethal working condition, class C joints must be butt jointed, and RT or PT testing can be omitted.

Can stiffening rings be used under lethal conditions?

In GB design, the reinforcement ring cannot be used for extremely high hazard. However, ASME does not mention whether the reinforcing ring can be used for death. In most cases, the owner has supplementary engineering regulations to limit whether the reinforcing ring can be used for death.
So users sometimes ask:

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According to UG-25 (e), there shall be no leakage indication hole under lethal working condition. Can this requirement of lethal working condition be applied to the indication hole of reinforcing ring in UG-37 (g)?

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The Committee replied: No.
The answer is very interesting. The Committee believes that the reinforcement ring under lethal working conditions can be provided with indication holes, so it can be considered from the side that the reinforcement ring can be used under lethal working conditions.
Therefore, in terms of ASME, reinforcing rings can also be used under lethal conditions.

Source: China Flange Manufacturer – Yaang Pipe Industry (

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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