US2756132A - Dry seal piston type gas holder - Google Patents

Description

y 1956 J. H. WIGGINS DRY SEAL PISTON TYPE GAS HOLDER 2 Sheets-Sheet 1 Filed Sept. 4, 1952 FIGS.

INVENTOR, y?! INS y W A TTORNE Y.

y 1956 J. H. WIGGINS 2,756,132

DRY SEAL PISTON TYPE GAS HOLDER Filed Sept. 4, 1952 2 Sheets-Sheet 2 FIG 9.

United States Patent DRY SEAL PISTON TYPE GAS HOLDER John H. Wiggins, Chicago, Ill.

Application September 4, 1952, Serial No. 307,936

1 Claim. (Cl. 48--176) This invention relates to dry seal piston type gas holders and other fluid storage apparatus, of the particular type or kind that are provided with a fabric seal for the space between the piston and the side wall of the container of the apparatus, and also equipped with abutment surfaces disposed in such relationship with said fabric seal that during the cycle of operations of the piston said abutment surfaces function as back stops that absorb pressure exerted on said fabric seal by the gases confined in the storage chamber of the apparatus. In general form or outline the above mentioned seal consists of a curtain like structure made of gas tight, flexible fabric, disposed and mounted in such a way as to seal the annular space between the piston and the container side wall and proportioned so as to provide for the rise and fall of the piston. It may consist of a relatively long or deep tubular or cylindrical member made in one piece or it may be composed of a plurality of tubular sections. In instances where the fabric seal is formed by a single tubular member, the portion of the container side wall located above the point at which the outer end of said tubular member is attached to said wall constitutes a stationary abutment surface or back stop for the fabric seal in certain positions of the piston, and the piston is provided with an upwardly projecting back stop against which the fabric seal is pressed by the gases in other positions of the piston. In instances where the fabric seal is composed of two tubular sections, one of said sections is attached to the container side Wall, the other section is attached to the piston and an additional, vertically movable structure provided with two concentrically arranged tubular shaped back stops is interposed between and attached to the two sections of the fabric seal, said additional or intermediate back stop structure being adapted to be reciprocated by the piston during the rise and fall of the piston. U. S. Pat. 2,606,824, dated Aug. 12, 1952, to Allen discloses a gas holder of the kind last referred to in which the fabric seal is composed of two sections attached to a vertically movable back stop structure positioned in the space between the piston and thecontainer side wall.

The fabric seal used in gas holders of the kind above described, Whether it be constructed in one piece or composed of a plurality of sections, consists simply of a fabric core impregnated and covered with rubber or the like so as to make it gastight. It may have a tensile strength of from 100 lbs. to 200 lbs. per linear inch before breaking and a stretch of from to 20% before breaking. I have discovered that there is an abnormally large stretch in the low range of tension; for example a tension of 2 lbs. per inch may cause a stretch of 1% and if said 2 lbs. per inch tension is held constant for several days, the fabric material of which the seal is constructed will increase its stretch and subsequently, when the load that caused the stretch is removed, the fabric does not come back, even closely, to its original condition. Now with greater tensions and especially in instances where the 2,756,132 Patented July 24, 1956 stored gases are of such a nature as to abnormally swell the rubber coating of the fabric, I find that in instances Where the fabric seal is formed by a single tubular member attached at one end to a back stop on the piston and attached at its opposite end to a back stop or abutment surface on the container side wall, said fabric seal will take a permanent stretch up to 4%. For example if the circumferential length of the container side wall is ft. and the circumferential length of the seal when it is first put into use was also 100 ft. so as to insure that it will lie snugly against said side wall, a few months service may cause the seal to stretch circumferentially approximately 4 ft. and thus change from a tubular or cylindrical member of approximately the same circumferential length as the container side Wall, into 'a member whose circumferential length is 4 ft. greater than the circumferential length of said side wall. During the rise and fall of the piston, folds, wrinkles, or creases form in the seal When the gases press it tightly against the previously mentioned side wall and abutment surfaces, due of course to the fact that the seal is 4 ft. longer, circumferentially, than the'container side wall. The flexing and bending of the seal as it folds and unfolds in adapting itself to the abutment surfaces which back it up, tends to break down the rubber coating of the seal and cause it to crack, thereby exposing the fabric core of the seal to the direct action of the gases with the result that the gastight life or period of usefulness of the seal is reduced.

The main object of my invention is to provide a piston type gas holder of the general kind above referred to, whose gastight fabric seal is of such construction that objectionable or destructive wrinkles, creases or folds will not form in same due to excessive permanent circumferential enlargement or elongation of the seal.

Another object is to provide a piston type gas holder of the general kind above referred to, whose fabric seal is of such construction or design, that the tension, flexing and pressure to which it is subjected when the gas holder is in use, will not injure or impair the efliciency of the impervious coating of the seal that is relied upon to make the seal gastight.

Another object is to provide a dry seal piston type gas holder which is of such construction or design that even after long or continuous usage the fabric seal will still be in substantially its original condition and will not excessively wrinkle or crease when it engages the pressure absorbing abutment surfaces with which it co-acts, during the rise and fall of the piston.

Still another object of my invention is to provide a substantially tubular shaped, curtain like fabric seal for gas holders, that is equipped with a novel means of simple design and construction for effectively preventing excessive permanent circumferential enlargement or elongation of the seal, due to stretching of the fabric core of the seal. Other objects and desirable features of my invention will hereinafter be pointed out.

Fig. l of the drawings is a fragmentary, vertical transverse sectional view of a dry seal piston type gas holder embodying my invention and equipped with a fabric seal formed by a flexible, curtain like member of tubular or cylindrical form that is adapted to co-act with twoabutment surfaces or back stops, namely a stationary back stop formed by the upper portion of the container side wall and a vertically movable back stop carried by the piston, said view being taken on the line 11 of Fig. 2.

Fig. 2 is a horizontal sectional view taken on the line 2-2 of Fig. 1, looking in the direction indicated by the arrows.

.Fig. 3 is an enlarged, fragmentary side elevational view of a portion of the fabric seal, looking at the air '9 on the :piston. :piston and also when said piston is in its lower most poopposite direction.

3 side of same and broken away so as to more clearly illustrate one of the tension bands attached to the seal so as top'revent circumferential enlargement or elongation of said seal.

Fig. 4 is a sectionaLview of the fabric seal taken on the line 4-4 of Fig. 3. Fig. 5 is a sectional viewtaken on the line 5-5 of Fig.3.

Fig. 6 is an enlarged side elevational view illustrating one means that may be used to attach the tension bands to the seal. e I

Fig. 7 is an edge view of the parts shown in Fig. 6.

Fig. 8 is an enlarged, fragmentary sectional view showing how the fabric seal is preferably attached to the container side wall, and Fig. 9 is a fragmentary, vertical transverse sectional view illustrating my invention embodied in a gas holder which differs from the gas holder shown in Fig. 1, in that the fabric seal is composed of two tubular or cylindrical sections, and in that an additional or third back stop is employed, said additional back stop being interposed between and attached to the two sections of the seal and said additional back stop being .provided with means that causes it to move vertically with the piston during a portion of the cycle of operations of the piston.

Referring to Figs. 1 to 8 of the drawings, the reference characters 1, 2 and 3 designate respectively the side wall, the bottom and the roof of the container of the apparatus. The piston 10 reciprocates vertically in the container and .the annular space between the piston and the side wall 1 of the container is sealed by a curtain like, gas tight seal .11 of substantially tubular or cylindrical shape in gen- .eral outline, attached in a gas fight manner to an intermediate portion of the container side wall and to the peripheral portion of the piston. In the form of my invention herein shown the outer edge of the seal 11 is secured by seal bars 5 and bolts 6 to a vertically disposed flange on an attaching member 4 of angle shape in cross section that extends circumferentially around the container side wall 1,.and the inner edge of said seal is secured in a similar manner to an annular flange or rim During the downward stroke of the sition as shown in full lines in Fig. 1,. the gases in the storage chamber of the apparatus press the curtain like seal 11 tightly against a cylindrical shaped back stop or abutment surface rigidlyattached to the piston 10 and projecting upwardly from the top side of same, and dur- :ing the upward stroke of the piston and also when the piston is in its. uppermost position as shown in broken lines in Fig. 1, the gases in the storage chamber press the seal 11 tightly against a stationary, cylindrical back stop a or abutment surface formed by a portion of the container wall 1 located above the point where the seal 11 is attached to said wall. .piston is of such construction that the seal contacting surface of same is made up of a series of vertically disposed corrugations, flutes or grooves separated from each other byverticalridges, so that when the seal is pressed into snug engagement with said surface the sinuous shape of .same will tend to prevent the seal 11 from creeping Preferably the back stop on the circumferentially, first in one direction and then in the In the gas holder herein illustrated, the back stop on the piston 10 is formed by a series of vertically disposed posts or abutment members 8 arranged in spaced relation as shown in Fig. 2 with their lower ends rigidly attached to the piston and their upper ends attached to a stiff girder 7 as shown in Fig. 1.

As previously stated the curtain like seal that is universally used in dry seal, piston type gas holders is made of fabric impregnated with rubber to make it gas tight,

I and the pressures and stresses to which such. a seal is seal to such an extent or degree that folds, wrinkles or creases are bound to form in same when the gases press the seal into snug engagement with the abutment surfaces or back stops provided for the seal. Also as previously stated the constant or continual folding and un' folding of the creases and wrinkles in the seal tend to break down and crack the rubber coating of the seal, thereby making the seal unsafe and in some instances useless.

My invention has for its main object, to overcome or eliminate the above mentioned inherent defect or hazard of the conventional fabric seal generally used in dry seal, piston type gas holders. To this end I have devised a tubular or cylindrical seal composed of a fabric core impregnated and covered with an elastic, impervious substance such as rubber or an equivalent material, and provided with one or more tension bands that prevent excessive permanent circumferential elongation or enlargement of the core, due to stretching the fabric, each of said bands being of such construction that it will not distend or elongate circumferentially permanently, and being incorporated in or attached to the fabric core in circumferential relation with the core. When a plurality of bands are used said bands are arranged in vertically spaced relationship with each other. It is essential that each band have a tensile strength per unit of height or per inch of height in excess of the tensile strength per unit of height or per inch of height of the fabric core. The said tension bands are herein illustrated as consisting of limber or flexible annular bands having a width of from one-half an inch to several inches attached preferably to the air side of the fabric core of the seal, and made of material or constructed in such a way that they have great tensile strength (from 1000 lbs. per inch to 5000 lbs. per inch, or even more) depending on the size of the gas holder and the pressure of the gas in same. In addition to being limber and of a tensile strength far greater than the tensile strength of the fabric, said tension bands must be of such a nature or construction, that they have nearly perfect elastic properties so that in the event they stretch slightly under a tension far greater than they are normally subjected to they will always, and for their full life, return substantially to their original circumferential length when the abnormal tension subsides. Generally each tension band will be made of several ring shaped elements made of small diameter cable, embedded in rubber that is molded so as to produce a substantially flat casing that snugly surrounds the fabric core of the seal and which is securely attached to same by an adhesive or by fastening devices. Or said bands may be made of chains or even single bare cables.

I have herein illustrated the seal 11 as being provided with numerous horizontally disposed tension bands, each of which comprises a plurality of ring shaped elements 18 made of cables, ropes or cords and arranged in superimposed relation in a casing 19 made of rubber as shown in Fig. 3. Said bands are attached to the seal at vertical intervals sufficiently close to give to the seal the control I desire. These intervals may be from about 2 ft. to 5 or 6 ft. depending on the size of the seal, the pressure of the gasholder and the type of gas stored. Such gasholders are built in sizes from a few hundred C. F. to several million C. F. And they may be built in different shapes for the same volume, i. e., tall and narrow or short and wide.

Said tension bands in the roundabout direction, may be attached to the seal 11 either continuously or at intervals. If they are attached at intervals they must be attached on the outside of the loop of the seal in order to function properly. They may be cemented to the seal or attached to it mechanically, i. e., by bolts or clamps. In any case it is better to attach the bands on the outside or air side of seal since the seal is pressed hard against the band by the internal gas pressure whenever the seal lies against the back stop portion of the container wall or against a vertically movable abutment surface,,..and hence little or no .stress is thus set up between the sealandthe bandsby 'the seal has crept a slight amount sidewi'se. .Thus as each band moves out toward the side wall land receives lts full tension, the seal at that band is properly'positioned circumferentially. v

Now consider the case Where the container side wall is 6" out of round and consider a 40 ft. radius-container where, the band is constructed to the circumferential length of 39 11" radius. The band sincefit' is free, triesto go But This means container side wall for some distance and at other places willbe more than 1 inch away from the wall.

Thus depending on how the length .and stretch of the tension band is designed and how well built is the container wall, the band may bear against the wall in many places. Container side walls sometimes havellocal buckles in the plates which will throw parts of the wall 1 inch or more off a true radius. But to build the wall even closely to a true circle would increase the cost very much.

The ideal case would be to have a tension band which would have sufficient tension in it to position the seal 11 circumferentially, lie within say inch of the wall all around and also contract perfectly each time the tension is released even after the seal had been in use several years. But in this type of structure it wouldbe difficult to build such a ten-sionband.

In practice the bands will be held away from the side wall an appreciable average distance-1" to 3". In some places the bands will be closer to the sidewall than at others and in fact may bear against the sidewall locally due to forces applied to the band by the seal or because the sidewall is out of round or buckled or all three conditions can occur simultaneously.

In Figs. 6 and 7 of the drawings I have shown one means that can be usedfor attaching the tension bands to the seal 11, said means comprising small metal plates 14 overlapped by strong fabric pads 20 that are securely attached by an adhesive to the air side of the seal, a stud 15 on each of the plates 14 that projects outwardly through the rubber casing 19 of the control band, a washer 1-6 on said stud arranged in overlapping relation with the casing 19 and a nut 17 on the stud that bears against a washer or clamp plate 16. If the tension bands are attached to the air side of the seal 11 at intervals of from one to three feet along the height or depth of the seal and if the piston is provided with a vertically fluted or corrugated seal contacting surface of the kind previously referred to, the tension bands will not interefere with the flexing of the seal as said seal is progressively stripped off the back stop on the piston and progressively applied to the back stop portion of the container side wall during the upward stroke of the piston, and progressively stripped off said side wall and progressively applied to the back stop on the piston during the downward stroke of the piston.

In order to make it clear that my invention is not limited to use with a gas holder of the kind shown in Fig. 1 in which the fabric seal consists of only a single tubular or cylindrical member that is adapted to be backed up by a portion of the container side wall and by a back stop attached to the piston, I have shown in Fig. 9, a gas holder that differs from the one shown in Fig. l in the following respects, namely (a) the fabric seal is composed of two tubular or cylindrical sections 11a and 11b, (b) an additional vertically movable back stop structure provided with a horizontal annular base piece a equipped with two upwardly projecting back stops or surfaces 8a and 8b is arranged in' the space between the piston and the container side wall, the back stop 8b is supported by upwardly projecting posts 23 on the base piece 10a, (c) said additional or intermediate back stop structure is provided at its upper end with an annular girder 21 arranged in overhanging relation with the back stop on the piston so that during the upward stroke of the piston theback stop on the piston will engage said girder 21 and impart upward movement to said additional or intermediateba'ck stop structure, and

(d) the container is provided at its lower end with a supporting structure 22 that is set some distance above the bottom of the container so as to serve as a stop that arrests or limits the downward movement of said additional vertically movable back stop structure during the downward stroke of the piston and permits said structure to remain at rest momentarily during the first portion of the upward stroke of the piston. The base piece 10a of said additional back stop structure is interposed between the seal sections 11a and 11b and attached'to same, the section 11a is attached to the sidewall of the container and the section 1111 is attached to the piston. The back stop or abutment surface So on said intermediate back stop structure is preferably vertically fluted or corrugated and it co-acts with the container side wall to back up the seal section 11a in certain positions of the piston. The other abutment surface 81) on said back stop structure is preferably uncorrugated or unfiuted and it co-acts with the back stop on the piston to back up the seal section 11b in certain positions of the piston. In all other respects the gas holder shown in Fig. 9 is substantially the same as the gas holder shown in Fig. l and accordingly I have used similar reference characters to designate corresponding parts of both gas holders.

From the foregoing it will be seen that my invention is restricted to a piston type, pressure gas holder of the particular kind in which the sealing means for the piston includes or comprises at least one substantially tubular experienced with piston type pressure gas holders of the particular kind above referred to, due to the fact that the pressure to which the fabric sealing element was subjected produced a permanent circumferential enlargement or stretching of the fabric of which the sealing element is constructed. This increase in the circumferential length of the sealing element (caused by permanent stretching of the fabric) caused deep wrinkles or folds to form in the sealing element when said element was pressed into tight engagement with the inner abutment member and eventually these folds or wrinkles were converted into sharp creases that often cracked and produced leaks in the sealing element.

I have overcome or greatly reduced the liability of leaks developing in the fabric piston sealing means of gas holders of the kind above referred to, by attaching to the sealing element one or more circumferential tension bands of the kind herein illustrated and described. In my improved gas holder each tension band must be exceedingly limber and must be able to rotate without resistance (like a string) through of arc about its own centrally located circular axis, so that it may pass from the outer abutment member over the upwardly disposed loop of the fabric sealing element (rotating about said axis) and moving into engagement with the inner abutment member. During the above described operation, the effective length r (i; e., a plan view) of the tension hand must shorten from 1 ft. to 8 or 9 ft., depending on the size of the gas holder, in gas holders of the kind where the piston sealing means consists of a single tubular shaped fabric sealing element arrangedbetween an abutment member on the piston and an abutment member on the container side wall. The tension hand must be capable of being pressed against both the inner and outer abutment members, and in order that the tension band cannot be kinked or bent in a haphazard. manner when it lies against the inner abutment member, said member must be of such construction as to cause the tension band and the portion of the sealing element to which it is attached, to take a predetermined sinuous shape, which shape (in circumferential length) must be at least as long as the circumferential length of the band.

As previously explained my invention relates to gas holders of the kind shown in Fig. l and also to gas holders of the kind shown in Fig. 9. Accordingly as the piston sealing means will always comprise at least one tubular shaped fabric sealing element interposed between and attached to two concentrically arranged, cylindrical abutment members or back stops, I have used this terminology in the claims to cover and apply to both forms of gas holders herein illustrated and described. In a gas holder of the kind shown in Fig. 1, the term inner abutment member is the one carried by the piston and the outer abutment member is the one formed by or carried by the side wall of the container, In a gas holder of the kind shown in Fig. 9, the inner abutment member may either be the one carried by the piston or the one designated 8 that is attached to the vertically movable abutment strucure positioned between the piston and the container side Wall and adaped to be raised and lowered by the piston. Similiarly in a gas holder of the kind shown in Fig. 9, the o-uter" abutment member may either be the one formed by or carried by the side wall of the container or the one designated 8 that is attached to the vertically movable abutment structure arranged in the space between the piston and the container side wall.

Having thus described my invention, what I claim and diameter of said cylinder so that the perimeter of said piston is spaced radially inwardly with respect to the inner surface of said cylinder, an upwardly extending peripheral skirt on said piston, an axially extending tubular diaphragm of gas impervious flexible material having a circumference in its unstressed condition no greater than the inner circumference of said cylinder, said diaphragm having one of its ends secured in gas-tight relation to the periphery of said piston and its other end secured in gastight relation to said cylinder for sealing the space between said piston and said cylinder to prevent escape of gas thercbetween, a substantial portion of said tubular diaphragm encompassing and being pressed by the pressure of said gas against said skirt when said piston is in its lower position and being pressed by said gas against the inner surface of said cylinder when said piston is in its upper position, said diaphragm being progressively turned axially inside out as said piston is moved from one of its positions to the other so that only a given surface of said diaphragm contact-s said skirt and said inner surface of said cylinder, and a plurality of axially spaced apart flexible circular hoops intimately bonded to said given surface of said diaphragm and extending circumferentially thereabout, each of said hoops having a fixed circumference n0 greater than the circumference of said inner surface of said cylinder so as to prevent permanent stretching of said diaphragm by the pressure of the gas and thus prevent the formation of wrinkles in said diaphragm when said diaphragm is in contact with said inner surface of said cylinder, said hoops being sufficiently flexible and pliable to permit said hoops to rotate about their respective centrally located circular axes as said diaphragm is turned axially inside out.

References Cited in the tile of this patent UNITED STATES PATENTS 2,466,951 Hunter Apr. 12, 1949 2,490,767 Allen Dec. 13, 1949 2,554,765 Allen May 29, 1951 2,554,767 Allen May 29, 1951 2,571,372 Martin Oct. 16, 1951 2,584,953 Wiggins Feb. 5, 1952 2,606,824 Allen Aug. 12, 1952 2,633,172 Teiber Mar. 31, 1953 FOREIGN PATENTS 676,844 Germany June 13, 1939 798 Great Britain of 1873 314,920 Italy Feb. 9, 1934

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