ASME code, small vessels & Lethal service

Read Section VIII, Div. 1 U-1(c)(2)(i). Any vessel greater than 6" in diamter irregardless of pressure is outside the scope of the Code. Lethal service does not enter in the determination of Code applicability.

I am only familiar with ASME Section X and RTP-1 standard. With Section X, anything 6" diameter and under is outside scope of the code. It also only applies to great than 15 psig pressure. Note: Section X is for fiberglass reinforced thermoplastic vessels in which an "RP" stamp is applied

Because of the broad history and breadth of fabrication techniques that are out there for fiberglass vessels, ASME thought it would be prudent to develope a standard called RTP-1 - this is an "RTP" stamp. The RTP-1 standard covers full vacuum to 15 psig. In addition, RTP-1 has a "critical service" designation - not sure if this is what you mean by lethal service. Critical service has 12.5:1 safety factor vs. normal 10:1 safety factor on internal pressure design. There are more details to critical service as well.

Let me know if you would like more information. ghopkins@rl-industries.com

Hope this helps, Greg