WO2006108770A2

WO2006108770A2 - Pressure regulating device for natural gas

Info

Publication number: WO2006108770A2
Application number: PCT/EP2006/061242
Authority: WO
Inventors: Michele Bernardi; Paolo Calciolari; Fabio Greco Lucchina; Maurizio Miotello
Original assignee: Pietro Fiorentini Spa
Priority date: 2005-04-13
Filing date: 2006-03-31
Publication date: 2006-10-19
Also published as: WO2006108770A3; ITVI20050109A1

Abstract

The invention is a device (1; 100; 200; 300; 400; 500; 600) for regulating the gas pressure and/or flow rate, comprising a 'fail close' throttling valve (2; 401; 116) positioned between a duct (A) for conveying high-pressure gas and a duct (M) for conveying gas at a lower pressure than that of the gas contained in the conveying duct (A), control means (4; 201; 301; 403; 501) of the throttling valve (2; 401; 116) provided with a pressure chamber (5; 117; 202; 302; 404; 502) in which the gas coming from the conveying duct (A) is collected, and first pressure control and regulation means (9; 405) equipped with a pipe (10; 203; 303; 406; 504) for conveying high-pressure gas to the pressure chamber (5; 117; 202; 302; 404; 502) and with means (11; 410) for connection to the outlet way (2B; 401B) of the throttling valve (2; 401; 116). The device (1; 100; 200; 300; 400; 500; 600) comprises second pressure control means (12; 101; 204; 407; 505) positioned upstream of the first control means (9; 405) and provided with a first pipe (13; 102; 205; 304; 408; 506) for connection to the first control means (9; 405), with connection ducts (14) for conveying the gas withdrawn from the conveying duct (A) of the throttling valve (2; 401; 116) to the first pipe (13; 102; 205; 304; 408; 506) and with a three-way coupling (16; 118; 207; 306) that connects the conveying pipe (10; 203; 303; 406; 504), a supply/discharge line (47; 210; 311) of the pressure chamber (5; 117; 202; 302; 404; 502) and a vent pipe (15; 103; 208; 305) for the gas contained in the pressure chamber (5; 117; 202; 302; 404; 502).

Description

Description of the Letters Patent entitled: "DEVICE FOR REGULATING THE GAS PRESSURE AND/OR FLOW RATE FOR PRESSURE REGULATING STATIONS BELONGING TO GAS TRANSPORTATION AND/OR DISTRIBUTION SYSTEMS". In the name of the Company PIETRO FIORENTINI SPA - Via lppolito Rosellini, 1 - 20124 MILANO - ITALY. DESCRIPTION

The invention concerns a device for regulating the gas pressure and/or flow rate for pressure regulating stations belonging to natural gas transportation and/or distribution systems.

A similar regulating device currently available and manufactured according to the known art performs all the functions required for the normal operation of a regulating valve for industrial processes, usually excluding the protection function required by the latest European regulations, according to which these devices must prevent the pressure of the pressure equipment connected downstream of them from exceeding the allowable limits. This last function is one of the main requisites for compliance with European Directive 97/23/EC, known as the PRESSURE EQUIPMENT DIRECTIVE (PED). It is known that natural gas extracted under high pressure from reservoirs is brought to the users' gas intake through suitable transportation and distribution pipelines.

The main transportation pipeline that connects the reservoir to the different distribution pipelines that branch off from it is usually equipped with intermediate compression systems that compensate for the gas pressure drop along the transportation pipeline.

Upstream of each distribution system there is a pressure regulating station that makes it possible to reduce the pressure of the combustible gas to be delivered to a successive distribution or transportation network or to single users.

The pressure regulating station comprises isolating valves and a plurality of pressure devices where gas is substantially filtered, sometimes heated, expanded to reduce its pressure and sometimes measured and integrated with odorizing substances to make it available to the successive distribution network or to single users. In all the pressure equipment installed downstream of the pressure regulating station, the operating pressure is lower than the pressure upstream of the system.

According to the regulations in force, each one of the pressure devices that make up the pressure regulating station must bear the value of the maximum allowable pressure PS on its rating plate.

This data represents the pressure value beyond which the pressure equipment runs the risk of causing gas leaks in the atmosphere, damage and/or breakages. Considering that the fluid transported and handled in these systems is flammable and explosive, it is extremely important to prevent the pressure in all types of pressure equipment from exceeding the allowable limits. In this regard, according to the above mentioned European Directive PED, all pressure equipment must be protected by means of safety devices that must meet certain requirements in order to be actually capable of avoiding pressures above the allowable limits.

According to a known technique, the pressure of the gas delivered by the pressure regulating station is often controlled by a regulating device comprising at least one throttling valve of the type known in the field as "fail close" valve, and a control and regulation loop.

In other known alternatives, the pressure regulating device with "fail close" throttling valve is installed upstream of another regulating device, comprising a "fail open" throttling valve, to perform an in-line monitoring function and automatically replace the "fail close" valve for reducing the pressure when the latter does not work.

To complete the information provided, it is important to explain that a "fail close" throttling valve is a valve that stops the upstream-downstream flow of the gas in case of reasonably predictable breakages of some of its main parts or in case of lack of pressure in the gas that regulates its operation. This valve has an inlet connected to the conveying duct of the high-pressure gas coming from a gas supply network, and an outlet connected to the delivery pipe of the gas with lower pressure than that of the gas in the conveying duct. The delivery duct is usually connected, in turn, to a gas transportation or distribution network or to at least one user. The "fail close" throttling valve also comprises a gas flow regulating shutter, connected to a control head provided with a pressure chamber and a feed pipe through which the gas taken from the high pressure side is introduced in the pressure chamber itself to adjust the position of the shutter. The introduction of gas in the pressure chamber is managed by the control and regulation loop, which comprises positioning means equipped with a first way connected to the pressure chamber feed pipe and a second way communicating with a pressure reducer for the gas coming from the conveying duct. The positioning means also comprise a third way that communicates with data collecting and processing means belonging to the control and regulation loop and constituted, for example, by a data processor and by a pressure measuring device positioned downstream of the "fail close" throttling valve. In other known solutions, the control and regulation loop comprises a pneumatic regulator, connected through a pipe to the delivery way of the "fail close" throttling valve, having the same functions as the data collecting and processing means.

The data collecting and processing means cooperate with the positioning means to move the shutter according to the pressure measured downstream. When the pressure does not correspond to a preset value, in fact, they send a control signal to the positioning means and these change the position of the shutter in the "fail close" throttling valve, until the above mentioned preset pressure value is restored.

The positioning means are fed by gas coming from the system that supplies gas for the plant instruments, from the gas conveying duct after any pressure reduction carried out through a pressure regulating unit or, when the pressure values allow this option, directly from the conveying duct. Therefore, if the pressure upstream of the equipment installed downstream of the "fail close" throttling valve exceeds a given safety value, near the allowable pressure, the control and regulation loop closes the shutter, preventing a further supply of gas from causing a pressure increase above the mentioned limit.

The regulating device intervenes also when, for example, the downstream pressure drops below values that cause an excess flow rate to be withdrawn from the supply network, with consequent application of the penalties provided for by the gas supply contracts. The known pressure regulating devices used in the gas pressure regulating stations have some considerable drawbacks when they have to be classified as safety devices according to the provisions of the PED directive. A first drawback is due to the fact that the control and regulation loop, in order to be operated, needs to be fed with pressurised gas and very often with electric current.

In some cases, the gas used for feeding the control and regulation loop is taken from the duct upstream of the "fail close" throttling valve, so that, in the presence of gas, the mechanical energy necessary for the operation of the loop itself is always available.

In normal operating conditions, there is no risk that the downstream pressure exceeds the preset value due to the lack of energy for the operation of the control and regulation loop. On the other hand, in case of lack of pressure in the upstream duct, the problem of an excess downstream pressure does not exist.

However, in many embodiments of the invention the control and regulation loop is connected to an external power supply network, so that any interruptions in the supply of electric current or malfunctions in the operation of the network negatively affect the operation of the regulating device. A further recognized drawback is due to the fact that, in some cases, breakages or failures in one or more of the components of the control and regulation loop may cause the incorrect introduction of gas in the pressure chamber and make the "fail close" throttling valve open inappropriately, with inevitable and uncontrolled pressure increases in the delivery duct. For the reasons explained above, the regulating device carried out according to the known art cannot be classified as a safety device according to the PED Directive.

Another, yet not the least drawback, is represented by the fact that, to avoid the risk of stoppage of the pressure and/or flow rate regulating device due to the lack of external electric energy, it is necessary to equip the system with auxiliary power sources, such as an uninterruptible power supply unit, to compensate for any blackouts in the power supply network of the data collecting and processing means. The installation of these auxiliary power sources, however, makes the system more complex and expensive, and also requires routine maintenance to guarantee its efficiency over time.

The present invention aims to overcome the drawbacks described above.

In greater detail, the main object of the present invention is that any regulating device equipped with "fail close" throttling valve currently on the market or installed before the coming into force of the PED Directive, should be capable of ensuring protection against pressure values exceeding the maximum allowable limits for the equipment installed downstream, so that it can be classified as a safety device according to the PED Directive.

It is a further object of the invention to simplify, compared to the known art, the construction form of the regulating devices equipped with "fail close" throttling valve, when these must also be classified as safety devices according to the above mentioned PED Directive.

The objects mentioned above are achieved through the implementation of a device for regulating the gas pressure and/or flow rate for pressure regulating stations belonging to gas transportation and/or distribution systems that, according to the main claim, comprises:

- at least one "fail close" throttling valve positioned between a duct for conveying high-pressure gas coming from a gas supply network, and a duct for delivering gas at lower pressure than said gas in said conveying duct, destined for a transportation and/or distribution network or at least one user;

- means for controlling said throttling valve, provided with a pressure chamber inside which the gas coming from said conveying duct is collected; - first pressure control and regulation means, provided with a pipe for conveying the high-pressure gas coming from said conveying duct into said pressure chamber and with means for connection to the outlet of said throttling valve, and is characterised in that it comprises second pressure control means arranged upstream of said first control and regulation means and equipped with:

- a first pipe for connection to said first control and regulation means;

- connection ducts for conveying the gas withdrawn from the inlet of said throttling valve to said first pipe; - a three-way union that connects said first high-pressure gas conveying pipe, a supply/discharge line of said pressure chamber and a vent pipe for the gas contained in said pressure chamber.

Advantageously, any regulating device equipped with "fail close" throttling valve currently available on the market, even if already installed, becomes a safety device according to the PED Directive, independently of the construction and/or functional characteristics of the first control and regulation means. This is achieved thanks to the installation of second pressure control means arranged upstream of said first control and regulation means. The invention makes it possible, in particular, to classify the already existing pressure regulating devices that were installed before the coming into force of the PED Directive as safety devices according to the provisions of said directive, with no need to replace them.

Still advantageously, the pressure regulating device carried out according to the invention can be classified as a safety device according to the PED Directive even in case of lack of electric energy, since it can operate correctly even with the gas pressure only.

Therefore, the pressure regulating device, classified as a safety device according to the PED Directive, does not pose the described drawbacks to be found in the devices carried out according to the known art and due to blackouts or malfunctions in the power supply network.

Still to advantage, the second control means prevent the first control and regulation means from conveying gas in an uncontrolled manner in case of breakages or failures in one or more of their components, the pressure chamber, the control means of the "fail close" throttling valve. As will be better explained below, this is achieved by stopping the gas supply to the first control and regulation means from the second control means. Advantageously, furthermore, the pressure regulating device of the invention has a simpler construction form than the known regulating devices to be classified as safety devices according to the PED Directive. The objects and advantages described above will be highlighted in greater detail in the description of some preferred embodiments of the invention, provided indicatively with reference to the attached drawings, wherein: - Figure 1 is a diagram of the regulating device subject of the invention in a first operating condition; - Figure 2 is a diagram of the device of Figure 1 in a second operating condition;

- Figure 3 shows an enlarged detail of Figure 1 ;

- Figure 4 shows an enlarged detail of Figure 2;

- Figure 5 shows a construction variant of Figure 3; - Figure 6 shows a diagram of a first construction variant of Figure 1 ;

- Figures 7 and 8 show a diagram of a second construction variant of Figure 1 in two distinct operating conditions;

- Figures 9 and 10 show a diagram of a third construction variant of Figure 1 in two distinct operating conditions; - Figures from 11 to 13 show three further construction variants of Figure 1. The device for regulating the gas pressure and/or flow rate for pressure regulating stations belonging to gas transportation and/or distribution systems is represented in two different applications in Figures 1 and 2, where it is indicated as a whole by 1. It can be observed that the regulating device 1 comprises a "fail close" throttling valve, indicated as a whole by 2, provided with an inlet way 2a connected to a duct A for conveying high-pressure gas coming from a gas supply network, not represented herein, and with an outlet way 2b connected to a duct M for delivering gas at a lower pressure than the gas contained in said gas conveying duct A and destined for a transportation and/or distribution network or for at least one user, not represented herein. From this point onwards, for the sake of simplicity, the term "throttling valve" shall mean exclusively a "fail close" throttling valve. The throttling valve 2 is also equipped with a shutter 3 for regulating the gas flow inside it between the inlet way 2a and the outlet way 2b.

The regulating device 1 also comprises means, indicated as a whole by 4, for controlling said throttling valve 2, said control means being provided with a pressure chamber 5 inside which the gas coming from the conveying duct A is collected. Preferably, inside the pressure chamber 5 there are an elastic membrane 6, a rod 7 fixed to the latter and connected to the shutter 3 of the throttling valve 2, and elastic means, indicated as a whole by 8, resting on the elastic membrane 6 on the side opposite the rod 7. The regulating device 1 also comprises first pressure control and regulation means, indicated as a whole by 9, provided with a pipe 10 for conveying the high-pressure gas coming from the gas conveying duct A into the pressure chamber 5 and with means, indicated as a whole by 11 , for connection to the outlet way 2b of the throttling valve 2.

According to the invention, the regulating device 1 comprises second control means, indicated as a whole by 12, arranged upstream of said first control and regulation means 9 and equipped with:

- a first pipe 13 for connection to the first control and regulation means 9;

- connection ducts 14 for conveying the gas withdrawn from the inlet way 2a of the throttling valve 2 to said first pipe 13; - a three-way coupling, indicated as a whole by 16, that connects the high-pressure gas conveying pipe 10, a supply/discharge line 47 of the pressure chamber 5 and a vent pipe 15 for the gas contained in the pressure chamber 5.

Figures 1 and 2 show that the three-way coupling 16 is a T coupling, having a first way connected to the conveying pipe 10, a second way connected to the supply/discharge line 47 of the pressure chamber 5 and a third way connected to the vent pipe 15.

In this case the vent pipe 15 is directly connected to the second control means 12, also called "pneumatic control loop", which in turn comprise: - a block/switching valve, indicated as a whole by 17, which places the first pipe 13 in communication with a feed pipe 18 connected to the inlet way 2a of the throttling valve 2;

- an actuator, indicated as a whole by 19, mechanically connected to the block/switching valve 17, provided with a first way joined to a second pipe 20 for connection to the outlet way 2b of the throttling valve 2 and with a second way joined to a first union pipe 21 connected to the feed pipe 18. According to the preferred embodiment of the invention described herein, the block/switching valve 17 is of the five-way type, wherein a first way communicates with a first vent 22 for venting into the atmosphere, a second way communicates with the first pipe 13, a third way with the feed pipe 18, a fourth way with a second vent 23 for venting into the atmosphere and a fifth way with the vent pipe 15.

The block/switching valve 17 is of the slide type, comprising a valve body 24 inside which there are two sliding switching members 25, 26, arranged in series and integral with each other. The construction form of the actuator 19 is represented in detail in Figures 3 and 4, where it is possible to observe that it comprises a body 27, in which there is a central duct 28 housing a moving rod 29 connected at one end 29a to an elastic element 30 and at the opposite end 29b to a main pressure chamber 31.

The moving rod 29 is provided at its end 29b with an elastic membrane 46 that delimits the main pressure chamber 31.

According to another construction variant of the invention, illustrated in Figure 5, a pair of elastic membranes 46a, 46b, one as a spare, is provided instead of a single elastic membrane.

The moving rod 29 cooperates with the switching members 25, 26 of the block/switching valve 17.

In the body 27 of the actuator 19 there is also a transverse duct 32 housing a piston 33 connected at one end 32a to the switching members 25, 26 of the block/switching valve 17 and at the opposite end 32b to a secondary pressure chamber 34.

The main pressure chamber 31 is connected to the outlet way 2b of the throttling valve 2, while the secondary pressure chamber 34 is connected to the inlet way 2a of the throttling valve 2. The block/switching valve 17 is provided with resetting means, indicated as a whole by 45 and preferably with manual control, used to restore the gas flow to the positioning means, indicated as a whole by 35.

Figures 1 and 2 also show that the regulating device 1 comprises a first pressure regulating unit, indicated as a whole by 43, provided with an inlet connected to the inlet way 2a of the throttling valve 2 and with a delivery way connected to the second control means 12.

The regulating device 1 also comprises a second pressure regulating unit, indicated as a whole by 44, provided with an inlet connected to the second control means 12 and a delivery way connected to the first control and regulation means 9.

The pressure regulating units 43 and 44 are provided in those regulating devices where the pressure equipment positioned downstream cannot bear certain operating pressures present upstream. In other embodiments of the invention, the regulating device may be without one or more of the above mentioned pressure regulating units, according to the pressure values required by the equipment positioned downstream.

In these conditions, the first control and regulation means 9, which in the sector are also known as "control and regulation loop", comprise:

- data collecting and processing means, indicated as a whole by 36, connected to the outlet way 2b of the throttling valve 2 through the connection means 11 , in this specific case constituted by electric cables;

- positioning means 35, operatively associated with the shutter 3 of the throttling valve 2, connected to the pressure chamber 5 of the control means 4 through the conveying pipe 10 and to the second control means 12 through the first pipe 13.

Preferably, but not necessarily, the data collecting and processing means 36 are constituted by a data processor 37, connected to the positioning means 35, and by a pressure transmitter 38, electrically connected to the data processor 37 and in communication with the outlet way 2b of the throttling valve 2.

The positioning means 35 are, on the other hand, constituted by an electropneumatic converter 39, electrically connected to the data processor 37, provided with a delivery way connected to a third pipe 41 and with a way connected to the first pipe 13 through a second union pipe 42. The positioning means 35 also comprise a positioning device 40, having a delivery way connected to the conveying pipe 10, a way connected to the first pipe 13 and a way connected to the third pipe 41.

Figure 6 shows a first construction variant of the invention, in which the regulating device, indicated as a whole by 100, is differentiated from the one described above due to the different configuration of the second control means, indicated as a whole by 101.

In fact, they comprise a first block/switching valve, indicated as a whole by 104, of the three-way type, provided with a first way that communicates with a first vent 107 for venting into the atmosphere, with a second way that communicates with the first pipe 102, and with a third way that communicates with the feed pipe 106.

The second control means 101 also comprise a second block/switching valve, indicated as a whole by 105, of the three-way type, provided with a first way that communicates with a second vent 108 for venting into the atmosphere, with a second way that communicates with a third vent 109 for venting into the atmosphere, and with a third way that communicates with the vent pipe 103. Both the block/switching valves 104, 105 are of the slide type, each one comprising a corresponding valve body 110, 111 inside which there is a sliding switching member, indicated by 112, 113, respectively. The switching member 112 of the block/switching valve 104 is operatively connected to the switching member 113 of the block/switching valve 105 through a rod 114 connected to one end of the switching member 113 and of the switching member 112 that is mechanically connected to the actuator, indicated as a whole by 115. It is important to note that the three-way coupling, indicated as a whole by 118, is equal to that present in the embodiment described above. The successive Figures 7 and 8 show a third construction variant of the invention, wherein the regulating device, indicated as a whole by 200, is distinguished from the previous ones due to the fact that the three-way coupling, indicated as a whole by 207, takes the form of a three-way actuated valve equipped with a control member 209.

The three-way coupling 207 has a first way connected to the conveying pipe 203, a second way connected to the supply/discharge line 210 of the pressure chamber 202 of the control means, indicated as a whole by 201 , and a third way connected to the vent pipe 208 leading into the atmosphere.

The control member 209 is connected to a fourth pipe 206, connected to the first pipe 205 that, in normal operating conditions, contains high-pressure gas that operates the control member 209 of the three-way valve. In the construction variant shown in Figures 9 and 10, the regulating device, indicated as a whole by 300, is provided with a three-way coupling, indicated as a whole by 306, like that shown in Figures 1 and 2, that is, T coupling. If, on the one hand, the first and the second way are still respectively connected to the conveying pipe 303 and to the supply/discharge line 311 of the pressure chamber 302 of the control means, indicated as a whole by 301 , the third way, instead, is connected to the vent pipe 305 that communicates with the atmosphere by activating a check valve 307 and through the first pipe 304 and the second control means, more specifically the block/switching valve 308, as will be better explained below. Figure 11 shows a further construction variant of the invention, in which the regulating device, indicated as a whole by 400, is differentiated from those of the embodiments described above due to the configuration of the first control and regulation means, indicated as a whole by 405.

According to the preferred embodiment of the invention described herein, they comprise: - a pneumatic regulator 409, connected to the outlet way 401b of the throttling valve, indicated as a whole by 401 , through connection means indicated as a whole by 410 and constituted by a fifth pipe, and to the first pipe 408 through a second union pipe 411 ;

- a pneumatic positioner 412, operatively connected to the shutter 402 of the throttling valve 401 , connected to the pneumatic regulator 409 through a third pipe 413, to the pressure chamber 404 of the control means, indicated as a whole by 403, through the conveying pipe 406 and to the second control means, indicated as a whole by 407, through the first pipe 408.

Figure 12 shows a further construction variant of the invention, in which the regulating device, indicated as a whole by 500, is equipped with positioning means, indicated as a whole by 507, whose configuration is different from that of the previous construction variants.

In fact, they are constituted by an electropneumatic positioning device 508, electrically connected to the data processor 509 of the data collecting and processing means, indicated as a whole by 503.

The electropneumatic positioner 508 has a delivery way connected to the conveying pipe 504 that connects it to the pressure chamber 502 of the control means, indicated as a whole by 501 , and an inlet joined to the first pipe 506 that connects it to the second pressure control means, indicated as a whole by 505.

In this case and depending on the specific pressure conditions, the regulating device 500 comprises only the first pressure regulating unit, indicated as a whole by 510.

In the construction variant shown in Figure 13, the regulating device, indicated as a whole by 600, is differentiated from the previous ones due to the fact that the block/switching valve, indicated as a whole by 601 , is provided with automatically controlled resetting means, indicated as a whole by 602, for example elastic means.

From an operating point of view, for the regulating device 1 the pressure transmitter 38 constantly measures the gas pressure value at the delivery way 2b of the throttling valve 2, and then sends it to the electronic processor 37. If, for example, the pressure drops below the normal operating value of the system, the electronic processor 37 send an electric control signal to the electropneumatic converter 39, which converts it into a pneumatic control signal for the positioning device 40.

The latter introduces pressurised gas in the pressure chamber 5 of the control means 4, thus allowing the shutter 3 to be opened and increasing the gas flow rate in the delivery duct M. If, on the other hand, the downstream pressure value is higher than the set value, the first control and regulation means 9 intervene through the positioning device 40 and make the gas flow outside, so that the elastic means 8 positioned in the control means 4 close the shutter 3 and stop the gas flow. If the first control and regulation means 9, due to failures and/or breakages, wrongly continue to convey gas into the pressure chamber 5, lifting the shutter 3 and thus opening the valve 2, the second control means 12 intervene automatically, thus preventing abnormal pressure increases in the delivery duct M.

Under similar circumstances, a first condition for the intervention of the second control means 12 is an increase in the pressure value at the outlet way 2b of the throttling valve 2.

In this case, the pressure value inside the main pressure chamber 31 of the actuator 19 increases and, consequently, the elastic element 30 does not balance the thrusting action of the rod 29, which moves upwards, as shown in Figure 4, allowing the operation of the switching members 25, 26 of the valve 17, which slide from the operating position of Figure 1 , where the first pipe 13 and the feed pipe 18 are connected, to the position where the gas flow is interrupted, as shown in Figure 2.

The gas contained inside the pressure chamber 5, which keeps the shutter 3 open, thus flows out through the vent pipe 15 connected to the first vent 22, as shown in Figure 2.

The elastic means 8 thus allow the shutter 3 to be closed and the gas supply downstream of the throttling valve 2 to be interrupted.

The restoration of the normal operating conditions of the regulating device 1 , that is, the gas supply to the positioning means 35, is achieved by manoeuvring the resetting means 45, associated with the slide valve 17, which, moving from the position shown in Figure 1 to the position shown in Figure 2, translate the switching members 26, 25 until restoring the gas flow between the first pipe 13 and the feed pipe 18.

If, on the other hand, the downstream pressure drops below the set values, the main pressure chamber 31 of the actuator 19 does not balance the elastic force developed by the elastic element 30 associated with the rod 29. The rod 29 thus moves vertically downwards, operating the switching members 25, 26 of the slide valve 17 again, closing the communication between the first pipe 13 and the feed pipe 18, and thus preventing the supply of gas to the positioning means 35.

In this way, the gas flows out of the pressure chamber 5 of the control means 4 and the shutter 3 is closed.

This situation, which in itself does not represent a danger for the devices positioned downstream of the throttling valve 2, should in any case be avoided, in order not to withdraw an excessive quantity of gas from the transportation line, which would lead to the application of a penalty by the supplier. The closing of the throttling valve 2 due to an increase or drop in the downstream pressure represents two alternative situations that may take place alternately in different moments. This takes place since the actuator 19 is equipped both with the maximum pressure and minimum pressure elastic elements 30.

Furthermore, with the maximum and minimum pressure elastic elements 30, the conditions for the intervention of the actuator 19 are satisfied also in case of gas leaks from the main pressure chamber 31 , for example due to breakages of the elastic membrane 46, since even in these conditions the rod 29 moves downwards and closes the shutter 3, as described above. Rather, this operating condition is an essential requisite for compliance with the PED Directive, since a safety device for blocking a further gas flow must be capable of stopping said flow also in case of reasonably predictable breakages of some of its components.

In the case illustrated in Figure 5, however, the actuator 19a shall operate regularly also in case of breakage of one of the elastic membranes 46a, 46b, since the broken one can be replaced by the spare membrane that shall serve the same function, that is, shall limit the pressure value inside the main pressure chamber 31a. This operating condition, too, also meets an essential requirement set by the

PED Directive for the safety devices, the so-called "principle of redundancy", aimed at guaranteeing correct operation also in case of reasonably predictable breakages of some components. A condition of intervention of the actuator 19 takes place also if the pressure in the first union pipe 21 that feeds the actuator 19 drops below a minimum value that allows the operation of the block/switching valve 17.

This happens, for example, if the first pressure regulating unit 43 upstream of the actuator 19 gets clogged or does not operate correctly and causes the closing of the block/switching valve 17 through the piston 33 present in the actuator 19.

For the regulating device 100, if the conditions for the operation of the second control means 101 are satisfied and the pressure conditions downstream of the throttling valve 116 are unsuitable, the switching member 112 of the block/switching valve 104 slides from the operating position shown in Figure 6 to the position in which the second pipe 102 communicates with the first vent

107, blocking the passage of gas to the first pipe 102 and thus the gas supply to the pressure chamber 117.

During its movement, the switching member 112 moves the switching member 113 of the block/switching valve 105 through the rod 114, so that the vent pipe

103 communicates with the second vent 108.

The gas contained in the pressure chamber 117 flows out through the first pipe

102 and the vent pipe 103.

For the regulating device 200, Figure 8 shows that the release of the gas contained in the pressure chamber 202 takes place at the vent pipe 208 of the three-way actuated valve, which is operated following the pressure release in the fourth pipe 206 due to the displacement of the switching member 212 of the block/switching valve 211 that stops the supply of gas to the first pipe 205.

In these conditions, the control member 209 of the three-way valve of the coupling 207 cannot counteract the thrusting action coming from the pressure chamber 202.

The residual gas of the first pipe 205 and of the fourth pipe 206, instead, is released at the vent 213.

The regulating device 300 substantially behaves as the regulating device 200. Following the displacement of the switching member 309 of the block/switching valve 308, the gas supply to the first control and regulation means is interrupted and the first pipe 304 is connected to the first vent 310, as shown in Figure 10.

Thus the pressure inside the first pipe 304 cannot counteract the pressure of the gas contained in the pressure chamber 302, so that the check valve 307 opens and the gas is released at the first vent 310.

The construction variants shown in Figures 11 and 12 represent embodiments of the invention without significant operating differences compared to the embodiment illustrated in Figure 1 , in fact the regulating devices 400 and 500 present only a different configuration of the respective first control and regulation means, but have a three-way coupling 414, 511 that is equal to the three-way coupling 16 shown in Figure 1.

Finally, Figure 13 shows that the operating conditions of the regulating device 600 after interruption of the gas supply to the positioning means are restored with the resetting means 602 that automatically act on the block/switching valve 601.

According to the above, it is clear that the device for regulating the gas pressure and/or flow rate that is the subject of the present invention achieves all the aims and offers all the advantages described. The invention achieves the aim to allow any device for regulating the gas pressure and/or flow rate to be classified as a safety device against pressures exceeding the allowable pressure limits set for the equipment installed downstream of the regulating device. This is obtained without the installation of external power sources, which is required for the devices of the known art in order to guarantee their operation also in case of breakage or of failures of the energy sources themselves. Furthermore, every regulating device with "fail close" throttling valve already installed, when equipped with the second controls means of the invention can be classified as a safety device according to the PED Directive, with no need to install further equipment.

It is also evident that the construction forms described with reference to the attached drawings represent only some examples of regulating devices available on the market, especially as regards the shape of the control means of the shutter of the throttling valve and of the first pressure control and regulation means. The second pressure control means may in any case be adapted to any kind of known regulating device equipped with "fail close" throttling valve present in pressure regulating stations.

Furthermore, in other construction variants the second control means may be different from those previously described and illustrated, provided that they comply with the requirements of the PED Directive, and all this shall not affect the advantages offered by the present patent.

All the variants described and mentioned herein, but not represented in the attached drawings, must be considered protected by the present patent, provided that they fall within the scope of the following claims.

Claims

1 ) Device (1 ; 100; 200; 300; 400; 500; 600) for regulating the gas pressure and/or flow rate for pressure regulating stations belonging to gas transportation and/or distribution systems, comprising: - at least one "fail close" throttling valve (2; 401 ; 116) positioned between a duct (A) for conveying the high-pressure gas coming from a gas supply network, and a duct (M) for delivering gas at a lower pressure than said gas in said conveying duct (A) destined for a transportation and/or distribution network or at least one user; - means (4; 201 ; 301 ; 403; 501 ) for controlling said throttling valve (2; 401 ; 116), provided with a pressure chamber (5; 117; 202; 302; 404; 502) inside which the gas coming from said conveying duct (A) is collected;

- first pressure control and regulation means (9; 405), provided with a pipe (10; 203; 303; 406; 504) for conveying the high-pressure gas coming from said conveying duct (A) into said pressure chamber (5; 117; 202; 302; 404;

502) and with means (11 ; 410) for connection to the outlet way (2b; 401 b) of said throttling valve (2; 401 ; 116), characterized in that it comprises second pressure control means (12; 101 ; 204; 407; 505) arranged upstream of said first control and regulation means (9; 405) and equipped with:

- a first pipe (13; 102; 205; 304; 408; 506) for connection to said first control and regulation means (9; 405);

- connection ducts (14) for conveying the gas withdrawn from said conveying duct (A) of said throttling valve (2; 401 ; 116) to said first pipe (13; 102; 205; 304; 408; 506);

- a three-way coupling (16; 118; 207; 306) that connects said first high-pressure gas conveying pipe (10; 203; 303; 406; 504), a supply/discharge line (47; 210; 311 ) of said pressure chamber (5; 117; 202; 302; 404; 502) and a vent pipe (15; 103; 208; 305) for the gas contained in said pressure chamber (5; 117; 202; 302; 404; 502).

2) Device (1 ; 100; 300; 400; 500; 600) according to claim 1 ), characterized in that said three-way coupling (16; 118; 306; 414; 511 ; 603) is a T coupling having a first way connected to said conveying pipe (10; 303; 406; 504), a second way connected to said supply/discharge line (47) of said pressure chamber (5; 302; 404; 502) of said control means (4; 301 ; 403; 501 ) and a third way connected to said vent pipe (15; 103; 305).

3) Device (200) according to claim 1 ), characterized in that said three-way coupling (207) is a three-way actuated valve equipped with a control member (209) and having a first way connected to said conveying pipe (203), a second way connected to said supply/discharge line (210) of said pressure chamber (202) of said control means (201 ), and a third way connected to said vent pipe (208) for venting into the atmosphere.

4) Device (1 ; 100; 400; 500; 600) according to claim 1), characterized in that said vent pipe (15; 103) is directly connected to said second control means (12; 101 ; 407; 505).

5) Device (300) according to claim 1 ), characterized in that said vent pipe (305) communicates with the atmosphere through the activation of a check valve (307) and through said first pipe (304) and said second control means. 6) Device (200) according to claim 3), characterized in that said control member (209) of said three-way valve is connected to a fourth pipe (206) connected to said first pipe (205).

7) Device (1 ; 100; 200; 300; 400; 500; 600) according to claim 1 ), characterized in that said second control means (12; 101 ; 204; 407; 505) comprise:

- at least one block/switching valve (17; 104, 105; 211 ; 308; 601 ) that places said first pipe (13; 102; 205; 304; 408; 506) in communication with a feed pipe (18; 106) connected to the inlet way (2a) of said throttling valve (2; 401 ; 116); - an actuator (19; 19a; 115), mechanically connected to said block/switching valve (17; 104, 105; 211 ; 308; 601 ), provided with a first way connected to a second pipe (20) for connection to the outlet way (2b) of said throttling valve (2; 401 ; 116) and with a second way connected to a first union pipe (21 ) connected to said feed pipe (18; 106). 8) Device (1 ; 400; 500; 600) according to claim 7), characterized in that said block/switching valve (17; 601 ) is of the five-way type, wherein a first way communicates with a first vent (22) for venting into the atmosphere, a second way communicates with said first pipe (13; 408; 506), a third way communicates with said feed pipe (18), a fourth way communicates with a second vent (23) for venting into the atmosphere and a fifth way communicates with said vent pipe (15).

9) Device (100) according to claim 7), characterized in that said second control means (101 ) comprise:

- a first block/switching valve (104), of the three-way type, provided with a first way that communicates with a first vent (107) for venting into the atmosphere, with a second way that communicates with said first pipe (102), and with a third way that communicates with said feed pipe (106);

- a second block/switching valve (105) of the three-way type, provided with a first way that communicates with a second vent (108) for venting into the atmosphere, with a second way that communicates with a third vent (109) for venting into the atmosphere, and with a third way that communicates with said vent pipe (103).

10) Device (1 ; 100; 200; 300; 400; 500; 600) according to claim 7), characterized in that said block/switching valve (17; 104, 105; 211 ; 308; 601 ) is of the slide type and is constituted by a valve body (24; 110, 111 ) inside which there is at least one sliding switching member (25, 26; 112, 113; 212; 309).

11 ) Device (1 ; 100; 200; 300; 400; 500; 600) according to claim 10), characterized in that said actuator (19; 19a; 115) comprises a body (27) in which it is possible to identify:

- a central duct (28) that houses a moving rod (29) connected at one end (29a) to at least one elastic element (30) and at the other end (29b) to a main pressure chamber (31 ; 31a), suited to cooperate with said switching member (25, 26) of said block/switching valve (17; 104, 105; 211 ; 308; 601 );

- a transverse duct (32) that houses a piston (33) connected at one end (33a) to said switching member (25, 26) of said block/switching valve (17; 104, 105; 211 ; 308; 601 ) and at the other end (33b) to a secondary pressure chamber (34). 12) Device (1 ; 100; 200; 300; 400; 500; 600) according to claim 11 ), characterized in that said main pressure chamber (31 ; 31a) is connected to said outlet way (2b; 401 b) of said throttling valve (2; 401 ; 116) and said secondary pressure chamber (34) is connected to the inlet way (2a) of said throttling valve (2; 401 ; 116). 13) Device (1 ; 100; 200; 300; 400; 500; 600) according to claim 11 ), characterized in that said moving rod (29) is provided with at least one elastic membrane (46; 46a; 46b) that delimits said main pressure chamber (31 ; 31a).

14) Device (1 ; 100; 200; 300; 400; 500; 600) according to claim 1 ), characterized in that it comprises at least a first pressure regulating unit (43) provided with an inlet way connected to the inlet way (2a) of said throttling valve (2; 401 ; 116) and with a delivery way connected to said second control means (12; 101 ; 204; 407; 505).

15) Device (1 ; 100; 200; 300; 400; 600) according to claim 1 ), characterized in that it comprises at least a second pressure regulating unit (44) provided with an inlet way connected to said second control means (12; 101 ; 204; 407) and with a delivery way connected to said first control and regulation means (9; 405).

16) Device (1 ; 100; 200; 300; 500; 600) according to claim 1 ), characterized in that said first control and regulation means (9) comprise: - data collecting and processing means (36; 503) connected to said outlet way (2b) of said throttling valve (2; 116) through said connection means (11 );

- positioning means (35; 507), operatively associated with said shutter (3) of said throttling valve (2), connected to said pressure chamber (5; 202; 302; 502) of said control means (4; 201 ; 301 ; 501) through said conveying pipe (10; 203; 303; 504) and to said second control means (12; 101 ; 204; 505) through said first pipe (13; 103; 205; 304; 506).

17) Device (400) according to claim 1 ), characterized in that said first control and regulation means (405) comprise: - a pneumatic regulator (409), connected to said outlet way (401 b) of said throttling valve (401) through said connection means (410) and to said first pipe (408) through a second union pipe (411 );

- a pneumatic positioner (412), operatively associated with said shutter (402) of said throttling valve (401), connected to said pneumatic regulator (409) through a third pipe (413), to said pressure chamber (404) of said control means (403) through said conveying pipe (406), and to said second control means (407) through said first pipe (408).

18) Device (1 ; 100; 200; 300; 400; 500; 600) according to claim 16), characterized in that said data collecting and processing means (36; 503) comprise: - an electronic processor (37; 509) electrically connected to said positioning means (35; 507);

- a pressure transmitter (38) connected to said electronic processor (37) and communicating with said outlet way (2b) of said throttling valve (2; 116). 19) Device (1 ; 100; 200; 300; 600) according to claim 18), characterized in that said positioning means (35) comprise:

- an electropneumatic converter (39) electrically connected to said electronic processor (37), provided with a delivery way connected to a third pipe (41 ) and with a way connected to said first pipe (13; 102; 205; 304) through a second union pipe (42);

- a positioning device (40) having a delivery way connected to said conveying pipe (10; 203; 303), a way connected to said first pipe (13; 102; 205; 304), and a way connected to said third pipe (41 ).

20) Device (500) according to claim 18), characterised in that said positioning means (507) are constituted by an electropneumatic positioning device (508) electrically connected to said electronic processor and having a delivery way connected to said conveying pipe (504) and an inlet way connected to said first pipe (506).

21 ) Device (1 ; 10; 200; 300; 500; 600) according to claim 16), characterized in that said connection means (11 ) are constituted by electric cables.

22) Device (400) according to claim 16), characterized in that said connection means (410) are constituted by a sixth pipe.

23) Device (1 ; 100; 200; 300; 400; 500; 600) according to claim 7), characterized in that said block/switching valve (17; 104, 105; 211 ; 308; 601 ) is provided with resetting means (45; 602) for restoring the gas flow to said first control and regulation means (9; 405).

24) Device (1 ; 100; 200; 300; 400; 500) according to claim 23), characterized in that said resetting means (45) are manually controlled means.

25) Device (600) according to claim 23), characterized in that said resetting means (602) are automatically controlled means.