Steel pressure tanks and cylinders have been used for decades for propane storage and transportation. Above-ground storage tanks range from one hundred to tens of thousands of gallons. In the past several years, there has been increasing interest in burying tanks at customer sites, both residential and commercial. While underground tanks may have safety advantages, such as removing the tank from traffic areas, the main reason for burying propane tanks is for aesthetics, as a buried tank is out of sight, except for the access lid. Unlike the environmental issues associated with the underground storage of other fuels such as gasoline and fuel oil, the environmentally nontoxic nature of propane eliminates concerns regarding potential soil and water contamination (Sympson, 2005). Without proper corrosion protection, however, underground steel tanks are susceptible to corrosion and potential problems stemming from corrosion issues, such as a propane leak at a site in the tank wall that has corroded through (May, 2005; Nicholson II, 2005-2006; Eastern Propane, 2004; NPGA, 1991; NPGA, 1994). For additional details regarding general corrosion and corrosion protection of steel underground propane tanks, the reader is referred to the Phase I report for this project (PERC Docket #11728, Muellerleile, et al., 2005). The corrosion assessment reported in this present Phase II report, described below, considers the corrosion of appurtenances without the presence of general cathodic protection associated with standard underground steel propane tanks.
Steel costs have dramatically increased in response to surging worldwide demand. Additionally, the costs involved with underground installation, cathodic protection, and monitoring result in the price of procuring and installing underground steel tanks to raise even higher (Sympson, 2005; Ryman and Ryman, 2005). In the past five years, steel prices increased sixfold, from just over $200 per ton in 2001 to over $1200 per ton in the summer of 2008, before falling back to $800 per ton at the end of 2008 (MEPS, 2009). Worldwide demand, especially in rapidly developing countries such as China, is also leading to shortages and increasingly stiff competition from European and Asian manufacturers, which are also driving steel prices higher (Ostroff, 2006; Rey, 2004a).
Composites can offer a number of significant advantages over standard steel for cylinder and tank applications. Composite resistance to corrosion, especially for underground applications, is particularly attractive, as it eliminates the need for cathodic protection and monitoring of the tank. Its lighter weight also provides ease of handling for transport, installation, and removal compared to its steel counterparts (Rey, 2004b).
Based upon these advantages of composites, and in response to continuing skyrocketing steel prices, the Propane Education & Research Council (PERC) continues to investigate alternative materials for underground propane tanks. To that end, the purpose of the present Phase II work
Alternative Underground Propane Tank Materials, Phase II—Final Report
September 2009 Battelle and Lincoln Composites