US2315453A - Tank support - Google Patents

Description

March 1943' E. w. PITTMAN 2,315,453

TANK SUPPORT Filed Aug. 1, 1938 2 Sheets-Sheet 1 J 1 wen H011 E RN E51 W. PITTMAN March 30, 1943.

E. w. PITTMAN 2,3155453 TANK SUPPORT 2 Sheets-Sheet 2 Filed Aug. 1, 1938 1 wen for,

ERNESTW PiTTMAN.

"JMDI 6 MM}? Patented Mar. 30, 1943 UNITED STATES PATENT OFFICE TANK SUPPORT Ernest W. Pittman, Beaumont, Tex., assignor to The Petroleum Iron Works Company of Texas Application August I, 1938, Serial No. 222,463 2 Claims. (Cl. 220-18) My invention relates to means and methods of supporting tanks of the type which have curved bottoms. Tanks of the type which have curved bottoms are usually supported by a plurality of upright structural members or by supporting walls. With supports of this type the load is concentrated on the uprights or the walls and it is necessary to provide a substantial foundation for each upright or wall. The usual practice is to make excavations and to build concrete footings for the support of these uprights or walls, and then to build the tank thereon.

The present invention contemplates a support construction for curved bottom tanks wherein the supporting base may be positioned directly upon earth or can be placed upon any other type of footing so that the load will be distributed over the entire horizontal cross sectional area of the tank. This invention is particularly advantageous for supporting tanks containing petroleum liquids or other liquids with a superimposed gas or vapor pressure.

It is one of the objects of the invention to provide a tank support wherein a uniform pressure is applied on the bottom of the tank in order to support the load therein.

Another object of the invention is to provide a container for a body of liquid which liquid will serve to support the bottom of the tank structure.

Still another object of the invention is to support a tank structure upon a body of liquid so as partially to balance the load on the inside and the outside of the tank bottom.

It is also an object of the invention to provide a tank bottom upon which the internal and external pressures are partially balanced so that the tank bottom need not be constructed of material capable of supporting the liquid load in the tank.

- Still another object of the invention is to support a tank upon a body of liquid and to provide gauges to indicate the internal and external pressures.

A still further object is to provide, in combination with a liquid supported tank, an arrangement for a stand pipe so that the pressure of the liquid supporting the tank can be varied in accordance with the total weight of the tank and contents thereof so as to balance the internal and external pressures on the base of the closed compartment,

Other and further objects of the invention readily will be apparent when the following description is considered in connection with the accompanying drawings wherein:

Fig. 1 shows a vertical sectional View of the tank and its support and illustrates the arrangement of the parts.

Fig. 2 shows a similar view of a spherical tank.

It is a well known principle of hydraulics that the fluid pressure within any region of a closed container at the bottom of a stand pipe is a function of the density of the fluid and the head, regardless of the extent of the closed container and of the cross sectional area of the stand pipe, neglecting fluid friction and capillarity. Primarily, my invention is an adaptation of this principle to the hydraulic support of large tanks. The liquid content of the tank is supported by the fluid Within the closed container, and the entire weight of liquid content of tank and fluid within the closed container and stand pipe thence is distributed directly to the supporting foundation with uniform unit pressure over the entire cross sectional area of the bottom.

The earth formation upon which the tank is to be deposited is illustrated generally at 2 and of course may be of any desired location where the tank is to be erected. This earth formation may be leveled ofi and the support construction 3 applied directly upon the earths surface, or if desired a thin slab of concrete or other supporting material 4 may be deposited on the earth in a slight excavation 5. The provision of such a material would merely insure a uniform compactness of the surface on which the tank is to be erected.

The tank support generally includes the base I. which may be a fiat plate assembly by welding or otherwise which is of an area approximately equal to the horizontal cross sectional area of the tank.

Around the edge of this base 1 is an upright wall 8 which may be of any desired height depending upon the curvature of the tank bottom ll which is to be disposed therein. The bottom 9 may take any desired configuration depending upon the tank being constructed but it is intended that the side walls 8 and the curved surface 9 will merge together as at In and be suit ably welded or otherwise fixed together so as to form a fluid tight joint at the elevation 10 entirelyaround the tank. In this manner a closed chamber 12 is provided which is defined by the base I, the side walls 8 and the bottom 9. This chamber I2 is to befilled with a suitable liquid as'water, oil or any other liquid which can be introduced into the chamber. This liquid serves as a support for the tank bottom 9, and may be maintained at a pressure approximately equal to the pressure induced by the head of liquid within the tank.

The inlet pipe l5 serves to introduce the liquid and is controlled by a valve 5. A standpipe I8 has been connected to the inlet pipe [5 between the valve l6 and the tank. This standpipe rises to an elevation at preferably equal to the height of the entire tank 2|. In this manner if the tank were filled with liquid of the same specific gravity as the chamber 12, then the pressure would be exactly balanced, when the heads in the standpipe and in the tank are equal. If the tank is filled with a liquid having a less specific gravity than the liquid I2, then the head in the stand pipe must be proportionately less than the head of liquid in tank 3!. On the other hand in some instances there may be a vapor pressure in the top of the tank, but the curved bottom tank head is designed to resist this pressure. When a tank or container has a fiat bottom and is subjected to an internal vapor pressure the pressure on the top of the tank tends to lift the tank and tends to curve the bottom so that when a tank is designed to withstand an internal Vapor pressure as well as a fluid load the base is constructed of a regular or curved shape such as spherical, conical, or ellipsoidal configuration so that there will be little or no tendency for it to buckle under pressure.

In order to exhaust any air or vapor which may occur in the chamber l2 a vent pipe has been provided which is controlled by a valve 25 and terminates in an upstanding pipe 2! inside of the chamber l2 closely adjacent the point ID at the top of the chamber l2.

The tank body may be of any desired configuration and extends above the area l0 and carries the top portion 3| of the tank. A pres sure relief valve 32 and vacuum relief valve 36 may be provided on the top of the tank. The inlet and outlet pipes. for the liquid within the tank are not shown as they are conventional and form no part of the invention.

If desired a pressure gauge 40 may be fixed to the tank and the pressure responsive element 4| thereof disposed in the chamber [2 closely adjacent to the tank bottom so as to indicate the pressure on the liquid in the chamber l2. A similar gauge 42 may have its pressure responsive element 43 inside of the tank bottom 9 to indicate the pressure therein, whereas a third gauge 44 has its pressure responsive element 45 inside of the top of the tank above the liquid level to indicate the vapor pressure.

It seems obvious that the pressure gauge 40 should be maintained at such a reading so that the pressure in the chamber I2 will always substantially equal the difierence between the readings on the gauges 42 and 44 because this difi'erence wil1 indicate the pressure of the liquid 35 and this is the pressure which should be balanced by the liquid in the chamber l2.

As an instance, if the liquid 35 stands at 30 feet above the bottom of the tank and its density is 43 pounds per cubic foot, the liquid pressure at the bottom of the tank is approximately 9 pounds per square inch. If the gas or vapor pressure above the liquid 35 is 15 pounds per square inch, then the reading on pressure gage 44 is 15 pounds per square inch and the reading on pressure gage 42 is 24 pounds per square inch. For this condition the pressure on gage 45 of the liquid in compartment l 2 should be the difference between the gage readings at 42 and 44 or 9 pounds per square inch, and assuming the liquid in compartment 12 to be water with a density of 62.4 pounds per cubic foot, the height of liquid in standpipe I8 is approximately 2| feet above the bottom of the tank. Then the internal pressure on the base I of compartment [2 balances the external pressure on the base 1 necessary to support the entire structure and its contents. The pressure on the top of tank bottom 9 is the difference between the readings on gages 40 and 42, or 15 pounds per square inch which is the gas or vapor pressure at the top of the tank, and curved head 9 is proportioned to resist this pressure under all conditions of loading.

The provision of the features just described permits the construction of the tank bottom 9 to be relatively thin steel plate material because the liquid pressures on it are substantially balanced, and is designed to resist vapor pressure only. This results in a very. economical construction due to the cost of materials and the arrangement of the base by omitting an expensive foundation, also contributes to the economies of the invention.

When the tank is being emptied the outlet vent 50 will be opened so as to drain the liquid I2 out of the chamber in proportion to the reduction in liquid pressure inside of the tank as the liquid is discharged. When the tank is being filledthe chamber l2 may be filled to apply pressure in proportion to the rateat which the tank is being filled.

While manually operated valves are shown and described for regulating pressure of the fluid l2, in actual practice the same results may be attained by mechanically or electrically operated valves, actuated and controlled by the same pressures and pressure differentials already described for the three indicating gauges. Or the closed compartment may be filled, compressed, decompressed and emptied, as required, without the use of valves or standpipe, by using for the purpose a pump with automatic controls and the two way valve. All valves, pressure indicating gauges and pump may be placed at a convenient location remote from the immediate vicinity of thetank.

Fig. 2 shows a similar construction to that described in connection with Fig. 1 except that a spherical container or tank has been shown. The arrangement of the parts however is identical with that described in connection with Fig. 1 except that the earth's surface may be excavated slightly to accommodate for the roundness for the spherical bottom of the tank. The same reference characters have been applied to Fig. 2 as have been used in Fig. 1.

Broadly the invention contemplates a liquid supporting base for tanks so that the load will be distributed over the entire cross sectional area of the tank and wherein the pressures on the tank bottom may be balanced to eiie'ct additional economy.

What is claimed is:

1. A tank comprising a closed tank body constructed to withstand internal fluid pressure and having a curved base portion of the diameter of the tank, a base for said body, said base comprising a supporting bottom. having a depressed central portion substantially complementary to the curved base portion of the body, said base being uniformly supported from beneath, side walls attached to the supporting bottom and extending upwardly therefrom, the upper ends of said Walls being sealably anchored to the curved base portion of the tank body to form an enclosed chamber within the base and beneath the tank body, and a liquid filling said chamber whereby the tank and contents are supported by a pressure exerted uniformly over the entire area of the base portion.

2. A combination tank and hydraulic supporting base therefor comprising a tank, a concave bottom therefor, a base of the diameter of the tank, including upstanding side walls of the diameter of the tank rigidly secured in sealing relation to said tank about the periphery of the bottom so as to enclose said bottom and form a chamber therebeneath, and means to maintain a fluid under pressure in said chamber so as to support a load approximating the load in said tank.

ERNEST W. PITTMAN.

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