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Pipeline Safety: Strapping Table Calibration for Pipeline Breakout Tank Operators

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Information about this document as published in the Federal Register.

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Office of Pipeline Safety (OPS), Pipeline and Hazardous Materials Safety Administration (PHMSA), DOT.


Notice; issuance of advisory bulletin.


This advisory notice alerts pipeline operators of all hazardous liquid pipeline facility systems about the need to validate the accuracy of breakout tank strapping tables. Under certain circumstances, strapping table errors can potentially lead to dangerous conditions.

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Joy Kadnar by phone at (202) 366-0568, by fax at (202) 366-4566, or by e-mail, General information about the Pipeline and Hazardous Materials Safety Administration's Office of Pipeline Safety (OPS) programs may be obtained by accessing the home page at

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I. Background

A breakout tank exploded and subsequently ignited in Glenpool, Oklahoma on April 7, 2003. The accident involved an 80,000-barrel breakout tank that exploded and burned as it was being filled with diesel. The resulting fire burned for over 20 hours and damaged two other nearby breakout tanks. While there were no injuries or fatalities, the cost of the accident exceeded two million dollars, residents adjacent to the accident site were evacuated, and area schools were closed for two days.

The National Transportation Safety Board (NTSB) conducted an investigation into the accident and subsequently published a Pipeline Accident Report titled “Storage Tank Explosion and Fire in Glenpool, Oklahoma.” In its findings adopted on October 13, 2004, the NTSB issued a recommendation to OPS to issue an advisory bulletin to liquid pipeline operators to validate the accuracy of their tank strapping tables.

The breakout tank that exploded contained an internal floating roof system equipped with pontoons that float on top of the product at a certain level. The tank also had legs that supported the roof whenever the product was drained and the volume of liquid in the tank decreased to the level at which the roof no longer floated. Additionally, the tank had two Supervisory Control and Data Acquisition System (SCADA) alarms to alert controllers when the volume was nearing the level at which the roof would no longer float. The alarm set points were based on the landed height of the floating roof assumed in the operator's strapping table.

NTSB determined that based on the height measurement of the floating roof documented on the construction inspection report, and based on measurements investigators made after the accident, the strapping table was incorrect. Specifically, the distance from the bottom of the pontoon to the datum plate was found to be higher than indicated on the pre-accident strapping table. The surface of the charged diesel was within approximately two inches of the pontoons at the time of the explosion. This, according to NTSB, is the most likely time for a static discharge to occur. Based on this finding, as well as other contributing factors, the NTSB determined that an incorrect measurement on the strapping table contributed to the cause(s) of the accident.

II. Advisory Bulletin ADB-05-02

To: Owners and Operators of All Pipeline Facilities Who Rely on Strapping Tables to Determine Volume Based on Measured Height For Product Level.

Subject: Validation of Strapping Tables to Reduce the Likelihood of Errors That May Lead to Dangerous Conditions in Breakout Tanks.

Purpose: To advise owners and operators of all hazardous liquid pipeline facilities about the need to validate strapping tables.

Advisory: Strapping Tables are commonly used to determine the commodity volume based on product level within breakout tanks. If the strapping table is incorrect, operators may expose themselves and the community to unnecessary risks.

OPS seeks to advise operators that they should review and, if necessary, revise their breakout tank operating procedures to minimize risk. The strapping tables should be validated to reduce the potential for errors that may lead to dangerous conditions, such as static discharge inside a tank after a floating roof has been either intentionally or unintentionally landed. Pipeline operators, therefore, may need to adjust the measurements on their strapping tables to ensure accuracy.

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Issued in Washington, DC, on March 18, 2005.

Theodore L. Willke,

Deputy Associate Administrator for Pipeline Safety.

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[FR Doc. 05-6729 Filed 4-5-05; 8:45 am]