FR2944517A1 - DEVICE FOR DETECTING LEAKS IN A LPG DISTRIBUTION FACILITY - Google Patents

Abstract

The device has a buried liquefied petroleum gas (LPG) storage tank (1) containing an LPG liquid phase (2) surmounted by an LPG vapor phase (3). A distributing apparatus (6) is equipped with a flexible pipe on which a dispensing nozzle is connected. A central controller (8) is connected to a controller (44) for controlling a transfer pump (42) and an electro valve (45). A detection unit detects passage of current in an electric control circuit (9) to trigger an alarm and/or to control interruption of distribution of LPG in absence of current in the circuit.

Description

The present invention relates to a device for detecting leaks in a liquefied petroleum gas (LPG) distribution system. LPG, which consists essentially of a mixture of butane and propane from petroleum refining and natural gas processing, is a fuel that is increasingly used. This is indeed a fuel considered clean, which has the additional advantage of preserving vehicle performance and reducing engine wear, while generating less noise and vibration than conventional fuels. . As a result, the use of LPG vehicles is being promoted by the Authorities and more and more service stations are equipped with LPG distribution facilities. Such installations essentially comprise a buried LPG storage tank or tank associated with at least one dispensing apparatus. LPG is stored under its own vapor pressure, so that the storage tank contains a liquid LPG phase on-mounted by a vapor LPG phase. The dispensing apparatus is conventionally equipped with a flexible hose to which is connected a dispensing nozzle, a volumetric meter associated with electronic counting and display devices, as well as LPG degassing members. in the liquid phase to be dispensed. The LPG distribution facilities are also equipped with: a liquid-phase LPG transfer line connecting the storage tank to the dispensing apparatus and provided with a transfer pump and at least one solenoid valve allowing or blocking the passage of the transferred liquid, and a return line of the LPG in the vapor phase separated by the degassing members equipping the dispensing apparatus and connecting this apparatus to the storage tank. This return line is associated with a return pump which is generally mounted on the inner part of the dispensing apparatus. The LPG transfer and return lines consist of buried pipelines.

2 LPG distribution operations in the vehicle tank are controlled from a central computer via a controller connected to the transfer pump and to the solenoid valve for transferring liquid LPG flow rate.

Until recently, LPG lines in the liquid phase and LPG vapor return lines were produced in many countries from welded metal pipe elements. Such underground pipes have the disadvantage of oxidizing and deteriorating over time due to the moisture of the LPG circulating therein. These phenomena lead to risks of leaks of LPG which can have serious consequences insofar as this fuel has the characteristic of being very flammable and explosive. This risk of explosion is all the more important in case of leaks, the liquid phase fuel flowing in the pipes is depressurized and is boiled. In addition, LPG leaks result in environmental pollution and in addition significant financial losses 20 for the managers of the distribution facilities. To overcome these drawbacks, the metal pipes are now replaced by plastic pipes, in particular thermoformed pipes, and all the new LPG distribution installations that are currently built are thus equipped. On the other hand, the metal pipes of the old installations are only very rarely replaced by plastic pipes. Indeed, the pipes being buried, it is impossible to detect a leak. Moreover, if a leak is assumed (for example from differences between the delivered volume and the volume initially present in the storage tank), the only way to have the proof is to unearth the pipes. 35 And because of the very high cost of the necessary work and the downtime of the installation resulting from this work, such a replacement is not possible in practice, especially on mere suppositions.

3 As a result, the replacement of the installation is only envisaged when one is almost certain of the presence of leaks and that the financial loss proves too important. In this context, the object of the present invention is to provide a device for detecting leaks in a LPG distribution installation making it possible to carry out such a detection very easily and at a lower cost, while avoiding having to dig up the pipelines installed. For this purpose, the present invention relates to a leak detection device of the aforementioned type essentially comprising two pressure switches calibrated at a threshold value. These elements are on the one hand respectively connected to the LPG transfer line in the liquid phase and on the LPG return line in the vapor phase and, on the other hand, connected in series to an electrical control circuit, generally supplied with electricity. current from the network, preferably via a transformer. The pressure switches close the electrical control circuit when the LPG pressure in the liquid phase circulating in the transfer line and the LPG pressure in the vapor phase circulating in the return line are greater than the threshold value while they open this circuit when one of these pressures becomes lower than the threshold value so as to prevent the passage of current in it. According to the invention, the leak detection device also comprises means for detecting the passage of current in the electrical control circuit which are associated with the central computer so as to make it possible to trigger an alarm and / or to control the interruption of the distribution of LPG in the absence of current in this circuit. The lack of current in the electrical control circuit is in fact interpreted by the central computer as representative of the presence of LPG leaks in the LPG transfer line in the liquid phase and / or in the LPG return line in phase. steam. According to the invention, after the detection of leaks, the LPG distribution installation can preferably be restarted only after authorization by an authorized person.

According to a preferred characteristic of the invention, the means for detecting the passage of current in the electrical control circuit consist of an electromechanical relay comprising a coil mounted on this circuit in series with the two pressure switches and a contact 4. which closes under the action of the electromagnetic field induced by the current flowing through this coil to transmit a correct operating signal to the central computer. In the absence of such a signal, this computer detects the presence of a leak and triggers an alarm and / or controls the interruption of LPG distribution. The characteristics of the leak detection device which is the subject of the invention will be described in more detail with reference to the accompanying nonlimiting drawings in which: FIG. 1 is a schematic representation of a LPG distribution installation equipped of a leak detection device according to the invention, Figure 2 is a schematic representation of the electrical control circuit. According to FIG. 1, the LPG distribution installation essentially comprises a buried storage tank 1 and a dispensing apparatus 6 which is shown schematically. The storage tank 1 contains a LPG fraction in the liquid phase 2 surmounted by a fraction of LPG in the vapor phase 3. The dispensing apparatus 6 is conventionally equipped with a flexible pipe to which is connected a dispensing nozzle, a measuring device volumetric associated with electronic counting and display organs as well as liquid LPG degassing organs to be dispensed. These different elements are not represented. According to FIG. 1, a liquid-phase LPG transfer line 4 connects the storage tank 1 to the distributor apparatus 6 so as to allow delivery of LPG in the liquid phase to the tank of motor vehicles. This transfer line 4 is conventionally equipped with nonreturn valves 41, 47 and solenoid valves 45, 48 enabling or blocking the transfer of LPG in the liquid phase to the dispensing apparatus 6. This transfer is ensured by a transfer pump 42 mounted downstream of the first non-return valve 41 in the LPG circulation direction, at the outlet of the storage tank 1, so as to suck LPG in the liquid phase 2 stored in this tank. The transfer pump 42 is driven by a variable speed motor 43 whose speed is controlled from a central computer 8 via a controller 44. This controller 44 is also connected to the solenoid valve 45 to enable the control of the control valve. opening or closing thereof on instruction of the central computer 8 and notify the end of the delivery. The LPG transfer line in the liquid phase 4 is further equipped with a filter 46, in particular of the Y type, making it possible to eliminate the solid impurities that may be present in the LPG in the transferred liquid phase. According to FIG. 1, the LPG distribution installation also comprises a return line 5 in the storage tank 1 of the LPG in the vapor phase separated by the degassing members equipping the dispensing apparatus 6.

The vapor phase LPG thus separated is reintroduced into the vapor LPG phase 3 at the top of the storage tank 1 where the return line 5 opens. This reintroduction is ensured by a not shown return pump which is in fact mounted to 6. The return line 5 is furthermore equipped with non-return valves 51, 57 and a solenoid valve 58. According to FIG. 1, two pressure switches 7a, 7b calibrated at a rate of 50.degree. their threshold are respectively connected to the transfer line 4 and 25 on the return line 5 and are connected in series to an electrical control circuit 9 which will be described in more detail later in this description. As shown diagrammatically in FIG. 1, this electrical control circuit 9 is connected to the central computer 8 so as to make it possible to detect the presence of LPG leaks in the transfer line 4 or in the return line 5. It should be noted that in a LPG distribution system, the normal operating pressure is between 7 and 15 bar and can be limited to 23 bar by safety valves calibrated in sequence. In the presence of leaks on the transfer line 4 or on the return line 5, the pressure drops significantly with respect to this normal operating pressure.

As a result, the two pressure switches 7a, 7b may for example be calibrated to a threshold value of 4 bars, this threshold value not being necessarily the same for the two pressure switches. According to FIG. 2, the electrical control circuit 9 on which the two pressure switches 7a, 7b are connected in series is connected to the central electrical network 10 of voltage 220 volts and supplied with current by a transformer 13 which makes it possible to convert the 220 Volt input voltage at an output voltage, typically 12 volts or 24 volts.

The phase electrical wires cp and that of the neutral N of the network 10 are connected to two terminals 11. A wire directly connects the neutral terminal to the transformer 13 while the phase terminal is connected to this transformer via a protective circuit breaker 12 .

The contacts 71a, 71b of the pressure switches 7a, 7b make it possible to control the opening or closing of the electrical control circuit 9. More precisely, the electric control circuit 9 is closed in the case of normal operation, that is, that is, when the LPG pressure in the liquid phase in the transfer line 4 and the pressure of the LPG in the vapor phase in the return line 5 are greater than the threshold value, and opens automatically when the one of these pressures becomes lower than this threshold value to prevent the passage of current in this circuit 9.

According to FIG. 2, the electrical control circuit 9 also comprises an electromechanical relay 15 comprising a coil 16 mounted on this circuit 9 in series with the pressure switches 7a and 7b as well as a contact 17 whose two terminals are connected to the central computer 8 In view of this arrangement, when the electric control circuit 9 is closed, the electromagnetic field induced by the current flowing through the coil 16 of the electromechanical relay 15 closes the contact 17 of this relay. The central computer 8 then receives a signal RD (Received Data) and transmits in response to this signal a signal TD (Transmit Data) representative of a normal operation of the distribution installation. According to FIG. 2, a fuse 14 makes it possible to limit the current flowing in the electronic control circuit 9 to a maximum value so as to protect the pressure switches 7a, 7b. The transformer 13, the pressure switches 7a, 7b, the fuse 14 and the coil 16 of the electromechanical relay 15 are thus mounted in series on the electrical control circuit 9. The operating mode of the device according to the invention is as follows: In the case of a correct operation, that is to say in the absence of leaks in the pipes of the transfer line 4 or in the pipes of the return line 5, the pressure of LPG flowing in these lines 4, 5 is greater than the threshold value; as a result, the contacts 71a and 71b of the two pressure switches 7a and 7b are closed and the current flows into the electrical control circuit 9. The coil 16 of the relay 15 is thus supplied with current and induces an electromagnetic field causing the closure of the contact 17 of the electromechanical relay 15. The central computer 8 thus receives a signal and thus detects a correct operation of the installation. On the contrary, in the presence of leaks in the pipes of the transfer line 4 or in the lines of the return line 5, the LPG pressure flowing in at least one of these lines 4, 5 falls and becomes smaller than the threshold value so that the contact 71a, 71b of the pressure switch 7a, 7b associated opens. The current can no longer pass through the electronic control circuit 9, in particular in the coil 16 of the electromechanical relay 15, and the contact 17 of this relay therefore remains open. As a result, the central computer 8 receives no signal and interprets this absence of signal as representative of the presence of 30 leaks on at least one of the transfer lines 4 or return 5. The central computer 8 then transmits back a signal to trigger an alarm and / or to control the interruption of LPG distribution. This delivery remains blocked until this problem is solved and can be restarted only after intervention by an authorized person.

NOMENCLATURE

1 Storage tank 2 Liquid LPG phase 3 Steam LPG stage 4 Liquid LPG transfer line 5 LPG gas return line 6 Dispenser 7a, 7b Pressure switches 8 Central computer 9 Electrical device 10 Central electrical network 11 Terminals 12 Power circuit breaker protection 13 Transformer 14 Fuse 15 Electromagnetic relay 16 Coil 17 Contact 41, 47 Check valves 42 Transfer pump 43 Motor 44 Control controller 25 45, 48 Solenoid valves 46 Filter

51, 57 Check valves 30 58 Solenoid valve

71a, 71b Switches 35

Claims (1)

CLAIMS1 °) Device for detecting leaks in a LPG distribution installation comprising: a buried LPG storage tank (1), this tank containing a liquid LPG phase (2) surmounted by a vapor LPG phase (3) , a dispensing apparatus (6) equipped with a flexible hose to which is connected a dispensing nozzle, a volumetric measuring device associated with electronic counting and display devices, as well as LPG degassing bodies in the liquid phase. to distribute, a LPG transfer line in the liquid phase (4) connecting the storage tank (1) to the dispensing apparatus (6) and provided with a transfer pump (42) and at least one solenoid valve (45), a vapor LPG return line (5) connecting the dispensing apparatus (6) to the storage tank (1) and provided with a return pump, and a central calculator (8) connected to a controller (44) for the transfer pump (42) and the electro valve (45), characterized in that it comprises: two pressure switches (7a, 7b) calibrated at a threshold value, on the one hand respectively connected to the LPG transfer line in the liquid phase (4) and on the line back of LPG in the vapor phase (5), and secondly mounted in series on an electric control circuit (9) so as to fer-mer this circuit when the LPG pressure in the liquid phase in the line of transfer (4) and LPG pressure in the vapor phase in the return line (5) are greater than the threshold value, and to open this circuit (9) when one of these pressures becomes lower than the threshold value to prevent the passage of current therein, and means for detecting the passage of current in the control circuit (9) associated with the central computer (8) to enable it to trigger an alarm and / or to control interruption of LPG distribution in the absence of current in this circuit (9). 2) Device according to claim 1, characterized in that the control circuit (9) is supplied with current from the network (10), preferably via a transformer (13). 2944517 lo 3 °) Device according to any one of claims 1 and 2, characterized in that the means for detecting the passage of current in the electrical control circuit (9) consist of an electromechanical relay (15) cur- carrying a coil (16) mounted on this circuit in series with the two pressure switches (7a, 7b) and a contact (17) which closes under the action of the electromagnetic field induced by the current flowing through the coil (16) for transmit a correct operating signal to the central computer (8). lo