Pressure Vessel for Human Occupancy

The American Society of Mechanical Engineers defines a Pressure Vessel for Human Occupancy (PVHO) as a container that is intended to be occupied by one or more persons at a pressure which differs from ambient by at least 2 pounds per square inch (0.14 bar).[1] Since 1977, the ASME's PVHO committee has published standards governing the construction of a number of PVHO applications. The current design standard is PVHO-1-2023.[2] The current code for maintenance and operation guidances is ASME PVHO-2-2019.[3] Similar standards are published by a range of national and international standards organisations.

List of PVHO types

Types of pressure vessels for human occupancy include:

A typical pressure vessel is not defined until there is at least one atmosphere (14.7 psig) of contained gas pressure. Less than that is typically a storage tank, even if there is some overpressure added by design. The rules for PVHO are invoked at 2 psig (13.8 kPa), per Section 1-2.1 "Application" of the ASME PVHO-1 code.[2] This lower threshold is due to the potential for serious injury if a person under pressure as low as 2 psig is rapidly decompressed.[4][5]

Section 1-3 "Exclusions" specify nuclear reactor containments, aerospace cabins, caissons are not considered under the ASME PVHO-1 code. This is because each of those types of occupied pressurized chambers are under other jursidictions and therefore under other design codes. It is noted while "caissons" are under other applicable rules depending on the specific application, the Occupational Safety and Health Administration specifies the chambers in pressurized tunnel boring machines are under ASME PVHO-1 and any chamber used to decompress tunnel workers must meet ASME PVHO-1.[6]

Titan submersible implosion

In 2018, prior to the 2023 Titan submersible implosion, William Kohnen, the chair of the Marine Technology Society Submarine Committee, drafted a letter with 38 signatures to respond to OceanGate's public stance on not using existing codes and standards.[7] The cause of the implosion is still under investigation, but it was noted the other nine submarines that could reach the depth of the wreck of the Titanic were all designed using recognised engineering codes.[8]

References

  1. ^ "Introduction to PVHO" (PDF). NOAA Office of Marine and Aviation Operations. April 2022. Retrieved 2024-09-30.
  2. ^ a b "Safety Standard for Pressure Vessels for Human Occupancy". Codes and Standards. American Society of Mechanical Engineers. Retrieved 25 April 2020.
  3. ^ "Safety Standard for Pressure Vessels for Human Occupancy: In-Service Guidelines". Codes and Standards. American Society of Mechanical Engineers. Retrieved 25 April 2020.
  4. ^ Benton, Peter; Woodfine, James; Westwood, Paul (January 1996). "Arterial gas embolism following a 1-meter ascent during helicopter escape training: a case report". Aviation and Space Environemental Medicine. 67 (1): 63–64. PMID 8929206. Retrieved 25 March 2024.
  5. ^ Hampson, Neil; Moon, Richard (September 2020). "Arterial gas embolism breathing compressed air in 1.2 metres of water". Diving and Hyperbaric Medicine. 50 (3): 292–294. doi:10.28920/dhm50.3.292-294. PMC 7819734. PMID 32957133. Retrieved 25 March 2024.
  6. ^ "Are pressure vessels for human occupancy involved in tunnel boring required to be fabricated and documented in accord with the ASME PVHO-1 standard, "Pressure Vessels for Human Occupancy"?". OSHA Interpretations. Occupational Safety and Health Administration. Retrieved 27 March 2024.
  7. ^ Marine Technology Society (March 27, 2018). "Marine Technology Society Letter to OceanGate Inc" (PDF). media.defense.gov.
  8. ^ Cooke, Ryan (21 June 2023). "Marine group says 10 subs in the world can dive to Titanic depths. Titan is the only one not certified". Canadian Broadcast Company. Retrieved 25 September 2023.


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