US 3554227 A
Description (OCR text may contain errors)
United States Patent  Inventor William C. Yocum Mount Lebanon Township, Allegheny County, Pa.
 App1.No. 814,472  Filed Dec.30, 1968  Patented Jan.l2, 1971  Assignee Superior Valve Company Washington, Pa. Continuation-in-part of application Ser. No. 672,273, Oct. 2, 1967, now abandoned. This application Dec. 30, 1968, Ser. No. 814,472
 FAIL-SAFE SHIPPING CONTAINER FOR COMPRESSED FLUIDS 7 Claims, 9 Drawing Figs.
 U.S.Cl... 137/588  Int.Cl F16k45/00  Field olSearch 137/588, 614.17,614.16,614.18;251/368,337
 References Cited UNITED STATES PATENTS 1,453,471 5/1923 Tarte 251/337 2,178,444 10/1939 Ware..... 25l/337X 2,729,228 l/1956 Stevenson 137/614.18X 2,771,093 11/1956 Wilson 137/614.17X 2,820,473 l/1958 Reiners 137/614.17X 2,962,038 11/1960 Bird 137/6l4.17X
Primary Examiner-Samuel Scott AtrorneyBuell, Blenko and Ziesenheim ABSTRACT=Apparatus for shipping and storing compressible fluids and for controlled withdrawal and use of said fluids without danger of explosion. Specifically disclosed is apparatus comprising thin-walled metallic container means and thermoplastic valve means therefor. Container means has an opening therein for receiving thermoplastic valve means whereby fluids are sealed within container means when the valve means is closed. Thermoplastic valve means has constructed therein safety valve means including (i) first and second bores, (ii) sealing means interposed between said bores, and (iii) spring means urging against said sealing means at a selected pressure to block fluid passage between said bores whereby fluid is contained in the container means at internal pressures of fluid within the container means below the selected pressure. Thermoplastic valve means is of a composition which is at least deformable under pressures up to said selected pressure when heated to an elevated temperature above normal working temperatures but below the annealing temperature of the container means.
a a I5 8 SWEET 1 BF 2 Fig.4.
INVENTOR William C. Yocum PATENTEDJANIZIHII 3.554.227
SHEET 2 [1F 2 INVENTOR William C. Yocum .vided with a valve from which the fluid can be withdrawn as necessary, as for introduction into a refrigerating circuit. Such tanks are quite commonly nonrechargeable single trip tanks intended to be discarded and scrapped when they have been emptied. 5
When such tanks are properlyfilled'anadequate expansion space is maintained above the liquid forjexpansion. Proper filling in a commercial plant is commonly controlled by weighing the tank and contents until the proper quantity of fluid has been introduced into the tank. Under such conditions, the major portion of the tank contains the-refrigerant in liquid form with a smaller portion containing gaseous uncondensed refrigerant.
It is becoming the practice in the refrigerant industry to construct single-trip nonretumable containers for shipping refrigerants, such as flourocarbons and the like, with relatively thin walls. Typical is a container having steel or aluminum walls of a thickness 0.035 to 0.100 inches- Here, asis the case with all compressed fluids in closed containers, the danger of explosion exists. ln practice the danger is multiplied since, although such containers are intended to be used for a single trip only and despite explicit instructions to that effect, in many cases the containers are improperly and often illegally recharged for further use. Such unauthorized and usually unskilled recharging results in the possibility that I little or no room for expansion is left in the container and, in that case; even the addition of a small amount of heat can cause a dangerously, high hydrostatic pressure to' build up within the container. i
lt-has heretofore'been common practice toprovide such containers withvarious types of safety devices in an effort to overcome dangers of explosion presented by too high a pressure. It has been proposed to place a plug of fusemetal into the valve upon the tank. Fuse metal is well known and melts'at about 157 When such a plug melts it'will provide an escape path for fluid within the tank. In case of aifire on the premises where such tanks are stored, the fuse metal-will melt and allow the contents to discharge. When a tank'is'overfilled, however, and there is only local or solar heating, adangerous pressure may be encountered when the fuse metal plug is far below its melting temperature. Since fuse metal is entirely insensitive to pressure rises due totemperatures below its melting point, it is an unsatisfactory safety device where low temperatures and high pressures exist. Additionally, the incorporation of a fuse metal plug into a conventional metal valverequires the boring, or provision by other means, of a seat fortheplug or a fitting of the plug within the valve. Valves of that'type are expensive and it is impracticalto use such-valveswith throw-away containers such as thin-walled single-tripcontainers for shipment of compressed fluids such as compressed refrigerants lt hasalso been the practice to place a spring-loaded relief in a port in-the side of a'brass valve of conventional design. Such an arrangement will allow escape of fluid in case of overpressure but does not act to completely vent the container in case of fire. Moreover, it is an expensive and, sometimes, awkward arrangement.
After the liquid contents of a container have escaped, the pressure within the container is reduced. Dueto the reduced pressure a spring-loaded safety device will reseal, usually at a.
pressure substantially greater, than atmospheric and thereby trap vapor within the container. F or example, a spring-loaded safety valve designed to release (open) at 480 psi. is required by the Bureau of Explosives for use inthe Department of Transportation to have a minimum reseal pressure of 70 per cent of its flow rating (opening) value, or 336 psi. Thus, the container after expelling its liquid contents will retain vapor exerting a pressure of 336 p.s.i. against the walls of the vessel. Under normal conditions a thin-walled shipping container is strong enough to prevent explosion at that pressure. However.
under fire conditions the walls of such containers are subjected to rapid increase in-temperature because there is no contained liquid refrigerant which normally would absorb the heat as heat of vaporization and thereby delay temperature rise in the container walls. Accordingly even brief exposure of an empty or nearly empty container to fire may cause the temperature to rise tending to-anneal and soften the container walls leading to the possibility of rupture and explosion at an abnormally low pressure; Moreover, such heating and annealing may be localized due to' a sudden fire on one side of the container.
A need therefore exists for an economical fail-safe thin walled container for compressed fluids, suitable for single-trip applications, having a safety device which will not only expel its liquid contents'to compensate for dangerous overloading pressures due to temperature rises encountered in normal use. but which will also expel the container's entire contents under fire conditions and the like where the danger of annealing of vessel walls exists.
' l have invented apparatus for shipping and storing compressible fluids and for controlled withdrawal and use of such fluids which is explosion or ruptureproof under all conditions, and is economical and practical in. use. 1 provide apparatus comprising a thin-walled metallic container having an opening therein for receiving thermoplastic valve. means for sealing fluids within said container and for controlling fluid flow therefrom. The thermoplastic valve means includes springloaded safety valve means comprising (i) first and second bores in said thermoplastic valve means which together forma passage extending from within said container to the outside thereof, (ii) sealing means interposedbetween said first and second bores, (iii) yielding means urging said sealing means at a selected pressure to a position blocking saidbores whereby said sealing meansprohibits fluid passage from saidsecond to said first bore and whereby said compressible fluid is con" tained within said container means at fluid pressures below said selected pressure; The container means has thin metallic walls, and the thermoplastic valve means is of a composition which is at least deformable under. pressures upto said selectedpressure when heated to an elevated temperature above normal working temperatures but below the annealing.
temperature of the container.
ln another aspect of my invention, l provide'preferred valve apparatus for effectively protecting against excessively. high pressures in fluid containers and the like. I provide a valveassembly having valve body, valve stem means rotatably engaging the valvebody, and fitted withina bore in the valvebod'y;
safety valve means fitted within the bore of the valve stem' means and spring means'yieldingly closing the safety 'valve' means. I preferably form the valve body ineansandthevalve stem means of two integral pieces of plastic'material l provide the valve body means with a fitting surface adapted'to connect to a fluid container and a discharge passage for: discharge-10f:
fluid from the valve assembly. I prefer ,to-provide aborein'the valve body which becomes of smaller diameter, toward: the;
threadably engage the valve body and form a sealing 'relation ship with the valve body at'a valve seat formed by the' 'differential diameter of the valve body bore. 1 further -provide a bore, including a valve seat, within'the valve stemmeanse l provide a valve seat internally of the. valve stemmeans and' provide sealing meansyieldingly urged against'said valve seat;
bodiments thereof wherein:
FIG. 1 shows a sectional view of a novel preferred thermoplastic valve means having a spring-loaded safety valve means useful in my invention wherein the spring-loaded safety valve means is located in the valve stem;
FIG. 2 is an enlarged view showing the safety valve seat in the valve stem means of FIG. 1;
FIG. 3 is a side elevation taken in section of a safety valve cage contained within the valve stem means of FIG. 1;
FIG. 4 is a plan view of the cage shown in FIG. 3;
FIG. 5 is a plan view of the safety valve retaining spn'ng washer;
FIG. 6 is a sectional view taken along line Vl-Vl of FIG. 5;
FIG. 7 is a sectional view taken along line VII-VII of FIG. 5;
FIG. 8 shows a partial sectional view of a thin-walled container containing a compressed fluid and having operably attached thereto the spring-loaded thermoplastic safety valve shown in FIG. 1; and
FIG. 9 shows a partial sectional view of a thermoplastic spring-loaded safety valve useful in my invention wherein the spring-loaded safety valve means is located in the valve body.
Referring now to FIG. 1 the valve shown is that described and claimed in my copending application Ser. No. 672,273 wherein the valve comprises a valve body 1 into which a valve stem 2 is threadably fitted. The valve body includes a fitting surface 3 adapted to contact a fitting connected to or forming a part of a fluid container. Conveniently, the fitting surface is a threaded fitting of standard type, but a bayonet fitting, a gasket, or the like could be substituted. A bore extends through the axis of valve 1. A section of smaller diameter 4 is provided adjacent the fitting surface and a larger section 5 is provided remote from the fitting surface. At the point at which bore section 5 narrows to bore section 4 a tapered seat 6 is formed internally of valve body 1. A fluid discharge passage is provided from valve body 1. It extends transversely from the valve body on the side of valve seat 6 remote from the bore section 5 of larger diameter. A thread 8 for connection to a standard flared fitting is formed around discharge passage 7 to enable the valve to be connected to a delivery hose or the like for conducting fluid from the valve to the point of use. A still larger bore section 9 is provided at the end of valve body 1 remote from fitting surface 3. It is equipped with an internal thread 10 which threadably engages valve stem 2.
Valve body 1 is formed from a single piece of thermoplastic material of the character hereinabove described with nylon and Delrin being preferable materials. Other thermoplastics of like character, such as the common thermoplastics polystyrene, polyethylene and polypropylene may also be employed, all of which have relatively low melting points or heat distortion temperatures.
Valve stem 2 is likewise preferably fonned from a single piece of thermoplastic material. It is in the form of a wing nut having wings 11 which project from the axis of the valve stem. A threaded portion 12 is provided near the wings to engage threads 10 within the bore 9 of valve body 1. The lower end of valve stem 2 has a tapered sealing surface 13 which contacts seat 6 when valve stem 2 is threadably advanced into valve body 1. In this manner the valve is sealed against passage of fluid from the valve inlet to discharge passage 7. A bore is provided aligned with the axis of valve stem 2. It comprises successively larger bore sections 14, 15, 16, and 17 extended respectively, from the seat end to the wing nut end. A safety valve seat 18 is provided at the point of enlargement from bore section 14 to bore section 15. The seat includes an annular sealing surface 19 which is raised above the bottom of bore section 15, so that a relief 20 surrounds sealing surface 19. An annular slot 21 is formed in the outer circumference of valve stem 2 intermediate threads 12 and sealing surface 13. An 0- ring 22 placed in the slot seals against escape of fluid through bore section 5.
A preferred sealing means for the safety valve comprises a safety valve disc 23 positioned within bore section with its face against sealing surface 19. Disc 23 is preferably formed of an elastomeric material and is of smaller diameter than bore 15 so that fluid may escape between disc 23 and bore 15 when the disc moves away from sealing surface 19.
Disc 23 is held in position by a retainer 24. Retainer 24 has three depending legs 25 which hold washer 23 and which give retainer 24 an effective diameter approximating the diameter of bore section 15. In this manner disc 23 is axially aligned with bore 15. Retainer 24 has a centering bore 26 over which a spring 27 is fitted. Portion 26 may also be shaped to engage the coils of spring 27 to aid in locating disc 23 and retainer 24 in position.
The opposite end of spring 27 is positioned behind a splined washer 28. Washer 28 is dished so that its center portion is concave on the lower side. Four of the splines 29 extend upwardly and have sharp corners 30 which will dig into the wall of bore 16 when pressure is exerted upwardly on washer 28. Four of the splines 31 are turned downwardly and continue the concave shape of the washer.
In assembly of the valve disc 23 is placed in position in retainer 24 and they and spring 27 are fitted into position in the bore in valve stem 2. Washer 28 is pressed into bore 16 with the splines 29 projecting upwardly and thereby locking washer 28 against return movement. Splines 31 hold spring 27 centered against washer 28. Washer 28 is inserted to compress spring 27 to such an extent that an internal tank pressure of perhaps 350 to 450 p.s.i.g. will be required to lift disc 23 off sealing surface 19. Stem 2 is assembled and tightened in valve body 2 and the valve is fitted to a pressure tank.
In FIG. 8, the valve of FIG. 1 is operably connected to thinwalled container 30 through the thread engaging portion of spud 31 welded to vessel 30 adapted to receive threads in valve fitting surface 3. I prefer a threaded spud-type attachment of the valve to the thin-walled container, but the valve may be attached to the thin-walled container by any convenient means whereby the valve effectively seals compressed fluids within the vessel. I prefer that thin-walled container 30 be composed of carbon steel or aluminum having a wall thickness of from about 0.035 to 0.100 inches.
In a typical operation container 30 is charged with a compressible fluid such as a Freon refrigerant, whose liquid and vapor portions occupy approximately the parts of the container indicated in FIG. 2 and may exert a pressure of some to I25 p.s.i.g. Sufficient expansion volume is provided to absorb expansion due to ordinary local or solar heating. Should the container be overfilled or should a significant rise in ambient temperature occur the pressure exerted upon valve disc 23 will cause the spring-loaded safety device to open and prevent generation of a pressure sufficient to rupture the container. It may for example, allow only a small amount of fluid to escape and then reseal as the pressure is reduced. In the event of a fire, the container will first discharge through the safety valve its entire liquid contents with the possibility of the valve rescaling after the liquid has been discharged. Moreover, the heat required to vaporize the liquid will be substantial and will tend to limit temperature rise of the container. At this point there remains at least within the vessel sufficient vapor to exert considerable forces against the inner walls of the vessel. The containers thin metallic walls have the capacity to absorb heat quickly and rise in temperature very rapidly. Under such circumstances the thin metal walls are prone to anneal and lose strength thereby becoming susceptible to rupture or explosion due to the pressure of the residual vapor within the vessel. However, upon such heating the thermoplastic valve body and/or its components will deform and even become molten thereby destroying the valves seal and completely discharging the containers contents. The melting or deforming of the valve or its components thus provides an escape path or vent for discharging the containers residual vapor and thereby prevents explosion or rupture of the container.
It will be noted that the cross-sectional area of valve stem 2 of the preferred valve of FIG. 1 is relatively light intermediate wing nut 11 and threaded portion 12, and that the springloaded safety valve mechanism is below that area of light cross section. The safety valve and springare thereby protected by both the valve stem and valve body. In the event the pressure vessel and valve are accidentally dropped and breakage occurs, the break will take place just below the wing nut leaving the safety valve intact and operative. 7
FIG. 9a spring-loaded safety valve is shown somewhat similar to that of FIG. 1 with parts having prime number notation corresponding to like parts in the valve of FIG. 1. The spring-loaded safety valve means is located in appendage 40 in valve body 1' at an angle, generally transverse to the vertical axis of the valve. Appendage 40 is bored forming a-housing for the spring-loaded pressure relief assembly shown which includes sealing means preferably comprising a retainer 41 having raised ribs 42 for holding and carrying a sealing disc 23. Disc 23' is preferably comprised of an elastomeric material and is maintained in sealed position as shown in the FIG. by biasing spring 27' having one end urging against retainer 41 and an opposite end urging against cap 43 threaded into the bore of appendage 40.Cap 43 has a hole 44 therein to allow for escape of fluid and may adjust the pressure exerted on sealing disc 23' through spring 27. by being advanced to desired positions in appendage 40. The bore in appendage 40 is interconnected with fluid passage 4' through communicating bore 44 in valve body 1'; the bores together forming a passage from within a container to the outside thereof and constituting an escape path for fluids under pressure in the container. Spring 27' may be designed or selected to exert any selected pressure against sealing disc 23' to block fluid passage and maintain a seal between the bores at fluid pressures below the selected pressure. In operation and under fire conditions the valve in FIG. 3 prevents explosion in the same manner as the valve in FIG. 1. v
The thermoplastic spring-loaded safety valves useful in the invention are easily manufactured,for, example, as by injection molding, and are economical in comparison with conventional brass valves having fusible metal plugs or inserts. The combination of the thermoplastic spring-loaded safety valve with a thin-walled metallic container provides for the first time an economical fail-safe single-trip shipping and storing container for compressible fluids such as refrigerants, and the like.
While I have illustrated and described certain present preferred embodiments of my invention, it is to be understood that the invention is not limited thereto and may be otherwise variously practiced within the scope of the following claims.
1. Safety apparatus for use with a disposable, thin-walled, metallic container for carrying compressible fluids, said apparatus comprising: thermoplastic valve means in sealing arrangement with said container, said thermoplastic valve means comprising:
I. first and second bores which together form a passage extending from within said container to the outside thereof and which constitute a path for the escape of fluid under pressure within said container to the atmosphere; 2. sealing means interposed between said first and second bores; and j 3. yielding means disposed within said second bore urging said sealing means to a position blocking said bores at a selected pressure whereby said sealing means prohibits fluid passage from said first to said second bore and whereby said compressible fluid is contained within said container means at pressures of fluid within the container below said selected pressure; said thermoplastic valve means being of a composition which is at least deformable under pressures up to said selected pressure when heated to an elevated temperature above normal working temperatures but below the annealing temperature of said container, whereby upon the occurrence of deformation of said thermoplastic valve means, said container is vented either through or around said thermoplastic valve means to the atmosphere. 2. The apparatus of claim 1 wherein said sealing means comprises an elastomeric disc and disc holding means comprising a backup member having retaining means for holding and engaging said disc means.
3. The apparatus of claim 1 wherein said yielding means comprises a spring.
4. The apparatus of claim 1 wherein said thermoplastic is selected from the group consisting of nylon. polyethylene. polypropylene, polystyrene and Delrin.
5. In an apparatus for shipping and storing compressible fluids and for controlled withdrawal and use of said fluids, said apparatus including a thin-walled metallic container, a safety device comprising:
thermoplastic valve means in sealing arrangement with said container, said thermoplastic valve means comprising 1. first and second bores formed within said valve means and coaxially aligned generally normal to a wall of said container, which bores together form a passage extending from within said container to the outside thereof and which constitute a path for the escape of fluid under pressure within said container to the atmosphere,
sealing means interposed between said first and second bores; and
a spring disposed within said second bore urging said sealing means to a position blocking said bores at a selected pressure whereby said sealing means prohibits fluid passage from said first to said second bore and whereby said compressible fluid is contained within said container at pressures of fluid within the container below said selected pressure;
said thermoplastic valve means being of a composition which is at least deformable under pressures up to said selected pressure when heated to an elevated temperature above normal working temperatures but below the annealing temperature of said container, whereby upon the occurrence of deformation of said thermoplastic valve means, said container is vented either through or around said thermoplastic valve. means to the atmosphere.
6. The apparatus of claim 5 wherein said sealing means comprises: an elastomeric disc and disc holding means comprising a backup member having retaining means for holding and engaging said disc means.
7. The apparatus of claim 5 wherein said thermoplastic is selected from the group consisting of nylon, polyethylene, polypropylene, polystyrene and Delrin.