US2538875A - Liquid storage apparatus - Google Patents

Description

Jan. 23, 1951 W. G. LAIRD LIQUID STORAGE APPARATUS 2 Sheets-Sheet 1 Filed Jan. 12, 1946 INVENTOR "ll-BUR 1RD ATTORNEY Jan. 23, 1951 w. s. LAIRD 2,538,375

LIQUID STORAGE APPARATUS Filed Jan. 12, 1946 2 Sheets-Sheet 2 INVENTOR a1 W/LBUR a. LAIRD Patented Jan. 23, 1951 UNITED STATES PATENT OFFICE LIQUID STORAGE APPARATUS Wilbur G. Laird, Pleasantville, N. Y.

Application January 12, 1946, Serial No. 640,751

18 Claims.

This invention relates to improvements in the storage of liquids and more particularly of valuable liquids such as petroleum oils, and apparatus therefor.

This application is a continuation in part of pending application Serial No. 448,823, filed June 27, 1942, for Method of Storing Liquids and Apparatus Therefor,. now abandoned.

Large quantities of petroleum products are stored in tanks provided with floating roofs in which no attempt is made to save vapors, while still larger quantities of such products are stored in covered tanks without such roofs. Some closed storage is provided where there is good protection from loss by vaporization.

The present invention is directed to the object of improving and reducing the cost of storage by utilizing a floating roof type of tank in such a manner as to completely enclose or bottle-up the liquid at the level of the liquid in the tank. The improved method and apparatus may be applied to the storage of oil and other liquids in large tanks of the field type, and is suitable also for bulk storage and for underground storage at air fields and other points of use or supply.

One object of the invention is to provide an improved method of storing liquids by which the liquid in a tank is sealed-in or bottled-up at the level of the liquid regardless of the fact that different levels may be assumed at different times.

A further object of the invention is to provide an improved method of storing liquids in floating roof tanks in which the roof is permitted to move freely up and down during the filling or emptying of the tank, but in which the roof is locked to the tank wall and the liquid completely closed-in during the time the liquid is held under storage conditions.

An additional object of the invention is to provide an improved method of storing liquids in floating roof storage tanks in which the liquid is bottled-up in the storage tank and protected against contamination by the outside atmosphere, rain water, and other foreign materials.

Another object of the invention is to provide an improved apparatus for accomplishing the improved method.

According to the objects of theinvention, the liquid is introduced into a storage tank, preferably of the upright cylindrical type which is provided with a buoyant floating roof. When the filling operation is completed with the roof floating freely on the surface of the liquid, the margin of the roof is locked with respect to the inside wall of the tank and the space between the two enclosed with a clamping and gripping means so that the liquid is bottled-up, foreign matter is excluded, and vapor cannot escape around the rim of the roof into the upper atmosphere of the tank. If it is desired to introduce more liquid or withdraw liquid from the tank the roof is unlocked for the time required and then again locked at the new level.

In preferred form of the invention the roof is locked in place and the space between the edge of the roof and the tank is enclosed by inflating an annular tire or tube secured to the floating roof between its outside rim and the inside wall of the tank. This may be accomplished by hand operation or automatically. The floating roof or deck of tanks of relatively small diameter may be provided with or include a movable diaphragm or flexing portion, preferably of large area, to take care of the normal changes in the volume of liquid in the tank due to changes in temperature of the liquid when the roof is locked in place. In the case of large tanks other means are preferably provided to accommodate such volume changes. A suitable locking means other than a tire-type lock Or grip may be used between the roof and tank wall.

It is acknowledged that various attempts have been made to enclose the space around floating roofs, for example by providing multiple liquid seals on floating roofs, as shown by the patents to Bohnhardt No. 1,666,525 and De Castro No. 2,125,771. Inflated and uninflated tubes, tires, etc., have also been proposed as marginal seals for floating roofs as shown by the patents to Bown No. 1,575,033; Glass No..1,650,340; Haupt No. 1,735,461; Patrick No. 2,014,264; and Horton No. 2,085,752. However, in all of these instances the floating roof is left free to move up and down with the seals sliding freely on the tank wall as the liquid level changes and in no case is there any attempt to lock the roof or seal in place at any level. Flexing roof plates for floating and fixed roofs have been proposed and used in some instances as illustrated by the patents to Bailey No. 1,619,401; Wiggins No. 1,854,534; Wiggins No. 1,904,339 and Day No. 2,008,686. As far as known, however, such plate or diaphragm roofs are used exclusively for the accommodation of changes in the volume of gas or vapor collected under the roof.

The commercial development of the buoyant floating roof has resulted in almost universal adoption of the pontoon buoyant roof or deck which is somewhat smaller than th internal diameter of the tank, and provided with a margi nal seal (so-called) in an attempt to cover the space between the edge of the roof and the tank wall. This space is usually from six inches to a foot wide, to provide for the usual irregularities in the character of the tank wall, Since steel tanks, such as upright cylindrical oil tanks irequenfly are not made and kept in the form of perfoot cylinders.

The so-called seals used on floating roofs are not seals in the technical sense because, almost, if not all of them are made and used in such a way as to allow the escape of gases and vapors around the edge of the roof. Furthermore, it is generally believed in this art that provision must be made for the escape of gases and vapors around a floating roof. One of the most common seals used on floating roofs is an elaborate heavy structure including a ring of spaced vertical steel shoes (which slide along the wall of the tank), connected together with strips of Waterproof fabric, the ring of shoes being supported by spaced pivoted supports from the roof so that the weight of the ring of shoes (or springs bearing' against the shoes) causes them to bear against the tank wall. The space between the edge of the roof and the ring of shoes is closed with an annular piece of water-proof fabric, one edge of which is secured to the roof and the other of which is secured to the ring of shoes.

This so-called seal provides a metal-to-metal rubbing contact in which th shoes grind along the tankwall as th roof moves up and down in the tank with corresponding changes in liquid level. Gases and vapors formed from the liquid in the tank escape freel around the shoes along the tank wall and rainwater and other foreign matter enter the liquid along the tank wall in addition to the scale and rust ground on the tank wall b the steel shoes.

The marginal seal used with floating roofs or decks is never, as far as known, a seal at all but merely a kind of flexible loose cover for the space between the edge of the roof and the tank wall.

(Horizontal flexibility is regarded as importantbecause of tank wall irregularities.) These seals are never intended to function like the marginal packing of a dry gasholder, in which a gastight job is essential; Such gas holders, of course, are constructed with precision, so that they are smooth and of uniform shape and size hroughout, whereas steel liquid storag tanks are not. Furthermore, dry gas holder packings and the shell walls thereof are thoroughly lubricated by a fluid lubricant applied under pressure to provide slip, to make the packing an effective seal against gas, and to prevent corrosion of the wall. It is of course possible to construct an oil storage tank on a suitable heavy foundation and with the precision necessary for the use of a packed floating roof, but the cost has always been and is likely always to be prohibitive. The structural materials and foundation used for dry gasholders would obviously be inadequate to withstand the deforming, settling and other effects which would be produced by a substantial column of liquid. Moreover,- a packed piston putin an oil tank as a buoyant roof, if the tank shell were constructed to take one, would simply convert the tank into a combination oil tank-and dry gasholder in which the piston might never fcat on the liquid because of the presence of vapor and gas above the oil. Pon oons, of course would not keep a packed piston roof horizontal on gas and vapor.

Oils, such as crude. oil, stored intank farms and around refineries, may not be moved for long periods of time, sometimes for months or a year or more. The same is true for oil products in bulk storage stations and other storage depots. Oil stored for such periods in ordinary tanks in water displacement type storage, and in tanks provided with the common type of floating pontoon roof is subjected to man hazards which can be avoided by the use of the present invention. Oil products in floating roof. tanks are obviously contaminated with steel corrosion products, Wat-er and other foreign matter deposited in the tank from wind storms and other agencies. Rain water, dust, and-tank scale enter such tanks around the roof seal because it is merely a loose affair, and because the roof and seal move up and down with'all of the changes in level of liquid in the tank, even with the change of a few inches caused by the normal thermal expansion and contraction of the oil.

In most cases oil products which are contaminatedin'storage must be refined beforeuse; For example, fuel oils of the bunker Ctype may emulsify with rain water to such an extent as to fail to conform to specifications. Finishedgasol-ines and otherproducts may require additional treatmentor new supplies of inhibitor, etc;, after being contaminated in storage.

Ordinary oil storag i always; a serious fire hazard and experience hasshown that present floating roof tanks are'often-flred.

The presentinvention provides an effective and inexpensive method and apparatus-bywhich oils and oil products may bestoredunder bottle tight conditions for an desired period of time and be safe from contamination and fire hazards;

From the following more detailed description of the invention it will-be apparent that a new and advantageous method" and apparatus for storing liquids has-been discovered.

In the drawings-forming a' part of this application:

F-ig. 1 isa vertical sectionalview of afloating roof storage tank which the features of the invention are illustrated:

Figs. 2- and 3 arebrekenvertical sectional views illustratingmod'iflcd forms of" portions of the apparatus-shown in Fig. l.

Fig. i is a broken vertical sectional- View ofa floatingroof storage'ta-nk'for liquids illustrating a for-mof control mechanism suitable for use with tanks oflarge-diemeter:

Fig; 5'isa bi'oken planviewlooking-down on a portion of the mechanism shown in- Fig. 4.

Fig. 6 is a view similar to that of 4=-showing a portion of the apparatusin retracted position.

Fig. 7 is a broken view partly in section showing a modified form of a portion oftheapparatus shown in Figs. 4-, 5, and 6.

Referring-to Fig. 1' of the drawings which illustrates the invention in connection with a storage tanksuitablefon use in bu storage stations, the apparatus includes an upri htcylindrical wall 2., a bottom late sand" aventilated' conetype roof 6: for weatherprotection. This tank is provided with a floating roof" the decktype which includes an annular-rim section 8 which maybe made'of relatively-heavyorrigid-steel in the channel-likeform' shown, and a deck plate Ii secured tothe lower horizontal portion of section 8 which coversmost of the cross-sectional area of the tank and which is made of relatively thin sheet steel or other suitable-material, in-the form. of a diaphragmadapted to flex upward assasn and downward, as indicated in broken lines. The diaphragm plate Hi may be made of stainless steel, especially for small tanks. The upper portion of the rim of the deck is provided with an annular flange l2 including a horizontal portion which fits the horizontal upper portion of the section '8. The annular flange I2 and the upper part of section 8 provides an annular outside pocket in which a fluid-tight hose or tire I is mounted and may be secured to the outside of the deck. The hose or tire may be provided with an integral fabric flange section which may be secured between the horizontal upper section of the element 8 and the horizontal section of the annular flange E2, or the tire may be fastened to the deck in any other suitable manner.

The hose I4 is preferably of endless tire type construction and adapted to be inflated with gas to such an extent that its outer surface will firmly grip the side wall of the tank and will lock the deck with respect thereto. The hose or tire i4 is also adapted to be deflated so as to release or unlock the floating deck during the withdrawal of oil from 01' introduction of oil into the tank, and means is provided for effecting the inflation and deflation of the tire l4 either automatically or by hand operation.

In filling the tank the oil, for example gasoline, is introduced through a line it which may be provided with a hand-operated valve iii, the handle of which is interconnected as shown, to a valve 20, for effecting the inflation and deflation of the tire E4. Assuming that the floating deck is locked at some level in the tank and it is desired to introduce additional oil into the tank, the opening of the valve 18 for this purpose operates valve 20 to open it to a vent 22 which connects through the valve 26 to a hose line 2% threaded over sheaves 26, 28 and 3E, and connected through an automatic valve mechanism 32 and a line 34 to the tire 4. The hose line 24 is long enough to accommodate the full movement of the deck, the slack being taken up by the weighted sheave 23 which rides on the hose in the manner shown. The venting of the tire i4 releases the deck and allows it to float up'freely until the desired amount of oil has been introduced. In closing the valve it, the valve 26 is operated to cut ofi the vent 22 and admit gas through a supply line 35 at the desired pressure to inflate the tire it. The gas from the line 35 flows through lines 24 and 3G, to the tire I4, inflates it between the deck and wall to lock the tire onto the wall at the particular vertical position of the deck, closes-in the space between the deck and the tank wall and bottles-up the oil.

A hydrocarbon gas is preferably used in tire I4 in the storage of oils although the gas supplied through the line 35 may be air, nitrogen, CO2, propane, ethane, natural gas, or other suitable gas. Bottled gases are available around oil refineries and readily obtainable for other tank cations. Many refineries have piped gas available as pressures sufiicient to inflate the tire E4. The gas pressureused in the hose or tire i l will depend to some extent on a number of local factors including the character of the tank wall and stored liquid, etc. The pressure can be decided upon in advance and governed so that the gas will be constantly supplied in the line 35 at the proper pressure wheich will not be high enough to over-strain the tank wall but will be sufflciently high to lock the deck or roof to the wall.

The tire l4 may be made like a bicycle or an,

6 such as a fabric base and oilproof rubber, and may or may not include an inner tube. The tire I4 may include any type of tread adapted to increase the eflectiveness of the grip on the tank wall and the tire may be fastened to the outside of the deck in any suitable manner so long as it is firmly secured thereto and in a fluid-tight manner when inflated. The inflation of the tire when merely set in an annular channel effects a seal to the deck as well as to the tank wall.

The showing in Fig. 1 of the drawings illustrates the condition of the apparatus with the tire l4 inflated and the valve l8 closed, the oil being efiectively bottled-up as though it were in drums or canned. There is no escape for vapors or gases, and no way for water, dirt or dust to enter the oil. Where the features of the invention are applied to an open-topped tank, the deck will be provided with a water drain line as commonly used in the art. The flexible deck I0 is shown in a straight position but it may be flexed up or down in response to changes in the volume of the oil under the deck. The flexibility of the deck plate in is preferably adapted to accommodate the ordinary expansion or contraction of the oil due to changes in temperature. The temperature of a large body of oil changes very slowly even with abrupt changes in the atmospheric temperature.

The effect of unusual expansion or contraction of the oil under the deck, or possible leakage at some point, is automatically taken care of by the automatic valve 32 which is operated by the plate It]. The valve 32 is mounted in fixed position with respect to the margin of the deckby being secured to a rigid cross piece 35 which extends across the deck and which is fastened to the elements 8 01' I2 or both. The automatic valve mechanism includes a two-prong spring trip lever 38, a vent pipe 40 which may discharge outside the tank if desired, and a trip rod 42. One end of the trip rod 42 is fastened to the diaphragm Ill as shown, so that the rod is moved vertically with any flexing of the diaphragm. The other end of the rod 42 includes spaced lugs 5d and 45 with an intermediate positioning lug 43.

Assuming that there is considerable rise in the temperature of the oil bottled-up under the locked deck, or an excessive amount of vapor is formed; as the oil "begins to expand the level will rise between the deck and wall 2, compressing the gas therein. The plate It] also starts to flex upward causing the rod 42 to operate the valve 32. The movement of the lug 48 merely tilts the trip lever '38 up a little and then disengages it, but the trip lever is then engaged by the lower lug 44 and is pushed up to a point where the valve 32 flips to open the line 34 to the vent pipe 40 and to cut off the supply of gas through line 2 3. The lug 44 is set on rod 42 so that thevalve 32 is thrown to vent when the deck plate is has been flexed up to the desired extent. As the valve 32 is opened to vent, the tire I4 is deflated and the deck released from the wall. The deck immediately assumes a normal position with the deck plate Ill approximately level. As the deck moves back to its normal position the intermediate lug 48 on the rod 42 engages the lower prong of the trip lever and throws the valve back to normal so that the vent 40 is cut off and the tire i4 is inflated to lock the deck with respect to the tank wall again. The downward flexing of the deck plate It] sufliciently to operate the valve 32, by contraction (or loss) of the oil in the tank, brings the upper lug 46 in contact with the upper prong of the trip lever 38 to throw the valve to vent and unlock the deck from th tank wall.- After the tire I4 is deflated by either operation, the deck quickly assumes a normal position so that the oil in the tank is uncovered or uncorked for only such time as is required for the deck to reach normal position. The deflation of the tire M by the automatic operation of the valve 32 should be a rare occurrence, since the movement of the diaphragm plate i5 beiore the valve is tripped is suflicient' to care for all normal variation in the volume of oil under the deck. Any vapor released upon the deflation of the tire M by the upward movement. of the diaphragm H3 is quickly dissipated in the upper part of the. tank and the concentration of hydrocarbon vapors even in the case of gasoline storage, will; be; unlikely to produce anigniiable mixture. When the diaphragm it flexes downward to the extreme point necessary to operate the valve 32, a small amount of air may pass below the deflated tire I4, but when the deck settles down, most of this will be pushed out before the tire can-beagain inflated.

The modified form of the apparatus illustrated in Fig. 2 shows an alternative arrangement for tripping the automatic valve 32 which is shown attached to the margin of the deck instead of-to a beam across the center as in Fig. 1. In 2 the operating rcd is attached to a float 53 mounted in an open-bottomed chamber 52 at-the edge of the deck. The diaphragm plate l flexes in the same manner as in Fig. 1 to take-care of changes in volume of the liquid inthe tank, but these changes act on the float 59 which in turn trips thevalve 32 in the same mannerand' under the same conditions. as described in connection with Fig. 1, the lugs 34 and 66 being: set at the proper points to throw the trip lever: of:valve 32 and deflate the tire i l when certainmaximum desired changes in the volume of oil in the-tank occur.

The modified form of apparatus shown in Big. 3 of the drawings illustrates the trip-valve mechanism shown in Figs. 1 and 2 in connection with a slightly different form of tank and deck adapted to retain a layer ofgas or vapo under the deck plate. In this a tank is-providedwith a floating deck comprising a fleizible diaphragm deck plate secured in fluid-tightmannerio a slightly below the bottom of apron so that liquid is always present in this chamber to 0perate the float 5t when in urn functions to trip the automatic valve 32 when the. liquidin the chain's r or falls to a predetermined extent. In 3 the tire is is IllOlllltBd'iH an annular chain l-shaped member 58 attached .to the upper part of the annular plate 5 5. Inthis instance, the valve 32 is mounted .at the. side of the deck on the, channel structure 53 as shown. If desired gas may be supplied to. or removed from the space under the deck plateli i. by any desired means not shown if it is desired either to maintain or prevent the accumulation of a layerol gas. The presence of a gas layer tends insulate the oil stored under the t9 deck and The" retard heat transfer fromthe deck plate." This is especially true in opentopped storagetanks;v

Instead of usinga float 5G to operate the valve 32 in the apparatus of Figs. 2 and 3, other suitable means may be employed such as for example, a bellows. or a separate diaphragm, or other device adapted to utilize the variations-in the volume or the pressure of the. stored liquid. The modified form of construction shown. in

Figs. 4, 5 and 6 comprises a tank having a wall- 69 and provided with a floating deck or roof, the latter including an annular rim section 6| and a. deck plate 62. The roof may be of pontoon construction or the rim 6| may extend below the plate 62 as in Fig. 3. The rim 6| has an upper inturned flangewhich serves to mount a tire or hose shown as comprising a casing 63 and an inner tube 64. The casing 63 is conveniently made of a sheet of material coverin theinner tube and having its edges clamped between the horizontal sections of a pair of annular flange members 65, which form an annular pocket for the tire as in Fig. 1. The tire is supplied with and relieved of gas through a r pipe 66 which terminates with a flange 6! in the inner tube 64.

The control mechanism shown in Figs. 4, 5 and 6 for automatically inflating and deflating the tire is illustrative of means adapted to operate in response to the up or down movement of the deck or roof. The mechanism is shown as mounted on a structural bracket 58 attached to the deck plate 62 and comprises a fixed cylinder 69 attached to the bracket 58, a long movable cylinder ll! having an attached or integral piston block H which operates in the cylinder 69.

A valve stem i2 is mounted axially in the cylinder 10 and carries sliding sleeve valves for controlling the flow of gas. Gas at the desired pressure is supplied from any suitable source to the control unit and to the tire through a flexible pipe 13, the pipe discharging into the right end of the cylinder 18 from which gas is also supplied to the pipe 56, also flexible. An irregular shaped cylindrical sleeve valve. 14 is attached to the valve stem 12 in the right end of the cylinder 18, while a second sleeve valve '55 is attached to the stem 12 Within the area of the piston block ll by means of a solid wall 18 which serves as a piston and to block the direct flow of gas through the sleeve 16 and the cylinder ill. The left end of the valve stem 12 is squared and extends beyond the end of the cylinder It. It operates in a spider-like head 8E3 fixed to the end of the cylinder 10, the member 85 having a square center openingwhich flts the square section of the valve stem and keeps it and the sleeves M and '15 from rotation relative to the cylinder H3.

The valve stem 52 extends through a suitable joint in the cylinder head at the right end of the cylinder re and is provided with a handle 8] and a spring 82 the latter engaging a washer and adapted to operate the valve stem under conditions described hereinafter. When the valve stem is pulled out by the handle 8| it may be looked in extending position by allowing the catch 83 to engage the washer used for retaining the spring.

The end of the cylinder it facing the tank wall iill'is provided with a pair. of arms 84 which may be integral with the member The ends of the arms carry a pivot pin and provide a pivoting support for a measuring wheel or disk 85 mounted on the pin between the arms. The

wheel 85 includes a rather wide arch shaped member 86 which carries a tread 88 of rubber or other suitable material for normally engaging the tank wall 60. Directly opposite the member 86 the disk 85 includes an integral fan shaped segment 90 of the same radius as the periphery of the tread 88. The segment 98 is part of a trip mechanism and normally engages the edge of a trip plate 9! attached to the end of the valve stem 12. A spring 92 tends to keep the disk or wheel 85 in the position shown in Figure 4 with the segment 9!! centered on the plate 9|. The cylinder 10 is kept from rotation by means of a guide rod 93.

The purpose of the mechanism shown in Figure4 is to provide means for normally maintaining the tire firmly gripping or locked to the tank wall but to automatically release the pressure in the tire if the roof is caused to move up or down a predetermined amount. The measuring or tracking means including the disk 85 and the tread 88 are normally held by the mechanism in firm engagement with the tank wall so that the disk or wheel 85 will rotate on its axis if the roof moves up or down. The gas supplied through the line, 13, under the conditions shown in Figure 4 of the drawings, is permitted to flow directly into the cylinder 10 through the opening shown in the sleeve'l i. Gas is then also free to fiow through the pipe 66 to the tire to inflate and lock it onto the tank wall.

The gas in the cylinder it, which is at the pressure of the gas in the tire and pipe 13 operates on the surface of the wall it to force and maintain the valve stem 12 against the segment 9%. At the same time gas flows through an opening 94 in the sleeve 76 and a matching duct 95 into the space to the right of the piston block H.

The space at the opposite end of the block isvented through a vent l and connecting duct TI. The gas pressure on this block forces the cylinder 70 to the left and maintains the tread 88 in firm engagement with the tank wall. As long as there is no substantial movement of the floating roof the control apparatus will remain in the position shown in Figure 4. With minor changes in the position of the roof the tire will be distorted and the segment 95 will slide along the trip plate 9i When a substantial change in the volume of the liquid under the roof occurs, as for example a contraction due to a temperature drop, the roof moves down so that the upper flange 65 presses against the tire. At the same time the wheel 85 is rotated in a clockwise direction to move the segment 90 across the trip plate 9!. Upon a predetermined movement the segment 9!! moves below the trip plate 9| which with'the valve stem 12 instantly shoots to the position shown in Fig. 6. The gas pressure against the piston wall 18 causes this instant action. The tripping of the valve stem M as described shifts the sleeves is and 16 to cut off the gas supply through line 73 and to open a vent 95 which permits deflation of the tire through the pipe 56. The shifting of the sleeve it, closes the opening es, opens a vent 9'! to a duct 98 and opens a duct 99 to the left side of the block I! so that the gas pressure available from the tire will movethe cylinder 19 instantly to the right and ret1 act the measuring wheel 85 from the tank wall. Fig. 6 shows the position of the mechanism immediately after the trip action occurred, with the tire still distorted.

When the tire deflates sufficiently itwill asure 4.

mechanism operates to inflate the tire and mainlO sume a normal position with respect to the flanges t5 and will be ready to be reinflated against the tank wall at a new level. In the tripping of the control mechanism the spring 82 is compressed so that it will be effective at the proper time to shift the valve stem E2 to the position of Fig. 4. The head of the cylinder "it includes a friction catch iilii, comprising a ball,

a spring and an adjustment screw, for temporarily holding the valve stem E2 in the position shown in Fig. 6. The ball of the catch Iiiii engages a notch or recess l 592 in valve stem.

After the tire is deflated so that it assumes its normal position, the pressure of gas against the piston wall 18 decreases to an extent sufficient to permit the spring 32 to move the valve stem '52 to the right, and with a snap action because of the friction catch tilt which releases the valve stem suddenly. The valve stem '52 then take the position shown in Fig. 4. and the same is true of the wheel 85 which is rotated to position by the spring 92 as soon as the valve stem is shifted; The spring 82 is calibrated so as not to shift the stem too far. If desired a catch on the latch 83 may be used to limit the movement of the stem "i2 by the spring 83. However, gas is soon flowing into the cylinder "iii from pipe to keep it and the valve stem in position and to reinflate the tire in its new position on the tank wall.

If it is desired to vent the tire by hand as for example in a contemplated filling operation, the handle 8! is pulled to the right and the latch 83 set against the washer. This operation shifts the valve stem to cut off the gas supply and open the vent 86. It will be noted also that the shifting of the sleeve it to the right, from its position in Fig. 4, will uncover the venting duct 98 and supply gas through the duct 99 from an inlet H33 in the sleeve, so that the piston block if as well as the wheel 85 are shifted to the right away from the tank wall. After a filling operation is finished in this manner and the roof comes to rest the latch 83 may be released and the valve stem pushed to'the position shown in Fig- In this position as explained above the tain the tread 88 against the tank wall.

Instead of using the handle Bi directly it may be operated by remote control in the manner shown in Figure 7 of the drawings. In this figure a small pneumatic or hydraulic cylinder lt i is attached to the head of the cylinder it. The cylinder mechanism includes a piston I35 returnable by a spring Hi6 mounted around a square shaft Hill; to the end of which is keyed an arm N38. The horizontal section of the arm its includes spaced lugs Hi9 and its mounted on opposite sides of the handles 8i. Liquid or gas is supplied to the cylinder we, as for example as from some point on the ground through a line i i2 which forces the piston m5 to the right so that the lug 109 will operate the handle 8! to move the valve stem to the right as in the hand operation described above. Ehe handle 8! may be held in the extended position as long as desired by maintaining the pressure in the line i it. When the pressure is released-the spring I96, il'l'CO- operation with'the lug He will return the valve stem i2 to the position shown in Figure 4, which is the position also shown in. Figure 7. The shaft it! being square prevents rotation of the arm I113; The space around spring lilii is vented as indicated. The springs 82 and 6% act in compression to position the valve stem. In either form the apparatus may be tripped and reset by 1 ll hand. The line $6 is provided with a safety relief valve lit to protect the tire.

The problem of providing a diaphragm such as shown in Fig. l,-ior tanks of large diameteris avoided by the use of mechanism of the type shown in Figs. 4 to 7. n tank of 120 feet in diameter holding 80,009 bbls. of oil with a 40 foot oil clumn, for examplemay involve some difliculty with a diaphragm. Such a column of oil would expand about 2 inches for each 10 F..rise in temperature, and this would amount to about 320 bbl s., which issome volume of oil to be taken care of. bya diaphragm or to provide a diaphragm for.

:In a large tank, an arrangement of the type shown-in Figs. 4 to 7, permits the roof proper to move up or down-a predetermined distance while the hose tire or other clamping and gripping seal is locked to the tank wall and sealed to it and the roof. A tire or hose is useful because it can be distorted by the up or down movement of the roof. A tire having a diameter of about 8 inches maybesubstantially distorted to provide appreciable up and down movement of the roof proper and without causing the tripping of the control means. The tire orihose need not be fixed to the roof but may be retained between flanges such as 65,-.andztherefore may partly roll when it is inflated between the tank wall and th roof, and the latter moves up or downto distort the tire.

'The measuring wheel trip mechanism. of Figs. 4 to 7 is responsive to a predetermined liquid level or volume change in the tank or to a. corresponding change in vertical position of the roof caused by the liquid level or volume changes. The valve trip mechanism maybe attached to the shell or other fixed part of the apparatus while the measuring shoe or tread 88 bears against a mast attached to the floating roof, either t3 a rigid part or to a diaphragm forming all or part of the floating roof.

The floating roof or deck shown in any of the views may be provided with marginal pontoons if desired. The deck of Fig. 3 for example can'be provided with marginal pontoons under the plate so that gas will collect and maintain a layer within the area surrounded'by the pontoons. The plate 62 of'Fig. 4 may be a pontoon plate. The use .of pontoons with the deck wi l tend to keep the deck level. Other means for keeping the decks level may be used in connection with the apparatus of the present invention.

The means shown for unlocking the clock when the-tank is to be filled oremptied, including the valve 2G and its connection to the valve H3 is merely illustrative of one means for accomplishing this result. It is not necessary that the valve 20 be operated from the hand lever of valve it since the valve it could be operated by hand, by the person charged with filling or emptying the tank. Even if the valve 25 were not operated to deflate or release the sealin means it would be unlocked .by the automatic operation of valve 32 assoon as suiflcient liquid is introduced or withdrawn. Outside manual operation in addition to the automatic feature has many obvious advantages howeverin any-form of the apparatus.

The apparatus of the present invention is well suited for underground storage in which the tank maybe of steel or of concrete. Water for displacement is not necessary. The floating deck effectively isolates the oil and keeps the oil more free from contamination than a water displace ment system would.

Th p cess and apparatus of the present in- ,vention are particularly usefuliin connection with the ilong itime storage of :petroleum oil products such-asforexamplein field storage tanks. Under such conditions, it will be apparent that the bfit'tlll'lg fllpflf lihejO-l1Wi11 have substantially the same effectas ,if the-oil were canned-or:stored indgrums. since the ,oil'will'bekept 'free'fromcontaminationand substantial loss. The 'locking up of :the oil-in the:manner described'preventssthe escapecof the-small amount of vapors WhlChEIlOT- mallyimight be formed'and"thereforermaintains' a definitezvapor pressure above "the liquid which "in turnzretardsor'suppresses the formation of additional quantities of vapor. In present floating roo'f tanks't-he vapor:is always free'todiffuseout around'therso-called sealsand air'is breathed in. Oil stored-under the "conditions described inconnection' with the present invention however cannot v:go through the breathing operations :which take ,place .in connection with oil stored in the usual floating :ro'of tank.

iIt will ebe apparent to those skilled in the art that yar'ious modifications maybe made in' the apparatus for carrying out the improvedmethod and that certain variations may'be'employed in efiecting the improved process. such changesare tobe includedwitliin the scope -of the present invention, as defined by claims.

Having described "the inventionin its preferred form, what is claimed-as new is:

1. In a cylindrical float ng roof "storage "tank for liquids which includes an upright cylindrical shell and a buoyant floating roof therein 'of slightly smaller diameter than that of the inside of the shell, improved means for preventin contamination of the stored liquid by the entry of foreign materials around the edge of the roof between it and the shell, comprising an inflatable and deflatable tire having a peripherial surface grip, the tire being mounted on the periphery of the roof in the annular space between the roof and the shell, said tire being connected to the roof in a fluid-tight manner and mounted thereon in such a way that upon inflation its peripherial 1 surface grip will contact the shell and produce a fluid-tight joint, means for inflating saidtire sufflciently to lock the roof with respect to the shell, and means responsive to predetermined changes in the volume of the liquid under the locked roof for deflating said tire and unlocking the rooffrom the shell.

.2. In a cylindrical floating roof storage tank as defined by claim 1 in which said floating roof is provided with a flexible deck plate adapted to flex up and down from a substantially flat position and arranged tooperate said deflating means.

3. In a cylindrical floating roof storage tank for liquids which includes an upright cylindrical shell and a buoyant floating roof therein of slightly smaller diameter than that of the inside of the shell, improved means for preventing contamination of the stored liquid by the entry of foreign materials around the edge of the floating roof and for locking the edge of the roof to the shell, comprising a locking and enclosing means engaging the periphery of the floating roof in a liquid-tight manner, said locking and enclosing means being adapted to completely close the space between the roofand the shell of the tank, and means for operating said locking and enclosing means to lock the roof with respect to the wall of the tank at any level therein, said operating means including mechanism responsive to predetermined changes in the volume of -liquid under the root,

4. In a cylindrical floating roof storage tank as defined by claim 3 in which means is provided for introducing liquid into the tank, and in which said introducing means is interconnected with said locking means and adapted to unlock the roof with respect to the tank wall when liquid is introduced into the tank.

5. In a cylindrical floating roof storage tank as defined by claim 3 in which said roof includes a flexible deck plate, and means connected with said deck plate for locking and unlocking the deck with respect to the tank wall.

6. In a cylindrical floating roof storage tank as defined by claim 3 in which said roof includes means for retaining a layer of gas under substantially the entire area of the floating roof.

7. In a storage tank for liquids including an upright cylindrical shell and a floating roof therein, an annular locking and sealing means attached to the outer portion of said roof for locking said roof onto and for sealing said roof v-Jith respect to the shell wall, and control means for releasing said locking means from its locking en gagement with the shell wall, said control means including means responsive to a predetermined change in the volume of the liquid under the roof when the roof is locked to the shellwall.

8. In a cylindrical floating roof storage tank for liquids which includes an upright cylindrical shell and a buoyant floating roof therein of slightly smaller diameter than that of the inside of the shell, a clamping and gripping means connected to said roof between the roof and shell, said means including means for sealing the space between the roof and shell and for locking said roof onto the shell wall at its floating position, said gripping means including means for unlocking said roof with respect to said shell wall, said roof including a flexible deck plate adapted to be flexed up anddown in response to increase and decrease, respectively, of the volume of liquid under the roof when the roof is locked in position in the tank, and connectingmeans between said flexible deck plate and said roof-unlocking means for operating said unlocking means when said deck plate flexes up or down to a predetermined extent.

9. In a cylindrical floating roof storage tank for liquids which includes an upright cylindrical shell and a buoyant floating roof therein of slightly smaller diameter than that of the inside of the shell, an inflatable and deflatable sealing means mounted on the periphery of the roof between the roof and shell, means for inflating said sealing means to cause it to firmly grip the shell and thereby bottle-up the liquid in the tank, said inflating means including a valve control mechanism for effecting the inflation and deflation of said sealing means, and means responsive to a predetermined movement of said roof up or down with respect to said shell for tripping said valve mechanism and thereby cause deflation of said sealing means.

10. In a cylindrical floating roof storage tank for liquids which includes an upright cylindrical shell and, a buoyant floating roof therein of slightly smaller diameter than that of the inside of the shell, an inflatable and deflatable sealing means mounted on the periphery of the roof between the roof and shell, and means for supplying a gas for inflating said sealing means and cause it to firmly grip the she l wall, said gas supplying means including a trip valve mechanism having a means responsive to a predetermined change in volume of the liquid under the roof for tripping the valve mechanism, the mesh:

14 anism of said valve having one position for maintaining gas pressure in said sealing means and at least one position for permitting the deflation of said sealing means.

11. In a cylindrical floating roof storage tank for liquids which includes an upright cylindrical shell and a buoyant floating roof therein of.

sightly smaller diameter than that of the inside of the shell, an inflatable and deflatable sealing means mounted on the periphery of the roof between the roof and shell, means for supplying gas to said means for its inflation, said gas supplying means including a trip valve mechanism adapted to be operated so as to release gas from said sealing means and effect its deflation, and means responsive to a predetermined vertical movement of said roof for tripping said valve and effecting deflation of said sealing means.

12. In a cylindrical floating roof storage tank for liquids which includes an upright cylindrical shell and a buoyant floating roof therein of slightly smaller diameter than that of the inside of the shell, an inflatable and deflatable sealing 'means mounted on the periphery of th roof between the roof and shell, means for suppl ing gas to said sealing means for effecting its inflation including a valve mechanism mounted on said roof, said valve mechanism including a measuring wheel normally operating on said shell, a valve stem arranged to be tripped by a predetermined rotation of said wheel, said valve mechanism being arranged so that upon the tripping of said stem said sealing means is opened to vent and said wheel is retracted from said shell.

13. In a cylindrical tank for liquifs including an upright cylindrical shell and a bouyant roof therein of slightly smaller diameter than that of the inside of the shell and normally supported by the quid in the the improvement which comprises an annular sealing and gripping means attached in sealed relation to the periphery of the floating roof and having a surface normally sealed w th respect to and gripping the shell wall, actuating mechanism connected to said gripping means for forcing and holding surface in firm gripe-ing engagement with the shell wall at the position of the floating roof in the tank, pipe means for introducing liquid into and for withdrawing liqold from the tank, and a control means for controlling said actuating mechanism, said mechanism b 9 adapted to move the gripping surface of the gripping means to either of two positions. one in gripping relation to the shell wall and the other in released relation to the shell wall, control including means responsive to the introduction or Withdrawal of liquid from the tank for causing said gripping means to move to said other position.

14. A. storage tank as defined by claim 13 in which said control means includes means responsive to a predetermined vertical movement of the floating roof for releasing gripping means.

15. A storage tank as defined by claim 13 in which means is provided adjacent said pipe means for operating said control means to release said surface of the gripping means from the shell Wall.

16. In a cylindrical floating roof stora e tank for liquids including an upright cylindrical shell and a buoyant floating roof therein of slightly smaller diameter than that of the inside of the shell and normally supported by the liquid in the tank, the improvement which comprises an airnular sealing and gripping :means includingan inflatable and deflatable means in sealed relation to the periphery of the floating roof and having a surface normally gripping the shell Wall, actuating mechanism connected to said gripping means for moving and normally holding said surface in firm gripping engagement with the 'shell Wall at the position of the floating roof in the tank, pipe means for introducing liquid into and for Withdrawing liquid from the tank, a control means associated with and cooperating with the actuating mechanism and having one position for forcing the gripping surface into firm engagement with the shell wall and a second position for eleasing the gripping surface from the shell Wall, and means for actuating the control device to "said second position in response to the introductioninto or withdr vial of liquid from the tank.

17. In a storage tank f'or'liquids including an upright cylindrical :shell and a buoyant floating roof therein of slightly smaller diameter than that of the inside of the shell, an annular sealing and gripping means attached in sea-ling relation to '"ie outer p rtien of the roof for gripping and sealing the roof with respect to the shell Wall, means for causing said gripping means to grip the shell well, said sealing and gripping means being adapted to permit limited vertical movement of the floating roof When said sealing and gripping means is in grip-ping engagement with the shell Wall, and control means for releasing the gripping means from its engagement with the shell Wall, said control means including means responsive to a predetermined Vertical movement of the roof when the gripping means is in gripping engagement with the shell Wall.

-18. In a cylindrical i floating roof storage tank for liquids which includes an upright cylindrical shell and 'a buoyant floating roof therein of slightly smaller diameter than that of the vinside of the shell, an-infiatable and defiatable sealing means mounted in sealed relation on the periphery of the roof between the roof and shell, means for supplying gas to said sealing means for eifecting its .infiation and sealing engagement with the shell wall, said sealing means being adapted to permit limited vertical movement of the floating roof when said-sealing means is in sealing engagement with the shell wall, said meansr'for supplying gas including a valve mechanism mounted on said roof, a trip means for said valve mechanism for releasing gas fro'rnsaid inflatable "means, and operating means mounted on the roof and normally engaging the shell for operating the trip means in response to -a predetermined movement of the operating means with respect to th'ershell.

WILBUR G, LAIRD.

CES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 213,688 Prindle Mar. 25, 1879 572,471 vBurnham Dec. 1, 1896 1,575,033 Bown Mar. 2, 1926 1,735,461 Haup't Nov. 12, 1929 2,014,264 Patrick e Sept. 10, 1935 2,085,752 Horton et a1 July 6, 1937 2,368,911 Laird Jan. 9, 1945

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