WO2025169020A1

WO2025169020A1 - Accident management assembly for a double containment pipeline system

Info

Publication number: WO2025169020A1
Application number: PCT/IB2025/050372
Authority: WO
Inventors: Samuel HENCHOZ; Alberto Mian; Grégory MEERTENS; Thomas Wicht
Original assignee: Exergo Sa
Current assignee: Exergo Sa
Priority date: 2024-02-08
Filing date: 2025-01-13
Publication date: 2025-08-14
Anticipated expiration: 2026-08-08

Abstract

Double containment pipeline system comprising a pressurized pipeline (1-3) and a protecting casing (6,7) in which the pipeline (1-3) is contained and wherein the fluid pressure within the pipeline (1-3), at its triple point, is above the pressure within the casing (6,7); said system comprising control elements (4, 10, 11, 12a, 12b, 13-26) configured to regulate a change in the thermodynamic state within the casing and wherein said control elements (4, 10, 11, 12a, 12b, 13-26) configured to be actuated when a predefined threshold of said thermodynamic state has been reached.

Description

Accident management assembly for a double containment pipeline system

Field of invention

The present invention generally relates to pipeline systems, and more precisely to double containment pipeline systems dedicated to the transportation of a fluid whose pressure at the triple point is usually above the pressure of the pipeline surroundings.

State of the art

Pipelines featuring a double containment arrangement are a well-established technology used essentially when the risk posed by a single containment pipeline on people, the environment or things would otherwise be unacceptably high.

The double containment provides the following advantages with respect to a single containment pipeline:

1. The pressurized pipeline (the one transporting the fluid) is within a casing that protects it against external aggressions.

2. It allows for a more accurate monitoring of the leak from the pressurized pipeline.

3. It provides a channel to transfer and discharge reliably a leak where it can be done without posing a threat to people or more generally to the environment.

For the latter point, depending on the type of fluid present in the pipeline and its inherent characteristics that affect safety (toxicity, flammability, buoyancy...), a pipeline sectioning mechanism might also need to be integrated in conjunction with the double containment. That way the discharge of an excessive amount of fluid can be prevented or at least minimized.

Sectioning mechanisms can consist of many different technologies. Fundamentally they all include a detection mechanism that gives a fast and reliable indication that a problematic leak as started to occur, some sort of signal processing and actuation mechanism, and a device that once actuated will act as a shutoff valve, i.e. stop the fluid from flowing. Because these sectioning mechanisms are providing a safety functionality, they need to reach a level of functional safety commensurate with the threat posed if they fail to perform adequately. In general, for a given a task (like closing a sectioning valve) one can reach a higher level of functional safety when one reduces the number of components involved in the control loop.

When a pipeline transports a fluid, the triple point pressure of which is above the pressure prevailing in the surroundings of said pipeline, a leak, especially if the fluid is in liquid or dense supercritical state will lead to the appearance of a significant mass fraction of solid phase. When the leak occurs in a pipeline equipped with a double containment, a buildup of solid phase can occur in the space between the pressurized pipeline and casing, which can cause a blockage of the flow which not only prevents the controlled emptying of the damaged inner pipe, but also can cause a relatively erratic intermittent flow, as the solid phase builds-up, then ruptures, sending blocks of solid phase at highspeed within the casing before building up again. Such a situation can be hazardous as it can lead the people around or involved in inspecting the pipeline to believe that it is empty while there is still a pocket of pressurized fluid.

General description of the invention

The present invention addresses several challenges linked to the transportation of a fluid via pipeline where a double containment arrangement of said pipeline is required, and where the triple point pressure of said fluid is above that of the surrounding environment of the pipeline.

More precisely the present invention consists in a double containment pipeline system comprising a pressurized pipeline and a protective casing in which the pipeline is contained and wherein the fluid pressure within the pipeline, at its triple point, is above the pressure within the casing; said system comprising control elements configured to regulate a change in the thermodynamic state within the casing and wherein said control elements configured to be actuated when a predefined threshold of said thermodynamic state has been reached.

Detailed description of the invention

The present invention is disclosed in a more detailed manner in the present chapter, with nonlimiting examples.

Figure 1 shows a first example of the invention

Figure 2 represents pipeline sectioning valves triggered by an excessive overpressure within the casing

Figure 3 represents pipeline sectioning valves triggered by a lack of pressure within the casing

Figure 4 illustrates a leakage monitoring and alarm system

Figure 5 represents pipeline sectioning valves triggered by temperatures switches

Figure 6 shows a staged discharge of the fluid Figure 7 shows a staged pressure relief of the casing

Figure 1 shows an example of how the manholes and servicing ports can be used to install the pressurized components in the casings

Figure 2 shows an example of a pipeline sectioning valves installed within the casing and that is passively actuated by the rise in pressure within the casing

Figure 10 shows an example of a pipeline sectioning valves installed outside of the casing and that is passively actuated by the rise in pressure within the casing

Figure 11 represents a passive sectioning valve system made of two opposite excess flow valves

Numerical references cited in the figures:

Pressurized pipeline components:

1: Flexible pipe

2: Fitting to connect flexible and rigid components together

3: Rigid piping

4: Pressure Relief Valve (PRV)

5: Pipeline sectioning valve

Casing components:

6: Casing chamber

7: Casing pipe

8: Lid for closing in a gas tight fashion the casing around the pressurized pipeline.

9: Manhole of the chamber, with a lid secured in place in a gas tight fashion fit for pressure service.

10: Servicing port, with a lid secured in place in a gas tight fashion fit for pressure service.

11: Discharge vent of the casing 12: Staged discharge apparatus, 12a pressure operated discharge device for small leaks (.g. direct- loaded safety valve), 12b pressure operated discharge device for large leaks (e.g. rupture disk)

Pipeline sectioning and alarm components:

5: Pipeline sectioning valve

13: Pressure Switch High (PSH)

14: Gas detector (D)

15: Pressure Switch Low (PSL)

16: Casing pressurization and leak compensation device (compressor, gas bottle...)

17: Gas flow measurement (flowmeter or inferred from compressor characteristics/gas bottle weight)

18a: Distributed Temperature Sensing (DTS) - linear temperature probe

18b: Distributed Temperature Sensing (DTS) - signal processing unit

19: Temperature Switch High (TSH)

20: Temperature Switch Low (TSL)

Casing pressure sectioning valve passive actuation:

21: Feed port

22: Pressure reducing regulator

23: Pneumatic actuator

24: Exhaust port

25: Excess flow valve

26: Valve position switch The illustrated system (see figure 1) comprises a pipeline comprising various components such as flexible pipes 1, pipe fittings and couplers 2, rigid pipes 3, pressure relief valves 4 and pipeline sectioning valves 5. These components constitute the pressurized pipeline. The pressurized pipeline is installed partly or entirely in a casing, that comprises casing chambers 6, casing pipes 7, lids for closing in a gas tight fashion the casing around the pressurized pipeline 8, manholes to access the chambers, with a lid secured in place in a gas tight fashion and fit for pressure service 9, servicing ports with a lid secured in place in a gas tight fashion and fit for pressure service 10, one or several discharge vents 11, each equipped with a staged discharge apparatus 12, comprising a pressure operated discharge device for small leaks 12a and a pressure operated discharge device for large leaks 12b. The resulting double containment pipeline allows for a safe and reliable transportation/containment of a fluid whose triple point is at pressure higher than the ambient pressure in its direct surroundings. Said safe transportation/containment is achieved through the following:

I. The casing 6-12 protects the pressurized pipeline 1-5 from third party aggressions and external loads.

II. The pressure relief valves 4, 12a and 12b (installed on each segment that can be hydraulically isolated) protect all the equipment against overpressure (see figures 1, 6 and 7).

III. In the event of a failure of one or several of the pressurized pipeline components, the resulting leak will be transported via the casing to the discharge vent 11 for being safely discharged in the environment without causing any significant harm (Notice that the discharge vent can be directly on the casing (no pipe connecting the staged discharge apparatus 12 to the rest of the casing).

IV. The staged discharge apparatus 12 is a safety feature that guarantees that in the event of a leak from the pressurized pipeline into the casing, said leak will not lead to a significant amount of solid phase within the casing (that could prevent the fluid from discharging safely) by maintaining the pressure within said casing above that of the triple point for a duration long enough to have only a gas phase present within both the pressurized pipeline and the casing before letting the pressure go back down below that of the triple point. Note that at the start of the leak the pressure in the casing might be lower than that of the triple point causing the appearance of a solid phase in the leaking flow. However, since the staged discharge apparatus will let the pressure rise in the casing above that of the triple point before starting to vent out, said solid phase will liquify again almost instantaneously (when compared to the total discharge duration) once the pressure reaches that of the triple point. For further detail see Figure 6 and 7. Figure 6 more precisely represents staged discharge of the fluid. In the event of a leak from the pressurized components into the casing that as a flowrate small enough such that the pressure in the casing rises up to the opening pressure of the pressure operated discharge device for small leaks (here depicted as a pressure relief valve) 12a but not up to the set pressure of the pressure operated discharge device for large leaks (here depicted as a bursting disk) 12b. the thermodynamic state of the fluid within the pressurized components and within the casing during the whole discharge avoids entering the domain in the phase diagram where a solid phase can exist thereby eliminating the risk of clogging caused by solid particles that otherwise could impede the safe discharge of the fluid.

Figure 7 represents staged pressure relief of the casing. In the event of a leak from the pressurized components into the casing that as a flowrate large enough such that the pressure in the casing rises up to the opening pressure of both the pressure operated discharge device for small leaks 12a and for large leaks 12b. The thermodynamic state of the fluid within the pressurized components and within the casing during the whole discharge avoids entering the domain in the phase diagram where a solid phase can exist thereby eliminating the risk of clogging caused by solid particles that otherwise could impede the safe discharge of the fluid. It is noteworthy that fluid in the casing enters the two-phase domain where liquid and vapour coexist, thus the isenthalpic process of expansion through the 12a and 12b will lead to the appearance of a fraction of solid phase at their exhaust that as however no detrimental effect on the discharge process since it happens in an unconfined space.

V. To further reduce the risk sectioning valves 5 might also be installed to limit the amount of fluid leaked out via the discharge vent 11 and the staged discharge apparatus 12. Said sectioning valves can be triggered via various signal depending on the following events: a. Leak from the pressurized pipeline into the casing. A pressure swich high PSH 13 triggers the closure of the sectioning valves 5 when the pressure within the casing goes above a preset value. (See Figure 2) b. Leak from the pressurized pipeline outside of the casing. A gas detector 14, sensitive to the gas being transported by the pipeline triggers the closure of the sectioning valves 5 when a concentration above a preset value is reached. (See Figure 2) This mechanism is useful to protect areas where a double containment is not necessary/possible and an overpressure is not feasible (for instance in a technical room) c. Leak from the casing into the ambient. It is possible to maintain a slight overpressure within the casing (compared to the pressure in the ambient), via a casing pressurization and leak compensation device, for instance an air compressor 16. that will pressurize the casing and automatically compensate for small leaks from the casing into the ambient. In the event of a leak (such a leak could be caused by an aggression from a third party on the casing, for instance an excavator damaging the casing) from the casing large enough for said pressurization and leak compensation device to ne be able to compensate the said leak, one or several pressure switch low PSL 15 will preventively trigger the closure of the pipeline sectioning valves 5. (See Figure 3) d. It is also possible to use directly the pressure of the fluid in the casing (that will rise in the event of a significant leak) to feed the actuator of a pneumatically actuated sectioning valve 5, 21-24, thus providing a passive sectioning mechanism that does not require any external source of energy. (See Figure 9 and 10).

Figure 9 precisely shows an example of a pipeline sectioning valves 5 installed within a chamber 6 of the casing and that is passively actuated by the rise in pressure within the casing in the event of a significant leak from one or several of the pressurized components into the casing. The rise in pressure within the casing will create a pressure differential between the feed port 21 and the exhaust port 24, that will cause the pneumatic actuator 23 to close the valve 5, since the pressure in the casing can rapidly rise above the maximum feed pressure of the actuator a pressure reducing regulator 22 that avoids exceeding said maximum feed pressure.

Figure 10 shows an of a pipeline sectioning valves 5 installed outside of the casing that is passively actuated by the rise in pressure within the casing in the event of a significant leak from one or several of the pressurized components into the casing. The rise in pressure within the casing will create a pressure differential between the feed port 21 and the exhaust port 24, that will cause the pneumatic actuator 23 to close the valve 5, since the pressure in the casing can rapidly rise above the maximum feed pressure of the actuator a pressure reducing regulator 22 that avoids exceeding said maximum feed pressure. e. A passive pipeline sectioning valve 5 can also comprise two excess flow valves 25, that will close when the flow goes above a preset value. Said preset value must be selected above the maximum flowrate of the transported fluid during normal operation. Said valves must also be installed in series and close to one another but with an opposite closing direction of flow, thus allowing for a sectioning of the pipeline regardless of the position of the leaking point with respect to the sectioning valve location. Each valve can be equipped with a valve position switch VPS 26, to report the position of said valves, and be able to detect which segment of pipe has been isolated. Said segment being located between two consecutive valve position switch 26 that report a close valve. Note that if an excess flow valve can have closing excess flows in both directions, it can substitute the two opposite valves arrangement described previously. In that eventuality, if valve position switches are to be used, both closed position of the valve would need to be reported (closed on the right or closed on the left) to be able to indicate which pipeline segment has been isolated. (See Figure 11)

VI. It is also possible to incorporate pipeline integrity monitoring mechanisms such as: a. By using the same pressurization and leak compensation device 16 and creating a small vent hole from the casing to create a controlled small leak. And using either a flow meter or a proxy measurement of the flowrate through said controlled leak 17, it is possible with the help of at least one gas detector but preferably two 14, to measure the amount of fluid leaked from the pressurized pipeline into the casing, and this from potentially very small leaks up to the point the pressure in the casing starts to rise significantly. The proposed arrangement provides a mean to continuously assess the integrity of the pressurized pipeline allowing for detecting a deterioration of the said pressurized pipeline from virtually the onset (See Figure 4). b. It is also possible to use a distributed temperature sensing system made of a linear probe 18a and of a signal processing unit 18b to measure the temperature profile along the pressurized pipeline. In the event of a leak, the temperature around the leaking point will be lower and can be detected and located. A temperature swich low 20 can be used to trigger an alarm and/or the sectioning valves 5. It is also possible to detect and locate an abnormal temperature rise, for instance caused by a nearby fire, and use a temperature swich high 19 to send an alarm and/or even preventively trigger the closure of the sectioning valves 5. (See Figure 5) VII. The use of chambers 6 with appropriately located and sized manholes 9 as well as servicing ports 10, allows for installing the pressurized pipeline within the casing rapidly. It also provides inspection points at appropriate location, where the equipment can be installed and serviced. It also leaves the possibility to replace pressurized pipeline components without damaging the casing. (See Figure 7).

VIII. Figure 3 provides an example of how the manholes 9 and servicing ports 10 of the chambers 6 can be used to install the pressurized components in the casing and how they can be used to replace said components if needed.

Claims

1. Double containment pipeline system comprising a pressurized pipeline (1-3) and a protecting casing (6,7) in which the pipeline (1-3) is contained and wherein the fluid pressure within the pipeline (1-3), at its triple point, is above the pressure within the casing (6,7); said system comprising control elements (4, 10, 11, 12a, 12b, 13-26) configured to regulate a change in the thermodynamic state within the casing and wherein said control elements (4, 10, 11, 12a, 12b, 13-26) configured to be actuated when a predefined threshold of said thermodynamic state has been reached.

2. Pipeline system according to claim 1 wherein said casing (6,7) comprise a discharge vent (11) connected to a staged discharge apparatus made of a pressure operated discharge device for small leaks (12a) and pressure operated discharge device for large leaks (12b); said discharge devices (12a, 12b) being configured to ensure the absence of any significant amount of solid phase within said casing (6,7), hence guaranteeing a continuous and controlled discharge even when the fluid transported in said pressurized pipeline exhibit a pressure at the triple point above the pressure prevailing in the environment directly surrounding said pipeline system.

3. Pipeline system according to claim 1 or 2 wherein said casing comprises several casing chambers (6) connected to each other via casing pipes (7).

4. Pipeline system according to anyone of the previous claims wherein said pipeline (1-3) includes at least one sectioning valve (5) and at least one sensor (13, 14, 15, 18a) communicating with said valve (5), in such a way that the valve (5) may be actuated when a predefined value is measured by said sensor (13, 14, 15, 18a).

5. Pipeline system according to anyone of the previous claims including a passively actuated valve mechanism (21,23,24) comprising a pneumatic actuator (23), a feed port (21) and an exhaust port (24); wherein said actuator (23) is configured to close said valve (5) when the pressure differential between said ports (23,24) has reached a preset value.

6. Pipeline system according to claim 5 wherein said pneumatic actuator (23) is located within a casing (6).

7. Pipeline system according to claim 5 wherein said pneumatic actuator (23) is not located within a casing (6).

8. Pipeline system according to anyone of the previous claims comprising two excess flow valves (25) mounted in series and with their respective direction of excess flow in the opposition direction.