US1801580A

US1801580A - Liquid storage tank

Info

Publication number: US1801580A
Authority: US
Inventors: John H Wiggins
Original assignee: Individual
Current assignee: Individual
Priority date: 1927-05-02
Filing date: 1927-05-02
Publication date: 1931-04-21
Anticipated expiration: 1948-04-21

Description

A ril 21 1931. J. H. WlGGlNS 1,801,530

LIQUID STORAGE TANK Filed May 2, 1927 2 Sheets-Sheet 1 lNVEINTOR ABYBM TTORNEY April 1931- J. H. WIGGINS LIQUID STORAGE TANK Sheets-Sheet 2 Filed May 2, 1927 lNVEN-I-OR' J26 /4-r- TOE/\IK Patented Apr. 21, 1931 UNITED STATES JOHN H. WIGGINS, OF BARTLESVILLE, OKLAHOMA i LIQUID STORAGE TANK Application filed May 2, 1927. Serial No. 188,386.

This invention relates to tanks of the kind that are used for storing gases and volatile liquids, and particularly to a tank of the general type described in my pending application for patent for storage tank for volatile liquids, Serial No. 132,540, filed August 30, 1926, which tank is providedwith a metal top or roof connected at its peripheral edge to the side wall of the tank and constructed or designed so that it is capable of flexing and movlng upwardly and downwardly relatively to the side wall of the tank in normal operation, so as to increase and decrease the vapor space'or gas space of the tank without setting injurious strains 1n the neutral fibre of the metal from which said roof is constructed.

One object of my present invention is to provide a storage tank of the general type 29 mentioned, whose top or roof is of such crosssectional shape that it can be designed so as to produce a vapor space or gas space of the requisite volume or cubical contents when it is in its inverted or upwardly-flexed con dition, without producing an abnormally large rain pocket or water receiving cavity on the top side of the roof when it 1s in its normal or downwardly flexed condition.

When the roof is in its normal or down- 30 wardly flexed condition it is substantially concave shape in cross section, the same as the roof of the tank described in my said pending application for patent, but instead of being of inverted cone form, it is of inverted frusto-conical form, thereby giving the least possible water load in the case of a heavy rain but giving a large volumetric displacement when it is in its upwardly flexed or inverted condition.

40 Another object of my invention is to provide a novel means for preventing or controlling the bending of the peripheral portion of the roof that is attached to the side wall of the tank, so as to eliminate excessive strains on the weld at the edge of said peripheral portion.

Another object is to provide an automatically-operating venting apparatus for a storage tank of the general type disclosed in my said pending application. which is constructedin such a manner that it can be adjusted easily from the upper side of the roof and without liability of an excessive amount of gas leaking from the tank during said adj usting operation.

Another object of my invention is to provide a venting apparatus for a tank of the general type mentioned, that is sure to operate or function properly, even though an amount of gas or liquid in excess of the amount the venting apparatus is intended to handle, enters the tank or develops in the gas space of the tank when the roof is in its inverted condition.

And still another object of my invention is to provide a tank roof or top of the general type mentioned that is inexpensive to construct and of such design that the portion of the roof in which most of the bending or flexing occurs is composed of radially-disposed plates whose side edges are riveted or welded together, thereby reducing the tendency of leaks to develop in the roof when it flexes upwardly and downwardly, due to the fact that most of the bending of the roof occurs across radial seams. Other objects and desirable features of my invention will be hereinafter pointed out.

Figure 1 of the drawings is a vertical transverse sectional view of a storage tank constructed in accordance with my present in- Vention.

Figure 2 is a fragmentary top plan view of said tank.

Figure 3 is a detail sectional view, illustrating my novel method of producing a welded joint at the peripheral edge of the roof of the tank.

Figure 4 is an enlarged vertical sectional view of the venting apparatus.

Figure 5 is a top plan view of said venting apparatus; and

Figures 6, 7 and 8 are detail sectional views, illustratingseveral different means that can be used for preventing or limiting the bending of the peripheral edge portion of the roof adjacent the side wall of the tank.

In the accompanying drawings which illustrate the preferred form of my invention, A designates the side wall ofthe tank. and 109 B designates the top or roof of the tank. Said roof operates in the same manner and has the same general characteristics as the roof of the tank described in my pending application for patent previously referred to, in that it is constructed from metal plates in such a way that it is capable of flexing and moving upwardly and downwardly relatively to the side wall of the tank, so as to increase and decrease the vapor space or gas space of the tank without setting up injurious strains in the neutral fibre of the metal from which said roof is constructed. Then it is in its normal or downwardly flexed condition, it is sustained by a supporting structure on the inside of the tank, composed of uprights 1 and cross pieces 2, and a venting apparatus is combined with said roof so as-to automatically relieve the internal pressure of the tank, and thus prevent the internal pressure from reaching a dangerous degree under certain conditions, said venting apparatus being of such construction that it is operated or rendered operative by the movementof the roof B relatively to the side wall A of the tank.

The roof B is concave in transverse cross section, as shown in Figure 1, when it is in its normal or downwardly flexed condition, but instead of being constructed so that it is of inverted cone shape, as disclosed in my said pending application, it is provided with a substantially flat or horizontally-disposed central portion :2: that merges into an upwardly-inclined peripheral portion y whose outer edge is connected by a gas-tight oint to the side wall of the tank, thereby producing a roof that is of inverted frusto conical form when it is in its normal or downwardly flexed condition.

Several advantages accrue from making the roof of this particular cross sectional shape, the most important of which is that the roof can be designed so as to produce a vapor space or gas space of the requisite volume without producing a pocket or cavity on the top side of the roof that will receive and hold an abnormally deep pool of rain water when the roof is in its downwardly flexed condition. Suppose, for example, that the total downward pitch of the inclined peripheral portion 3 of the roof is two feet, then the maximum water load that can be placed on the roof when it is in its normal position is the said two feet. If the roof sloped downwardly from its peripheral edge to its center, thus forming a roof of inverted cone shape, and if the total downward pitch of the roof weretwo feet, the volume of such a roof, when it is in an inverted or upwardly flexed condition, would be materially less than the inverted volume of the roof first referred to, i. e., a roof of inverted frusto-conical form, as herein illustrated. Accordingly, a much less total pitch may be used with a roof of inverted frusto-conical form than is necessary with a roof of inverted cone form, in or der to obtain a gas space of the requisite volume when the roof is in its upwardly flexed condition, and this slight pitch results in forming a water pocket on the top side of the roof that is of considerably less depth, and hence, less load per square foot, than the water pocket of a roof of inverted cone shape. Another advantage of a tank roof of inverted frusto-conical form is that the venting apparatus can be so adjusted that it will not operate to relieve the internal pressure of the tank i until at approximately the time the roof reaches its extreme upwardly flexed position, due to the fact that the roof comprises a substantially flat or horizontally-disposed central portion a: of relatively great area, that is capable of flexing upwardly and assuming a dome shape, in the event more gas or liquid is forced into the tank or in the event the internal pressure continues to increase, after the roof has reached its upwardly flexed or inverted condition. With a roof of inverted cone shape it is necessary to set or adjust the venting apparatus so that the relief valve will open, and thus relieve the internal pressure, before the roof reaches its extreme upwardly flexed position, in order to eliminate the possibility of the roof being subjected to an excessive strain produced by gas being forced into the tank, or pressure continuing to develop in the tank after the roof has reached its extreme upwardly flexed position. Consequently, a tank roof of inverted frusto conical shape, as herein illustrated, is an improvement on a tank roof of inverted cone shape, in that it is safer, the full upward limit of travel of same can be utilized to increase the vapor space of the tank, and it can be designed so as to carry a relatively small water depth when it is in its normal or downwardly flexed condition without diminishing the volume of the vapor space or gas space displaced when it moves from its normal down position to its upwardly flexed condition.

In order to further increase the volume of the vapor space and also eliminate the possibility of the metal in the roof being subjected to excessive tensile strains, produced by an abnormal pressure being exerted on the underside of the roof when it is in its inverted or extreme upwardly flexed condition, I construct the roof in a manner which insures the central portion a: of the roof being provided with suflicient excess metal to cause wrinkles to form in said central portion, when the roof is in its normal position. This excess metal permits the central portion of the roof to dome slightly without straining the metal, in the event of an abnormal pressure produced, for example, by forcing gas into the tank after the roof has reached its extreme inverted or upwardly flexed condition, faster than the vent is designed to relieve it. As the central portion of the roof is capable of doming slightly without stressing the metal in the roof, the volume of the gas space or vapor space is increased more or less, depending upon the ex tent to which the central portion of the roof domes, this increase in volume of the gas space being attained without increasing the water load on the roof when it is in its normal or downwardly flexed condition. The method that I employ for insuring excess metal being incorporated in the central portion of the roof consists informing said central portion from metal plates that are sustained by a slightly dome-shaped or slightly cone-shaped temporary supporting structure during the operation of connecting said plates together, and then removing said temporary supporting structure after said plates have been connected together, whereupon the disk-shaped device formed by saidplates will flatten out and come to rest on the cross pieces 2 of the permanent supporting structure inside of the tank, the metal from which said disk-shaped device is composed wrinkling sufficiently to permit said device 'to assume a horizontal position on the permanent supporting structure. In F igure 1 of the drawings I have indicated by the dot-and-dash line 100 the approximate shape of the central portion w of the roof before the temporary supports are removed, the temporary supports being sustained usually by the cross pieces 2 of the permanent supporting structure.

While the excess metal in the central portion at of a tank roof of conventional size, for example, approximately 115 ft. in diameter, is very small, nevertheless, said excess metal makes it possible for the central portion of the roof to assume a dome shape or flex upwardly into the position indicated by the dotvand-dash line 101 in Figure 1, before the metal in the roof becomes subjected to excessive tensile stresses. Consequently, the wrinkles in the central portion a: of the roof prevent straining of said portion, and they also permit said central portion to assume a slightly dome shape, thereby increasing the sizefof the vapor space, without straining the roo The peripheral portion y of the roof is connected to the side wall A of the-tank, preferably by a welded joint 3 between the edge of said peripheral portion, and a flange or angle 4 attached to the upper edge of said side wall, as shown in Figures 6, 7 and 8. Accordingly, if the edge portion of the roof is subjected to considerable bending movement, whenthe roof rises and falls, due to variations in the internal pressure of the tank, there is a tendency to rupture or break the weld 3 at the edge of the roof. Therefore, I propose to equip the tank with means for controlling or eliminating bending in the edge portion of the roof adjacent the side wall of the tank. One means that may be used for this purpose consists of rods 5 connected by welding or in any other suitable manner to the inner face of the side wall of the tank adjacent its upper edge, as shown in Figure 6, and arranged so that they project upwardly through holes 6 in the edge portion of the roof, and provided at their upper ends with threaded portions that receive nuts 7 which can either be adjusted so that they bear upon the top side'of the roof, or adjusted so that they serve as stops againstwhich the roof strikes when it flexes upwardly. The holes 6 in the roofthrough which the rods 5 project are normally covered by removable caps 8 which are screwed intof sleeves attached to the top side of the roo Another. means for accomplishing the same result, illustrated in Figure 7, consists of rods 5 attached to the peripheral edge portion of the roof and projecting downwardly from same, and adjustably connected by means of chains or other suitable devices 7 a to loops 6} fastened to the inner face of the side wall of the tank.

In Figure 8 the edge portion of the roof is rigidly secured by rivets 5 to the horizontal leg of the angle 4 on the side wall of the tank, said rivets causing the roof to bend at the point where the rivets are located when the roof flexes upwardly, and thus preventing the weld 3 from being subjected to a strain.

In order toproduce a weld 3 at the peripheral edge of the roof that is not liable to fail or rupture when the roof flexes upwardly and downwardly, even if the tank is not equipped with a means for preventing or controlling the bending of the peripheral portion of the roof, I prefer to arrange the plates y that constitute the peripheral portion of the roof in an upwardly-inclined position, as shown in full lines in Figure 3, dur-.

ing the operation of forming the weld 3. The angle at which said plates are held during the welding operation is approximately the maximum upward position that the roof will ever assume, and after the weld 3 has been completed, said plates are permitted to flex downwardly, into the position shown in broken lines in Figure 3, and come to rest on the inclined cross pieces 2 of the permanent supporting structure inside of the tank. Accordingly, when the tank is in service there is little liability of the, weld 3 breaking, because the upper part of said weld is held in tension while the roof is in its normal, downwardly flexed condition, and any upward movement of the roof relieves the stresses in the weld. Another advantage of this method of forming the weld at the edge of the roof is that a defective vweld will show up as soon as the plates are permitted to flex downward- 11y from the position shown in full lines in igure 3 into the position shown in broken lines in said figure, thereby permitting the defect to be remedied before the tank goes that is preferably used for actuating said valve consistin of a lever or other suitable actuating mem er carried by the roof and combined with a chain or equivalent means that is attached to the bottom of the tank or to an anchoring device arranged adjacent the bottomof the tank, in such a manner that the upward movement of the roof causes said chain or means to exert a pull on the valve lever in a direction to open the valve. The field conditions for erecting this type-of tank roof are such that there may be several inches difference in the height of the uprights 1 of the supporting structure which sustains the roof when it is in its downwardly flexed condition, and therefore, it is often necessary to change the length of the chain or other means that is used to actuate the valve lever. Accordingly, I have devised a venting apparatus that can be easily adjusted I from the top side of the roof to vary the position of the roof at which the relief valve opens, said apparatus being preferably constructed in such a Way that said adjustment can be made without liability of excessive leakage around the valve, thus making it possible to adjust the relief valve when the tank is in service and the roof of same is being flexed upwardly by the pressure inside of the tank. In Figure 4 of the drawings I have illustrated a venting apparatus having the characteristics above referred to, said apparatuscomprising a relief valve 9 areranged above a valve seat 9 that surrounds 'a vent 9 in the cover late 10 of a manhole on the roof of the tan a lever 11 pivotally mounted on the underside of said plate and arranged so that one end of same is adapted to move upwardly into engagement with a depending stem 9 on the valve, thus causing the valve to open or unseat, a chain 12 or other equivalent means attached preferably to an anchoring means 13 adjacent said bottom, and an adjustable connection between said chain and the opposite end of the lever 11 that is accessible from the top side of the roof of the tank. In the preferred form of my invention herein illustrated a screwthreaded rod 14 that is attached to the chain 12 projects upwardly through a hole 15 in the lever 11 and through a sleeve 16 that is arranged above said lever, and a nut 17 is mounted on the rod 14 above the upper end of the sleeve 16, so asto enable the effective length of the operating device formed by the chain 12 and rod 14 to be changed by screwing the nut 17 up or down on the rod 14. The sleeve 16 projects upwardly through a hole in the manhole cover 10 and is surrounded by a housing 18 connected to the manhole cover and provided at its upper end with a removable cover 19 that is normally mounted on said housing so as to prevent the escape of gases that enter said housing through the hole that surrounds the sleeve 16.

The cap 19 is removed from the housing 18 preparatory to adjusting the nut 17, and when said nut is being adjusted very little gas escapes from the tank, because the hole in the cover plate 10 through which the sleeve 16 passes is only large enough to provide for a free movement of said sleeve.

With a storage tank of the general type to which my invention relates, it is possible that any emergency may arise, in which an excessive amount of gas or liquid be forced into the tank which would be greater than the capacity of the relief valve to handle. In this case if the chain 12 or equivalent means of the venting apparatus were attached directly to the bottom of the tank or to some object which is fixed with relation to the tank, then the load exerted on the lever 11 might become so excessive as to break said lever. If this should occur, then the valve 9 would drop back onto its seat and close, thus making the tank substantially gas-tight with no relief. This latter condition would eventually cause the roof to.rupture. To overcome this I attach the lower end of the chain or equivalent means to a weight or anchor 13 that normally rests on the bottom of the tank. In the above described emergency the weight 13 would be lifted off the bottom of the tank. Thus, the roof would be forced above its adjusted upper position with the vent wide open. If the emergency were not too great, the vent would remain open until the emergency had passed and the roof would adually come down to the adjusted openm position of the vent, the weight 13 coming into its normal position on the bottom of the tank and the valve 9 coming to rest on its seat without having caused any injury to the venting apparatus.

So far as my broad idea is concerned, it is immaterial how the plates constituting the central portion a; and the peripheral portion 3 of the roof are arranged and connected together, so long as the roof is of substantially inverted frusto-conical shape in cross section when in its normal position. I prefer, however, to form the peripheral portion 3 of the roof from plates that are arranged radially, as shown in Figure 2, thereby causing most of the bending of welded or riveted seams to occur across radial lines. The central portion of the roof is preferably formed from rectangular plates which can be made of a uniform size, thus reducing the costof constructing the roof.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a gas or liquid storage tank of the type Whose roof is connected to the side wall of the tank and is capable of flexing or moving in a direction to increase or decrease the volume of the vapor space in the tank under certain conditions, a roof that is of substantially inverted frusto-conical form when in its normal condition.

2. In a gas or liquid storage tank of the type that is provided with a metallioroof connected to the side wall of the tank and capable of flexing or moving in a direction to increase or decrease the volume of the vapor space in the tank under certain conditions, a roof comprising a portion that is capable of doming slightly without stressing the metal after the roof has reached its inevent the pressure which caused the roofto flex upwardly continues to build up after the roof reaches its upwardly flexed condition.

4. In a gas or liquid storage tank of the type that is provided with a metallic roof connected to the side wall of the tank and capable of flexing or moving in a direction to in-' crease or decrease the volume of the vapor space in the tank under certain conditions, a roof comprising an inclined peripheral portion and a substantially flat, horizontally-disposed central portion that contains suflicient metal to permit said central portion to assume an upwardly domed form, without stressing the metal, under certain conditions.

5. In a gas or liquid storage tank of the type that is provided with a'metallic roof connected to the side wall of the tank and ca pable of flexing or moving in a direction to increase or decrease the volume of the vapor space in the tank under certain conditions, a roof comprising a substantially flat, horizontally-disposed central portion and a peripheral portion disposed at an angle to said central portion and made up of plates that are arranged radially.

6. In a gas or liquid storage tank of the type that is provided with a metallic roof connected to the side wall of the tank and capable of flexing or moving in a direction to 1 a roof comprising an inclined peripheral portion made up of radially-disposed plates and a substantially flat, horizontally-disposed central portion made up of rectangular plates. 7. In a gas or liquid storage tank of the type that is provided with a metallic roof connected to the side wall of the tank and capable of flexing or moving in a direction to increase or decrease the volume of the vapor space in the tank under certain conditions, a welded joint at the peripheral edge of the roof of the tank formed so that the top side of said weld is in tension when the roof is in its normal condition, and any upward movement of the roof tends to relieve the stresses in said weld.

8. In a gas or liquid storage tank of the type that is provided with a metallic roof connected to the side wall of the tank and capable of flexing or moving in a direction to increase or decrease the volume of the vapor space in the tank under certain conditions, a welded joint at the peripheral edge of the roof of the tank whose upper part is in tension when the roof is in its normal downwardly flexed condition, said joint being formed when the peripheral portion of the roof is maintained in an upwardly-inclined position that represents approximately the maximum upward position that the roof will ever assume.

9. In a gas or liquid storage tank of the type that comprises a metallic roof connect-- ed to the side Wall of the tank and capable of moving or flexing in a direction to increase or decrease the volume of the vapor space in the tank under certain conditions,

and a venting apparatus comprising a relief valve, the combination of a lever on the underside of. the roof for operating said valve, a device leading upwardly from the bottom of the tank, an ad ustable connection between said device and lever that projects 11 wardly through a hole in the roof of the ta and a housing that normally encases said connection.

10. In a gas or liquid storage tank of the type that comprises a metallic roof connected 'to the side wall of the tank and capable of moving or flexing in a direction to increase or decrease the volume of the vapor space in the tank under certain conditions, and a venting apparatus comprising a relief valve, the combination of a means or unseating said relief valve consisting of a device that leads upwardly from below the roof, and a weight attached to said device so as to serve as an an: chor for said device. I

11. In a gas or liquid storage tank, the combination of a side wall portion, a metallic roof joined by a gas-tight joint to said side wall portion and constructed so that it is capable of flexing upwardly and downwardly to increase and decrease the volume of the vapor space of the tank, and means for limiting the upward flexing of the peripheral portion of t e roof relatively to said side wall portion, so as to eliminate strains on the joint between the roof and side wall portion.

12. In a as or liquid storage tank, the combination o a side wall portion, a metallic roof'joined by a gas-tight joint to said side wall portion and constructed so that it is adapted to flex upwardl and downwardly relatively to said side wall and decrease the volume of the vapor space of the tank, and an adjustable means for controlling the upward flexing of the peripheral portion of the roof relatively to said side wall portion so as to eliminate excessive strains on the joint between the roof and side wall portion. a

13. In a gas or liquid storage tank, the combination of a side wall portion, a metallic roof joined to-said portion and constructed so that it is adapted to flex upwardly and downwardly relatively to same to increase and decrease the volume of the vapor space in the tank under certain conditions, a venting apparatus operated by the upward movement of the roof relatively to said side wall ortion comprising a relief valve, a member or unseating said relief valve, an actuating device leading downwardlfy from said member towards the bottom 0 the tank, and an adjustable connection between said member and actuating device, operable from the top side of the roof.

JOHN H. WIGGINS.

portion to increase