Method of sealing the space between the wall
US 3125346 A
Description (OCR text may contain errors)
March 17, 1964 E. J. POLTORAK 3,125,346
METHOD OF SEALING THE SPACE BETWEEN THE WALL OF A STORAGE TANK AND A FLOATING ROOF Filed Sept. 16, 1959 2 Sheets-Sheet 1 INVENTOR.
Emu. J'. POLTORAK POLTORAK 3,125,346 THE SPACE BETWEEN THE WALL NK AND A FLOATING ROOF March 17, 1964 METHOD OF SEALING OF A STORAGE TA 2 Sheets-Sheet 2 Filed Sept. 16, 1959 INVENTOR Emu 3'. Panama ATTORNEY United States Patent C) "ice 3,125,346 METHOD OF SEALING THE SPACE BETWEEN THE WALL OF A STORAGE TANK AND A FLOATING ROOF Emil J. Poltorak, Somerville, N.J., assign'or to Johns- Manville Corporation, New York, N.Y., a corporation of New York Filed Sept. 16, 1959, Ser. No. 840,380 2 Claims. (Cl. 277-1) This invention relates generally to the sealing of clearance space between spaced members. More particularly, it relates to improvements in floating roof seals employed in connection with volatile liquid storage tanks.
A desideratum in roofs, used with the above referred to tanks, is a construction which will reduce evaporation losses, deter contamination, and eliminate fire hazard.
Fire hazard is eliminated by providing a floating roof which will move with the changing level of the liquid and thus minimize the formation of explosive vapors.
In order to accommodate the movement of the roof in correspondence to the changing liquid level, clearance space is provided between the roof and the wall of the tank. Provision must then be made to adequately seal this clearance space to reduce the tendency of the liquid to evaporate and to deter the possibility of foreign substances falling through the space and contaminating the stored liquid.
Tanks of the type contemplated by this invention are generally of large diameter, extending as much as 100 ft. Consequently, the contours of both the tanks and the roofs are likely to deviate from a regular pattern and produce an irregular clearance space.
Such tanks are also subject to adverse weather conditions. Therefore, it is preferred to provide insulation for the large liquid surface, particularly to prevent boiling losses which may be occasioned by rising temperatures. In large diameter tanks, it is readily apparent that any sealing construction involves a material handling problem, not only because of the bulkiness of the sealing material but also in having the material conform to the tank configuration.
Accordingly, a further desideratum in floating roof seal construction is the provision of a seal comprising low density insulating material which can conform to any preferred configuration and which is sufficiently resilient to respond to deviations from the preferred configuration, and one which can be formed in situ to reduce any material handling problems.
Heretofore, various complicated devices have been suggested to seal the space between the tank shell and the roof of fluid storage tanks. One of these devices employs a steel sealing ring in combination with pantograph hangers which apply pressure at intermittent vertical flexures against the tank sidewall. A continuous fabric is then used to close the space between the sealing ring and the roof. Such a construction presents several disadvantages, among which are: complexity and difficulty in constructing complementary sealing surfaces; great weight of the sealing apparatus; and metal to metal contact in a volatile vapor environment.
Inflated tube seals around the periphery of floating roofs have also been suggested heretofore to form an airtight construction which would deter evaporation of the 3,125,346 Patented Mar. 17, 1964 stored liquid. However, a disadvantage concomitant with inflated seals is that they are subject to puncturing. Punctures may be ocacsioned by abrasion of the tube as it moves along the tank wall, by foreign articles which have lodged between the seal and the wall, and by other foreign instrumentalities.
Another design which has been suggested to compensate for irregularities in construction is one which employs adjustable roof sectors together with a series of rubber wipers forming the seal between the roof and the tank sidewall. Such rubber wipers are very susceptible to being disturbed or dislodged by foreign elements and consequently disrupt the sealing engagement. Furthermore, the wipers, per se, do not offer suflicient resilient resistance to the adjusting action of the roof to center the roof in relation to the tank. Hence, there may exist a very narrow spacing between portions of the roof tank peripheries and a wide spacing between other portions and thus reduce the effectiveness of the seal.
In accordance with the above, an object of the present invention is to provide a method of making a non- ,metallic puncture proof sealing or packing for use between spaced members which will automatically adjust itself, without the need of complicated devices, to irregularities to maintain sealing engagement between the members.
Another object of the invention is to provide a method of making a packing for use in connection with volatile liquids which is not adversely affected by such liquids.
A further object of the invention is to provide a method of forming a puncture proof sealing member for sealing the space between a tank and a floating roof which can be carried out in situ to alleviate handling problems.
Still another object of this invention is to provide a method of making an improved floating roof seal construction which will overcome the disadvantage of prior construction.
One feature of this invention resides in a foam filling or core bounded by a fluid impervious and flexible sheathing. A subsidiary feature, is the provision of a foam filling which is self-adhesive to its sheathing.
Another feature of this invention involves a buoyant puncture-proof sealing material having suflicient resiliency to respond to deviations from a preferred contour and yet maintain sealing pressure and engagement with its associated elements throughout their peripheries.
Still another feature of this invention resides in a foam filling which may be produced in situ and will conform to any desired contour, being limited only by the confines in which it is placed.
The above and other objects and features of this invention will be understood more fully from the following detailed description when read with reference to the accompanying drawing wherein:
FIG. 1 is a fragmentary and cross-sectional perspective view of a typical sealing member contemplated by the invention;
FIG. 2 is a vertical sectional view of a floating roof seal construction embodying the sealing member of FIG.
' ing the seal to the floating member;
FIG. 4 is a view similar to FIG. 2 showing the seal in another position wherein it is subjected to an irregularity;
FIG. 5 is a vertical sectional view showing an alternate form of seal construction; and
FIG. 6 is a fragmentary elevational view of the seal, illustrating a method of injecting the foam forming elements.
A preferred embodiment of this invention to be described in detail involves a sealing member comprising a flexible fluid impervious envelope or sheathing having an inner resilient filling or core of urethane foam formed by reacting polyisocyanates with compounds containing active hydrogen. The sealing member is positioned 'between the wall of a volatile liquid storage tank and a floating roof and is preferably secured to the roof. The nature of the materials employed and the construction enables the sealing member to be formed in situ and thus conform to any dimensional irregularities in the tank androof.
Referring to the drawings, in FIG. 1 is illustrated a preferred embodiment of the sealing member, generally designated by the numeral 10. The member 10 is comprised of a casing or sheathing 12, of generally tubular or bulb configuration, with a tail portion 13. One leg 14 of the tail portion 13 may be made longer than the other leg 16 and provided with holes 17 to facilitate subsequent mounting.
In order to resist deterioration by abrasion, portions of the sheathing may be increased in thickness to provide wearing surfaces 18. It will be apparent that the wearing surfaces 18 may also be provided by securing, as by bonding, additional suitable material to the main sheathing body.
Within the sheathing 12 is disposed a filling 20 of urethane foam. The foam is made by metering the correct amount of each ingredient to a mixing head, which may be of the form shown in FIG. 6 and designated by the numeral 20. The mixed materials are deposited in the sheathing 12, allowed to foam, gel and cure.
Urethane foams are made by reacting hydroxyl terminated resins called polyols with a diisocyanate and water in the presence of a catalyst such as N-methyl morpholine. First, the diisocyanate reacts with the hydroxyl groups in the resin to provide a means of terminating the resin with NCO groups. Second, the diisocyanate reacts with the water to liberate carbon dioxide. As the resin polymerizes, the liberated gas is trapped to form the foam. The reactions of isocyanates are exothermic and provide the necessary heat for curing.
As an alternative to the above process of forming the foam, the isocyanate and resin may be prereacted to form a prepolymer containing an excess of diisocyanate. The prepolymer may then be subsequently reacted with a water/catalyst mixture to produce the foam.
The above processes of forming the foam are described more fully in a bulletin Urethane Resilient Foams-Made from Polyestens, published by the Elastomer Chemicals Department of E. I. Dupont de Nemours & Co.
While the sheathing 12 is illustrated in FIGS. 1 and 2 to be generally of the bulb and tail configuration referred to above, it will be understood that the sheathing may be made to assume any desired configuration without departing from the spirit and scope of the invention.
The sheathing 12 may comprise a fabric such as nylon, asbestos, orlon or the like which has been coated with a compound having fluid impervious and temperatures and weather resistant properties. In one embodiment, the opposing ends of a width of the fabric are brought to gether in over-lapping or mutually opposing relation to form a tubular construction adapted for filling. The mutually opposing ends are then subjected to heat under pressure or vulcanization, to seal them together. Intermittent openings 21 may be provided to form peripheral inlets for introducing the constituents of the urethane foam. Otherwise, the constituents may be introduced through one of the longitudinal ends 22 of the formed sheathing.
The sheathing 12 may be preformed and brought to the situs where the foam may be formed before or after the sheathing is positioned in place, contiguous to the roof. When the foam is to be formed after the sheathing is positioned, it is preferred that the foam forming constituents be introduced simultaneously through a plurality of inlets.
However, a single mixing head and nozzle may be employed to fill one segment of the peripheral length of sheathing at a time. A segment corresponding to each inlet would comprise a longitudinal distance extending about halfway to the next adjacent inlets, indicated by phantom line 23, on either side of the inlet being filled.
Upon foaming, the polyurethane forms a strong bond with the sheathing. Such a bond deters lateral shifting of the core or filling and consequent disruption of the sealing engagement between the packing and adjacent members.
The sealing member or packing 10 is secured to the roof for movement therewith by suitable means such as clamp members 25. The clamp members 25 are provided with slotted holes 27 for adjustable positioning over stud members 29 of the roof 30. The gaps 31 between the clamping members 25 may be covered with suitable shields 33 indicated in phantom lines, if desired.
In the embodiment illustrated in FIG. 5, a substantially circular sealing member 10' is positioned between overlying portions 35 and 36 of roof 30' which extend at least to the vertical center line 37 of the member 10. The overlying portions together with curved member 39 define a pocket 40 for receiving the member 10 and thus obviate the need for additional securing means. However, if rugged service is expected to be encountered the member 10' may be additionally bonded to the roof with a suitable adhesive.
The construction of the invention, and the method of producing it provide several desirable advantages. The urethane foam provides a puncture proof and resilient filling for adapting the sheathing into movable sealing engagement with an associated wall that may have dimensional irregularities. The combination of the fluid impervious sheathing with the urethane foam provides a light weight buoyant sealing member which is particularly adapted for use in floating roof tank construction and one wherein the filler is self adhering to the outer covering or sheathing. The multicellular structure of the urethane foams is about half the weight of regular rubber compounds and is formed in a manner whereby most of the cells are interconnecting without the need of rupturing the cell walls. Since the reactions of the isocyanates are exothermic, no additional heat being required for curing, the forming of the sealing material may very conveniently be performed in situ. The formation in situ in large installations reduces material handling very substantially. The further provision of wearing strips on the flexible sheathing serves to increase the life of the sheathings without a material concomitant less in resiliency.
1. A method of making a seal for sealing the space between the wall of a storage tank and a floating roof which comprises: securing a flexible and fluid impervious sheathing to said roof; introducing a polyisocyanate compound together with a suitable catalyst into the interior of said sheathing, when said roof with the sheathing secured thereto is positioned in said tank; an expanding said sheathing and compressing the exterior surface of said sheathing into yieldable sealing engagement with said wall by the reaction of the polyisocyanate compound with said catalyst to produce an enlarged foam core.
2. A method of making a seal for sealing the space between the wall of a storage tank and a floating roof, comprising the steps of: impregnating a fabric sheath- References Cited in the file of this patent UNITED STATES PATENTS 6,974 Moat Dec. 25, 1849 15 6 Osgood et al. Aug. 12, Haupt Nov. 12, Hooper et al. June 28, Ferngren Aug. 30, Betts Oct. 27, Freyssinet Dec. 22, Goldsby et a1. Sept. 26, Allen Jan. 16, Slaughter Nov. 3, Fino Feb. 21, House Dec. 10, Alderfer et al. Aug. 11, Swick Nov. 17,