| 摘要 |
An underground storage tank for fluids such as gasoline or chemicals is provided with L-shaped piping means for venting vapor pockets that would normally be trapped inside an inclined tank. The tank has a generally cylindrical top surface with one or two vent tubes secured inside the top of that surface, each tube extending from a point immediately adjacent a head wall to an upstand exiting through the manway cover. When a pair of such tubes and upstands is provided, vapor can be vented or discharged to the atmosphere, regardless of which way the tank is inclined. Such venting of trapped vapor prior to a hydrostatic test on an underground storage tank permits accurate determination of tank leakage and integrity. Existing tanks may be retrofitted with such venting means.
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