The Importance of Adhering to Quality Management Requirements in Vessel Design and In-Service Inspections

January 13, 2021

Sunken gaseous resources necessitate a unique focus on equally unique variables, such as the composition of the soil and the likelihood of unforeseen subterranean site irregularities. This is because geological and geographical sciences hold sway down here, and they require almost as much consideration as any engineering problem or architectural issue. In evaluating these subterranean variables, we need to assess the efficiency and quality requirements of this below-ground scenario. That all sounds a little ambiguous, which isn't a word that should ever be allowed in an engineer's vocabulary, so details are needed.

ASME stands for the American Society of Mechanical Engineers. It developed the codes to regulate the quality of pressure vessels in the USA but now the codes are adhered to by other countries as well, such as our country of Australia. A specific section of the ASME Codes is the Boiler and Pressure Vessel Code or the BPVC, which explains all the mandatory construction requirements for pressure vessels. This code contains the following three subsections or divisions:

• Division One stipulates the requirements for the design and fabrication processes as well as the testing and inspection stages. On top of all this, it covers the certification of vessels that clearly states that they must be able to withstand internal and external pressures of over 15 psi. This holds true regardless of how the pressure is created. Direct heat, indirect heat and firing up a source are three examples of creating pressure in these vessels. Also, this subsection discusses specifications for acceptable construction materials for these vessels as well as brazing, forging, welding and other approved fabrication processes. Division one also contains numerous mandatory appendices that dictate design features, methods of non-destructive inspections and various testing standards along with UM, UV and U designators.
• Division two describes materials, design processes and non-destructive testing procedures in more detail than division one does to ensure the reader fully understands. It also mentions that utilization of U2 and UV designators. These regulations are specific to pressure vessels made for diving.
• Division three contains the in-depth details for the pressure vessels that must withstand internal and external pressures of over 10,000 psi. However, it does not dictate any minimum or maximum pressure limits for the above two sections. Also, it includes the regulations for using U3 and UV3 designators.

When Local Legislation Meets Structural Design

Advanced structural shoring techniques define the outer boundaries of an underground enclosure, but much of this infrastructure is already in place below ground. Old salt mines and natural aquifers are classed as injectable gas storage sites. Likewise, previously occupied oil fields can play host to pressurized gas reservoirs, but there are certain factors that will naturally affect how well these natural storage sites can perform when the pressure rises. Thankfully, millions of years of geological action have shaped these underground chambers, so they're well-suited for this repurposing role.

Accounting For Site-Relevant Geological Factors

Rocky strata bands as it's compressed, so its characteristics change sharply at different depths. The porosity and permeability of the layers vary, so those layers require a quality assessment study before site deliverability rate can be properly established. Sedimentary samples may be required to gauge the geological and physical characteristics of a salt cavern, but depleted storage areas are usually already well understood, for they were studied when the oil or gas was first recovered.

Contact Details

Fusion - Weld Engineering Pty Ltd
ABN 98 068 987619

1865 Frankston Flinders Road,
Hastings, VIC 3915

Ph: (03) 5909 8218

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