US2855122A - Floating roof seal arrangement - Google Patents

Description

Get. 7, 1958 m JLM mL 2,855,122

FLOATING ROOF SEAL ARRANGEMENT Filed April 8, 1957 United States Patent The invention :relatesito lield storage "tanks ofthe iioating roof variety and particularly to a seal arrange- 'ment therefor.`

As is wellknolwnin'the art, tanks 'of the type vemploy a cylindrical shell having an open top, said shell being 'substantially closed by a roo'f'which is `arranged to float on the product inthe 'tank.- Of course, tanks of this nature are relatively large and field erected and it is ytherefore rextremely'diificult to maintain'per'fect concentr'icit'y between "the roofand the shell with the 'result the 'froof is constructed somewhat smaller in diameter "than the shell so'verticalmovenient oft'sam'ewill b'e accommodated during filling and evacuation of product frorn "the tank.l I`he`differenc`e 'in diameter 'between the tank shell and the roof 'leaves an 'annular opening therebetween 'which is'usually provided withr'amovable sealing 'ar'rang'einentto'preventiproduct lo'ss due to evaporation and to aid in avoidingjcontamination of" ther product by entrance of 'foreignfmaterial into the annular'space.

It lis therefore `a lprimary object of the invention `to provide `a floating 'roof seal arrangement iof-'new land Vnovel design.

It is a further object ofthe invention to :provide 'a tight tting, flexible ltseal which 'is effective `in 'minimiz- Vin g product `loss through vapo'rization.

It is a further object of the invention to provide 'an arrangement 'of the type described wherein 'vapor l'space isreduced t'o a practical'minimum. The relatively small vapor space provided isso designed that itu'sually contains vapors of suchconcentration that Tthey yare `above the explosiverangeof stored volatileiproduct.' Another feature of thedesign is that the space above-'the seal is open 'and ventilated so escaping vapors will lnt become trapped itherein `in explosive concentrations.

lIt is an ladditional object of'the `invention Ito yprovide a=-no`vel seal arrangement that will effectively maintain the roof in a central `position in the tank and further will accommodate'maximum roo'f rtravel totheitopland the tank'therebyincreasing 4the effective capacity thereof.

These and other' objects of the invention will 4become apparent in the course of the following des'criptionand from an examination of the concerned drawings, wherein:

Figure -1 is `a fragmentary sectional vie`w` takenalong line 1-1 of 'Figure =2 fand illustrating the `plan arrangement of vsupporting fstructure,

Figure 22 is a fragmentary vsectional view in elevation and taken along line'Z ofFgure -1, and

Figure 3 is afragment'ary sectional view` in elevation and taken along "line33" of Figure 1.

Describing the invention in detail and'riirecting 'attention `first to'Figure `1,1itwill be -seen ythat the arrangement comprises `atcy'lindric'al tank 2, "s'aid tank `being formedof an upstanding shell `4 :having a ioating roof .therein.

ableto inantainftleroof 6 'n a centrali-locationthe arrangement and to facilitate vertical rriveheiit Eef thereof; in is `vthereforefthe-s panics@ er itue'lifrvenon A'to I.provide faecal-'arrangementwliidhfwill pro afnfr' tical and effective fseaLfinaintainhe roof c 15 cate-d in the tank, 'and reati-ee to alpfactic'aliniaaaffne fire hazardincide'ntltc "this l'type 'of storage. l

It will be noted that a p'e'iphrfalseal ringlz'niye formed of "a lplurality Vof horizontal' 'elongated Ashoes l'f4 placed in end to 'endrel'atio'nship to eaclrotlier. Inia preferred'embodiment the :shoesfare' joined in such a Zr'n'anner as to 'admit'fof some relative'fmotion therebetwe'e'nfor reasons that lare 'vi/elliA understood Iintthe art andnotfhre important. A 7

Directing attention vto Figures 'lf and 2, it will be seen received within the internal 'diameter of 'the `adjaerit endsfofithespring y l The arrangement is "provided with 'a fp lurality-@of Ahangers, indicated "generallyat 20, s'aid hangers 'c mprising longitudinal -exibleV fel'e'ments l22 liavin'g their upper -en`ds pivotally connected as at 24 to af bracket Z6 lower ends of the hangers 20 are pivotally connectedias at I28 yto r af-lower'end "off'a fthangersuppot channel 30 preferably by Welding to the rim 8 as dat 32.' fs'eal mounting plate 36 is annularly arrangedon-andsecured 'to the rim 8 at au point `-infupwardly spaced 'relation to the bottom: of the roof =6and 4slightly 'abovefthe normal surface- 10 ofthe stored product, @said pl'at'e 36 serviigas a mounting member forfafsefal fabric 38 'which has-'its inner edge `secured"'thereto Vbyi'n'eans of a plurality "of vclamping bars 140.. The other Vorout'er 'edge 'of the fabric 38 is securedto thesh'oes fl4-adjacent their npper'edges by v n'ieans `of `a `plurality yof fabric iclips 42. Itwill thus be understood that Vthe fabric 38 in 'combination with the plate 36 `is "arranged tor'cover 'the annular space S around the entire periphery 'ofthe roof. -Eac'h fabric yclip 42 is provided lwithia-n Linwardly'eX- 'tending shelf 44 arranged1to be in substantially perpendicular relationship to the inner :surface lof `the Eshoe1'4 and immediately below the fpoint vof connection between thefabric 38 'and the "shoe `14. The s'helf 441is spaced vslight1y above-the plate 36, as seen' in side elevational view and is arranged to supportthe-'fab'ic l38 andiprevent pockets for`the like from Aforming ftherein lwhich would accommodate `the collection kof lTrain Ywater "and other-foreign-material.

At a plurality oftlpoints fperipher'ally spaced -n the plate 36 and inboardly of the pointfof-conectioh'between the'plate`36 and the -relatededgeofithe fabric 38 a lplurality ofholesorapetures 48'rnaybe located. A pipe `arrangement 50 is welded'fto the 4lower-surface"of the `plate 36 so'as -to 'register lwith each "aperture n48. Each pipe arrangement 50i-'extends downwardly whereat it is -telescopically received in achamber -52 `de'iinedbfy ahousing'54 `which'lias an upwardly'facing'open end. "It willnbe -clearly understood 'that the aperturestt48, drain pipes 50 and housings 54 are peripherally located at con venient intervals around the entire circumference of the roof. It will be noted that the housing 54 is secured to the roof a short distance below the plate 36 and below the product surface 10. The pusher springs are also normally entirely immersed in the product to aid in the prevention of corrosion and deterioration thereof. The shoe 14 normally has its lower portion located in the product and extends only a short distance below the bottom plate or disk 56 of the roof 6. Further, the upper portion of the shoe 14 extends only a short distance above the surface 10 when the roof is in oating position in the tank. v

As a result of this structure a relatively shallow vapor space 60 is provided immediately above the surface of the product 10. Because of this smaller vapor space it has been found that the vapor concentration in the space 60 is very rich and therefore considerably above the usual explosive or combustible range. The space S above the fabric 38 is openly vented to atmosphere whereby vapor concentration therein is reduced to an effective minimum and usually below the explosive or combustible range. Thus the disclosed structure is effective to reduce to a practical minimum the possibility of rim re.

As noted the shelf 44 supports the outer portion fabric 38 a slight distance above the plate 36 thus preventing the collection of water and other foreign material thereon and accommodating drainage thereof to the plate 36 from whence it is carried downwardly via the pipes 50 and to the chambers 52. In the usual circumstance the chamber 52 is partially filled with water so that the lower edge of the pipe 50 is normally covered thereby rendering it impossible for vapors to escape through the pipe 50 to atmosphere. Noting that water has a specific gravity considerably higher than the product stored in the tank, it will upon lling escape from the chamber 52 and into the product whereat it will move downwardly to the bottom of the storage tank and there it may be drained or otherwise disposed of in any conventional manner.

Additionally, should a rim fire occur the space S is such that it readily accommodates the disposition of foam or other re ghting material to effectively and quickly smother the fire.

Thus it will be seen that we have provided a novel, highly eicient sealing arrangement for tank structures of the type described which provides a tight fitting, flexible seal arrangement which in the rst instance reduces vapor loss and secondly reduces the possibility of rim -res and explosions by reducing vapor space to a minimum so that trapped vapors collecting will normally be above the combustible range of the product and further will provide maximum venting from the space above the seal so that vapors in the latter space are normally below the combustible range of the stored product. The arrangement further accommodates maximum roof travel to the top of the tank thereby making available the full utilization of the maximum storage capacity of the tank without the possibility of the seal becoming functionally inoperative. It has been found that in structure of this type the tank can be lled to overflow and still the seal will functionally operate.

The invention as shown and described is by way of illustration and not limitation and may be subject to modifications without departing from the spirit thereof and thev scope of the appended claims.

What is claimed is:

l. In a seal arrangement of the type described, `a eld storage tank having a vertical cylindrical wall, a roof floating on the product in the tank and having a rim gen- .erally paralleling the wall and separated therefrom to define an annular space therebetween, a flexible seal shoe abutting the wall and opposite the rim, mounting means on the outer periphery of the rim extending out- .wardlytherefrom and located immediately above vthe normal level of product inthe tank, a flexible fabric arranged to close the annular space, said fabric having its inner edge connected to the mounting means in spaced relation to the rim, fabric clip means connecting the outer edge of the fabric to the shoe at a point vertically above the mounting means, as seen in elevational view, a plurality of liquid drains communicating with said annular space above the fabric, liquid collection means operatively associated with said drains, spring means interposed between and engaging the rim and the shoe, and hanger means having opposed ends operatively connected to the shoe and roof to oer support for the former from the latter.

2. A seal arrangement according to claim l, wherein said mounting means comprises a peripheral ledge secured to and extending outwardly from the rim, the inner edge of the fabric being connected to the ledge adjacent the outer edge thereof, and said fabric clip means comprises a shelf horizontally extending into the space from said shoe and underlying said fabric, said shelf being slightly vvertically above the ledge as seen in elevational view to cause the fabric to assume a downward slope from the shelf to the ledge and whereby foreign matter is prevented from collecting on the fabric.

3. A seal arrangement according to claim 2, wherein each of said hanger means comprises a member secured to the roof and extending downwardly below same, and a hanger arm having its lower end pivoted to the lower extremity of the member and its upper end pivoted to the shoe.

4. A seal arrangement according to claim 3, and including a drain compartment secured to the roof below the ledge, and pipe means secured to the ledge and communicating with the upper surface thereof and extending downwardly into the compartment.

5. In a seal arrangement, a field storage tank having a vertical cylindrical wall, a roof arranged to float on the product in the tank, said roof having a vertical peripheral rim defining with the wall an annular space around the roof, said roof being arranged so that the level of product in the tank when the roof is floating thereon is normally above the lower edge of the rim, a seal arrangement for the annular space arranged to provide a minimum vapor space in said annular space and above the level of said product, said arrangement comprising a ledge horizontally extending from the outer periphery of the rim and immediately above said product level, a sealing shoe having a vertical dimension substantially less than the'vertical dimension of said rim and arranged to abut the wall opposite the lower portion of said rim whereby the lower portion of said shoe is normally immersed in the product in said tank and the upper portion of the shoe extends only slightly above the level of said product in said tank, rigid members secured to the roof and extending below the bottom thereof, hangers having their lower ends pivoted to the members adjacent the lower extremities thereof, said hangers extending upwardly and outwardly as seen in elevational view and having their upper ends pivoted to the shoe at points at or slightly below the level of product in the tank, spring means compressively interposed between the rim and the shoe and arranged to engage the latter at the approximate vertical level of said points as seen in elevational view, and a seal fabric of exible material disposed in said space and having its inner edge connected to the ledge and its outer edge connected to the shoe slightly above the level of the ledge as seen in elevational view.

6. A seal arrangement according to claim 5, and including a shelf horizontally projecting into said space from shoe at a point slightly above the level of said ledge and below said fabric as seen in elevational view.

7. A seal arrangement according to claim 6, and including drain means comprising apertures in said ledge communicating with downwardly extending pipes, and compartments secured to the roof. and below the level References Cited in the ile of this patent UNITED STATES PATENTS Wiggins Apr. 18, 1933 Moyer Nov. 27, 1951 Ulm Mar. 6, 1956 Wiggins July l0, 1956 Ulm Aug. 6, 1957

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