In 2004, Port Technology International published my article titled: ‘The installation of an aluminium internal floating roof is a sound investment.’ The title statement of that article was defined and corroborated mathematically employing current monetary values of that time in conjunction with government mandated/industry accepted formulae for quantifying emissions. Go to www. aluminumfloatingroofs.com to download this article.
Balancing profits and environmental care
In the US, petroleum storage tank emissions are quantified and regulated by the Environmental Protection Agency (EPA). The goal in the US to reduce and eliminate harmful emissions is mandatory and is certainly achievable with regard to petroleum storage tanks. Properly designed, constructed and operated floating roofs reduce tank emissions by a minimum of 95 percent. There are considerations involved in choosing the type of floating roof, and often price is the key factor involved in the purchase decision. Everyone wants to breathe clean, fresh air and since economics are always a factor in the decision process in industry, regulations are a necessary factor to define the minimum standards. Businesses have to be profitable or they go out of business but there must be a balance that allows production through distribution, without unnecessary negative impact on the environment for the sake of profits.
But there is the good news: the installation of an aluminium internal floating roof (AIFR) is an even better investment today than it was in 2004. In addition, if you already have an AIFR, we will discuss a certain type of retrofitting that is also a profitable investment.
Calculating investment potential
For all emissions loss calculations we will use the US EPA Tanks 4 program. This program was developed over a period of many years as a cooperative endeavour between the EPA and the US American Petroleum Institute (API). This is the standard method for quantifying emissions losses for permitting and enforcement purposes in the USA. See the US EPA web site: http://www.epa. gov/ttn/chief/ap42/indec.html for information and download. For comparison purposes we will use the same tank parameters we used in the 2004 equation. The fixed steel dome roof tank, painted white is 120 feet (36.5 metres) in diameter by 48 feet (14.6 metres) high, with standard appurtenances and is located in Houston, Texas, USA. The product service is motor petrol with a Reid Vapour Pressure of 10 psi and experiences 36 turnovers per year. The perimeter seal is a double wiper and the AIFR is cable suspended in lieu of fixed or two position pipe support legs. In this location and configuration the emissions losses to the atmosphere are 0.3 percent. This tank is 99.7 percent efficient. Without an AIFR, the emissions lost would be 1,499,403 pounds. per year. Let’s apply the dollar cost to the pounds lost using 6 pounds per US gallon, and applying the Houston spot price of US$2.738 per gallon for conventional motor petrol on January 29, 2013. The resultant cost of emissions losses is USD $684,228. This is more than four times the price of a pontoon and skin type AIFR used in this example and more than two times the price of a full contact honeycomb AIFR which would have even lower emissions losses.
Let us now analyse a simple retrofit of an existing AIFR. In this case we will discuss an AIFR that has conventional fixed or two position pipe legs. I wrote an article entitled ‘Hang in There’ describing the numerous benefits of suspending an AIFR with cables in lieu of pipe legs and another entitled ‘API 650 H Revisions’ that detailed the API revisions relating to cable suspension systems. These papers can also be found on my website. In this example we will discuss the emissions losses and the resultant financial benefits using the same tank and location. The emissions losses through the pipe leg sleeves account for approximately 30 percent of the total emissions losses for the tank. The approximate losses in this case are 449,820 pounds. per year.
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