US2685982A

US2685982A - Seal hanger

Info

Publication number: US2685982A
Application number: US307655A
Authority: US
Inventors: Frederick D Moyer
Original assignee: Chicago Bridge and Iron Co
Current assignee: Chicago Bridge and Iron Co
Priority date: 1952-09-03
Filing date: 1952-09-03
Publication date: 1954-08-10
Anticipated expiration: 1971-08-10

Description

SEAL HANGER Filed Sept. 3. 1952 Patented Aug. '10, 1954 SEAL HANGER Frederick D. Moyer, Chicago, Ill., assigner to Chicago Bridge & Iron Company, a corporation of Illinois Application September 3, 1952, Serial No. 307,655

7 Claims. 1

This invention relates to a seal hanger and more particularly to a hanger device for supporting a. sealing ring about the periphery of a iloating roof in a liquid storage tank.

The storage of crude oil, gasoline and other petroleum products always presents the problem of evaporation and loss of marketable product, which in some instances, has been solved by the provision of iioating roof storage tanks. These tanks are cylindrical open-topped tanks of considerable size. The iioating room is, as its name implies, a closure which is buoyant and rises and falls with the liquid level in the tank. Ordinarily the roof is slightly smaller than the inner diameter of the tank leaving an annular space between the roof and side walls when the roof is centered in position. This space must be sealed and is usually provided with means to accomplish such result.

One of the most effective methods of sealing the space about a iloating roof is by using a ring of relatively thin material and holding this ring in sliding contact with the tank side walls. With the ring in such position, a gas imperviousriiexible sealing material may be bridged between the ring and the roof to seal the space therebetween. The present invention is concerned with the devices used in supporting such a sealing ring.

The invention will be described in a preferred embodiment by reference to the accompanying drawing in which the gure illustrates a broken vertical section through the periphery of the floating roof and the adjacent tank sidewall, illustrating one seal hanger in operative position for supporting the sealing ring against the side walls.

The figure of the drawing shows the tank side wall l which is composed of plates given a ourvature to conform to the cylindrical curvature of the tank. Liquid Il is shown within the tank and oats a closure member generally designated a oating roof i2. The particular roof illustrated has plates I3 forming a top deck, plates I4 forming a bottom deck and an upstanding substantially vertical rim i5 which is joined to the top and bottom decks to form a liquidtight enclosure. The top and bottom decks illustrated may be part of a pontoon or simply the structures of a double deck roof without affecting the particular application of the seal hanger to be described. Ordinarily all oating roofs are provided with an upstanding peripheral rim i 5 to give the roof a draught and to provide the roof with a capacity for storing rain water.

The sealing ring generally designated I6 is preferably constructed in accordance with the teachings of Goldsby and Orr Patent No. 2,586,813, issued February 26, 1952. This is made up of a number of shoes defined by portions of the ring between vertical extending exures.

The ring can ride against the side wall to provide a seal therewith and the flexures permit the ring to change its shape in response to a change in the shape of the side wall section against which it is pressed.

A sealing fabric I1 extends from the upper edge of the sealing ring to the peripheral upper deck edge of the floating roof. The fabric is preferably gastight and may be made of cloth impregnated with a synthetic rubber composition. This seal is provided with suicient length to permit the roof to move toward and away from the side walls of the tank without damaging the material.

The supporting device for the sealing ring, as illustrated in the gure of the drawing, rests mainly between the rim l5 of the floating roof and the side wall of the tank. The support for the sealing ring is provided by a lever and a link. Lever 2i) may be called an L-shaped member in that it has an integral leg or arm 2l extending inwardly under the roof. The level1 20 is pivotally attached to the sealing ring at 22 and eX- tends downwardly to the lower portion of the roof where a pin 23 which is secured to the lever 20, is caught in a vertical slot 24 formed by X- ture 2E attached to the lower portion of the roof rim i5. Thus, it will be obvious that the lower portion of lever 26, may travel vertically by moving the pin 23 in the slot 24 and may pivot about 22, its attachment to the sealing ring. The purpose of this type of connection will be obvious from the following description.

The link .30 is pivotally secured to the upper portion of the rim at 3l and is pivotally attached to substantially the mid-point of lever 20 between the points 22 and pin 23 on the lever 20. This point is shown at 32, it being understood that suitable brackets and pin connections are provided at the points indicated.

The pivotal connections of each of the lever and link respectively to the sealing ring and to the floating roof, namely points 22 and 3|, are in the same horizontal plane. The pin 23 which travels in slot 24, is vertically aligned with the pin 3| and retains this alignment at all times. This construction permits the roof to move laterally of the side wall of the tank without changing the vertical position of the sealing ring with respect to the side wall. Stating this proposition in another manner, the sealing ring willnot slide upon the side wall surface merely because the roof changes its position within the tank such that it moves closer to one side of the tank and away from the opposite side. Upon such movement of the roof, the pin 23 on lever 29 merely travels vertically in the slot 24 and the sealing ring maintains its same relative position.

The seal hanger is provided with means for pushing the sealing ring against the side Wall and at the same time, providing a force to center the roof within the tank. In the illustrated embodiment, these forces are provided by a tension coil spring 49. The integral arm. 2-l on lever 2a extends under the roof to a point where its inner end 26 is positioned under a cylindrical well 4l formed through the decks of the floating roof; A link 43 is pivoted at 44 to the arm 2l and extends upwardly within the well to a connection at 45 with the spring 4B. A- short link 46 provided with lock nuts 41 atfitsupper end. bears against a cap 48 on the yell to hold the spring in tension. An adjustment is provided by the nuts 41 to vary the pull of the coil spring.

In order to fully understand the operation of the forces provided by spring 4%, a mathematical consideration of the forces acting on the hanger may clearly demonstrate that a centering force is provided and that the force pushing the sealing ring against the side wall is independent of the Weight of the sealing ring or any forces acting. in the plane of the ring. These latter forces might be friction between the sealing ring and. side wall orresistance to movement caused by a protuberance on the side wall coming in contact with the sealing ring. For purpose of this illustration let W equal the weight of the sealing ring acting downwardly,

F equal the pull of the spring upwardly on the link 43,

l-I- equal the horizontal distance between the line of action of the force F and the pin 23 in the slot 24,

It equal the distance between the pivotal connections respectfully of lever 2l] and link 30 to thezsealing ring and the roof, and

V equal the vertical distance between the pivotal connection 22 of lever 20 to the sealing ring and the pin 23 in the slot 24.

These forces will result in an upward force on the pin 3l connecting link 3u to the roof of W minus F. In solving the balance of force on the hanger let R1 be equal to the force directed on the pivotal connection 3l inwardly on the roof and outwardly on the hanger system;

R2 be equal' to the force on the pin 23, inwardly on the roof and outwardly on the lever 2B of the hanger and.

R3 be equal to the force inwardly onv the hanger system and outwardly on the sealing ring directed at ,the pivotal connection 22.

The equation of moments about the pivotal connection 32 considering the forces on the lever 20 is:

rIihe equation of moments about the pivotal connection 3| on the whole hanger system is:

Toviind R3 consider the horizontal forces on the hangerl system as being in equilibrium. This gives:

R3 is the horizontal force at the pivotal connection 22 on the sealing ring. It will be noted thatthe forceF provided by the spring will vary inversely with relation to the distance. between the sidewall and roof, designated h. I-I varies very slightly and V varies also slightly. The coil spring 40 is chosen so that the force it provides varies considerably faster in proportion than does thev distance h. Inthis manner a centering force is built into the hanger for keeping the roof automatically centered within the tank. When the roof moves toward one side of the tank, the force pushing` the sealing ring against the side wall increases considerably at that side of the roof and correspondingly decreases at the diametrically opposite side of the roof, thus returning the rooiflto its center position.

It will also be noted from a considerationA of the force Re pushing the sealing ring against the side wall, is totally independent of W', which is the weight ofthe sealing ring or any force. acting in the plane of the sealing ring.. Thus the. ring is always forced against the. side wall with the same force irrespective of whether frictionA is greater or lesser than at other times and irrespective of the weight of the ring. The ring is alwaysV held inl the same vertical position with relation to the roof without regard to kthe position. of the roof within the tank. These advantages contribute to longer life for the sealing ring andinore successful operation of the sealing of the floating roof tank against the sidewalls of the tank.

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

I claim:

l. A hanger for supporting a sealing ring about the periphery of a floating roof in a liquid storage tank, comprising, a substantially upwardly extending lever pivotally connected to the ring and vertically slidably and pivotally connected to the roof, a link pivotally connected to -the roof and pivotally connected to the central. portion of said lever, the respective pivotall connections of said lever and link'to the roof and ring being in the same horizontal plane whereby no vertical force in the plane of the ring affects the pressure between the ringl and tank, an inwardly extending arm on the lower end of the lever and a coil spring secured to the inner end of said arm and to the roof providing an upwardly directed force on the arm pushing the ring against the tank through the lever and link.

2. A seal hanger for supporting a sealing ring about a floating roof in contact with side walls of a liquid storage tank, comprising, a lever pivotally connected to the sealing ring and vertically slidably and pivotally connected to the roof therebelow, a link pivotally connected to the roof in the same horizontal plane as said pivotal connection of said lever'and pivotally connectedy to the central portion of said lever, said pivotal connection to the roof and slidable connection to the roof being in the same vertical plane, an arm on said. lever extending inwardly under the roof, and spring means connected to said arm andsaid'. roof providing an upwardly directed force on the arm to urge said ring against said tank side walls through said lever and link.

3. A hanger. as specified in claim 2. wherein said spring means provides a force substantially inversely proportional to .the distance between the horizontally aligned pivotal yconnections of said lever and link.

4. A hanger as specified in claim 2 wherein said arm is integral with said lever and means are provided for varying the force o-n said arm.

5. In a liquid storage tank having a iioating roof and one or more shoes adapted to slidably contact the inner side walls of the tank, a seal hanger comprising a generally L-shaped member having one leg pivotally secured to a shoe and the other leg extending inwardly under the roof with the angle of the L being vertically slidably oonnected to the roof, a link pivotally connected to the roof in the same horizontal plane as the pivotal connection of the L-member to the shoe and pivotally connected -to the L-member substantially midway between its pivotal and slidable connections whereby no vertical force in the plane of the shoe affects the pressure between the shoe and the side walls, and spring means connected to the inwardly extending leg of the L-member yieldingly urging said leg upwardly to press the shoe against the side walls.

6. A seal hanger as specied in claim 5 wherein said spring means is positioned in a well in the roof and is connected to a pair of rods, one pivloted to the L-member and the other connected to the roof with adjustable means thereon for varying the force supplied by the spring means to the L-member.

7. A seal hanger as specified in claim 5 wherein said spring means includes a coil sp-ring capable of providing a force that increases at a proportionally greater rate than the rate at which the distance between the roof and shoe decreases when the hanger is in use.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,471,404 Boberg May 31, 1949 2,542,444 Wilkin Feb. 20, 1951 2,554,497 Moyer May 29, 1951 2,576,136 Moyer Nov. 27, 1951 2,587,508 Moyer et al Feb. 26, 1952