The Mechanism of Disformation of Storage Tanks under Overpressure and How to Deal with It

Oil tanks may be overpressurized and thus build up a tremendous uplifting force overloading, rising of the liquid vapour pressure in tanks, shutting or blocking of breathers and vents as liquid is being pumped into tanks. Serious uplifting damages wiîl happen to tanks as soon as the upilfting force exeeds the downyard antiaction. The article enumerates a few uplifing cases that happneed in different situations, explains the calculation of the upifiting force, and obtains the permiscible uplifting force in 9 linds of vaults with a capacity of 100-10000 m³ and their respective crilical nplifing iozce. It is pointed out that the uplifting force neither increase with the incresse of tank volume, nor depends on the liquid level in the tank, just a little static pressure in the tank will be enovgh to build upmense uplifting force. In view of the tauk damage degrees made by uplifting force, lere it views that the tanks dimaged by uplifting force can, in general, be restored, and makes suggestions as to dealirg with serious as well as ligit damages by uplifting force. In addition, it makes analysis of the uplifting mechnism leading to tank collapse, explains in detail the measures to prevent uplifting at three key links, i.e. design, operation and maintenance, points out in particular that of all the measures to prevent uplifting, keeping the vents clean and breather taps flexible is the most effective.