US2031553A - Tank for storage of liquids, especially hydrocarbons - Google Patents

Description

Feb. 18; 1936.

A w. SYNDERGAARD 2,031,553 v TANK FOR STORAGE} OF LIQUIDS, ESPECIALLY HYDROCARBONS Filed July 15, 1954 5v art/7% I Patented Feb. 18, 1936 UNITED STATES ZMLSSE 1 TANK FOR STORAGE F LIQUIDS,

ESPECIALLY HYDROCARBONS Askan Willy Syndergaard, Copenhagen, Denmark Application-July 13, 1934, Serial No. 735,042 In Denmark January 6, 1934 6 Claims.

This invention relates to storage tanks for volatile liquids, such as gasoline or other hydrocarbons, to be stored in the open air.

By the storage of volatile liquids, such as gasoline or other hydrocarbons, in tanks standing in openair (as distinct frombeing sunk in the ground) it is well known that quite a considerable loss is suifered, due to a portion of the vapors formed in the tank, above the surface of the liquid contained therein, gradually escaping to the atmosphere, either through leaks in the tank or through the breathing holes usumly provided in the tank.

-A storage receptacle or tank standing in open in the tank owing to the contractions and expansions to which the'contents, especially the liquid vapors, of the tank are exposed owing to the unavoidable temperature variations. Thus, for instance, a temperature variation from C. to 30 C. will cause the mixture of air and liquid vapor standing above the surface .of the liquid to be expanded by about 10% to the result being that a corresponding volume of this gaseous mixture will escape by way or holes of the tank.

When the temperature decreases, the said mixture contracts, and air is then drawn in until the differential pressure is equalized, and during a new increase in temperature, a certain quantity of the mixture of air and vapors will therefore be discharged.

'As changes in temperature occur not only from day to night, but often repeatedlyrwithin twentyfour hours, for instance, during unstable weather conditions, when the tank is alternately exposed to direct sunshine and shielded from the sun, the loss caused thereby may be quite considerable. Barometrical variations have a similar effect to temperature variations and. may under certain conditions cause a quite considerable waste.

In order to remedy the losses due to temperature variations, it has formerly been proposed to cover the top side of the tank and the adjoining 'part of the vertical walls of the tank with heat-insulating layers, whereby the temperature changes, to which the top side and top part of the walls of the tank are subjected, should be reduced. A coating of the top side of a tank 5 with a heat-insulating layer does not, however,

of the breathing hole prevent the remaining part of the tank from being exposed to direct action of the rays of the sun, and in the vapor-filled space of thesetanks quite considerable variations are therefore produced, for instance, from day to night. If the 5 liquid surface in the tank is lowered below or essentially below the. bottom edge of the heat insulated top part of the tank, and further even if an iron tank be coated with a heat-insulating layer (which, of necessity, must be relatively thin 10 to be capable of practical application), either on top or all over, there will nevertheless frequently be passed through the insulating layer, for instance, owing to the influence of the sun heat during the daytime, an amount of heat suf- 15 ficient to cause the temperature of the vapors in the tank to vary approximately between the same ranges as the external temperature.

The object of the present invention is to reduce the loss of liquid, due to evaporation, in a 20 tank erected in the open air and exposed to changing temperature actions by the temperature variations to which the vapors in the tank are exposed during the' most unfavorable external temperature conditions in the 25 course of a certain period of time, for instance, twenty-four hours, a value not exceeding, but preferably being corsiderably less than, the value of the variations of the temperature of the atmosphere.

To this end, the top as well as the side walls of the metal sheet tank are, according to the invention, fited with an outer coating or layer of concrete, .or of another solid material having a heat-accumulating property of the same order 35 as a layer of concrete. This means that instead of concrete there may be used materials of such kind that an elevation of 1 C. of the temperature of a certain volume of the material requires the supply to the latter of an amount of heat, being 40 of the -same order or even higher than the amount of heat which under the same conditions was to be supplied to the same volume of concrete. Such other materials are, for instance, clay, mortar and asphalt. The thickness of the 45 said coating is selected so as to insure that the temperature variations of the vapors in the interior of the tank produced by the external temperature variations are reduced to any desired minimum due to the accumulation of heat in the said material. This layei or coating is hereinafter called the heat-accumulating coating.

In order to keep the thickness of the abovementioned coating within reasonable limits, it

would be suitable, according to a further object I 'having a thickness of 75 to 2 of the invention, to cover the said coating with e., a material which has of heat conductivity, for instance, a coatingconsistlng ofplates prepared from wood fibers. This layer is hereinafter called the heat-insulating layer.

By ma of example, it may be mentioned that the variations of the temperature of the vapors from wood fibers and having a thickness of about A further object of the invention is to reinforce the tank in such a manner that it will be possible to make it air-tight and sumciently strong to resist the excess pressure or vacuum produced therein by the maximum temperature variations and barometrical variations likely to occur during the course of, for instance, twenty-four hours.

To this end, the heat-accumulating layer is made from reinforced concrete, with which the top side as well as the side walls of the iron tank On the outside of the reinforced concrete the layer of heat-insulating material is disposed, and on the outside of the heat-insulating layer there may be provided, as a protection against huiron or some similar weather-resisting material.

The invention is used in connection with already existing iron tanks as well as for the construction of new tanks. In the last mentioned case iron sheets only 3 or 4 millimetres in thickness may be used instead of the heretofore employed rather heavy iron plates, of which the tank wall proper is consisting, and in that casethe reinforcement of an air-tight tank is given such a strength that the same alone will be able to resist the tensile and compressive stresses due partly to the high and low prwsures produced in the tank by temperature variations, and partly to variations in the atmospheric pressure, and gnaltly aklso to the pressure due to the liquid in materials with a high specific heat than just concrete, for instance clay.

The further details of the inventionappear from the following description of a tank shown diagrammatically and in vertical section on the drawing.

I is the interior wall of a tank built of iron sheets, 2 is a layer of reinforced concrete, with which the vertical sides as well as the top side of the tank are covered, and 3 is a heat-insulating layer with which the outside of the concrete layer 2 is covered.

On the outside of the heat-insulating layer 3 there may, if desired, be provided a protective layer 4 of watertight plaster, galvanized iron I quantity of heat penetrating through the heatinsulating layer 3 and the layer of reinforced concrete under the most unfavorable conditions, during for instance twenty-four hours, cannot produce such a great variation in the temperature of the vapours above the contents of liquid in the tank that dangerous high or low pressures will be produced in the hermetically closed tank. These temperature variations may for instance be reduced so as not to exceed 5 to 10 C., or less than that. It should be noted, however, that the invention is not restricted to the maintenance of temperature variations within these limits. The said variations may be greater or-as mentioned-also smaller. The essential feature is merely that the reinforcement should be constructed in accordance with the selection of the permissible temperature variations, in such a manner that the reinforcement at any time will be able to resist the resulting compressive and tensile stresses. The tank wall I may be of a thickness varying from 3 millimetres to one centimetre or more, and the tank has no breathing holes, through which any air or vapours can escape. The reinforcement must therefore be made sufliciently powerful to enable the reinforced tank to resist the high or low pressures produced in consequence of the temperature variations and the variations in the atmospheric pressure.

The tank is fitted with safety valves, not shown, which open themselves if the permissible maximum or minimum pressures in the tank for some reason or other are exceeded. It may further be necessary to provide firegates in the top side of the tank, which gates open themselves automatically in the case of an explosion.

The bottom I of the tank is made for instance for iron and rests, in the construction shown, on a suitable concrete footing. The latter may in: heat-insulated on the outside in similar manner as the concrete layer 2. The iron bottom, however, may also rest directly on the ground.

In the construction. of new tanks it may be suitable to use the heat-insulating cover 3 as outer forms for the pouring of the concrete layer 2.

If an alreadyexisting tank is to be converted into an air-tight tank according to the present into the space between the latter and the tank concrete has reached the top wall I. When the previously been supported from the insideby means suitable for the purposawhich means, if desired, can be removed after the concrete has hardened. Finally the insulating plates are deposited, which are to cover the top side of the tank, and these plates are held in position, in the same manner as the insulating plates on the side walls of the tank, by means of hooks or the like projecting into the concrete. Then the insulating plates are suitably, but not necessarily, covered' with wire netting and fltted with an external layer of plaster.

The procedure in building a new tank'is similar, although in such a tank the iron wall may as a rule be constructed. of thinner iron sheets than the already existing tanks, and may be.

assembled by welding instead of by riveting.

If the tank is not to be closed in an air-tight manner for instance if ordinary breathing holes are provided in the top of the tank, then it is not necessary to reinforce the concrete coating serving as a heat-accumulating layer. If this layer is prepared from'cellular concrete, a separate heat insulating layer may according to circumstances be admitted, because cellular concrete has also heat-insulating properties.

Having now particularly described and ascertained the nature of my invention and in what manner the same is to be performed I declare that what I claim is:--

1. A fluid-tight storage tank, comprising a sheet metal receptacle. a layer of concrete on the outer surface of the receptacle, and a heat insulating cover on the outer surface of the said layer of concrete.

2. An air-tight storage tank, comprising a reinforced air-tight sheet metal receptacle, 9. layer or concrete on the outer surface of the walls and. top of said receptacle, and a heat insulating cover on the outer surface of the concrete.

3. An air-tight storage tank to be freely mounted in the open, comprising an air-tight sheet metal receptacle, a reinforced outer layer of concrete in direct contact with the wall and. top surface of the receptacle, and a heat insulating layer covering the outside of the reinforced concrete.

4. An air-tight storage tank to be freely mounted in the open, comprising an air-tight sheet metal receptacle, a layer of concrete on the outer surface of the said tank, the thickness of the layer of concrete being so chosen that the heat accumulating capacity of the layer is sufficient to limit the maximum variations of the temperature of the vapors in the tank during a certain period of time to a predetermined value being less than the maximum variations of the temperature of the external air during the same period of time and not exceeding 5 C.

' 5. An air-tight closed tank according to claim 4, on which the outer insulating layer is covered by a layer of material capable of protecting the insulating material against the influence of humidity and mechanical actions.

6. A fluid-tight storage tank comprising a sheet metal receptacle, a layer of material, having a heat-accumulating property of the same order as that of concrete, on the outer surface of the said receptacle, and a heat-insulating cover on the outer surface of the said layer.

ASKAN WILLY SYNDEGAARD.

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