Tuesday, May 14, 2013

SP001 Inspections for ASTs: What you need to know

If your organization operates shop-fabricated or field-erected aboveground storage tanks (ASTs), you’re likely at least somewhat aware of the Spill Prevention, Control and Countermeasure (SPCC) requirements for regular inspections of these tanks. If you have ASTs that are required to conform to these regulations, there is an article in this quarter’s edition of the PEI Journal that you should read.

Titled, Integrity Testing Shop-Fabricated Aboveground Storage Tanks, the article by Alex Ralston, POE, provides an excellent summary of the inspection requirements and procedures required by STI SP001, which is the Standard for the Inspection of Aboveground Storage Tanks.

The SP001 standard applies to portable containers, shop-fabricated tanks and field-erected tanks up a maximum shell height of 50 feet, and a maximum diameter of 30 feet. In the article, Ralston summarizes the essential elements of this standard: 
"The STI SP001 standard is not a tightness test similar to those performed on underground tanks. The standard measures construction integrity; compliance with fire codes, building codes, industry standards and OSHA standards; and the integrity of the thickness of the metal tank shell as compared to the original tank shell thickness. That last requirement is essential. The shell thickness determines the suitability of the tank for continued service – specifically, whether the tank should continue in service or be taken out of service for repair or replacement. The inspection also sets the date of the next formal inspection."
The article goes on to include a detailed summary of what a certified inspector looks for in a SP001 inspection. It’s an excellent read if this is an area of concern for your fueling operation.

Tanknology provides SP001 inspections and testing. If you would like to set up an inspection program, review your existing approach, or learn more about our AST related services, email us at info@tanknology.com or call us at 1-800-964-1250.

Wednesday, May 1, 2013

Update on research targeting corrosion in ULSD systems

A significant topic in the petroleum storage and dispensing world in recent years has been the extreme rate of corrosion being experienced in some UST systems containing ultra-low sulfur diesel (ULSD). As early as 2008, this phenomenon was observed and by 2011 major industry organizations were in high gear in search of answers.

These organizations, which form the Clean Diesel Fuel Alliance (CDFA), awarded to the Battelle Memorial Institute with the support of Tanknology a research project intended to gain an understanding of what is causing the corrosion so that they might create a solution.

Battelle and Tanknology have now completed this initial project and the detailed findings are being reported in the current issue of the PEI Journal.

As a result of the sampling and analysis program in this study, the ultimate hypothesis was that the corrosion is likely due to the dispersal of acetic acid through the USTs.  This acid is likely produced by Acetobacter bacteria feeding on low levels of ethanol contamination. Dispersed into the humid vapor space and by disturbances during fuel deliveries, the acetic acid is deposited throughout the system. This results in a cycle of wetting and drying of the equipment, concentrating the acetic acid on the metal equipment and corroding it severely and rapidly. (The fill riser and STP photos to the right illustrate the severity of ULSD corrosion.)

But where is the ethanol contamination coming from? Initial study points to two possibilities: From switch loading or from a gasoline tank ventilation system that is manifolded with the diesel tank.

While this initial project provided an important step in possibly identifying the root cause of this rapid rate of corrosion, it did not provide enough certainty to justify changing the ULSD fuel distribution system.

The CDFA task force is now pursuing a next-level research project. In this advanced project, the hypothesis of the initial research will be further studied in order to prove or disprove it, as well as to provide a basis for alternative hypotheses if necessary and to identify the leading factors promoting the corrosive environment of ULSD systems.

According to Brad Hoffman, Tanknology’s lead scientist on the initial study, there is a clear sense of urgency in the work of the task force. “Corrosion at this rate of speed is very concerning,” Hoffman said. “So everyone is very anxious to understand why it’s happening and what needs to be done to stop it. At this point, we have what appear to be strong indications of what’s going on, but those need to be proven out so that corrective measures can be designed to mitigate this problem.”

So what can be done to minimize the potential for such corrosion in the meantime? According to Hoffman, “Until the absolute cause and a cure are identified, we recommend that operators keep their tank bottoms as absolutely free of water as possible. This is an important practice for any tank, but is particularly true of diesel tanks. Water is the enemy of fuel – especially diesel – in a UST.”