Flammable liquids, diking for

FIG. 23-63 Methods of diking for flammable liquids (a) traditional diking method allows leaks to accumulate around the tank. In case of fire, the tank will be exposed to flames that can be supplied by fuel from the tank and will be hard to control, (b) In the more desirable method, leaks are directed away from the tank. In case of fire, the tank will be shielded from most flames and fire will be easier to fight. (From Englund, in Advances in Chemical Engineering, vol. 15, Academic Press, San Diego, 1990, pp. 73-135, by permission.)... 

Volume 1 of National Fire Codes (National Fire Protection Association, Quincy, Massachusetts) contains recommendations (Code 30) for venting, drainage, and dike construction of tanks for flammable liquids. 

The design in Fig. 2A is usually undesirable for flammable liquids because it will allow flames from an ignited spill within the diked area to cook the tank. Such a fire may be very dangerous and hard to control because of the possibility of rupturing the tank. The better design in Fig. 2B will divert spills from the immediate area of the tank. In the event of a fire, the tank will be shielded by the fire wall. This safeguards the tank from direct exposure to the flames. Such a fire is easier to control, and the tank is less likely to rupture. 

Control If a leak of hazardous material does occur, there should be safety systems that reduce the effects. For exanple, chemical facilities often have emergency isolation of the site from the normal storm sewers, and large tanks for flammable liquids are surrounded by dikes that prevent any leaks from spreading to other areas of the plant. Scrubbing systems and relief systems in general are in this category. They are essential, because they allow a controlled, safe... 

Diking is a common industry practice for spill retention around flammable liquid storage vessels. Regulations and codes require that exclusion zones be placed between storage vessels to maintain the structural integrity of nearby vessels or process equipment in the event of a fire within the dike (Welker, 1987). Studies of flammable vapor boiloff rates as a function of dike design have been used in the natural gas industry to evaluate optimal materials of construction (Arthur D. Little, Inc., 1974). In recent... 

In the event of a leak or break in any storage tank or piping the flap valve will prevent the loss of valuable tank contents and allow for the recovery of the tank contents retained within the diked area. It will also prevent any large amounts of hazardous and flammable liquids from entering the sewer system, which would create the possibility of a hazardous fire condition should the tank contents be of a volatile nature. 

Precautions required for the safe handling of all flammable gas must be observed with vinyl chloride. Adequate electrical grounding of all lines and equipment, and ditching or diking in storage tank areas to control the liquid in the event of vessel rupture are among recommended precautions. Ditching is preferable because the... 

---