BREAKAWAY ANTI POLLUTION SAFETY VALVE IN A FLUID DUCT

Abstract: Two flanged cylinders (2, 3), one of which slides inside the other, are kept selectively in firm contact with each other by the engagement of elastic elements (2) and their terminal tooths with grips (8), the said elastic elements and grips being fixed, respectively, on the outer perimeter of the inner cylinder and the outer perimeter of the outer cylinder, the said engagement being maintained until the traction force applied to the two cylinders exceeds a predetermined value.

Description: Breakaway anti pollution safety valve in a fluid duct. The present invention concerns a breakaway anti pollution safety valve in a fluid duct. The field of the invention is that of safety valves capable of coming into action prior to the breakage of marine ducts - be they submerged or on the surface - carrying a fluid and liable to become subjected to the action of abnormal traction forces, especially a duct carrying oil extracted from an underwater source and pumped into a buoy or an oil tanker. Prior art valves suitable for this purpose consist of two cylindrical parts, each of which is provided with two butterflies on its inside that in noπnal conditions are closed since they are kept in position by appropriate means of engagement and, when they become detached from these means, open under the action of springs to interrupt the oil flow in the duct. It should be clarified that the term "butterflies closed" is hereinafter to be understood as referring to the position in which they are held when the duct is open and operating, while "butterflies open" refers to the position they assume after being released to close the duct. Both the cylindrical parts are provided with circular flanges along the entire outer perimeter of the cylinder, so that they can be fixed to each other by means of appropriate bolts. In normal operating conditions these bolts maintain the valve assembled and the separation of the two parts of the valve following a breakaway occurs as a result of the failure of the said bolts, which are designed and calibrated to fail at a given traction force. Indeed, the separation of the two parts of the valve must necessarily occur before the duct actually breaks. The best known valves of this prior art type are manufactured by the Atema, Gail Thomson and MIB companies. The principal drawback of the known valves is that the fixing system of the two parts of the valve requires all the fixing elements to be substituted following a breakage of the duct, while a second drawback is constituted by the fact that the calibrated bolts may not all fail at the same time when the valve is subjected to bending in addition to tension; in that case the two parts of the valve would separate on one side and remain in contact on the other. Such a partial misallignment would not cause the butterflies to become released, so that oil would gush from the duct. A further drawback deriving from this fixing system is the considerable weight and size of valves of this type. The present invention obviates these drawbacks and, as characterized in the claims, comprises two flanged cylinders, one of which slides inside the other, that are kept selectively in firm contact with each other by the engagement of a plurality of elastic elements ending by tooths with a plurality of grips, the said pluralities of elastic elements and grips being fixed, respectively, on the outer perimeter of the inner cylinder and the outer perimeter of the outer cylinder, the said engagement being maintained until the traction force applied to the two cylinders through the opposite parts of the duct exceeds a predetermined value. In the course of this description the flanged cylinders will be called more simply outer cylinder and inner cylinder, while the elastic elements ending by tooths will be referred to as tooths. An external casing associated with the upper surface of the flange of the said cylinders encloses the said tooths and grips, the enclosure being made watertight by means of appropriate gaskets. The engagement of said tooths with said grips is precalibrated in order to fail before a possible duct breakage. Each of the said cylinders is conventionally provided on its inside with two butterflies kept closed by a suitable engagement, this too arranged on the inside of the cylinder. Upon the detachment of the two cylinders, these butterflies become released from the said suitable engagements to close the duct and interrupt the oil flow, each butterfly moving under the action of two torsion springs. Lastly, the fixing of this valve to the duct is made by associating the flange of each cylinder with a connection flange forming part of the duct end to be joined by the valve. The principal advantage of the valve according to the invention over prior art valves consists of the fact that it can be completely reassembled after a duct failure and does not call for any repairs or replacements; a second advantage consists of the fact that, even when the valve is loaded in both tension and bending, the two parts of the valve will always completely separate along the longitudinal axis; yet another advantage is provided by the fact that the said engagement permits the valve to be smaller than its prior art counterparts. The present invention will now be described in greater detail by means of an embodiment example illustrated with the help of the attached diagrammatic drawings wherein Figures 1 to 4 are longitudinal sections through the valve. Figures 1, 2, 3 and 4 show one and the same valve 1 in successive phases of the separation of the two cylinders when the latter come under the action of a traction force exceeding a predetermined value through a pipe line carrying oil (though the oil flow is not shown on the drawings). Identical numbers in these figures always refer to identical parts. In particular, these figures show a valve 1 consisting of an outer cylinder 2 that slides on an inner cylinder 3 , the said two cylinders being provided, respectively, with the flanges 4 and 5 . A ring 6 is fixed to the flange 5 by means of the bolts b' carries, arranged at a suitable distance from each other, the elastic elements 7 , each of which terminates in a hook that enables them to engage with a grip consisting of a calibrated ring 8 and thus keep the cylinders 2 and 3 in firm contact with each other up to a predetermined traction force, the said calibrated ring 8 being attached to the outer perimeter of the said outer cylinder 2 . A gasket 9 arranged between the two sliding surfaces of the said cylinders prevents the leakage of oil. The flanges 4 and 5 are each fixed by means of bolts b" to the respective connection flanges 10, 1 1 which in their turn are fastened to the two parts of the pipeline 12 . When the traction force applied to the two cylinders through the pipeline 12 , as indicated by the arrows F, exceeds a predetermined value, the elastic elements 7 will deform and become disengaged from the calibrated ring 8 , thus permitting the cylinders 2 and 3 to come apart and avoid breakage of the pipe elsewhere. The exact geometry of the contact surfaces of the elastic elements 7 and the calibrated ring 8 , together with the elasticity of the said elastic elements, constitute the calibration of the resistance that the valve can oppose to a predetermined traction force. Furthermore, it can be seen from Figure 1 that inside each cylinder there are two butterflies 13 that are kept closed by an appropriate engagement not shown in the figure. The details of the functioning of these butterflies will not be described here, since the arrangement is well known from the prior art. Figure 2, in particular, shows that the initial separation of the two cylinders 2 and 3 causes the disengagement of the elastic elements 7 from the calibrated ring 8 . In this phase the two butterflies are still closed. Figure 3, on the other hand, shows that the butterflies 13, little by little as the two cylinders move away from each other, disengage from the means that keeps them closed and begin to open in the direction of the arrows P under the action of two torsion springs, though neither the means of engagement nor the torsion springs are shown in the figure. The figure also shows that at this stage the elastic elements 7 have become completely disengaged from the calibrated ring 8 . Figure 4 shows the phase in which the butterflies 13 are completely open. In this phase one notes that the pipe becomes completely closed, thus blocking the oil flow. The figure further shows that inside the cylinders 2 and 3 , as already happens in the case of some known valves, there forms a chamber 14 to limit the loss of oil. In fact, the largest quantity of oil that can become spilt after the two cylinders come apart is the volume contained in this chamber. Unlike the previous figures, Figure 4 shows that the engagement of the elastic elements is assured by a groove 15 in the outer surface of the cylinder 2 . This figure also shows the casing 16 that encloses the elastic elements and the engagement by means of gaskets 17 that render it watertight. The said casing is fixed to the upper surface of the flange 4 by screws 18 and is only in rest on the upper surface of flange 5 in such a way as not to cause any interference when the cylinders 2 and 3 move away from each other.

Claims: CLAIMS 1. A breakaway anti pollution safety valve (1) in a fluid duct (12) that comprises two flanged cylinders (2, 3), one of which slides inside the other, characterized in that the said cylinders (2, 3) are kept selectively in firm contact with each other by the engagement of a plurality of elastic elements (7) and their terminal tooths with a plurality of grips (8), the said pluralities of elastic elements and grips being fixed, respectively, on the outer perimeter of the inner cylinder and the outer perimeter of the outer cylinder, the said engagement being maintained until the traction force applied to the two cylinders through two opposite parts of the duct (12) exceeds a predetermined value. 2. A breakaway anti pollution safety valve (1) in accordance with claim 1, characterized in that the said plurality of elastic elements comprises a ring (6) that carries some appropriately spaced longitudinal extensions (7) terminating in tooths and that the said plurality of grips is an annular projection (8). 3. A breakaway anti pollution safety valve (1) in accordance with claim 1, characterized in that the said plurality of grips consists of an annular groove (15) on the outer surface of the said outer cylinder (4). 4. A breakaway anti pollution safety valve (1) in accordance with any one of the preceding claims, characterized in that a casing (16) associated with the outer surfaces of the said cylinders (2, 3) encloses the said plurality of elastic elements and grips (7, 8) in a water-tight manner.

Inventors: ABBA ANDREA, MONTI CORRADO, ABBA', ANDREA, MONTI, CORRADO
Applicants: ABBA ANDREA, MECAER MECCANICA AERONAUTICA S, MONTI CORRADO, ABBA', ANDREA, MECAER MECCANICA AERONAUTICA S.R.L., MONTI, CORRADO
Application year: 1998
Main classification: F16L55
IPC codes: F16L55