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Hydrocarbon Processing, the leading international magazine for petroleum refining, gas processing, petrochemical/chemical and engineer/constructor companies, features in its November issue the article "Preventing Storage Tank Fires," written by Richard Ritchie, Director of International Sales at SGS.

Above-ground atmospheric hydrocarbon storage tanks come in a wide range of types and sizes. Each type has its own set of fire hazards. Storage tanks can be broadly classified into several major categories based on roof design. Design specifications for most of the above-ground storage tanks are covered by standards from the American Petroleum Institute (API) and the British Standards Institute (BSI).

There are hundreds of above-ground atmospheric pressure hydrocarbon storage tank fires every year. One example happened in 2005, at the Buncefield Oil Depot in Hertfordshire, UK. Approximately 300 tons of gasoline poured over tank side walls and began to fill the containment dike. Eventually, the vapor cloud above the gasoline flowed over the dike and spread out through the facility and beyond its perimeters, and finally led to a massive explosion. A total of 23 storage tanks and majority of the terminal were destroyed. The fire left 43 people injured and homes and businesses as far as 5 miles away were damaged or destroyed. The economic cost from the incident was estimated at 894 million British pounds.

Just recently in October 2009, two oil depot explosions led to personal and material losses and have endangered the environment. Both accidents, one in Puerto Rico (October 23) and the other in India (October 29), appear to have been caused by leaking storage tanks.

In such disasters related to oil and fuel storage, it is not only the material damage – 21 tanks in Puerto Rico and 11 in India – that is high, in most cases personal injury is also involved. In India, 11 people were killed and 150 injured, while in Puerto Rico, 2 sustained wounds. In both cases the surrounding areas had to be closed off and thousands of people evacuated.

Each type of storage tank has different fire hazards. The most common fire hazards in above-ground storage tanks are overfill, vent, rim-seal as well as full-surface fires, which can be further divided into obstructed full-surface fires and unobstructed full-surface fires. Each type of fire has different preventive measures based on the causes of the fire.

While it is impossible to eliminate the danger of storage tank fires, the risk can be substantially reduced by ensuring that proper design, operation and maintenance guidelines are in place and strictly followed. Completing proper inspections according to the API 653 standard is essential in identifying design and maintenance issues in existing storage tanks.

Preventive Action – Storage Tank Inspections

There are three types of inspections detailed in API 653: Monthly routine In-service Inspections, formal in-service external inspections and out-of-service internal inspections.

Monthly routine in-service inspections include the Visual Inspection of tanks, the inspection of the exterior tank surface for leaks, shell distortions, and corrosion, as well as the verification of the foundation condition, paint coating, insulation system and appurtenances.

Formal in-service external inspections have to be conducted every 5 years and the areas inspected include the dike, foundation, shell, shell appurtenances, access structure, wind girder, roof, internal floating deck, fire protection system, and the tank mixer.

Out-of-service internal inspections must be done at least every 20 years unless a Risk-Based Inspection system is in place. If they do not have an established corrosion rate, they must be inspected within 10 years. In order to perform these inspections, the tanks must be emptied and cleaned. In addition to visual inspection, magnetic flux leakage testing and ultrasonic testing are employed. The primary purpose of the inspection is to assure continued tank integrity by verifying that the bottom is not severely corroded. Furthermore, the interior shell walls and the roof are inspected for general corrosion and pitting.

To inspect and evaluate the properties of the storage tanks without causing damage, several Non-Destructive Testing techniques can be applied. In addition to these inspections, proper procedures as well as trained personnel substantially eliminate the risk of storage tank fires.

Read the whole Hydrocarbon Processing Magazine article - Preventing Storage Tank Fires (PDF 777 KB)

SGS Storage Tank Inspection, Audit and Calibration

SGS Industrial Services has the experience, the accreditations and the equipment to carry out expert controls, inspections and measurements for the owners of storage tanks to ensure compliance with EN 14015, API 650 or 653, EEMUA 159 and ISO7504. With the competence of a notified body, SGS performs independent Assessment, Testing and Verification to guarantee the safe condition of storage tanks.

For further information, please contact:

Richard Ritchie

SGS Competence Centre Asset Integrity Management
406 W. US Highway 60
PO Box 548
Bartlesville, OK 74005
t: 918 332 3128
f: 918 332 3192

About SGS

The SGS Group is the global leader and innovator in inspection, verification, testing and certification services. Founded in 1878, SGS is recognized as the global benchmark in quality and integrity. With more than 56,000 employees, SGS operates a network of over 1,000 offices and laboratories around the world.