US2761771A - Gas storage vessel - Google Patents

Description

Q l I P 4, 1956 I. L. WISSMILLER 2,761,77 1

GAS STORAGE VESSEL Filed Oct. 15, 1951 4 Sheets-Sheet 1 7, Sept, 1956 p l. 1.. WISSMILLER 2,761,771

GAS STORAGE VESSEL Filed Oct. 15, 1951 4 sheqts sheet 2 I. WISSMILLER GAS STORAGE VESSEL Sept. 4, 1956 4 Sheets-Sheet 3 Filed Oct. 13, 1951 United States Patent O GAS STORAGE VESSEL Ivan L. Wissmiller, Chicago, Ill., assignor to Chicago Bridge & Iron Company,'a corporation of Illinois Application October 13, 1951, Serial N0.'25l,217

7 Claims. (Cl. 48-178) This invention relates to a gas storage system and device and more particularly to a vapor saving system for use with volatile liquid storage tanks.

This application is a continuation in part of my pending application Serial No. 146,379, filed February 25, 1950, now abandoned, which was a continuation in part of my application Serial No. 638,302, filed December 29, 1945, now abandoned, and my pending application 'Serial No. 702,625, filed October 11, 1946, now abandoned.

The storage of volatile liquids and particularly gasoline is often accomplished by the use of cylindrical tanks which have cone-shaped roofs. These tanks may be filled with a volatile liquid to various depths up to a level just'below the cone roof, and may vary in diameter from 20 feet up to as much as 290 feet. All space above the level of the liquid within these tanks will generally contain vapor of the stored liquid mixed with air, and the effect of change in temperature results in an increase or decrease in the pressure or volume of this vapor. The cone roofs are not built to withstand a great pressure, and are therefore provided with pressure-vacuum relief valves which may vent the vapors to atmosphere or. admit air into the tank when the pressure :or vacuum therein exceeds maximum allowable values. Such venting results in the waste of valuable vapors amounting in some cases to aconsiderable monetary loss. The present invention is concerned with a vapor saving system whereby these volatile vapors may be temporarily storedin a variable volume container and returned to the liquid storage tanks when the conditions therein so dictate.

The invention may .take the formof a separate .vapor storage vessel or a vessel combined with a liquid storage tank. These embodiments are illustrated in the accompanying drawings, in which:

Fig. l is a vertical section through the center of .a spherical gas holder made in accordance with the present invention; Fig. 2 is a broken vertical section similar to -Fig. 1 showing the ,holder full of gas; Fig. '3 is a plan view of the gas holder illustrated in Fig. 1;.Fig. 4 is .a broken vertical enlarged section through the equator of "the holder showing the connection of the diaphragm to the equator; Fig. 5 is an enlarged fragmentary vertical section through thejbottom manhole of the holder; Fig. 6 is a plan view partly broken away of a liquid storage ;tank embodying the vaporsaving device of this invention; .Fig. '7 is a horizontal sectional view through approximately the center of the liquid storagetank as indicated by lines 7--7 in Fig. 8; Fig. 8 is a vertical section ;through the 2 use of vapor saving systems with facilities for temporarily storing the vapor. It is with the last of these three methods that this invention is concerned.

In early applications of vapor saving systems a flexible gas bag was provided for receiving the-vapors from the tanks during periods when vapor was forced out of the tanks by breathing due to increasing temperature or by displacement during filling of the cone roof tanks. Experience disclosed that these bags were ineffective and a failure commercially. Following the use of the gas bags 9. number of cone roof liquid storage tanks were con nected by piping to a tank fitted with a vertically movable roof aptly termed a lifter roof tank. These tanks had a roof with a downwardly depending skirt which surrounded the main walls of the liquid storage tank. A fabric seal, or in some instances a liquid seal provided by a depending skirt dipping into a liquid trough, was used to seal the space between the roof and the side walls of the tank. The weight of these lifter roofs created an excessive amount of pressure, that is from 2 /2 inches of water to 7 /2 inches of water or greater. The use of such a system necessitated the reinforcement of the cone roofs of interconnected liquid storage tanks inasmuch as these latter roofs have been universally constructed within the industry to withstand a maximum pressure of 1% inches of water. In fact, such cone roof tanks are ordinarily provided with pressure and vacuum relief valves set at a. pressure of inch of water. As a result, this vapor saving system was extremely expensive when constructed to serve existing cone roof tanks since those roofs had to be reconstructed and reinforced.

By the device of the present invention applicant has provided an eflicient vapor saving system which operates under the same pressure that cone roof tanks are ror.dinarily built to withstand. In general, the device consists of the provision of a hemispherical diaphragm mounted within a hemispherical shell which will back up the diaphragm when the latter isin its uppermost position, that is corresponding to the condition in which the device is full of vapor. No stress is imposed upon the diaphragm since it floats freely upon the stored gas and is fully backed up by a metallic shell when it has reached its fully inflated position. in one embodiment, that being the provision -.of a spherical gas holder, the diaphragm is backed up in both its extreme upper and lower positions.

In both embodiments of the invention to be described in detail hereinafter, the diaphragm has a weight sufficient to be lifted by a pressure in the vapor storage space of approximately inch of water. A vacuum and pressure relief valve is adjusted so as toopen at 4 inch of water which corresponds with the maximum pressure allowable in the cone roof tanks. Ordinarily the vapor storage device is connected by piping with the vapor spaces of one or more cone roof liquid storage tanks. Vapor forced out of the tanksby breathing due to increasing temperature or displaced by filling, flows through the vapor lines into the vapor storage device belowthe diaphragm. Here these vapors are temporarily stored and then returned to thetanks when the conditions which cause their outflow are reversed.

.In the embodiment illustrated in Figs. '1-5, the device comprises a thin metal shell It), preferably in the form of a sphere, which shell maybe considered as divided into an upper hemisphere 11 and a lower hemisphere 12. Along the equator of the sphere, in a substantially horizontal "plane, a girder '26 is attached to the shell. The girder comprises an angle iron having one leg '27 secured by 'its'free end to the shell and another leg 28 extending downwardly therefrom. A flexible diaphragm 14 'of gas-tight fabric or the like is secured to the downwardly projecting leg 28 of the girder 26. A backing plate 29 clamps the free edge of the diaphragm to the leg 28 of the girder by bolts 30 or the like. It will be noted that the backing plate extends upwardly above the level of the upper surface of the leg 27. Any liquid trapped on the upper surface of the diaphragm 14 thus, when the diaphragm is in upper position, may drain into a drain trough 31 formed by the girder 26, the diaphragm 14 and the backing plate 29. The bolts 30 connecting the diaphragm to the leg 28 of the girder are easily accessible from the bottom of the vessel for repair or replacement.

The diaphragm 14 is in the shape of a hemisphere having substantially the same radius as the shell 10. The diaphragm is backed up by the upper or lower hemispheres when the vessel is full or empty, as the case may be.

Gas is admitted to the vessel through an inlet line which also serves as the outlet for the vessel. The inlet line 20 is connected with the lower hemisphere at a point adjacent and generally immediately below the equator of the vessel. In this position the diaphragm 14 does not fall against and block off the opening 20a of the inlet line to the vessel.

At a point circumferentially across from the inlet line a nipple 32 communicates with the lower hemisphere and has a conventional vent 21 mounted thereon. The vent 21 is adapted to open under pressure or vacuum. In operation of the vessel, gas admitted to the lower hemisphere is richest in vapor content near the inlet line. By positioning the vent 21 around the vessel from the inlet line, the least rich gases are vented to the atmosphere if the vent opens.

Near the bottom of the lower hemisphere 12 is a manhole 33 having a condensate drain 22 fitted with a valve 34. The manhole 33 is provided with a perforate cover 35 which has its upper surface flush with the adjacent inner surface of the lower hemisphere. The perforate cover prevents the diaphragm from entering the manhole while allowing any condensate to evaporate into vapor state from the manhole.

An opening 23 is positioned on the top of the upper hemisphere 11. This opening serves as a vent provided with a weather hood. Additional vents 24, 25 communicate with the upper hemisphere immediately above the equator of the vessel. As best seen in Fig. 4, the bottom portion of the opening 24a through the shell is substantially aligned with the drain trough 31 so that any liquid in the trough may drain through the vent opening to the atmosphere. A bird screen 24b is positioned in the bottom of the vent. The vent 23 with the vents 24 and 25 provides ventilation to purge any explosive gases from the vessel above the diaphragm. A continuous natural circulation of air through the upper hemisphere is induced by thermal currents of the air therein when heated by the sun, or otherwise. Some of the volatile gases diffuse through the diaphragm into the upper hemisphere and when combined with the air therein may, under certain circumstances, make a flammable mixture. The continuous purging of the space above the diaphragm rids the space of possible flammable mixtures.

The inlet line 20 is connected with the vapor space of one or more volatile liquid storage tanks. Generally the vessel is designed to have a volume equal to from 6 to 12% of the total volume of the connected tank or tanks. Within these limits it has been found that the gas storage vessel is of sufficient volume to collect and "store vapors from the connected tanks. The pressure created by the weight of the diaphragm aids in forcing the vapors back into the connected tanks upon the contraction of the vapors in the tanks.

In the operation of the device, assuming that the sphere is empty, the diaphragm 14 rests upon and is backed up by the lower hemisphere 12. When gas is admitted, the diaphragm is. displaced from the lower hemisphere, after which it will gradually move upwardly until, when the vessel is full, the diaphragm will contact the upper hemisphere 11.

It will be observed, therefore, that the diaphragm is fully backed up by the metal shell, both when it is fully deflated and when it is fully inflated. The vessel requires no complicated or special vents or fittings. It will withstand the same maximum pressure or vacuum as any vessel to which it may be connected. The shell of the vessel may be made with the lightest workable platematerial, generally A or A" steel plate. The plates of the lower hemisphere must be gas-tight and are generally welded on the inside and outside with the interior welds buffed smooth. The upper hemisphere plates are provided with rounded interior edges, and a single pass weld on the outside is suflicient to make it weather tight. The vessel is supported in any suitable manner, as upon angle supports 15 or structural columns resting upon conventional foundations 16.

A vessel of the above type operates under a pressure due to the weight of the flexible seal. In some installations it may be desirable to maintain a higher constant pressure on the gas in the lower hemisphere and in the inlet-outlet line. An air blower 40 may be connected by suitable passage 41 with the upper hemisphere. Air may be blown into the upper hemisphere in sufficient quantity to provide air pressure against the diaphragm to maintain a constant pressure on the gas in the vessel. The open vents above the diaphragm are omitted and a pressure relief vent set at the desired constant pressure is installed. A part of the air blown into the upper hemisphere is vented through this vent. This forced circulation of air purges the space above the diaphragm and prevents the accumulation of a flammable mixture of gas and air.

Such an air blower may be connected to the vessel if it is to be used, for example, in connection with a sewage disposal plant to collect gases and convey the collected gases to a burner which must be supplied with gas at a constant pressure.

While the invention has been illustrated in connection with a spherical shell, the bottom and top halves need not be exactly symmetrical. The diaphragm should be backed up by the shell in the extreme upper position. Thus the upper portion of the shell is shown as a hemisphere. In some cases it is desirable to have the diaphragm backed up in both upper and lower positions, hence the vessel is illustrated with both halves as hemispheres with the diaphragm in the shape of a hemisphere.

Referring particularly to Figs. 69, the vapor storage device may be combined in the roof portion of a liquid storage tank and connected with other liquid storage tanks having cone roofs so as to operate in substantially the same manner as described above for the separate spherical-shaped vapor storage vessel. In these figures is shown a storage tank having a shell 110, a bottom 111 and a roof 112. The central portion 116 of the roof is curved outwardly to provide a vapor storage space, the convex portion 113, in the embodiment shown, being generally hemispherical in shape. Attached to a girder 1 14, at the equator of the portion 113, is a flexible, vapor impervious sealing member 1 15. The seal is preferably a fabric coated with synthetic rubber, or the like. The sealing member has generally the same shape as the convex portion, and being flexible, is adapted to flex upwardly within the portion with increasing vapor volume within the tank. The convex portion 113 is provided with a screened vent to the atmosphere 116, the vent, of course, being positioned above the plane of attachment of the flexible seal. A drain 117, just above the plane of attachment of the flexible seal, allows moisture condensing on the upper portion of the seal to drain to the exterior. A plurality of supporting posts 11% supports the roof above the bottom, the posts being positioned generally about the circumference of the convex portion 113.

,Adapted tofloat upon the liquid within the tank is a float 1119 comprising an annular pontoon '120 and a plura ity of members 121 spanning across inside the annular pontoon, the diameter of the float being in the embodiment shown, approximately equal to the diameter of he por ion 113. a

The float maybe used in some installations where it is desirable to maintain the fabric of the diaphragm out of contact with the liquid which is stored within the tank. Ordinarily, in the case :of storage of gasoline and similar products it is not, necessary to keep the diaphragm out of contact With the liquid since the diaphragm itself is impervious to the liquid, and is not deleteriously affected by such contact. However, should the liquid stored have a strong solvent action such as would accelerate the deterioration of the seal, a float 119 may be supported on the surface of the liquid and positioned beneath the Scaling member to prevent that member from drooping into the liquid. The supporting posts serve to maintain the float centered in the tank, although other centering means may be employed. As shown in Fig. 9, when the liquid is near its high level position, the seal is supported by the float, as indicated by the dotted lines. Increasing vapor volume within the tank causes the seal to flex upwardly within the convex portion, as indicated by the solid lines of Fig. 9, the seal being backed up by the convex portion of the roof when flexed upward to its maximum position.

It is well known, that .a greater vapor storage capacity must be provided for a liquid storage tank when it is nearly empty than when the storage tank is nearly filled with liquid. 'Past installations have provided a vapor capacity generally capable of handling a nearly empty tank, and therefore, having .a capacity much greater than necessary for a nearly filled tank. In my invention, the vapor storage capacity of the tank decreases as the volume of liquid in the tank increases. For example, with a tank only partially filled, as illustrated in Fig. 8, the seal 1 15 droops entirely within the tank and the entire volume of the sphere defined by drooping seal [115 and the convex portion 113 is available for expanding vapors. When the tank is nearly full, as illustrated in Fig. 9, the float 119 rising on the surface of the liquid picks up the seal 1'15 .and carries it upward, reducing the vapor capacity of the tank while at the same time preventing the seal from contacting the liquid.

This vapor storage system also operates at a pressure within the maximum pressure which can be sustained in the cone roof tanks which may be connected with the space under the diaphragm 1'15. This pressure is approximately A3" of water for lifting the weight of the diaphragm and the vent setting is about A" of water. In both embodiments it is only necessary that the inflowing vapor lift the weight of the diaphragm itself and this weight remains substantially constant throughout the entire movement of the diaphragm from its lowermost position to its uppermost position in contact with the hemispherical shell portion. Since the pressure under which the vapor storage devices operate is so nearly uniform and is less than the maximum operating pressure of the connected cone roof liquid storage tanks, the roofs of the latter need not be reinforced or diflerently constructed from usual practice. In both devices herein illustrated, there .are no moving parts except for the diaphragm, and neither device requires attention from operating personnel.

The collection and storage of vapor from connected tanks and the return of vapor to those tanks is automatic in operation requiring no human act for its accomplishment. The seal or diaphragm is fully protected in that it is entirely backed up by the metallic shell in the position in which it might receive stress from pressure in the vapor space. The provision of the vents in the upper hemispherical portion of the shell and their particular location provides adequate air circulation above the diaphragm, thereby eliminating the hazard of explosive 6 mixtures of air and vapor, and also keeping the upper side of the diaphragm well drained.

While I have shown and described the invention in its preferred embodiments,,it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

1. A gas storage device comprising a spherical metal vessel, an annular girder secured to the equator of the vesso], a gas-tight flexible diaphragm secured to said girder, and being in the shape of a hemisphere having substantially the same radius as the vessel, said diaphragm dividing the vessel into upper and lower hemispheres, means for .admitting gas to and from the lower hemisphere and a vent connecting the upper hemisphere with the atmosphere and having its lower portion aligned substantially horizontally with the upper surface of said girder, said diaphragm and girder forming at their juncture a drain trough at the equator of the vessel whereby liquid on the top side of said diaphragm may be collected in said trough and drained from the vessel through said vent.

2. A gas storage device as claimed in claim 1 wherein said girder comprises an angle iron having a substantially horizontal first leg attached at its free end to the vessel and a second leg projecting downwardly from the first leg, and a back-up plate facing the second leg and extending above the level of the first leg, said diaphragm being secured between the back-up plate and the second leg.

3. A gas storage device comprising a spherical metal vessel, a gas-tight flexible diaphragm secured across the equator of said vessel to divide the vessel into upper and lower hemispheres, means for admitting and withdrawing gas to and from the lower hemisphere and means connecting the upper hemisphere with the atmosphere, the diaphragm being in the shape of a hemisphere having substantially the same radius as the vessel whereby in one extreme position it is substantially entirely backed up by the upper hemisphere and in the other extreme position it is substantially entirely backed up by the lower hemisphere, the construction and arrangement being such that gas admitted to said lower hemisphere is retained therein under the pressure of the weight of the diaphragm, and a vacuum and pressure relief valve communicating with said lower hemisphere at a point adjacent the equator and circumferentially spaced around the equator from said means for admitting and withdrawing gas to and from the lower hemisphere.

4. A gas storage device comprising a spherical metal vessel, a gas-tight flexible diaphragm secured across the equator of said vessel to divide the vessel into upper and lower hemispheres, means for admitting and withdrawing gas to and from the lower hemisphere and means connecting the upper hemisphere with the atmosphere, the diaphragm being in the shape of a hemisphere having substantially the same radius as the vessel whereby in one extreme position it is substantially entirely backed up by the upper hemisphere and in the other extreme position it is substantially entirely backed up by the lower hemisphere, the construction and arrangement being such that gas admitted to said lower hemisphere is retained therein under the pressure of the weight of the diaphragm, and a manhole positioned in the bottom of said lower hemisphere, a condensate drain passage communicating with the manhole and having a valve therein and a perforate cover over the manhole having its upper surface flush with the adjacent inner surface of said lower hemisphere.

5. A gas storage device comprising a metal vessel having a hemispherical upper shell portion and a gas-tight lower shell portion joined to the upper portion, a circular girder attached adjacent the major circle defining the juncture of the upper shell portion and the gas-tight lower portion, a gas-tight, substantially non-stretchable, flexible diaphragm secured to said girder to divide the interior of the vessel into upper and lower portions, open passage means connected with the lower portion below the juncture of the vessel shell portions for admitting gas to'and from the lower portion and means connecting the upper portion with the atmosphere, said diaphragm being in the preformed shape of a hemisphere having substantially the same radius as the upper hemispherical shell portion to be backed up by the upper portion in extreme upward position.

6. A gas storage device comprising: an upper shell portion constituting a dome which is generated by rotation of a line about a vertical axis intersected by said line, said point of intersection constituting the top of said dome and the base of said line constituting the base of the dome, a gas-tight lower shell portion joined to and communicating with the base of the dome, said upper and lower shell portion-s constituting a vessel, securing means positioned in a substantially horizontal plane in said vessel at the base of the dome, a gas-tight, substantially nonstretchable, diaphragm secured to said securing means, said securing means and diaphragm serving to divide the vessel into adjacent upper and lower sections, said diaphragm being preformed to dimensionally conform to the internal contour of the dome enabling said dome to back-up the diaphragm when the diaphragm is fully extended in its extreme upward position, and open passage means connected with the lower shell section below said securing means for admitting gas to and from said lower section of the vessel and means connecting said upper section of the vessel with the atmosphere.

7. A gas storage device comprising: an upper shell portion constituting a dome which is generated by rotation of a line about a vertical axis intersected by said line, said point of intersection constituting the top of said dome and the base of said line constituting the base of the dome, a gas-tight lower shell portion joined to and communicating with the base of the dome, said upper and lower shell portions constituting a vessel, securing means positioned in a substantially horizontal plane in said vessel at the base of the dome, a gas-tight, substantially non-stretchable, diaphragm secured to said securing means, said securing means and diaphragm serving to divide the vessel into adjacent upper and lower sections, said diaphragm being preformed to dimensionally conform to the internal contour of the dome enabling said dome to back-up the diaphragm when the diaphragm is fully extended in its extreme upward position, float means positioned below said securing means capable of floating in the vessel when said vessel is filled with a volatile liquid, said float means serving to separate the diaphragm from said liquid when the diaphragm is positioned below said securing means, and open passage means connected with the lower shell section below said securing means for admitting gas to and from said lower section of the vessel and means connecting said upper section of the vessel with the atmosphere.

References Cited in the file of this patent UNITED STATES PATENTS 1,666,666 Pew Apr. 17, 1928 1,715,112 Atwell May 28, 1929 1,726,281 Wilson et a1 Aug. 27, 1929 1,800,043 Atwell Apr. 7, 1931 2,097,985 Maryott Nov. 2, 1937 2,200,610 Weichsel May 14, 1940 2,257,941 Ellis Oct. 7, 1941 2,269,568 Wilkin Jan. 13, 1942 2,371,632 Lippincott Mar. 20, 1945 2,378,467 De Kiss June 9, 1945 FOREIGN PATENTS 307,179 Great Britain Mar. 7, 1929 318,397 Great Britain Sept. 5, 1929 565,958 Great Britain Dec. 6, 1944 924,422 France 'Mar. 10, 1947

Claims (1)

1. 4. A GAS STORAGE DEVICE COMPRISING A SPHERICAL METAL VESSEL, A GAS-TIGHT FLEXIBLE DIAPHRAGM SECURED ACROSS THE EQUATOR OF SAID VESSEL TO DIVIDE THE VESSEL INTO UPPER AND LOWER HEMISPHERES, MEANS FOR ADMITTING AND WITHDRAWING GAS TO AND FROM THE LOWER HEMISPHERE AND MEANS CONNECTING THE UPPER HEMISPHERE WITH THE ATMOSPHERE, THE DIAPHRAGM BEING IN THE SHAPE OF A HEMISPHERE HAVING SUBSTANTIALLY THE SAME RADIUS AS THE VESSEL WHEREBY IN ONE EXTREME POSITION IT IS SUBSTANTIALLY ENTIRELY BACKED UP BY THE UPPER HEMISPHERE AND IN THE OTHER EXTREME POSITION IT IS SUBSTANTIALLY ENTIRELY BACKED UP BY THE LOWER HEMISPHERE, THE CONSTRUCTION AND ARRANGEMENT BEING SUCH THAT GAS ADMITTED TO SAID LOWER HEMISPHERE IS RETAINED THEREIN UNDER THE PRESSURE OF THE WEIGHT OF THE DIAPHRAGM, AND A MANHOLE POSITIONED IN THE BOTTOM OF SAID LOWER HEMISPHERE, A CONDENSATE DRAIN PASSAGE COMMUNICATING WITH THE MANHOLE AND HAVING A VALVE THEREIN AND A PERFORATE COVER OVER THE MANHOLE HAVING ITS UPPER SURFACE FLUSH WITH THE ADJACENT INNER SURFACE OF SAID LOWER HEMISPHERE.

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