that such alternative material underground tanks are potentially competitive with steel construction from a life cycle cost standpoint.
The ASME design code for Fiber-Reinforced Plastic Pressure Vessels (ASME Boiler & Pressure Vessel Code, Section X) has more restrictive constraints for vessels that have both external and internal loads, such as when an empty tank is first buried and then filled. While the Section X constraint is intended for extensive load reversals, a propane tank will typically experience one load reversal during the initial burial followed by filling. The relaxation of this restriction could reduce the design margin, and therefore the manufacturing costs, of the composite tank for underground propane use.
The standard National Fire Protection Agency (NFPA) Liquefied Petroleum Gas Code (NFPA 58, NPFA, 2008) governs the installation of propane systems. Section 18.104.22.168 (LP-Gas Equipment and Appliances, Containers, General) requires that containers be designed in accordance with the regulations of the ASME Boiler and Pressure Vessel Code, Section VIII, “Rules for the Construction of Unfired Pressure Vessels.” Section VIII allows metallic materials only. As mentioned above, pressure vessels fabricated from composite materials are addressed in Section X. Therefore, NFPA 58 would have to be modified to allow Section X-designed (composite) vessels in addition to Section VIII-designed (metallic) vessels.
Alternative Underground Propane Tank Materials, Phase II—Final Report
September 2009 Battelle and Lincoln Composites