Drainage storage tanks

Cements are used mainly for jointing brickworks, drainage gullies, pipes and storage tanks. Portland cement has very poor resistance to acids but good resistance to alkaline liquors. 

Number of days since last accidental release of hazardous material. This measure distinguishes between routine emissions (such as from storage tank vents, or low pressure steam discharges) and accidental emissions resulting from maloperation or breakdown. Events that might count would be safety valve releases, accidental releases into inappropriate drainage systems and unconfmed spills during maintenance. 

Condensation should be reduced by allowing free circulation of air, or by air-conditioning. Storage tanks should be raised from the ground to allow air circulation and access for maintenance and provision should be made for complete drainage (Fig. 9.16). 

A major factor in location of storage tanks within a tank farm is the topography of the tank farm area. The slope of the natural topography can be used to assist in the drainage requirements for a diked area and minimized the accumulation of spilled liquids near a storage tank. Diversion dikes or curbing can be used to divert spillage so it runs off remotely to a safe location. 

Drainage slopes within tank areas should ensure that any spills are drained away from tanks, manifolds or piping. Small fires that can occur in gutters or drains around tanks weaken connections to the storage tank and release the contents of the tank. Any gutter encircling the tank should be located at a safe distance from the tank and drain basins should not be located under tank mixers, major valves or manway entrances to the tank. The diked areas should be provided with an impervious surface that is will collect liquids towards a drainage collection point. 

Storage tanks Dikes Emergency valves Inspections Procedures Specifications Limitations Design separation, inerting, materials of construction Capacity and drainage Remote control hazardous materials Flash arresters and relief devices Contamination prevention, analysis Chemical, physical and quality stability Temperature, time and quantity... 

Heavy vapours can spread for long distances in ditches, pipe tracks and drainage pipes and can accumulate in bunded areas, particularly if the bund walls are high. The manual clearing of sludges and deposits in the bottoms of storage tanks which have contained low-flash point solvents is particularly hazardous if low-level ventilation is not provided. 

---