Device for cleaning a pipeline

Abstract

Device (1) for cleaning a pipeline (2) which extends between a first (2a) and a second (2b) end of pipeline (2), the device (1) being configured to perform several times alternately: - an injection of gas into the pipeline (2) during a period of gas injection (PER1), and - an interruption of gas injection into the pipeline (2) during a period of interruption of gas injection (PER2).

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of plumbing, and more particularly to the field of cleaning a pipe such as a pipe in a heating or cooling system. The term "pipe" refers to the conduits (generally tubular) through which a heated or cooled liquid circulates, as well as the heat exchangers (such as radiators) through which the heated or cooled liquid (generally water, possibly containing glycol) circulates.

[0002] Various phenomena occur in a heating or cooling network pipe, such as: Pipe corrosion, caused by the presence of dissolved oxygen in the circulating liquid; pipe scaling, caused by the deposition in the pipe of limescale present in the liquid; the development of microorganisms due to the presence of bacteria in the circulating liquid, the development of which is favored by the rise in temperature of said liquid.

[0003] Over time, these phenomena contribute to the formation of what is known as "sludge." This sludge reduces the cross-sectional area of ​​the pipes, limits the heat exchange surface area of ​​the heat exchangers, and creates a layer that hinders heat exchange. This results in a degradation of the heating or cooling system's efficiency. Furthermore, this sludge is abrasive and therefore causes increased wear on the heating or cooling network pipes.

[0004] To remove this sludge, a cleaning agent (for example, citric acid-based) is generally added to the circulating heating or cooling system pipe, which extends between a first and a second pipe end. After a certain period of circulation with the cleaning agent, a pipe cleaning device, as described in US patent 5,007,444 A, is connected to the pipe to be cleaned. This device comprises: an inlet pipe ensuring fluid communication between: first connection means suitable for being connected in a watertight manner to the first end of the pipe to be cleaned, and an inlet of filtration means, a pump supply pipe ensuring fluid communication between: an outlet of filtration means, and an inlet of a hydraulic pump, suitable for discharging, according to a pump outlet, a liquid from the pump supply pipe, an outlet pipe ensuring fluid communication between: the outlet of the hydraulic pump, and second connection means suitable for being connected in a watertight manner to the second end of the pipe to be cleaned, gas supply means, configured to inject gas into the outlet pipe.

[0005] The injection of gas into the outlet pipe is always simultaneous with the injection of liquid into the outlet pipe, so that a mixture of gas and liquid is injected into the pipeline to be cleaned. This gas-liquid mixture is assumed to flow turbulently to carry the sludge to the filtration units, which then collect and remove it.

[0006] However, there is a drawback: injecting a mixture of gas and liquid can cause a kind of emulsion that hinders the flow of sludge to the filtration system, and can even clog the pipe being cleaned. Furthermore, the delivery of sludge to the filtration system could still be improved. DESCRIPTION OF THE INVENTION

[0007] One problem proposed by the present invention is to provide a device for cleaning a pipe limiting the risks of emulsification and facilitating the detachment of sludge and its removal from the pipe of a heating or cooling network.

[0008] To reach these objects and others, the invention proposes a device for cleaning a pipe extending between a first and a second end of the pipe, the device comprising: an inlet pipe ensuring fluid communication between: initial connection means suitable for a watertight connection to the first end of the pipe to be cleaned, and an inlet for filtration means, a drivingpump supply ensuring fluid communication between: an outlet of filtration means, and an inlet of a hydraulic pump, capable of discharging, according to a hydraulic pump outlet, a liquid from the pump supply line, an outlet line ensuring fluid communication between: the outlet of the hydraulic pump, and second connection means capable of being connected in a leak-proof manner to the second end of the pipeline to be cleaned, gas supply means, configured to inject gas into the outlet line; According to the invention, the device comprises control means, configured to perform several times alternately: i. an injection of gas through a gas inlet into the outlet line during a period of gas injection and simultaneously an interruption of liquid injection into the outlet line, and ii. an interruption of gas injection into the outlet line during a period of gas injection interruption and simultaneously a liquid injection into the outlet line, so as to generate successive and distinct volumes of gas and volumes of liquid over time which are put into circulation in the pipeline by injection into the pipeline via one of the first or second ends of the pipeline and by extraction out of the pipeline via the other of the first or second ends of the pipeline.

[0009] The control system allows for automated alternation between periods of gas-only injection and periods of liquid-only injection. This generates and circulates successive and distinct "gas trains" (or volumes of gas) and "liquid trains" (or volumes of liquid) within the pipe being cleaned over time. Surprisingly, this has been found to limit the risk of emulsification and also facilitates the removal of sludge and its removal from the pipe. Pipe cleaning thus requires less time and is therefore less expensive for the owner of a heating or cooling system who hires a contractor for pipe cleaning.

[0010] Furthermore, the circulation of said "gas trains" (or gas volumes) and "liquid trains" (or liquid volumes) as defined in the present invention, that is, by injection into the pipeline via one of the first or second ends of the pipeline and by extraction from the pipeline via the other of the first or second end of the pipeline, greatly improves the efficiency of sludge removal from the pipeline. Each volume of gas or volume of liquid thus travels the entire length of the pipeline in only one direction before exiting.

[0011] Preferably, the flow of gas and liquid volumes within the pipe to be cleaned should be continuous and constant between the first and second ends of the pipe (or vice versa). This prevents either end of the pipe from becoming obstructed when gas and liquid volumes are injected through the other end. This avoids compression of the gas volumes within the pipe, which can further bind sludge and impurities to the inner wall of the pipe.

[0012] In a first embodiment, it is advantageous to foresee that: The hydraulic pump is capable of delivering the liquid at a first pressure according to the hydraulic pump outlet; the gas supply means are configured to inject gas into the outlet line at a second pressure higher than the first pressure; the outlet line includes a non-return valve between the hydraulic pump outlet and the gas inlet.

[0013] This allows for a simple and efficient automated alternation of periods of injection of only gas and periods of injection of only liquid, while simultaneously limiting the risks of gas rising towards the pump, which could cause the pump to lose its prime or even damage it.

[0014] In a second embodiment, it is preferable to provide that the device includes: a gas distributor spool allowing to selectively establish or interrupt the injection of gas in the outlet line, a liquid distributor spool allowing to selectively establish or interrupt the injection of liquid in the outlet line.

[0015] In order to achieve an automated alternation of periods of injection of only gas and periods of injection of only liquid, the gas distributor spool and the liquid distributor spool are controlled in a synchronized manner: a passage is established with one while an interruption is caused with the other, then vice versa.

[0016] Of Preferably, the filtration means may include a shaped magnet to capture ferromagnetic particles circulating within the filtration means. The ferromagnetic particles, which are particularly abrasive, are thus effectively removed from circulation.

[0017] Advantageously, the cleaning device may include means for reversing the direction of the incoming and outgoing flows via the first and second connection means. Flat particles (particularly metallic particles that have detached from inside the pipe) may have accumulated by overlapping, somewhat like roof tiles. The reversing means allow the direction of liquid and gas flow in the pipe to be cleaned to be reversed, thus flushing these overlapping particles out of the pipe.

[0018] Advantageously, the cleaning unit can be mounted on a rolling chassis, preferably on a trailer designed to be towed by a vehicle. This allows the cleaning unit to be easily moved to a location near a heating or cooling circuit whose pipes need cleaning.

[0019] Preferably, the control means can be configured to control the gas supply means to inject gas into the outlet pipe according to a predetermined sequence. Pre-configured cleaning routines can thus be performed automatically.

[0020] Advantageously, the inlet pipe can include a solenoid valve designed to interrupt the flow of fluid in the event of a power failure to the hydraulic pump. This prevents the accidental discharge of all the fluid from the pipe being cleaned in the event of a power failure to the hydraulic pump (and avoids the loss of this fluid by causing the filtration system to overflow).

[0021] According to another aspect, the present invention proposes a method for cleaning a pipe extending between a first and a second pipe end, by means of a pipe cleaning device as described above, comprising a step during which the following are alternated several times: an injection of gas into said pipeline, by means of the gas supply means, during a period of gas injection and simultaneously an interruption of liquid injection into the outlet pipe, an interruption of gas injection during a period of interruption of gas injection and simultaneously an injection of liquid into the outlet pipe, so as to generate successive and distinct volumes of gas and volumes of liquid over time which are put into circulation in the pipeline by injection into the pipeline via one of the first or second ends of the pipeline and by extraction out of the pipeline via the other of the first or second ends of the pipeline.

[0022] In this way, successive and distinct "gas trains" (or volumes of gas) and "liquid trains" (or volumes of liquid) are generated and circulated in the pipeline to be cleaned over time, which limits the risks of emulsification and also facilitates the detachment of sludge and its efficient removal from the pipeline.

[0023] Preferably, it can be expected that: The period of gas injection (and simultaneously of interruption of liquid injection) has a duration of 2 to 6 seconds, and the period of interruption of gas injection (and simultaneously of liquid injection) has a duration of 2 to 6 seconds.

[0024] Such durations of gas injection period and gas injection interruption period have proven to be particularly effective.

[0025] Advantageously, during said step, the gas injection period may have a duration equal to the duration of the gas injection interruption period.

[0026] Excellent results were observed by predicting that, during said step, the gas injection period and the gas injection interruption period have durations equal to 3 seconds. SUMMARY DESCRIPTION OF THE DRAWINGS

[0027] Other objects, features and advantages of the present invention will become apparent from the following description of particular embodiments, made in relation to the accompanying figures, among which: [ Fig.1 ] There figure 1 is a schematic view of a first embodiment of a device according to the invention for cleaning a pipeline during a period of gas injection; [ Fig. 2 ] There figure 2 is a schematic view of the device of the figure 1 , during a period of gas injection interruption; [ Fig.3 ] There figure 3 is a schematic view of the device of the figure 1, during a period of gas injection, and by reversing the direction of flow in the pipe to be cleaned; and [ Fig. 4 ] There figure 4 is a schematic figure illustrating a step during which periods of gas injection alternate with periods of gas injection interruption, [ Fig. 5 ] There figure 5 is a schematic view of a second embodiment of a device according to the invention for cleaning a pipeline during a gas injection period

[0028] There figure 6 is a schematic view of the device of the figure 5 , during a period of interruption of gas injection. DESCRIPTION OF PREFERRED IMPLEMENTATION METHODS

[0029] When identical numerical references are used in several figures, embodiments or variants of the invention, these numerical references designate identical or similar elements in each of the figures, embodiments or variants.

[0030] On the figure 1 A first particular embodiment of device 1 according to the invention for cleaning a pipe 2 is schematically illustrated. The pipe 2 is a pipe in a heating or cooling network and comprises one or more (generally tubular) conduits allowing the circulation of a heated or cooled liquid, as well as heat exchangers (such as radiators) through which the heated or cooled liquid (generally water, possibly with glycol) circulates. The pipe 2 extends between a first 2a and a second 2b pipe end.

[0031] Device 1 comprises: an inlet pipe 3 ensuring fluid communication between: first connection means 4 adapted to be connected hermetically to the first end 2a of the pipe 2 to be cleaned, and an inlet 5a of filtration means 5; a pump supply pipe 6 ensuring fluid communication between: an outlet 5b of filtration means 5, and an inlet 7a of a hydraulic pump 7, adapted to discharge, via an outlet 7b of pump 7, a liquid from the pump supply pipe 6; an outlet pipe 8 ensuring fluid communication between: the outlet 7b of the hydraulic pump 7, and second connection means 9 adapted to be connected hermetically to the second end 2b of the pipe 2 to be cleaned; gas supply means (here air) 10, configured to inject gas into the outlet pipe 8; control means 100, configured to perform several times alternately: i.a gas injection through a gas inlet 10a into the outlet line 8 during a period of gas injection PER1 and simultaneously an interruption of liquid injection into the outlet line 8, and ii. an interruption of gas injection into the outlet line 8 during a period of interruption of gas injection PER2 and simultaneously an injection of liquid into the outlet line 8.

[0032] The hydraulic pump 7 is suitable for delivering the liquid at a first pressure P1 according to the outlet 7b of the hydraulic pump 7, while the gas supply means (here air) 10 are configured to inject gas into the outlet line 8 according to a second pressure P2 greater than the first pressure P1.

[0033] In practice, the second pressure P2 can advantageously be at least one bar higher than the first pressure P1. Satisfactory results have been observed with a first pressure P1 of 3 bar and a second pressure P2 of 4 bar. The second pressure P2 is preferably less than 6 bar to avoid the risk of damaging pipe 2.

[0034] The outlet pipe 8 includes a first non-return valve 16 between the outlet 7b of the hydraulic pump 7 and the gas inlet 10a.

[0035] The pump supply line 6 has a second check valve 17 between the outlet 7b of the hydraulic pump 7 and the gas inlet 10a.

[0036] The filtration means 5 include a filtration tank 5c collecting the liquid flowing from the inlet pipe 3.

[0037] The liquid flowing from the inlet pipe 3 is received in the tank 5c in a filter bag 11, which filters out impurities larger than a predetermined size. Several filter bags 11 can be used successively over time (by replacing one filter bag 11 with another) or simultaneously (by means of a series arrangement), with progressively finer mesh sizes.

[0038] The tank 5c comprises two compartments 5d and 5e separated by a partition 5f to limit turbulence. After passing through the filter bag 11, the liquid fills compartment 5d before passing over the inner partition 5f to enter compartment 5e, and then exits the filtration means 5 through outlet 5b.

[0039] In compartment 5d is placed a magnet 12 shaped to capture ferromagnetic particles circulating in the filtration means 5. Several magnets 12 can of course be provided. The magnet 12 can be periodically removed from compartment 5d in order to remove the ferromagnetic particles retained by the magnet 12.

[0040] Reversal means 13 allow the direction of incoming and outgoing flows to be reversed by the first connection means 4 and second connection means 9.

[0041] Here, the reversing means 13 include a first distributor spool 14a with two positions A and B. When the first distributor spool 14a is in position A ( Figures 1 And 2 ), the liquid enters pipe 2 through the second end 2b and exits through the first end 2a. When the first distributor spool 14a is in position B ( figure 3), the liquid enters pipe 2 through the first end 2a and exits through the second end 2b: the direction of flow in pipe 2 is thus reversed compared to the direction of flow in the figure 1 .

[0042] The control means 100 are configured to control the gas supply means 10 to inject gas (alone) or liquid (alone) into the outlet line 8 according to a predetermined sequence.

[0043] The 100 control systems are automated to perform predetermined sequences.

[0044] The gas supply means 10 include a gas compressor 15 (here an air compressor) with an air inlet 15a (the air intake is symbolized by arrow 15b) and a second distributor spool 14b with positions C and D. When the second distributor spool 14b is in position C ( Figures 1 And 3), gas (here air) is injected into the outlet pipe 8 through the gas inlet 10a (gas injection period PER1). When the second distributor spool 14b is in position D ( figure 2 ), the gas injection into the outlet pipe 8 is interrupted (PER2 gas injection interruption period).

[0045] The control means 100 are also configured to control the hydraulic pump 7 and the first distributor spool 14a.

[0046] To clean pipe 2 using device 1, after a given period of circulation of a cleaning product (e.g., citric acid-based) in pipe 2, the two ends 2a and 2b of pipe 2 are connected to the inlet pipe 3 on one side and to the outlet pipe 8 on the other, as illustrated in the diagram. figure 1. The first distributor spool 14a can be in position A for circulation in the pipe 2 in a first direction (from the second end 2b to the first end 2a).

[0047] The filter media 5c container can be filled with makeup liquid (such as water). The second distributor drawer 14b is in position D (no gas injection into the outlet line 8).

[0048] The control means 100 control the hydraulic pump 7 to circulate the liquid in the pipe 2: the liquid pushed by the hydraulic pump 7 enters the pipe 2 through the second end 2b and exits through the first end 2a. The liquid then enters the inlet pipe 3 of the device 1 and is conveyed to the filtration means 5 through the inlet 5a of the filtration means 5.

[0049] The liquid passes into the filtration bag 11, which retains the particles carried by the liquid and having a size beyond a predetermined size.

[0050] The liquid then flows into compartment 5d where the ferromagnetic particles are captured and retained by the magnet 12. The liquid then passes into compartment 5e, then exits the tank 5c through outlet 5b of the filtration means 5 to be brought to the hydraulic pump 7 via the pump supply line 6.

[0051] When the control means 100 actuate the second distributor spool 14b to position C, gas (here, air) is injected through the gas inlet 10a into the outlet line 8 for a period of gas injection PER1 and at a second pressure P2 higher than the first pressure P1. Due to the difference between the pressures P1 and P2, the second check valve 17 closes, and the injection of liquid into the outlet line 8 is thus interrupted during the gas injection period PER1. The second check valve 17 also prevents the injected gas from flowing back up the outlet line 8 to the hydraulic pump 7.

[0052] When the control means 100 actuate the second distributor spool 14b to position D, there is an interruption of gas injection into the outlet line 8 for a period of PER2 gas injection interruption. The second check valve 17 then opens and liquid injection into the outlet line 8 is thus restored during the period of PER2 gas injection interruption.

[0053] The diagram of the figure 4 illustrates the activation of the hydraulic pump 7 for injecting liquid (water, for example) IE and the injection of gas IG over time. As illustrated, to clean the pipe 2 using the device 1, at least one step E is carried out during which the hydraulic pump 7 is activated to inject liquid (water in this case) into said outlet pipe 8 at a first pressure P1, and this alternation is repeated several times: of a gas injection into said outlet line 8, by means of the gas supply means 10 according to a second pressure P2 greater than the first pressure P1, during a period of gas injection PER1 (which has the effect of interrupting the injection of liquid into the outlet line 8), of an interruption of gas injection into the outlet line 8 during a period of interruption of gas injection PER2 (which has the effect of restoring the injection of liquid into the outlet line 8).

[0054] In this way, successive and distinct "gas trains" (or volumes of gas) and "liquid trains" (or volumes of liquid) are generated and circulated in pipeline 2 over time t. The alternation of volumes of liquid and volumes of gas provides a surprisingly higher cleaning efficiency than a simultaneous injection of gas into the liquid as carried out in the prior art.

[0055] The PER1 gas injection period has a duration t1 of 2 to 6 seconds, and the PER2 gas injection interruption period has a duration t2 of 2 to 6 seconds.

[0056] Here, for a better result during said step E, the PER1 gas injection period has a duration t1 equal to the duration t2 of the PER2 gas injection interruption period.

[0057] Preferably, during said step E, the period of injection of PER1 gas and the period of interruption of injection of PER2 gas have durations t1 and t2 equal to 3 seconds.

[0058] The duration of step E can be chosen according to various parameters such as the length of pipe 2, its diameter, the number of exchangers it contains and its state of fouling.

[0059] After step E, a step E' can be carried out in which the alternation of PER1 gas injection periods and PER2 gas injection interruption periods is continued, progressively increasing the duration t2 of the PER2 gas injection interruption period (for example, 10 seconds for a few minutes, then 20 seconds for a few minutes, then 60 seconds for a few minutes, etc.). Step E' allows the sludge that was dislodged from pipe 2 during step E to be extracted.

[0060] Note that it may be necessary to repeat a step E, then a new step E', and so on alternately until a liquid with a sufficiently low estimated turbidity (for example, less than 130 ppm) is obtained at the input 5a of filtration means 5.

[0061] After carrying out a cleaning deemed sufficient in the first direction of traffic ( Figures 1 And 2), it may be useful to clean pipe 2 in the second direction of flow ( figure 3 ) by again carrying out a step E followed by a step E', or even a succession of steps E and E' alternating.

[0062] The cleaning device 1 is preferably placed on a rolling chassis, preferably on a trailer adapted to be towed by a vehicle.

[0063] On the figure 5 is schematically illustrated a second particular embodiment of device 1 according to the invention for cleaning a pipe 2.

[0064] This second embodiment differs from the first embodiment in that the second check valve 7 is replaced by a third distributor spool 14c (or the liquid distributor spool 14c) allowing the injection of liquid into the outlet line 8 to be selectively established or interrupted. The second distributor spool 14b can also be called the gas distributor spool 14b.

[0065] In order to achieve an automated alternation of periods of injection of only gas and periods of injection of only liquid, the gas distributor spool 14b and the liquid distributor spool 14c are controlled synchronously by the control means 100 by performing several alternating actions: the injection of gas into the outlet line 8 with the gas distributor spool 14b (position C) while an interruption of liquid injection into the outlet line 8 is caused with the liquid distributor spool 14c (position E) ( figure 5 ), the injection of liquid into the outlet line 8 with the liquid distributor spool 14c (position F) while an interruption of gas injection into the outlet line 8 is caused with the gas distributor spool 14c (position D) ( figure 6 ).

[0066] In all embodiments, the inlet pipe 3 may include a solenoid valve configured to interrupt the flow of fluid (and in particular liquid) in the event of a power failure to the hydraulic pump 7. This prevents the accidental purging of all the liquid from the pipe 2 to be cleaned in the event of a power failure to the hydraulic pump 7 (and the loss of this liquid by causing the tank 5c of the filtration means 5 to overflow).

[0067] The present invention is not limited to the embodiments that have been explicitly described, but includes the various variants and generalizations contained within the scope of the following claims.

Claims

1. Device (1) for cleaning a pipeline (2) extending between a first (2a) and a second (2b) end of pipeline (2), the device (1) comprising: - an inlet pipe (3) ensuring fluid communication between: • first connection means (4) adapted to be connected in a leak-proof manner to the first end (2a) of the pipeline (2) to be cleaned, and • an inlet (5a) of filtration means (5), - a pump supply pipe (6) ensuring fluid communication between: • an outlet (5b) of filtration means (5), and • an inlet (7a) of a hydraulic pump (7), adapted to discharge, via an outlet (7b) of the hydraulic pump (7), a liquid from the pump supply pipe (6), - an outlet pipe (8) ensuring fluid communication between: • the outlet (7b) of the hydraulic pump (7),and • second connection means (9) suitable for being hermetically sealed to the second end (2b) of the pipeline (2) to be cleaned, - gas supply means (10) configured to inject gas into the outlet pipe (8), , characterized in thatIt includes piloting means (100), configured to perform several times alternately: i. an injection of gas through a gas inlet (10a) into the outlet pipe (8) during a period of gas injection (PER1) and simultaneously an interruption of liquid injection into the outlet pipe (8), and ii. an interruption of gas injection into the outlet pipe (8) during a period of interruption of gas injection (PER2) and simultaneously an injection of liquid into the outlet pipe (8), so as to generate successive and distinct volumes of gas and volumes of liquid over time which are put into circulation in the pipeline (2) by injection into the pipeline (2) via one of the first (2a) or second (2b) end of the pipeline (2) and by extraction out of the pipeline (2) via the other of the first (2a) or second (2b) end of the pipeline (2).

2. Device (1) according to claim 1, characterized in that - the hydraulic pump (7) is suitable for delivering the liquid at a first pressure (P1) according to the outlet (7b) of the hydraulic pump (7), - the gas supply means (10) are configured to inject gas into the outlet line (8) according to a second pressure (P2) higher than the first pressure (P1), - the outlet line (8) has a non-return valve (17) between the outlet (7b) of the hydraulic pump (7) and the gas inlet (10a).

3. Device (1) according to claim 1 or 2, characterized in that It includes: - a gas distributor spool (14b) allowing the injection of gas into the outlet line (8) to be selectively established or interrupted, - a liquid distributor spool (14c) allowing the injection of liquid into the outlet line (8) to be selectively established or interrupted.

4. Device (1) according to any one of claims 1 to 3, characterized in thatthe filtration means (5) include a magnet (12) shaped to capture ferromagnetic particles circulating in the filtration means (5).

5. Device (1) according to any one of claims 1 to 4, characterized in that it includes means of reversing (13) the direction of the incoming and outgoing flows by the first means of connection (4) and second means of connection (9).

6. Device (1) according to any one of claims 1 to 5, characterized in that It is placed on a rolling chassis, preferably on a trailer adapted to be towed by a vehicle.

7. Device (1) according to any one of claims 1 to 6, characterized in that The piloting means (100) are configured to pilot the gas supply means (10) to inject gas into the outlet pipe (8) according to a predetermined sequence.

8. Device (1) according to any one of claims 1 to 7, characterized in thatthe inlet pipe (3) includes a solenoid valve shaped to interrupt the flow of fluid in the event of a power failure to the hydraulic pump (7).

9. A method for cleaning a pipe (2) extending between a first (2a) and a second (2b) pipe end (2), by means of a device (1) for cleaning a pipe (2) according to any one of claims 1 to 8, comprising a step (E) during which alternating severaltimes: - an injection of gas into said pipeline (2), by means of the gas supply means (10) during a period of gas injection (PER1) and simultaneously an interruption of liquid injection into the outlet pipe (8), - an interruption of gas injection during a period of interruption of gas injection (PER2) and simultaneously an injection of liquid into the outlet pipe (8), so as to generate successive and distinct volumes of gas and volumes of liquid over time which are put into circulation in the pipeline (2) by injection into the pipeline (2) via one of the first (2a) or second (2b) end of the pipeline (2) and by extraction out of the pipeline (2) via the other of the first (2a) or second (2b) end of the pipeline (2).

10. Method according to claim 9, characterized in that , during the stage E,the circulation of gas volumes and liquid volumes in the pipeline (2) to be cleaned is permanent and continuous between the first end (2a) of the pipeline (2) and the second end (2b) of the pipeline (2), or vice versa.

11. Method according to claim 9, characterized in that , during said step (E): - the gas injection period (PER1) has a duration (t1) of 2 to 6 seconds, and - the gas injection interruption period (PER2) has a duration (t2) of 2 to 6 seconds.

12. A method according to claim 9 or 10, characterized in that , during said step (E), the gas injection period (PER1) has a duration (t1) equal to the duration (t2) of the gas injection interruption period (PER2).

13. Method according to claim 11, characterized in that , during said step (E), the gas injection period (PER1) and the gas injection interruption period (PER2) have durations equal to 3 seconds.

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