Hydrocarbon storage tanks

Explosive Power of Vapor Cloud at Liquefied Hydrocarbon Storage Tank Farm... 

Figure 5. Typical drawing indicating zone classification of a hydrocarbon storage tank, Mariani et al. 2000. 

Figure 7. The lay-out of hydrocarbon storage tanks considering for the case-study.

Mariani, E. Rodriguez, M., 2000. Controlling the Risk of Fire caused by lightning in Hydrocarbon storage tanks. International Conference on Lightning Protection, Rhodes, Greece, 2000, pp 786-791. 

S.N. Ganesan, Performance-based Gas Detection System Design for Hydrocarbon Storage Tank Systems, Kenexis DMCC Oil Gas Industry Conclave e lOCL, Delhi, India http // www.isssource.com/wp-content/uploads/2012/06/062312KenexisPaperl. pdf. 

The following guidance applies to hydrocarbon storage tanks, sometimes referred to as API Tanks ... 

In refineries and other facilities that process hydrocarbons, storage tanks may develop a layer of water below the hydrocarbons. The water typically enters the tank in small quantities, phases out, and settles at the bottom of the tank. The water can enter the tank with the process streams, through leaks in steam coils, and through leaks in the tank roof and open hatches. Sometimes, the water will create an emulsified product with the hydrocarbons. This product is referred to as a rag layer or bottoms sediment and water (BS W). 

Solids materials that are insoluble in hydrocarbon or water can be entrained in the crude. These are called bottom sediments and comprise fine particles of sand, drilling mud, rock such as feldspar and gypsum, metals in the form of minerals or in their free state such as iron, copper, lead, nickel, and vanadium. The latter can come from pipeline erosion, storage tanks, valves and piping systems, etc. whatever comes in contact with the crude oil. 

API Publ 2027, Ignition Hazards Involved in Abrasive Blasting of Atmospheric Storage Tanks in Hydrocarbon Service, 2nd ed., July 1988. 

Ammonium nitrate is made at Fisons Ltd and stored in solution in two heated tanks to prevent ciystalization. One tank holds 3,100 tonnes and the other 6,200 tonnes of 92% aqueous ammonium nitrate solution. Trains laden with oil refinery products from the Mobil and Shell refineries pass the factory on a near embankment. A derailment could spill and ignite hydrocarbons from a rail tank car to explode an ammonium nitrate storage tank. Suggestions were made to mitigate or prevent such a domino effect... 

Taking into account the possibility of highly directional blast effects, Eichler and Napadensky (1977) recommend the use of a safe and conservative value for TNT equivalency, namely, between 20% and 40%, for the determination of safe standoff distances between transportation routes and nuclear power plants. This value is based on energy it should be applied to the total amount of hydrocarbon in the largest single, pressurized storage tank being transported. 

Organic chemicals Most organic liquids, other than the stronger acids, only attack zinc slowly. Zinc is, therefore, suitable for storage tanks for liquid hydrocarbons such as motor fuels, for phenols and for trichlorethy-lene degreasers. Zinc or zinc-coated vessels are not recommended for use in contact with acid foodstuffs, but are regularly used for dry foods. Zinc in small quantities is beneficial in the human diet. 

There are several different situations in which petroleum hydrocarbons pose a threat that has attracted solution by bioremediation. These include (1) oil-refinery waste and contamination of the surrounding soil, (2) leakage from oil pipelines and underground storage tanks or basins, and (3) spillage of crude oil in the marine enviromnent after accidents at sea. 

A heat flux rate is commonly specified during consequent modeling of hydrocarbon fires. Heat flux is considered the more appropriate measure by which to examine the radiation effects from a fire. A radiant heat flux of 4.7 kw/m (1,469 Btu/ft. ) will cause pain on exposed skin, a flux density of 12.6 kw/rrfl (3,938 Btu/ft.2) or more may cause secondary fires and a flux density of 37.8 kw/m (11,813 Btu/ft. ) will cause major damage to a process plant and storage tanks. 

Lightning is generally considered a form of static electricity that is being discharged from particles in the atmosphere. Many instances of lightning induced hydrocarbon fires have been recorded, especially at atmospheric storage tanks. 

For means of protection, the use of water based suppression systems may be a hazard due to the disposal of firewater water, which will freeze quite readily in exposed locations. This may also be the case with exposed hydrocarbon fluid lines that, if isolated, say for an ESD activation, may freeze up due to lack of circulation. This will hamper restart operations for the facility. Typical use in the past has been the reliance on gases fire suppression agents for enclosed area, particularly Halon. Other methods include fire water storage tanks that are kept warm, together with fire mains deeply buried and continually circulated. 

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