GB2111629A - Emergency disconnecter for fluid loading and unloading lines - Google Patents

Abstract

An emergency line disconnecter for an LNG loading/unloading line or the like which is capable of accommodating bi-directional fluid flow comprises a pair of couplings 1,2 having sliders 16,17 within the fluid passageways in the couplings arranged such that a substantially uniform cross-sectional flow path is provided for the fluid and sealing devices 22,23,34, 35 are mounted on the sliders 16,17 to cut off fluid flow through the device, and such devices 34,35 are designed so as to be resiliently operable at the extremely low temperatures of LNG. To dissipate the fluid shock due to rapid closure of the device, a fluid shock absorber employing restrictive passageways may be used to slow the advance of the sliders to their cut-off positions. <IMAGE>

Description

SPECIFICATION Emergency disconnector for fluid loading and unloading lines The present invention relates to an emergency disconnector for disconnecting a fluid line in an emergency to cut off the flow of fluid being conveyed through the line.

Fluid loading and unloading lines are used in such applications as in unloading liquified natural gas (hereinafter referred to as "LNG") from an LNG tanker alongside a sea berth to a storage tank, or in loading LNG from a storage tank to the LNG tanker.

Under rough weather conditions, the LNG tanker tends to separate from the sea berth due to strong winds or high waves while loading or unloading LNG. in such an emergency case, it is necessary that couplings in the fluid line be disconnected to sever the fluid connection and cut off the flow of dangerous LNG to prevent unwanted leakage. To meet such a requirement, the fluid line generally includes an emergency line disconnector for disconnecting the line in an emergencyto quickly stop the fluid flow.

Figs. 4(A) and 4(B) of the accompanying drawings illustrate a conventional emergency line disconnector. The line disconnector comprises a pair of couplings C1, C2 interconnected by a connector B and having a pair of slide valves V1, V2, respectively.

The coupling C1 has a stopper ring R for limiting the sliding movement of the slide valve V1. The slide valve V2 includes a spacer rod L contacting the slide valve V1 to maintain the slide valves V1, V2 spaced from each other by a clearance which serves as a fluid passage between couplings C1, C2 and hence between the slide valves V1, V2. The slide valves V1, V2 are normally urged by compression springs, respectively, to move toward open ends of the couplings Ci, C2. The slide valves V1, V2 have on their heads seal packings S of rubber secured thereto by heat treatment.

During normal operation in conveying a fluid, the fluid flows from the coupling C2 through slots SL in the slide valve V2 and slots SL in the slide valve V1 into the coupling C1, from which the fluid is discharged, as shown in Fig. 4(A). In an emergency case requiring fluid cutoff, the connector B is removed to allow the couplings C1, C2 to be disconnected, as illustrated in Fig. 4(B), whereupon the heads of the slide valves V1, V2 are brought into abutment against the edges of the open ends of the couplings C1, C2, respectively, under the resilient force of the com pression springs, thereby cutting off the stream of fluid.

With the known emergency line disconnector, the fluid, while being normally conveyed, passes through a passageway having varying cross-section al areas, as seen from Fig. 4(A), which gives rise to an increased pressure loss when transporting a highly viscous fluid. Since a stopper ring R is disposed in the coupling C1 only, with no such stopper ring being provided in the coupling CZI fluid flow in a direction opposite to that shown in Fig. 4(A) would push the slide valve V2 back out of predetermined position until the slots SL would be complete lyclosed off by the inner wall of the coupling C2, thus stopping fluid flow. Therefore, two fluid loading and unloading lines, each with an emergency line disconnector of the foregoing type, have been needed for respectively loading and unloading fluids.

Also, the spacer rod L projects an increased distance from the coupling C2 when the couplings C1, C2 are disconnected in an emergency, and hence is liable to get caught in the coupling C1. When this happens, it is a time-consuming task to separate the spacer rod L from the coupling C1. With the seal packing S secured to the heads of the slide valves V1, V2, replacement of the seal packings S due to their damage or wear requires that the slide valves V1, V2 per se be replaced with new slide valves, a procedure which is troublesome and highly costly. Further, adequate steps have not been taken in the past to insure that the seal packings used could endure sustained usage at extremely low temperatures (-196 or lower) commonly encountered with LNG.

In addition, since the couplings of the above-desired emergency disconnector are sealed off in a very short period of time, after having been separated, by the resilient force of the springs and fluid pressure, the kinetic energy of the fluid flowing through the line is converted into a pressure upon sudden cutoff of the fluid flow, resulting in problems such as water hammer.

With the foregoing prior art shortcomings in view, it is an object of the present invention to provide an emergency disconnectorforfluid loading and unloading lines, which prevents an increased pressure loss when conveying a high-viscosity fluid in normal use, which is capable of bidirectional fluid transportation, has spacer rods that project a reduced distance from the couplings permitting easy disconnection thereof, and which also has seal packings which are easily replacable and less costly.

According to the present invention, there is provided an emergency disconnector for disconnecting a pair of couplings in a fluid line in an emergency to thereby cut off the fluid flow through the fluid line, including a pair of couplings having a pair of joint openings defined by edges, respectively, and a pair of fluid passages, respectively, a pair of slide valves axially slidably disposed in the couplings, respectively, and having a pair of valve heads, respectively, from which a pair of spacer rods extend, respective ly, toward each other, a pair of means biasing the slide valves toward the joint openings, respectively, in the couplings, the slide valves being movable by the biasing means into abutment against the aforementioned edges to cut off the fluid passages with the spacer rods projecting a minimum interval from the joint openings, respectively, when the couplings are disconnected from one another, and also movable against the force of the urging means with the spacer rods held against each other to open the fluid passages when the couplings are intercon The drawings originally filed were informal and the print here reproduced is taken from a later filed formal copy.

nected, and a pair of stopper rings mounted in the couplings, respectively, for limiting the strokes of the movable slide valves to maintain the fluid passageways open when the couplings are interconnected, the slide valves being shaped such that they will provide a space of a substantially uniform cross-sectional configuration between inner surfaces of the couplings and the slide valves, the valve heads having a pair of removable seal packings, respectively, extending fully circumferentially therearound and pressable against the edges of the joint openings, respectively.

It is a further object of the present invention to provide an emergency disconnector capable, in an emergency, of disconnecting a fluid loading and unloading line to reliably cut off the flow of a fluid and particularly a fluid at extremely low temperatures while the fluid is being transported through the line.

The above object can be achieved by providing an emergency disconnector for disconnecting a pair of couplings in a fluid loading and unloading line in an emergency to thereby cut off the fluid through the fluid line, including a pair of couplings, each having a fluid passageway extending through a barrel of a uniform cross section to be joined to one end of the fluid loading and unloading line to an end joint opening, a first inner tapered wall disposed in the fluid passageway and having an inner end closer to the barrel and larger in diameter, and a second inner tapered wall disposed in the fluid passageway and closer than the first inner tapered wall to the barrel and having an inner end larger in diameter and an opposite end of a diameter equal to or greater than the larger diameter of the first inner tapered wall; a pair of slide valves axially slidably inserted in the couplings, respectively, and having a pair of confronting valve heads, each of the slide valves having a retainer disc removably attached to each of the valve heads, and an annular seal packing mounted circumferentially around the valve head and having a portion projecting radially outwardly from the valve head, each of the slide valves being slidable by biasing means, when the couplings are disconnected from each other, to press the second seal packing against the second inner tapered wall and also press a circumferential taper end face of the retainer disc against the first inner tapered wall to thereby close the joint openings of the couplings, the slide valves being retainable away from each other against the force of the biasing means, when the couplings are joined together, with spacer rods which project axially from centers of the retainer discs being held in abutment against each other, to thereby open the joint openings of the couplings; a pair of stopper rings for limiting the strokes of the sliding movement of the slide valves, respectively to permit communication of the fluid passageways in the couplings when the couplings are jointed to each other; and a pair of cover rings mounted on inner walls defining the fluid passageways, respectively, between the barrels of the couplings and the second inner tapered walls and having fluid passageways continuous to the fluid passageways in the cou plings, the cover rings being engageable with outer peripheral surfaces ofthe seal packings of the slide valves, each of the seal packings being composed of an elongate seal cover capable of being resilient at extremely low temperatures and a resilient body extending through the seal cover over the entire length thereof.

It is a still further object of the present invention to provide an emergency disconnector for fluid loading and unloading lines which is capable of sealing the couplings a predetermined period of time after the couplings have been separated from each other without abruptly cutting off the kinetic energy of fluid being transported through the line, so that problems such as water hammer can be avoided.

The above object can be achieved by providing an emergency disconnector for separating, in an emergency, a pair of couplings in a fluid loading and unloading line to slide slide valves in the couplings under an urging force and fluid pressure to thereby seal off the couplings to cut off the flow of a fluid being loaded or unloaded through the fluid loading and unloading line, the emergency disconnector comprising a pair of guide rings mounted respectively on the slide valves circumferentially therearound in areas which the fluid can enter, and a pair of enclosing rings mounted on inner walls of the outer barrels of the couplings, respectively, the guide rings and the inner walls of the outer barrels, and the enclosing rings and the slide valves defining therebetween gaps serving as fluid restrictors or separate restrictor holes, the guide rings, the enclosing rings, the slide rings, and the inner walls of the outer barrels being capable of defining fluid sealing chambers when the slide valves are moved.

The present invention will now be described by way of example with reference to the drawings, in which; Figure 1 is an axial cross-sectional view of an emergency disconnector for a fluid loading and unloading line constructed in accordance with the present invention; Figure 2 is an enlarged fragmentary cross-sectional view of an encircled portion A in Fig. 1, showing a seal packing attached to a slide valve; Figure 3 is a fragmentary cross-sectional view of the emergency disconnector, illustrating the couplings when disconnected; Figure 4(A) is an axial cross-sectional view of a conventional emergency disconnector; Figure 4(B) is an axial cross-sectional view of the emergency disconnector of Fig. 4(A) when separated.

Figure 5 is an axial cross-sectional view of a second embodiment of an emergency disconnector for a fluid loading and unloading line constructed in accordance with the invention.

Figure 6 is an axial cross-sectional view of the emergency disconnector as it is separated; Figure 7 is a perspective view of a cover ring; Figure 8 is a perspective view of a seal packing; Figure 9(A) is a fragmentary cross-sectional view of a portion around the seal packing as positioned when the couplings are joined together; Figure 9(B) is a fragmentary cross-sectional view of a portion around the seal packing as positioned when the couplings are disconnected; Figure 10 is an enlarged cross-sectional view of the seal packing shown in Fig. 9(A) and surrounding parts; Figure 11(A) is an enlarged cross-sectional view of the seal packing held against a second innertapered wall; Figure 11(B) is an enlarged cross-sectional view of the seal packing shown in Fig. 9(B) and surrounding parts;; Figure 12 is an axial cross-sectional view of a third emergency disconnector for a fluid loading and unloading line constructed in accordance with the present invention; Figure 13 is an enlarged cross-sectional view of a fluid sealing chamber thereof; Figure 14 is a fragmentary cross-sectional view illustrative of the manner in which fluid starts to be sealed in the fluid sealing chamber after the couplings have been disconnected; Figure 15 is a fragmentary cross-sectional view showing the manner in which the fluid leaks out of the fluid sealing chamber to allow a slide valve to be held against a seal surface; and Fig. 16 is a side elevational view, with parts cut away, of couplings as they are separated.

Fig. 1 shows, in axial cross section, a first emergency line disconnector according to the present invention, which includes a pair of couplings 1, 2 having an identical cylindrical shape. The couplings 1,2 have barrels 3, 4, respectively, including at opposite ends thereof a pair of mating flanges 5, 6, respectively, and a pair of joint flanges 7, 8, respectively. The mating flanges 5, 6 are joined together by an annular clamp 9 extending fully around the circumferential edges of the mating flanges 5, 6. In an emergency requiring disconnection of the couplings 1, 2, the clamp 9 can immediately be detached from the mating flanges 5, 6 by a power cylinder (not shown) actuatable by an actuation signal generated upon the occurrence of such an emergency.

The joint flange 7 of the coupling 1 is bolted to a joint flange 11 of a connector pipe 10 projecting from a side of the tanker (not shown). The joint flange 8 of the coupling 2 is bolted to a joint flange 13 of a transport pipe 12 on an loading arm (not shown) which constitutes a part of a fluid loading and unloading line. The transport pipe 12 is coupled to a storage tank (not shown). The loading arm is capable of freely moving and positioning the coupling 2 in three dimensions into axial alignment with the coupling 1.

The couplings 1, 2 have fluid passages 1 a, 2a with identically shaped inner walls. Portions of the fluid passages 1 a, 2a which extend from the joint flanges 7, 8 to the barrels 3, 4, respectively, have a uniform cross-sectional shape of an inside diameter R1, and portions of the fluid passageways 1 a, 2a which extend from the barrels 3, 4 to joint openings 14, 15 in the mating flanges 5, 6, respectively, have a cross-sectional shape gradually increasing into an inside diameter of R2 (R2 > R1) and another cross sectional shape gradually decreasing into an inside diameter of R3 (R2 > R1 > R3). The couplings 1, 2 are held in communication with one another through joint openings 14,15 which have an inside diameter R3.

The couplings 1, 2 contain in their fluid passageways 1 a, 2a a pair of slide valves 16, 17, respectively, a pair of stopper rings 18, 19 secured to the inner walls of the barrels 3,4, respectively, for limiting the strokes of the slidably movable slide valves 16, 17, a pair of compression coil springs 20, 21 urging the slide valves 16, 17 respectively against inner wall edges 14a, 1 Sa, of the joint openings 14, 15, and a pair of annular spring stops 20a, 21 a, affixed to the inner walls of the barrels 3,4, respectively, and against which ends of the compression coil springs 20,21 are held, respectively.The slide valves 16, 17 are of an identical cylindrical configuration, and have ends closed off by a pair of valve heads 22,23 with the other ends open as inlet openings 24. 25 for admission of a fluid therein. The cylindrical surfaces of the slide valves 16, 17 have axially oblong slots 26, 27, respectively, defined at equal intervals in the circumferential direction. The slide valves 16, 17 have an outside diameter selected such that the slide valves 16, 17 are respectively insertable in the barrels 3,4 having the inside diameter of R1 with a predetermined dimensional tolerance.

A pair of spacer rods 28, 29 project axially of the slide valves 16, from central portions of the valve heads 22, 23, respectively. The spacer rods 28,29 are of an axial length such that when the couplings 1,2 are connected together, the spacer rods 28, 29 push against each other to displace the slide valves 16, 17 toward the stopper rings 18, 19, against the force of the compression springs 20,21, thereby providing fluid passage spaces between the valves heads 22, 23 of the slide valves 16, 17 and the inner wall edges 14a, 15a of the joint openings 14,15. Cones30,31, 32,33 are disposed on the spacer rods 28, 29 and in the slide valves 16, 17, respectively.The cones 30,33 are mounted on inner surfaces of the valve heads 22, 23 with their pointed ends directed toward the joint flanges 7,8, respectively. The cones 31, 32 extend respectively between the valve head 22 and the spacer rod 28 and between the valve head 23 and the spacer rod 29. In and around the corners of the valve heads 22,23, there are provided a pair of replaceable annular seal packings 34,35 of an elastic material such as nitrile rubber secured to rings b and fixed respectively to the valve heads 22, 23 by screws a.

The stopper rings 18, 19 are positioned such that when the couplings 1,2 are interconnected with the spacer rods 28, 29 pressed against each other, the slide valves 16, 17 are moved respectively against the stopper rings 18, 19, and the joint openings 14, 15 communicate through the slots 26, 27 with the fluid passages la, 2a, respectively. The cones 30,31, 32,33 have tapered walls inclined at an angle Q with respect to the axis of the cones, the angle 9 being selected such that when the couplings 1, 2 are interconnected, the tapered walls of the cones 30,31, 32,33 are spaced from the inner walls of the fluid passageways lea, 2a by a uniform distance, that is, to provide a substantially uniform cross section for the fluid passageways 1 a, 1 b throughout their length.

The operation of the emergency line disconnector of the foregoing construction is as follows: Under normal conditions of use, in which the couplings 1,2 are interconnected with the mating flanges 5, 6 joined to each other by the annular clamp 9, the spacer rods 28,29 are pressed against each other to push the slide valves 16, 17 slidingly toward the joint flanges 7, 8 against the resilient force of the compression springs 20,21, respectively, until the slide valves 16, 17 are limited in their sliding motion by the stopper rings 18, 19. The slide valves 16, 17 are thus fixedly retained between the stopper rings 18. 19.

When a dangerous fluid such as LNG is to be loaded from the storage tank into the tanker, the fluid flows from the transport pipe 12 through the fluid passage 2a in the coupling 2 into the inlet opening 25 of the slide valve 17 in the direction of the arrows. The fluid stream, as it flows out of the slide valve 17, is subjected to a reduced resistance due to the cone 33 and is divided thereby into spreading directions out of the slots 27. The fluid then passes through the spaces between the inner wall edge 15a of the joint opening 15 and the cone 32 and between the inner wall edge 14a of the joint opening 14 in the coupling 1 and the cone 31, and flows through the slots 26 in the slide valve 16 into the inlet opening 24 thereof, from which the fluid is loaded into the tanker through the connector pipe 10.

For unloading the fluid from the tanker into the storage tank, the fluid flows in an opposite direction from the connector pipe 10 through the passageway 1a in the coupling 1 into the inlet opening 24 of the slide valve 16 in a direction opposite to that of the arrows. The fluid stream, as it flows out of the slide valve 16, is subjected to a reduced resistance due to the cone 30 and is divided thereby into spreading directions out of the slots 26. The fluid then passes through the spaces between the inner wall edge 14a of the joint opening 14 and the cone 31 and between the inner wall edge 15a of the joint opening 15 in the coupling 2 and the cone 32, and flows through the slots 27 in the slide valve 16 into the inlet opening 25 thereof, from which the fluid is unloaded into the storage tank through the transport pipe 12.

In any case, the substantially uniform cross-sectional area of the fluid passageway between the slide valves 16, 17 minimizes any pressure loss resulting from friction even if the fluid to be loaded or unloaded has a high viscosity, and does not reduce the speed at which the fluid flows. With the slide valves 16, 17 fixedly retained between the stopper rings 18, 19, the fluid can stably flow in either direction through the emergency line disconnector.

In an emergency in which the tanker for example moves off the sea berth while loading or unloading fluid, the clamp 9 is immediately removed from the mating flanges 5,6 by a power cylinder (not shown), whereupon the couplings 1,2 are disconnected, as shown in Fig. 3. Upon disconnection of the couplings 1,2, the slide valves 16, 17 slide under the force of compression springs 20,21 until the valve heads 22, 23 are pressed respectively against the inner wall edges 14a, of the the joint openings 14,15. More specifically, the seal packings 34,35 close off the respective spaces between the valve head 22 and the joint opening 14 and between the valve head 23 and the joint opening 15, with the spacer rods 28,29 projecting slightly from the joint holes 14, 15, respectively.The fluid in the transport pipe 12 and the coupling 2 is cut off by the slide valve 17 against leakage through the joint opening 15 of the coupling 2. Likewise, the fluid in the connector pipe 10 and the coupling 1 is cut off by the slide valve 16 against leakage through the joint opening 14 of the coupling 1. Therefore, the fluid line is completely disconnected simultaneously with the separation of the couplings 1,2. Since the spacer rods 28,29 project only slightly from the couplings 1,2, respectively, there is no danger whatsoever of the spacer rods 28, 29 getting caught by the couplings 2, 1, respectively, and hence of the couplings 1,2 failing to be disengaged.

The seal packings 34,35 can easily and speedly be replaced with new ones as they are worn out or deteriorated by simply detaching the screws a without having to replace the slide valves per se as is the case with the conventional emergency line disconnector. Since the couplings 1,2 are constructed of substantially identical components and capable of bidirectional fluid transportation, they can be installed in place without concern over the direction of flow of the fluid to be loaded or unloaded through the emergency line disconnector.

With the arrangement of the present invention, as described above, there is provided an emergency disconnector for disconnecting a pair of couplings in a fluid loading and unloading line in an emergency to thereby cut off fluid flow through the fluid line, including a pair of couplings having a pair of joint openings defined by edges, respectively, and a pair of fluid passages, respectively, a pair of slide valves axially slidably disposed in the couplings, respectively, and having a pair of valve heads, respectively, from which a pair of spacer rods extend, respectively, toward one another, a pair of means for biasing the slide valves toward the joint openings, respectively, in the couplings, the slide valves being movable by the biasing means into abutment against the edges to cut off the fluid passages with the spacer rods projecting a minimum interval out of the joint openings when the couplings are disconnected from each other, and also movable against the force of the urging means with the spacer rods held against one another to open the fluid passageways when the couplings are interconnected, and a pair of stopper rings mounted in the couplings, respectively, for limiting the strokes of the movable slide valves are slidable to maintain the fluid passageways open when the couplings are interconnected, the slide valves being shaped such that they will provide a space of a substantially uniform cross-sectional configuration between the inner sufaces of the couplings and the slide valves, the valve heads having a pair of removable seal packings, respectively, extending fully circumferentially therearound and pressable against the edges of the joint openings, respectively. Under normal conditions of use, the emergency disconnector of the invention can largely prevent a pressure loss when either a low or high-viscosity fluid flows there through. The emergency disconnector is capable of bidirectional fluid transportation. Accordingly, fluid can be loaded and unloaded with a much higher efficiency. In case of emergency, the two spacer rods each project only a small interval, allowing the couplings to be disconnected smoothly and reliably.

The seal packing can easily be replaced with new ones at a reduced cost as there is no need to bodily replace the slide valves. The couplings, which are substantially identically constructed, can be manufactured, assembled, and installed with high efficiency.

Fig. 5 illustrates a line connector according to a second embodiment of the present invention, in which like parts with respect to the embodiment of Fig. 1 are designated by like reference numerals.

The couplings 1,2 have fluid passageways la, 2a with identically shaped inner walls. Portions of the fluid passageways lea, 2a which extend from the joint flanges 7,8 to the barrels 3,4, respectively, have a uniform cross-sectional shape with an inside diameter R1, and portions of the fluid passageways la, 2a which extend from the barrels 3, 4to joint openings 14, 15 in the seal rings 5,6, respectively, have a cross-sectional shape gradually increasing to an inside diameter R2 (R2 < R1), and another cross-sectional shape gradually decreasing to an inner diameter R3 at the joint openings 14, 15 (R2 > R1 > R3). The inside diameter R2 serves as inner wall portions 217,218 to which the cover rings 216,216 are attached, respectively.The couplings 1,2 are joined together by the clamp 9 and held in mutual communication through the joint openings 14, 15 having the inside diameter A3.

The cover rings 216,216 will now be described. As shown in Fig. 7, each of the cover rings 216,216 comprises an outer ring member 216a and an inner ring member 216b with a plurality of radial posts 216c extending therebetween and angularly spaced at equal angular intervals 0, the outer and inner ring members 216a, 216b being concentric with each other. The inner ring member 216b has on an inner peripheral surface thereof an engagement flange 216d extending radially inwardly. The outer and inner ring members 216a, 216b have equal widths or axial lengths I. The engagement flange 216d of the inner ring member 216b has an inside diameter D slightly larger than the outside diameter E of slide valves 22,222 (described later).The inner wall portions 217, 218 have a pair of attachment grooves 219,220, respectively, disposed between the barrels 3,4 and the seal rings 5,6. The outer ring members 216a, 216a of the cover rings 216,216 are respectively fitted in attachment grooves 219, 220 to attach the cover rings 216, 216 to the inner wall portions 217, 218, respectively. The engagement flanges 216d, 216d of the inner ring members 216b, 216b of the cover rings 216, 216 are located closer to the barrels 3,4, respectively, and the outer ring members 216a, 216a have inner peripheral surfaces lying flush with the inner wall portions 217,218, respectively.The outer periphery of the inner ring member 216b and the posts 216c have chamferred axial front and rear corners to provide a plurality of smooth fluid passageways 216e defined between the outer ring member 16a, the inner ring member 216b, and the posts 216c.

The couplings 1, 2 contain in their fluid passageways 1 a, 2a a pair of slide valves 221, 222, respectively, a pair of stopper rings 223, 224 secured to the inner walls of the barrels 3,4, for limiting the stroke of the slide valves 221,222, a pair of coil compression springs 227,228 urging the slide valves 221,222 respectively toward first inner tapered walls 225, 226 of the seal rings 5, 6, and a pair of annular spring stops 229, 230 affixed to the inner walls of the barrels 3,4, respectively, and against which ends of the coil springs 227,228 are held, respectively. The slide valves 221,222 are of an identical cylindrical configuration, and have ends closed off by a pair of valve heads 231,232 with the other ends open as inlet openings 233, 234 for the admission of fluid.

The cylindrical surfaces of the slide valves 221,222 have axially oblong slots 235, 236, respectively, defined at equal intervals in the circumferential direction. The slide valves 221,222 have an outside diameter F selected such that the slide valves 221, 222 may be inserted respectively in the barrels 3,4 having the inside diameter R1 with a predetermined dimensional tolerance.

The first inner tapered walls 225,226 have axial inner ends of larger diameter. To the valve heads 231,232, there are bolted a pair of retainer discs 237, 238 having a diameter equal to the outside diameter E of the slide valves 221,222 and supporting a pair of confronting spacer rods 239,240, respectively, projecting from the centers of the retainer discs 237, 248. The retainer discs 37,38 have a pair of tapered end faces 237a, 238a, respectively, extending fully circumferentially and shaped in complementary relation to the first inner tapered walls 225, 226 of the seal rings 5, 6.

The valve heads 231,232 have in corners thereof a pair of steps, respectively, extending fully along their circumferences. The valve heads 231,232 and the retainer discs 237,238 jointly define therebetween along the steps a pair of retainer slots 243,244 respectively, in which are placed a pair of annular seal packings 241,242 which can withstand extremely low temperatures. As illustrated in Figs. 8, 10 and 11, the seal packings 241, 242 are made of a material such as Teflon capable of withstanding extremely low temperatures (for example, -196"C of LNG) and retaining its elasticity at such extremely low temperatures without being deteriorated and damaged.

Each of the seal packings 241,242 is composed of an elongate seal cover 245 having a substantially U-shaped cross section and a spiral spring 246 fitted as a resilient body in the seal cover 245 and extending longitudinally thereof. The seal cover 245 includes opposite edges having on their outer surfaces a pair of pressers 248, 248 projecting away from each other and extending longitudinally of the seal cover 245. The seal cover 245 has a maximum width L1 across the pressers 248,248, the width L1 being greater than the depth L2 of the retainer slots 243,244. The seal packings 241,242 are received and axially positioned respectively in the retainer slots 243, 244 in the slide valves 221,222 fully along the circumference of the seal rings 241,242.The press ers 248 of the seal packings 241, 242 project out of the retainer slots 243,244 with open sides of the seal covers 245,245 being directed toward the barrels 3, 4, respectively, of the couplings 1, 2.

While the couplings 1,2 are joined together for normal use, the slide valves 221, 222 are caused by the spacer rods 239,240 to be kept away from each other against the force of the compression springs 227,228. When the slide valves 221,222 are positionally held by the stopper rings 223,224, respectively, the pressers 248 of the seal packings 241,242 are pressed against the inner peripheral surfaces of the inner ring portions 216b and the engagement flanges 216d of the cover rings 216.

When the couplings 1,2 are disengaged from each other in case of emergency, the slide valves 221,222 slide under the biasing forces of the coil springs 227, 228 to move the pressers 248 of the seal packings 241,242 into abutment against second inner tapered walls 249,250, respectively, located axially inwardly of the first inner tapered walls 225, of the couplings 1,2, respectively. The second inner tapered walls 249,250 have inner ends closer to the barrels 3, 4 and larger in diameter and opposite ends of a smaller diameter equal to or greater than the larger diameter of the first inner tapered walls 225, 226.

Cones 251,252,253,254 are disposed on the spacer rods 239,240 and in the slide valves 221,222, respectively. The cones 251,252 are mounted on inner surfaces of the valve heads 231,232 with pointed ends directed toward the joint flanges 7,8, respectively. The cones 253,254 extend respectively between the retainer disc 237 and the spacer rod 239 and between the retainer disc 238 and the spacer rod 240.

The stopper rings 223,224 are positioned such that when the couplings 1,2 are interconnected with the spacer rods 239,240 pressed against each other to slide the slide valves 221,222, respectively against the stopper rings 223,224, the joint openings 14, 15 communicate through the slots 235, 236 with the fluid passageways 1 a, 2a, respectively. The cones 251,252,253,254 have tapered walls inclined at an angle 0 with respect to the axis of the cones, the angle û being selected such that when the couplings 1,2 are interconnected, the walls of the cones 251,252,253,254 are spaced from the inner walls of the fluid passageways 1 2a by a uniform distance, that is, to provide a substantially uniform cross section for the fluid passageways 1 a, 2a throughout their length.

The operation of the emergency line disconnector of the foregoing construction is as follows: Under normal conditions of use, in which the couplings 1,2 are interconnected with the seal rings 5,6 joined to each other by the annular clamp 9, the spacer rods 239,240 are pressed against each other to push the slide valves 221,222 slidingly toward the jointflanges 7,8 against the resiliency of the coil springs 227,228, respectively, until the slide valves 221,222 are limited in their sliding motion by the stopper rings 223,224. The slide valves 221,222 are thus fixedly retained between the stopper rings 223, 224.As shown in Figs. 9(A) and 10, the seal packing 241 on the slide valve 221 is held against the inner peripheral surface of the inner ring member 216b and the engagement flange 216d of the cover ring 216, and the presser 248 of the seal packing 241 is pressed against the inner ring member 216b under the force of the spring 246 of the seal packing 241 which is pressed radially inwardly. Likewise, the presser 248 of the seal packing 242 on the slide valve 222 is pressed against the inner ring member 216b.

Therefore, the seal packings 241,242 are held in intimate contact with the cover rings 216,216 and the slide valves 221,222, respectively.

When a dangerous fluid such as LNG is to be loaded from the storage tank into the tanker, fluid flows from the transport pipe 12 through the fluid passageway 2a in the coupling 2 into the inlet opening 234 of the slide valve 222 in the direction of the arrows. The fluid stream as it flows out of the slide valve 222 is subjected to reduced resistance due to the cone 252 and is divided thereby into spreading directions out of the slots 236 and flows through the fluid passageways 216e in the cover ring 216.The fluid then goes through spaces between the first and second inner tapered walls 226,250 of the seal ring 6 and the cone 254 and the between the first and second inner walls 225,249 of the seal ring 5 and the cone 253, and flows through the fluid passageways 216e in the cover ring 216 in the coupling 1 and the slots 235 in the slide valve 221 into the inlet opening 233 thereof, from which the fluid is loaded into the tanker through the connector pipe 10.

For unloading the fluid from the tanker into the storage tank, the fluid flows in an opposite direction from the connector pipe 10 through the passageway 1 a in the coupling 1 into the inlet opening 233 of the slide valve 221 in a direction opposite to that of the arrows. The fluid stream, as it flows out of the slide valve 221, is subjected to reduced resistance due to the cone 251 and is divided thereby into spreading directions out of the slots 235 and flows through the fluid passageways 216e in the cover ring 216.The fluid then goes through a space between the second and first inner tapered walls 249,225 of the seal ring 5 and the cone 253, and flows through the fluid passageways 216e in the cover ring 216 in the coupling 2, and through the slots 236 in the slide valve 222 into the inlet opening 234 thereof, from which the fluid is unloaded into the storage tank through the loading arm.

In any case, there is no danger of the seal packings 241,242 buckling or being damaged under the axial force produced by the fluid as it passes, since the pressers 248 of the seal packings 241,242 are protected by the cover rings.

The substantially uniform cross-sectional area of the fluid passageway between the slide valves 221, 222 minimizes any pressure loss resulting from friction even if the fluid to be loaded or unloaded has a high viscosity, and does not reduce the speed at which the fluid flows. With the slide valves 221,222 fixedly retained between the stopper rings 223, 224, the fluid can stably flow in opposite directions through the emergency line disconnector. In an emergency in which the tanker moves off of the sea berth while loading or unloading fluid, for example, and the fluid loading and unloading line should be disconnected quickly, the clamp is immediately removed from the seal rings 5, 6, by a power cylinder (not shown), whereupon the couplings 1,2 are disconnected, as shown in Fig. 6.Upon disconnection of the couplings 1,2, the slide valves 221,222 slide under the force of the coil springs 227,228 toward the joint openings 14,15. As shown in Fig.

11(A), the presser 248 of the seal packing 241 is brought into engagement with the second inner tapered wall 249 of the seal ring 5, and similarly, the presser 248 of the seal packing 242 is pressed against the second inner tapered wall 250 of the seal ring 6. At this time, the tapered end face 237a of the retainer disc 237 is not abutted against the first inner wall 225 of the seal ring 5, and the end face 238a of the retainer disc 238 is not abutted against the first inner wall 226 of the seal ring 6.The slide valves 221, 222 are pushed under the force of the coil springs 227, 228 to force the pressers 248, 248 of the seal packings 241,242 onto the second inner walls 249, 250 of the seal rings 5,6, respectively, against the force of the springs 246,246, while the pressers 248, 248 are radially inwardly pressed by a radial dimensional difference T between the minimum diameter of the second inner tapered walls 249,250 of the seal rings 5,6 and the inside diameter of the wall portions on which the pressers 248,248 of the seal packings 241, 242 have been placed.

As the seal packings 241,242 are forced onto the second inner taper walls 249, 250 with a sufficient distance, the tapered end face 237a of the retainer disc 237 is brought into engagement with and positioned by the first inner tapered wall 225 of the seal ring 5, and likewise, the tapered end face 238a of the retainer disc 248 engages and is positioned by the first inner wall 226 of the seal ring 6, as shown in Figs. 9 (B) and 11(B).

Upon engagement of the end faces 237a, 238a with the first inner walls 225, 226, respectively, the seal packings 241,242 are positioned in the axial direction of the couplings 1,2, and the joint openings 214,215 in the seal rings 5,6 are fully closed off by the seal packings 241,242 simultaneously with the disconnection of the couplings 1,2. Therefore, the flow of the fluid which has been conveyed through the couplings 1,2 is immediately and reliably cut off without any risk of fluid leakage from the couplings 1,2.

In an emergency, as described above, the end faces 237a, 238a of the retainer discs 237,238 are pressed against the first inner tapered walls 225, 226, respectively so that the seal packings 241, 242 are positioned in a predetermined place axially of the couplings 1,2. Even when the seal packings 241, 242 and the seal rings 5,6 are subjected to different rates of dimensional shrinkage under the influence of a fluid having an extremely low temperature, any dimensional difference produced can be taken up by the radial dimensional difference T of the second inner walls 249, 250 by which the seal packings 241, 242 are radially pressable. There is therefore no danger of the seal rings 5,6 undergoing unwanted stress when the slide valves 221, 222 hit the seal rings 5, 6.The seal packings 241, 242 can retain their elasticity when in contact with fluid at an extremely low temperature, and hence are free from damage which would otherwise cause fluid leakage from the couplings 1,2 in case of an emergency.

The emergency disconnector for disconnecting a pair of couplings in a fluid loading and loading line in an emergency to thereby cut off a fluid flow through the fluid loading and unloading line, includes, according to this embodiment of the invention, a pair of couplings each having a fluid passageway extending through a barrel of uniform cross section to be joined to one end of the fluid loading and unloading line to an end joint opening, a first inner tapered wall disposed in the fluid passageway and having an inner end closer to the barrel and larger in diameter, and a second inner tapered wall disposed in the fluid passageway and closer than the first inner tapered wall to the barrel and having an inner end larger in diameter and an opposite end of a diameter equal to or greater than the larger diameter of the first inner tapered wall; a pair of slide valves axially slidably inserted in the couplings, respectively, and having a pair of confronting valve heads, each of the slide valves having a retainer disc removably attached to each of the valve heads, and annular seal packing mounted circumferentially around the valve head and having a portion projecting radially outwardly from the valve head, each of the slide valves being slidable by urging means, when the couplings are disconnected from each other, to press the second seal packing against the second wall and also press a circumferential tapered end face of the retainer disc against the first wall to thereby close the joint openings of the couplings, the slide valves being retainable away from each other against the force of the urging means, when the couplings are joined together, with spacer rods which project axially from centers of the retainer discs held in abutment against each other, to thereby open the joint openings of the couplings; a pair of stopper rings for limiting the strokes of sliding movement of the slide valves, respectively; and a pair of cover rings mounted on inner walls defining the fluid passageways, respectively, between the barrels of the couplings and the second walls and having fluid passages contiguous to the fluid passages in the couplings, the cover rings being engageable with outer peripheral surfaces of the seal packings of the slide valves, each of the seal packings being composed of an elongate seal cover capable of being resilient at extremely low temperatures and a resilient body extending through the seal cover over the entire length thereof. When the couplings are joined together, the seal packings are protected by the cover rings for protection against the fluid. With the couplings disconnected from each other, the seal packings with the resilient bodies therein are not pressed axially of the couplings for sealing, but are pressed radially by a radial dimensional difference with the second walls. In case of emergency, the emergency disconnector of the invention can cut off the flow of a fluid of extremely low temperature as well as an ordinary fluid being transported with an increased degree of reliability.

Figure 12 shows, in axial cross section, a third embodiment of an emergency line disconnector according to the present invention, which also comprises a pair of couplings 1,2 having an identical cylindrical shape.

The couplings 1,2 have fluid passages 113,114 of identical configurations. The fluid passageways 113, 114 include first inner walls 115, 116 extending from the joint flanges 7,8 to intermediate portions of the outer barrels 3,4 and having an inside diameter R, and second inner walls 117, 118 having an inside diameter D2 (D2 > R) and third inner walls 119, 120 having an inside diameter D3 (D3 > D2), the second and third inner walls extending from the intermediate portions of the outer barrels 3,4 toward the seal rings 5, 6.The portions of the fluid passageways which extend from the third inner walls 119,120to joint openings 121, 122 in the seal rings 5,6 have a cross-sectional area decreasing relatively gradually, and include tapered seal surfaces 123, 124, respectively, with which the slide valves 127, 128 are engageable. The third inner walls 119, 120 and the second inner walls 117,118 have steps therebetween to which enclosing rings 125, 126 are attached, respectively.

The couplings 1,2 are joined together by the clamp 9 with the fluid passageways being held in communication with each other through the joint openings.

The couplings 1,2 contain respectively in the fluid passageways 113, 114 thereof a pair of slide valves 127,128 a pair of springs 129, 130 for urging the slide valves 127, 128 against the seal surfaces 123, 124 of the seal rings 5,6, respectively, and a pair of stopper rings 131, 132 secured to the first inner walls 115,116, respectively, and against which ends of the springs 129, 130 are held.

The slide valves 127, 128, which are of an identical cylindrical shape, each have one end closed off by a valve head 133, 134 and the other ends formed as openings 135,136 through which a fluid can flow in.

The slide valves have slide rings 137, 138, respectively, having an outside diameter D1 smaller than the inside diameter D2 of the second inner walls 117, 118 and also smaller than the inside diameter H of the enclosing rings 125, 126, with a predetermined gap AS1 defined therebetween, as shown in Fig. 13.

The slide rings 137,138 have axial slots 139,140 defined at intervals around the circumference thereof. The slide rings 137, 138 also have, in inner peripheral surfaces thereof, steps 141,142, respectively, held in engagement with the other ends of the springs. A pair of guide rings 143,144 are fixedly mounted on an outer surface of the slide rings 137, 138 at their openings 135, 136 or rear ends thereof, and have an outside diameter smaller than the inside diameter D2 of the second inner walls 117,118 with predetermined gaps AS2 being defined as restrictor gaps between the guide rings and the second inner walls. The restrictor gaps AS2 have an axial length L.

A pair of central spacer rods 147, 148 project in confronting relation from the valve heads of the slide valves. Cones 149,150,151,152 are mounted on the spacer rods and in the slide rings 137, 138, respectively. The valve heads 133, 134 have a pair of seal packings 153, 154, respectively, attached to ends thereof and extending fully along the circumference thereof.

The first inner walls 115, 116 and the second inner walls 117, 118 have steps 145, 146 defined there-bet- ween and serving as stoppers against which the guide rings 143, 144 of the slide valves can be held, for limiting the stroke or sliding movement of the slide valves. The second inner walls 117, 118, the slide rings 137, 138 of the slide valves 127, 128, the guide rings 143,144, and the enclosing rings 125, 126, jointly define fluid sealing chambers 155, 156.

As illustrated in Figs. 12 and 13, when the couplings 1,2 are joined together for normal use with the slide valves urged against the bias of the spring and the guide rings 143,144 engaging the steps 145, 146, the fluid sealing chambers 155,156 communicate with the slots 139 through an opening width xa, as shown in Fig. 13. The guide rings 143, 144 are spaced from the enclosing rings 125, 126 by a distance E, which is greater than the distance x between the seal rings 153,154 and the seal surfaces 123,124.

The cones 149,150,151,152 have conical surfaces extending at an angle 0 with respect to the axis of the couplings 1,2, the angle being selected such that the fluid can flow through a substantially uniform cross-sectional area in the assembled couplings 1,2.

The operation of the emergency disconnector thus constructed will now be described.

When the couplings 1,2 are jointed to each other by the clamp 9 for normally loading and unloading a fluid therethrough, the slide valves are caused by the spacer rods to be pushed against the force of the springs into engagement with and retained in the predetermined position by the steps 145,146. The slots 139, 140 in the slide valves are partly open into the fluid sealing chambers 155, 156.

When loading the fluid from the storage tank to the tanker, the fluid flows from the loading arm through the first inner wall 116 of the coupling 2 into the opening 136 in the slide valve 128 in the direction of the arrows, from which the fluid goes through the slots 140, a space between the third inner wall 120 and the slide valve 128, a space between the cone 150 and the seal ring 6, and the joint openings 121, 122 into the fluid passageway 113 of the coupling 1.

The fluid introduced into the fluid passageway 113 passes through a space between the cone 149 and the seal ring 5, a space between the third innerwall 119 and the slide valve 127, the slots 139, the opening 135, and the first inner wall 115 into the connector pipe 10, from which the fluid is loaded into the tanker.

Conversely, when fluid is to be unloaded from the tanker to the storage tank, the fluid flows in a direction opposite to that described above. More specifically, the fluid flows in a direction opposite to that of the arrows from the connector pipe 10 through the slots 139, the joint openings 121, 122, the slots 140, and the loading arm into the storage tank.

Therefore, fluid can be stably loaded and unloaded bidirectionally through the joined couplings 1,2.

Since the slots 139, 140 are always open into the fluid sealing chambers 155, 156 when the fluid is loaded or unloaded, the fluid sealing chambers are filled with fluid at all times.

In an emergency where it is necessary to cut off the fluid loading and unloading line immediately, the clamp 9 is detached as shown in Figs. 14 through 15 to separate the couplings 1,2.

Simultaneously with the disconnection of the couplings 1,2, the slide valves are pushed under combination of the reactive force of the springs 129, 130 and the fluid pressure to cause the slide rings 137, 138 of the slide valves 127, 128 to slide to the right (Fig. 13) by the opening width x1, whereupon the fluid sealing chambers 155, 156 are confined between the guide rings 143, 144, the enclosing rings 125, 126, the outer barrels 3,4, and the slide rings 137, 138 to seal a mass M of fluid in each of the fluid sealing chambers. At this time, the seal packings 153,154 are spaced from the seal surfaces 123, 24 by a distance xp.

As the slide valves and the slide rings slide further, the distance between the guide rings 143, 144 and the enclosing rings 125, 126 becomes smaller to pressurize the mass M of fluid in the fluid sealing chambers 155,156. The mass M of fluid thus under pressure produces a cushioning effect on the guide rings 143, 144 and the enclosing rings 125, 126.

Then, the mass M of fluid begins leaking out of the fluid sealing chambers through the gaps AS1, AS2, which however serve as restrictors for limiting the amount of the fluid leaking out therethrough. Therefore, it requires a certain period of time for the slide valves to slide along until the seal packings 153,154 are brought into contact with the seal surfaces 123, 124, respectively, after having slid the distance x2.

There is thus no danger of the slide valves sliding freely and abruptly under the force of the springs 129, 130 and the fluid pressure, and hence of the couplings 1,2 to be cut off suddenly. The slide valves are accordingly allowed to slide at a reduced speed to thereby eliminate the problem of water hammer, for example, occurring in the couplings 1, 2. After a certain period of time required for the slide valves 127, 128 to slide to the end of their strokes, the seal packings 153, 154 of the slide valves are held against the seal surfaces 123, 124, thereby completely sealing off the couplings.

The time t required for the slide valves to slide thusly can be determined by the following equations: (1) The pressure under which the fluid is sealed:

where F: the combination of the reactive force of the spring and the fluid pressure; D1: the outside diameter of the slide ring; and D2: the inside diameter of the second inner wall.

(2) The amount of fluid which has leaked through the gaps AS1, AS2: Q

where R: the gap diameter D1/2 or D2/2; Cl: the fluid viscosity; and L: the length of the restrictor gap.

(3) The volume of fluid discharged from the fluid sealing chamber: V IT v= -(D21-D21).x2 (3) 4 where x2: the gap between the seal packing and the seal surface at the time when the fluid begins to be sealed.

Assuming that the equations (1) through (3) are equivalent to the restriction effects given by the gaps AS1, AS2, the valve sliding time t for the gap x2 can be expressed by: V 2.0 According to actual calculations, where AS = 0.05 mm, L = 12 mm in a shape for use with 3 in.

diameter the time t is 1.16 sec. when the fluid is water.

Instead of defining the gaps AS1, AS2 as the restrictors between the guide rings 143, 144, the outer barrels 3,4, the enclosing rings 125, 126, and the slide rings 137, 138, the guide rings, slide valves, or the enclosing rings themselves may have restrictor holes, for example, for limiting the speed of sliding movement of the slide valves.

With the arrangement of this embodiment of the present invention, as described above, the guide rings and the enclosing rings are mounted circumferentially around the slide valves in areas in which the fluid can enter, and the fluid restrictor gaps or holes are defined between the guide rings and the inner walls of the couplings and between the enclosing rings and the slide valves. When the slide valves slide, the guide rings, the enclosing rings, the slide valves, and the inner walls of the outer barrels of the couplings jointly define fluid sealing chambers. After the couplings have been disconnected from each other, the mass of fluid sealed in the fluid sealing chambers between the guide rings and the enclosing rings is capable of producing a cushioning effect. The restrictor gaps or holes serve to limit leakage of the fluid therethrough. Accordingly, a certain period of time is required before the seal packings on the slide valves are brought into contact with the seal surfaces. There is thus no risk of the slide valves suddenly cutting off the kinetic energy of the fluid being loaded or unloaded. The couplings are completely sealed off and the cause of the water hammer problem is eliminated.

Claims (24)

1. An emergency disconnector for a fluid loading and unloading line, comprising; a pair of couplings having joint openings, respectively, and fluid passages, respectively, a pair of sliders axially slidably disposed in said couplings and having a pair of valve heads from which spacer means extend, respectively, toward one another, means for biasing said sliders toward said joint openings, said sliders being movable by said biasing means into said joint openings to cut off said fluid passages, said sliders being shaped such that they provide a space of a substantially uniform cross-sectional configuration between inner surfaces of said couplings and said sliders.

2. A device as claimed in claim 1, said joint openings being defined by edge portions, said sliders abutting said edge portions to cut off said fluid passages.

3. A device as claimed in claim 2, wherein said sliders comprise slider valve elements, said valve heads including resilient sealing means.

4. A device as claimed in claim 1, said spacer means comprising spacer rods having contacting surfaces when said fluid passages are open, and positioning said sliders against the force of said biasing means.

5. A device as claimed in claim 4, said spacer rods projecting a relatively short distance out of said joint openings when said couplings are disconnected from one another.

6. A device as claimed in claim 1, further including stop rings mounted in said couplings for limiting the stroke of said sliders within said couplings.

7. A device as claimed in claim 6, wherein said stop rings are spaced such that said sliders contact said stop rings when said spacer means contact one another.

8. A device as claimed in claim 1, said valve heads including removable sealing means extending circumferentially therearound.

9. A device as claimed in claim 8, said sealing means being fixed to a ring member detachably connected to said valve heads.

10. A device as claimed in claim 8, said sealing means being movable with said sliders upon closure of said joint openings, to sealingly engage an inner surface of said couplings.

11. A device as claimed in claim 1, further comprising a pair of cover rings respectively mounted on inner walls defining said fluid passages and having fluid passages therein continuous with said fluid passages of said couplings.

12. A device as claimed in claim 11, said cover rings having inner peripheral surfaces, and said sliders carrying sealing means thereon, said sealing means normally contacting said inner surfaces of said cover rings.

13. A device as claimed in claim 12, said sealing means comprising an open, elongate element capable of exhibiting substantial resiliency at extremely low temperatures, and a tubular body extending within said open elongate element.

14. A device as claimed in claim 12, said sliders being movable during closure of said fluid passages so as to abut said sealing means against inner surfaces of said fluid passages, to cut off said fluid passages.

15. A device as claimed in claim 14, said valve heads including retainer disks thereon, said retainer disks abutting second inner surfaces of said fluid passages when said sealing means engage said inner surfaces.

16. A device as claimed in claim 1, said sliders each including guide rings mounted thereon and extending radially outwardly of the body of the slider.

17. A device as claimed in claim 16, wherein outer barrels of said couplings are provided with enclosing rings; an inner wall of said outer barrels, said guide rings, said enclosing rings and an outer surface of said sliders together defining fluid reservoirs.

18. A device as claimed in claim 17, said fluid reservoirs being substantially closed off when said sliders move to cut off said fluid passages, and constituting a damping means retarding movement of said sliders, said fluid reservoirs including restrictive outlets controlling damping of said sliders.

19. An emergency disconnectorfor disconnecting a pair of couplings of a fluid loading and unloading line to thereby cut off fluid flow through the fluid loading and unloading line, comprising; a pair of couplings, each having a fluid passage extending through a barrel of uniform cross section, a first inner wall disposed in said fluid passage and having an inner end closer to said barrel, and a second inner wall disposed in said fluid passage and closer than said first inner wall to said barrel and having an inner end larger in diameter and an opposite end of a diameter equal to or greater than the largest diameter of said first inner wall; a pair of slide valves axially slidably inserted in said couplings, respectively, and having a pair of confronting valve heads, each of said slide valves having a retainer disc removably attached to one of said valve heads, and an annular seal packing mounted circumferentially around said valve head and having a portion projecting radially outwardly from said valve head, each of said slide valves being slidable when said couplings are disconnected from each other, to press said seal packing against said second inner wall and also press a circumferential end face of said retainer disc against said first inner wall to thereby close the joint openings of said couplings.

20. An emergency disconnector as claimed in claim 19, said slide valves being retainable away from each other against the force of biasing means, when said couplings are joined together, by spacer rods projecting axially from centers of said retainer discs and being held in abutment against each other, thereby opening the joint openings of said couplings; a pair of stopper rings for limiting strokes of sliding movement of said slide valves, respectively; and a pair of cover rings mounted on inner walls defining said fluid passages, respectively, between said barrels of said couplings and said second inner walls and having fluid passages contiguous to said fluid passages in said couplings, said cover rings being engageable with outer peripheral surfaces of said seal packings of an elongate seal cover capable of substantial resiliency at extremely low temperatures, and a resilient body extending through said seal cover over an entire length thereof.

21. An emergency disconnector for a fluid loading and unloading line, comprising; a pair of couplings having joint openings, slide valves respectively disposed in said couplings, means biasing said slide valves in a direction to seal off the couplings to thereby cut off the flow of a fluid being loaded or unloaded through the fluid loading and unloading line, a pair of guide rings respectively mounted on said slide valves circumferentially therearound, and a pair of enclosing rings mounted on inner walls of outer barrels of said couplings, respectively, said guide rings and said inner walls of said outer barrels, and said enclosing rings and said slide valves respectively defining therebetween gaps serving as fluid restrictor means, said guide rings, said enclosing rings, said slide valves, and said inner walls of said outer barrels being capable of defining fluid sealing chambers upon sliding of said slide valves.

22. An emergency disconnector for a fluid loading and unloading line substantially as hereinbefore described with reference to and as shown in Figures 1,2 and 3 of the accompanying drawings.

23. An emergency disconnector for a fluid loading and unloading line substantially as hereinbefore described with reference to and as shown in Figures 5 to 11 of the accompanying drawings.

24. An emergency disconnectorfor a fluid loading and unloading line substantially as hereinbefore described with reference to and as shown in Figures 12 to 16 of the accompanying drawings.