WO2016174554A1

WO2016174554A1 - Safety or rupture element for pipelines and method for making said element

Info

Publication number: WO2016174554A1
Application number: PCT/IB2016/052290
Authority: WO
Inventors: Lauro Bosisio; Antonio DONADON; Mario Modena
Original assignee: Donadon Safety Discs And Decives S.R.L.
Priority date: 2015-04-28
Filing date: 2016-04-22
Publication date: 2016-11-03

Abstract

A safety or rupture element for a pipeline through which a fluid passes, comprises a sheet-like body (2) equipped with a rounded central portion (2a) and an annular peripheral portion (2b), wherein the concave face (5a) of the rounded central portion (2a) has at least one curved frangible line (6) that is proximal to the annular peripheral portion (2b) and realized by means of a laser. The curved frangible line (6) has a depth (P1) dimensioned so as to split open upon reaching a pre-established pressure on the convex face (5b), so as to define a petal (3) apt for reversing and enabling outflow of the fluid The element further comprises at least one reversal initiating and guiding zone (8), said zone being defined by at least a first (9a) and a second incision (9b), both of which are discrete and realized on said first face (5a) of the rounded central portion (2a);the first discrete incision (9a) is realized at a centre (C) of the rounded central portion (2a) and the second discrete incision (9b) is realized in an intermediate zone (I) between the centre (C) and the curved frangible line (6) so that a preferential reversal axis (A) oriented towards the frangible line (6) is defined between the incisions (9a, 9b).

Description

SAFETY OR RUPTURE ELEMENT FOR PIPELINES AND METHOD FOR MAKING SAID ELEMENT

The present invention refers to a safety or rupture element for pipelines and a method for making said element.

The present invention is advantageously used in the production of safety elements applied to systems along pneumatic or hydraulic lines, to ensure the necessary safety measures of the system, which can undergo conditions differing from those for which it was designed.

More specifically, these elements are applied to emergency lines in order to completely occlude the conduit on which they are applied.

A high-pressure fluid acts within one of the half-spaces defined by the element, whereas a lower pressure, for example atmospheric pressure, acts on the opposite half-space.

Alternatively, the safety elements of a known type can protect systems that operate at sub-atmospheric pressure. In this case as well, the element is subjected to a difference in pressure that acts between the two opposite surfaces thereof.

When the difference between the pressure acting within the system and the external pressure exceeds a pre-calculated safety threshold value, this disc splits open and enables the pressurized fluid to move beyond the safety element 1 so as to flow out of the system. In this manner, possible undesired excess pressure cannot damage other parts of the system.

In the case of systems that operate at sub-atmospheric pressure, rupturing of the safety disc enables the fluid under sub-atmospheric pressure to flow inside the system.

The safety elements to which reference is being made usually comprise a disc-shaped, sheet-like body with a surface on which the pressurized fluid acts and this surface can be flat, concave or convex.

Alternatively, said discs are square-shaped or rectangular, depending upon the conduit on which they need to be applied. Discs that do not have any pre-established frangible lines open in an undefined manner with possible separation of some parts. For this reason, in many cases, preferably discs with pre-established frangible lines are used; the pre-established frangible lines can be obtained by means of through or non-through incisions of various shapes. In the case of through incisions, a second continuous layer that ensures pneumatic and/or hydraulic sealing is needed and this second layer is weaker than the calibrated section. This is not necessary in the case of non-through incisions.

In any case, these discs can have a plurality of non-through incisions arranged on a surface of the disc in a suitable configuration so as to define respective frangible lines with pre-established rupturing.

In other words, when the threshold value of the fluid pressure is exceeded, the safety disc splits open at said pre-established frangible lines.

In the methods for making these discs, execution of said non-through incisions requires particular attention in terms of depth, length and width, but also as concerns maintaining the mechanical characteristics of the disc material near the non-through incisions. In particular, the crystalline- metallurgical structure of the material needs to remain unaltered.

The methods with the highest performances for realizing non-through incisions on rupture discs, without jeopardizing the crystalline structure thereof, comprise the use of high-frequency lasers and they have been developed by the Applicant in recent years.

Examples of these methods and the devices capable of implementing such methods are known from the international patents WO2008/155783 and WO2013/014614 also filed by Donadon SDD S.r.l.

Note that for the most part, the discs of the prior art have one central rupture portion that is dome-shaped, or rounded, on which a plurality of frangible lines are realized, or in some cases, only one frangible line is realized, and they delimit one or more "petals" apt for opening up when the pressure threshold is exceeded. This rupture portion can be direct- or reverse-acting.

"Direct-acting" is understood as a direct opening of the petal or petals of the rupture portion without reversal; this behaviour is obtained by designing the disc with the concavity facing the pipeline, that is, towards the part under pressure (or, in any case, under higher pressure).

On the contrary, "reverse-acting" is understood as defining the phenomenon by which the rupture portion begins to invert its concavity when a pre-established pressure is reached, and then begins to open along the frangible lines (generally only one circle defining a single petal. Disadvantageously, while the rupturing of the disc is "easily" guided owing to the realization of the frangible lines, governing and predicting the behaviour of the disc during the reversal process is much more difficult, so that even just the definition of the triggering point is a complicated matter. Therefore, the aim of the present invention is to make available a safety or rupture element for pipelines and a method for making said element that simplify calibration of the reversal pressure, improve reproducibility of the reversal phenomenon, and improve behaviour upon opening.

Said aim is achieved by a safety or rupture element for pipelines that has the characteristics of one or more of claims 1 to 7, and by a method for making said element according to one or more of claims 8 to 10.

In particular, this aim is achieved by means of a safety or rupture element for pipelines through which a fluid passes and comprising a sheet-like body equipped with a rounded central portion, or rupture portion, having a concave face and a convex face, and a peripheral annular portion, or junction portion, wherein the concave face of the central rounded portion has at least one curved frangible line that is proximal to the peripheral annular portion and realized by means of a laser, said curved frangible line having a first pre-established depth dimensioned so as to split open upon reaching a pre-established pressure on said convex face, so as to define a petal apt for reversing and enabling outflow of the fluid.

According to one aspect of the present invention, the rupture element comprises at least one reversal initiating and guiding zone, said zone being defined by at least a first and a second incision, both of which are discrete and realized on said first face of the rounded central portion.

The first discrete incision is realized at a centre of the rounded central portion and the second discrete incision is realized in an intermediate zone between said centre and said curved frangible line so that a preferential reversal axis oriented towards said frangible line is defined between said first and said second incision.

Advantageously, in this manner it is possible to define a reversal initiating and guiding zone, thereby ensuring the repeatability thereof.

Moreover, the presence of a reversal initiating and guiding zone made up of a succession of at least two discrete incisions makes it possible to facilitate the opening of the central portion, in that the reversal process develops principally along the preferential axis in a pre-established direction and enabling the splitting up of the frangible line, exploiting the thrust of the reversal action upon its initiation.

This is particularly advantageous in the elements used in pipelines through which a liquid passes, and in which the initiation of the reversal process generates an immediate drop in pressure at the rounded portion, which therefore requires a greater "thrust" in order to continue and bring about the opening thereof.

Note that use of the term "discrete" in this text is understood as specifying that the incision defining the reversal initiating and guiding zone is isolated from the frangible line.

More precisely, the incision has a closed surface of bi-dimensional extension, in which both dimensions are of the same order of magnitude (therefore of comparable dimensions).

These and other characteristics, as well as the advantages thereof, will prove to be more apparent in the following illustrative and thus non-limiting description of a preferred and therefore not exclusive embodiment of a safety or rupture element for pipelines according to the present invention, of which:

- Figures 1 , 2 and 3 include a schematic perspective view, schematic plan view and a schematic section view, respectively, of a safety or rupture element for pipelines according to the present invention.

With reference to the attached figures, number 1 indicates a safety or rupture element for pipelines according to the present invention.

As stated, the safety element 1 is mounted in pneumatic or hydraulic systems, along safety conduits. In particular, the element 1 comprises at least one sheet-like body 2 adapted to completely occlude the opening of the conduit on which it is applied and adapted to rupture after a predetermined pressure value has been reached inside the conduit.

The sheet-like body 2 is an element of a predetermined thickness "S1 " that is very thin, with respect to the other two dimensions thereof.

Note that the sheet-like body 2 is made of a metal material, including for example stainless steel, nickel, aluminium or other metals or particular metal alloys.

Preferably, the sheet-like body 2 is equipped with a central portion 2a, or rupture portion, having two opposite faces 5a, 5b and a peripheral annular portion 2b, or junction portion.

In particular, the annular peripheral portion 2b, when in use, is interposed between two flanges or tubular blocking bodies.

In other words, the annular peripheral portion 2b is close-packed between the flanges (unillustrated).

The central portion 2a instead defines the body that occludes the pipeline and as stated, it has a first face 5a and a second face 5b that are opposite each other. The pressurized fluid acts upon one face (the second face 5b) and the external ambient pressure acts upon the other.

In the case in which the fluid that is acting upon the second face 5b has a pressure higher than a threshold value, the sheet-like body 2 will split open so as to enable the fluid to pass into the safety conduit and enable discharge of excess pressure into an outside environment. The threshold value is determined as a function of the thickness of the sheet-like body, the diameter thereof (that is, the area of the central portion 2a) and the "ductility" given to it by means of one or more machining processes (discussed further herein below).

Preferably, the sheet-like body 2 is a disc, that is, its peripheral geometry is substantially circular.

Preferably, the central portion 2a is rounded, that is, it is dome-shaped. Therefore, the central portion 2a is dome-shaped with a circular base. Therefore, the first face 5a is concave, whereas the second face 5b is convex.

In the preferred embodiment, the central portion 2a is designed to burst at a specified pressure when the pressure is applied on the convex side, that is, on the second face 5b.

This type of safety disc is known as a "reverse type", given that the rupture process begins with a reversal process, that is, a process of overturning the convex portion. The safety disc of the reverse type is particularly suited for use when the acting pressure varies in a cyclic manner because the cyclic stresses do not cause stress due to fatigue in the crystalline- metallurgical structure.

Preferably, for the purpose of ensuring the opening of the sheet-like body 2 at a pre-established pressure, the rounded central portion 2a has at least one curved frangible line 6 that is proximal to the peripheral annular portion 2a and realized by means of a laser.

Note that the frangible line 6 is a non-through score preferably made on the first face 5a (or concave face) of the rounded central portion 2a.

The curved frangible line 6 has a pre-established depth (shallower than the thickness S1 of the body 2) dimensioned so as to split open upon reaching a pre-established pressure on said convex face, so as to define a petal 3 apt for reversing and enabling outflow of the fluid.

In fact, this frangible line 6 defines a guide for the rupture that makes it possible to calibrate the rupture pressure and to guide the rupturing of the central portion 2a in a predetermined and repeatable manner (that is, safely).

The incision defining the frangible line 6 can be of a constant or varying depth along the entire length thereof.

In the preferred embodiment, as the element is of the "reverse" type, the frangible line defines an arc 4 of a circle extending between two end points 4a that substantially face each other.

Therefore, the frangible line 6 extends along a separating edge between the rounded central portion 2a and the annular peripheral portion 2a, in proximity thereto.

In some (unillustrated) embodiments, the frangible line 6 corresponds to the separating edge.

Note that the frangible line thus formed defines a single petal 3 that can be overturned about said end points 4a.

More precisely, the two end points 4a of the arc 4 face each other so that a line (an imaginary line) joining them defines a reversal axis "A" of the petal 3.

According to one aspect of the present invention, the element 1 comprises at least one reversal initiating and guiding zone 8 defined by at least one incision, preferably two discrete incisions 9a, 9b realized on the same face of the frangible line 6.

Note that use of the term "discrete" in this text is understood as specifying that the incision 9a, 9b defining the reversal initiating and guiding zone 8 is isolated from the frangible line 6.

In other words, the incision 9a, 9b is isolated, that is, the incision is completely surrounded by parts of the rounded central portion 2a that are of a thickness equal to said thickness S1 of the sheet-like body 2.

Note that in some embodiments, the depth of the incision 9a, 9b differs from the depth of the frangible line 6.

Therefore, the depth of each discrete incision 9a, 9b is shallower than the predetermined thickness S1 and each incision is completely surrounded by parts of the rounded central portion 2a that are of a predetermined thickness S1 .

In the preferred embodiment, the incision 9a, 9b is of the same depth throughout the entire extension thereof.

However, alternatively, this depth can vary.

Therefore, each discrete incision 9a, 9b is isolated and completely surrounded by unincised or unengraved parts of the rounded central portion 2a.

In the preferred embodiments, each incision 9a, 9b has a closed surface of bi-dimensional extension, in which both dimensions are of the same order of magnitude (therefore of comparable dimensions). In other words, the incision 9a, 9b is not a line.

In particular, each incision 9a, 9b exhibits an axisymmetric shape.

More precisely, the first 9a and the second incision 9b have a substantially precise shape.

In particular, each incision 9a, 9b has a surface area that is less than 2% of the surface area of the central portion 2a.

Preferably, the first 9a and the second incision 9b extend on the surface along two dimensions that are substantially equivalent with respect to each other.

More preferably, the discrete incision 9a, 9b has a polygonal peripheral edge (in the illustrated embodiment it is square).

Alternatively, the discrete incision 9a, 9b has a rounded or circular peripheral edge.

According to one aspect of the present invention, the reversal initiating and guiding zone 8 is defined by at least a first 9a and a second incision 9b.

More precisely, the first discrete incision 9a is realized in the proximity of (or at) a centre C of the rounded central portion 2a, whereas the second discrete incision 9b is realized in an intermediate zone I between the centre C and said curved frangible line 6. Advantageously, in this manner, a preferential reversal axis A oriented towards said frangible line 6 is defined between the first 9a and the second incision 9b.

Note that the centre C of the rounded central portion 2a is the point at the greatest axial distance from a plane in which the annular peripheral portion 2b lies.

More precisely, the centre C of the rounded central portion 2a corresponds to a point of minimum (or maximum) depth of the concavity of the first face 5a.

Advantageously, the presence of a discrete reversal initiating and guiding zone 8 located centrally with respect to the rounded central portion 2a makes it possible to facilitate the reversal of this portion, exploiting the thrust of the reversal action upon its initiation located in the lowest point of the bulb.

The intermediate zone I is instead preferably located in a position distal from the reversal axis A with respect to said centre C.

Note that the intermediate zone I is preferably positioned along a median line (therefore passing through the centre C) of the rounded central portion

2a perpendicular to the reversal axis A.

This median line corresponds to the preferential axis "B".

Advantageously, in this manner, the reversal is initiated in a zone already aligned with the preferential direction thereof.

Preferably, the radial distance between the first 9a and the second incision 9b is comprised between 1 /3 and 2/3 of a radius of the base of said dome, more preferably it is about ½ of the radius of the base of said dome.

This is particularly advantageous in the elements used in pipelines through which a liquid passes, and in which the initiation of the reversal process generates an immediate drop in pressure at the rounded central portion 2a, which therefore requires a greater "thrust" in order to continue and bring about the opening thereof.

More precisely, this application makes it possible to guide the reversal of the central portion 2a in applications preferably with liquids and low pressure.

In this regard, in some embodiments, the reversal initiating and guiding zone 8 comprises a plurality of discrete incisions 9a, 9b arranged in succession (that is, spaced apart from each other) along said preferential axis B.

Increasing the number of incisions leads to greater precision in guiding the reversal towards the desired point on the frangible line 6.

Note that like the frangible line 6, said at least one discrete incision 9 is also realized by means of laser ablation.

Preferably, the engraving step and the step for realizing the incisions 9a, 9b thus preliminarily comprise selecting a pulsed laser beam L with a wavelength range of 300 nanometres to 1800 nanometres, in which the duration of each laser pulse is less than 10 nanoseconds, and preferably less than 1 nanosecond.

Preferably, in the preferred embodiments, the wavelength of the laser beam L is equal to approximately 343, 515, 1030 nanometres, and in any case preferably less than 1552 nanometres.

Preferably, the duration of each laser pulse ranges between 10 femtoseconds (10^*10-15 seconds) and 50 picoseconds; more preferably, this duration ranges between 300 femtoseconds and 10 picoseconds. Laboratory testing using a pulse duration of 800 femtoseconds has shown good results (as shall be described below). In these tests, the wavelength of the laser beam L was equal to 1552 nanometres.

Moreover, the incision step comprises selecting a laser pulse repetition rate (that is to say, the frequency with which each pulse is repeated) ranging between 15 KHz and 1 .5 MHz. Preferably, the pulse repetition rate ranges between 150 KHz and 1 MHz.

In a preferred embodiment, the laser pulse repetition rate ranges between 200 and 600 MHz.

The method further comprises the step of selecting a speed of relative motion between the laser beam L and the sheet-shaped body, that is to say, the speed at which the laser beam moves along the sheet-shaped body.

The method further comprises the step of selecting an energy value for each pulse of the laser beam L.

Preferably, the energy value of each pulse of the laser beam L ranges between 1 microjoule and 250 microjoules, more preferably less than 200 microjoules.

The power of the laser beam L is comprised between 1 and 80 W, preferably between 1 and 10 W.

The incision depth per single pass of the laser is also a function of the selection of the ranges and values cited above. According to the parameters cited hereinabove, the score depth of each single pass of the laser ranges between 0.005 μιη and 5 μιη.

Therefore, in a method for making a safety or rupture element for pipelines, engraving said rupture portion by means of a laser beam is comprised so as to realize at least one curved frangible line 6 having a depth P1 dimensioned so as to split open upon reaching a pre-established pressure so as to define a petal 3 apt for reversing and enabling outflow of the fluid.

More precisely, the engraving step comprises generating a relative rotational movement between said laser beam and said sheet-like body 2 so as to realize a curved frangible line 6 extending along an arc 4 of a circle between two end points 4a, in which the two end points 4a substantially face each other so as to define a reversal axis "A" of the petal 3.

The method preferably comprises a step for realizing, again by means of a laser beam, at least a first 9a and a second incision 9b on said first face 5a of the rounded central portion 2a.

In fact, it should be noted that the engraving and incision steps can be carried out in any order and also simultaneously. Preferably, both incisions 9a, 9b are discrete.

The first incision 9a is made by pointing the laser beam in proximity to (or at) a centre C of the rounded central portion 2a.

The second discrete incision 9b is made by pointing the laser beam at the intermediate zone I between the centre C and the curved frangible line 6. As stated, in this manner, a preferential (imaginary) reversal axis oriented towards said frangible line 6 is defined between the first 9a and the second incision 9b.

The depth of the first and the second incision preferably differs from that of the frangible line 6.

The invention achieves the set aims and offers important advantages.

In fact, the realization of discrete incisions makes it possible to ensure initiation of the reversal action in the proper position, making the process repeatable and reliable.

Moreover, by making the incisions in the central (lowest) zone and/or in the intermediate zone, the reversal can be guided in a reliable manner, adjusting the realization of the incisions as a function of the application.

Claims

1 . A safety or rupture element for a pipeline through which a fluid passes, comprising a sheet-like body (2) equipped with a rounded central portion (2a), or rupture portion, having a first concave face (5a) and a second convex face (5b), and an annular peripheral portion (2b), or junction portion, wherein the first face (5a) of the rounded central portion (2a) has at least one curved frangible line (6) that is proximal to the annular peripheral portion (2b) and realized by means of a laser, said curved frangible line having a depth dimensioned so as to split open upon reaching a pre-established pressure on said second face (5b), so as to define a petal (3) apt for reversing and enabling outflow of the fluid;

characterized in that it comprises at least one reversal initiating and guiding zone (8), said zone being defined by at least a first (9a) and a second incision (9b), both of which are discrete and realized on said first face (5a) of the rounded central portion (2a); said first discrete incision (9a) being realized in the proximity of a centre (C) of said rounded central portion (2a) and said second discrete incision (9b) being realized in an intermediate zone (I) between said centre (C) and said curved frangible line (6) so that a preferential reversal axis (A) oriented towards said frangible line (6) is defined between said first (9a) and said second incision (9b).

2. The safety element according to claim 1 , characterized in that said central portion (2a) is dome-shaped with a circular base and wherein the radial distance between the first (9a) and the second (9b) incision is comprised between 1 /3 and 2/3 of a radius (R) of the base of said dome.

3. The safety element according to claim 2, characterized in that the radial distance between the first (9a) and the second incision (9b) is about ½ of the radius (R) of the base of said dome.

4. The safety element according to any one of the preceding claims, characterized in that said first (9a) and said second incision (9b) are substantially precise in shape.

5. The safety element according to claim 4, characterized in that each one of said first (9a) and second incisions (9b) extends on the surface along two dimensions that are substantially equivalent with respect to each other.

6. The safety element according to any one of the preceding claims, characterized in that said incisions (9a, 9b) are axisymmetric in shape, preferably square or circular in shape.

7. The safety element according to any one of the preceding claims, characterized in that each one of said incisions (9a, 9b) has a surface area that is less than 2% of the surface area of the central portion (2a).

8. The safety element according to any one of the preceding claims, characterized in that said rounded central portion (2a) is of a predetermined thickness (S1 ); said depth (P2) of each discrete incision (9a, 9b) being shallower than said predetermined thickness (S1 ) and each incision being completely surrounded by parts of the rounded central portion (2a) that are of a predetermined thickness (S1 ).

9. The safety element according to any one of the preceding claims, characterized in that said frangible line (6) defines an arc (4) of a circle extending between two end points (4a) that substantially face each other; said frangible line (6) separating the rounded central portion (2a) from the peripheral portion (2b) at said arc (4) of a circle.

10. The safety element according to any one of the preceding claims, characterized in that said frangible line (6) defines an arc (4) of a circle extending between two end points (4a) that substantially face each other so as to define a reversal axis (A) of said petal (3); said second discrete incision (9b) being realized in said intermediate zone (I), in a position distal from said reversal axis (A) with respect to said centre (C).

1 1 . The safety element according to any one of the preceding claims, characterized in that said incisions (9a, 9b) are realized by means of a laser beam.