WO2017129187A1

WO2017129187A1 - Device for detecting gas in fluids

Info

Publication number: WO2017129187A1
Application number: PCT/DE2017/200008
Authority: WO
Inventors: Stefan Marx
Original assignee: Stefan Marx
Priority date: 2016-01-26
Filing date: 2017-01-25
Publication date: 2017-08-03
Also published as: GB2562925A; GB2562925B; NO20180976A1; DE102016201041A1; GB201811306D0; DE102016201041B4

Abstract

The invention relates to a device for detecting gas (130) in a fluid. Said device has a sensor arrangement (52) which has at least one gas sensor (54) and is in direct connection to a gas contained in the fluid. Moreover, the device (2) according to the invention has a second sensor arrangement (90) which has a gas sensor (92) that is identical to the gas sensor (54) of the first sensor arrangement (52) and is in connection to the environment of the device (2) via a buffer chamber (112).

Description

description

[Ol] The invention relates to a device for detecting gas in liquid.

[02] The detection of gases present in liquids is of great importance in various technical fields. An example is the offshore exploration and production of oil and gas. There, spills on underwater wells, conveyors, and production lines initially manifest themselves in an increased level of hydrocarbon gases in the immediate water environment of those facilities. It is therefore of particular interest to detect hydrocarbon gases present there in the water at an early stage in order to be able to take immediate measures against a leak detected in this way.

[03] WO 96/34285 A1 discloses a device provided primarily for detecting hydrocarbon gases in water. This device has a semiconductor sensor arranged in a measuring space for the detection of hydrocarbons, wherein the measuring space is completely encapsulated apart from an opening to the water environment of the device. The opening is closed by a gas-permeable, but otherwise impermeable membrane. Thus, only the gases present in the ambient water of the device can reach the measuring space by diffusion through the membrane, in which case the concentration of the hydrocarbon gases is then detected by the sensor. [04] However, a disadvantage of this known device is that the hydrocarbon concentration determined on the basis of the sensor signals can be subject to considerable inaccuracies, since different physical and / or chemical effects can lead to a measured value drift of the semiconductor sensor.

Against this background, the invention has the object to provide a device for detecting gas in liquid, which does not have the disadvantage of the prior art device.

[06] This object is achieved by a device having the features specified in claim 1. Advantageous developments of this device will become apparent from the dependent claims, the following description and the drawings. In this case, the features specified in the subclaims can advantageously contribute in the specified combination, but also, as far as is technically meaningful, alone or in another combination for the embodiment of the invention.

[07] The device according to the invention serves to detect gas in a liquid. Not only, but primarily, it is intended to review underwater installations for offshore exploration and offshore oil and gas production. In this context, the device may be used in conjunction with a cable-guided underwater vehicle (ROV), an autonomous underwater vehicle (AUV) or in conjunction with a long-term monitoring station located in close proximity to a submerged exploration or production facility. to detect leaks at the exploration and production facilities.

[08] The device has a sensor arrangement which is connected to the environment of the device and thus also to one in the environment contained gas. This sensor arrangement is equipped with at least one gas sensor, which supplies a corresponding measurement signal in the presence of a gas to be detected. As a gas sensor, such a gas sensor is preferably provided, which rather provides an electrical measurement signal. However, in particular with these gas sensors, a measured value drift may occur, so that the measurement signal provided by the gas sensor alone is not very meaningful, since it is constantly changing.

[09] This fact is taken into account by the invention insofar as the device according to the invention has a second sensor arrangement which has a gas sensor identical to the gas sensor of the first sensor arrangement, wherein the second sensor arrangement is connected to the surroundings of the apparatus via a buffer space. [10] In this case, the buffer space preceding the second sensor arrangement has the significance of forming a reservoir for liquid which keeps the gas to be detected away from the at least one gas sensor of the second sensor arrangement, but the gas sensor of the second sensor arrangement otherwise has the same physical and / or or chemical influences such as the gas sensor of the first sensor arrangement is exposed. This is expediently achieved in that the buffer space is already filled with liquid before the device is used, which does not contain the gas to be detected.

Since the gas sensor of the second sensor arrangement is of identical design to the gas sensor of the first sensor arrangement and apart from the fact that it does not come into contact with the gas to be detected, the same ambient conditions as the gas sensor of the first sensor arrangement is exposed, is its measurement signal influenced by these environmental influences in the same way as the measurement The gas sensor of the first sensor arrangement, ie, since the gas sensors of the two sensor arrangements have identical sensor properties, the measured values determined by the two gas sensors drift in the same direction with a comparable gradient. In this respect, the gas sensor of the second sensor arrangement provides a reference signal to the measurement signal of the gas sensor of the first sensor arrangement, which makes it possible to eliminate a measured value drift from the measurement signal of the gas sensor of the first sensor arrangement. This is preferably done by constantly comparing the measurement signals of the gas sensors of the two sensor systems in an electronic evaluation device and evaluating only the difference between the measured values of the two gas sensors, this difference value then forming the basis for calculating the concentration of the detected gas. This procedure results in the fact that the concentration of a gas can be determined with a very high accuracy even with a measured value drift caused by changing environmental conditions.

Preferably, the buffer space is open towards the liquid surrounding the device. Accordingly, there is an overflow possibility from the outside environment of the device to the gas sensor for an ambient liquid of the device via the buffer space. The overflow of the liquid into the buffer space and to the gas sensor of the second sensor arrangement or the associated filling of the buffer space with the liquid is expediently carried out when the gas to be detected is not contained in the liquid. If the device according to the invention is in an environment in which the liquid contains the gas to be detected, it must be ensured that the gas sensor of the second sensor arrangement does not interact with this gas when a gas in the liquid is detected by the gas sensor of the first sensor arrangement comes into contact. For this purpose, the shape and dimensions of the buffer space expediently to be selected such that the gas in the liquid during the detection of the gas by the gas sensor of the first sensor arrangement can not reach the gas sensor of the second sensor arrangement. [13] As an alternative to an embodiment in which the buffer space is designed to be open towards the liquid surrounding the device, such a configuration may also be advantageous in which the buffer space is closed towards the liquid surrounding the device by an elastic membrane. This elastic membrane is typically both liquid impermeable and gas impermeable. The buffer space is in this case filled with a liquid whose physical and chemical properties suitably correspond to those of the liquid in which the device according to the invention is used. The membrane in this case allows the pressure and the temperature of the ambient liquid of the device to be transferred to the liquid present in the buffer space, and at the same time reliably prevents gas present in the ambient liquid from penetrating into the buffer space and reaching the gas sensor of the second sensor arrangement , [14] In particular, in the case of a buffer space open to the liquid surrounding the device, this buffer space is advantageously formed by a multiply wound tube. In this case, preference is given to an embodiment of the tube in which it is helically wound, but the tube may optionally also have a different labyrinth-like turn. The multiplicity of turns of the tube has the advantage that, given a comparatively small installation space, the tube can have a relatively large length and thus forms a correspondingly large flow path from the liquid environment of the device to the gas sensor of the second sensor arrangement. For example, it has been shown that when capturing In water, the methane is required at a preferred inner diameter of the pipe of 0.5-10 mm and a preferred length of the pipe of 10-15 cm due to the diffusion of methane into water for at least two days to separate from that with the outside environment - Get tion in directly connected pipe end to the gas sensor of the second sensor assembly. With a corresponding increase in the tube length, this period of time can be considerably increased, so that it is ensured in any case that the gas in the water does not reach the gas sensor of the second sensor arrangement during the detection of the gas by the gas sensor of the first sensor arrangement.

[15] According to a further preferred development of the invention, the two sensor arrangements each communicate with a measuring space closed by means of a gas-permeable membrane. This is to be understood as meaning an arrangement of the two sensor arrangements in which the sensors of the sensor arrangements are in contact with the interior of the respective measurement space, wherein the sensors of the sensor arrangements can advantageously also be arranged completely within the measurement spaces. In addition, it is provided in this development that the membrane, which closes the measuring space in connection with the first sensor arrangement, forms a liquid-tight barrier directly to the outside environment of the device, and the membrane which forms the measuring space in connection with the second sensor arrangement closes, forms a liquid-tight barrier to the buffer space. Due to the liquid impermeability of the membranes, the measuring chambers communicating with the two sensor arrangements each contain only one gas phase. Through the membrane which closes the measuring space which is connected to the first sensor arrangement, the gas contained in the ambient liquid of the device and to be detected diffuses into the gas which is in contact with the first sensor arrangement. binding measuring room. The liquid itself can not pass through the membrane. The diffusion of the gas continues until a thermodynamic equilibrium is established between the gas and the liquid. For this to happen as quickly as possible, the internal volume of the measuring space should be kept as small as possible.

The two, the measuring chambers occluding membranes can generally be formed of all suitable membrane materials, it being only necessary to ensure that the membrane on the one hand are gas permeable and on the other hand liquid impermeable. According to the invention, however, the membranes are preferably silicone membranes. In particular, when the device at high fluid pressures, such. B. when using the device in the field of offshore exploration and offshore production of oil and / or natural gas is used in large water depths, can be advantageously provided that the membranes are each supported on a correspondingly pressure-resistant, gas-permeable plate. This plate may for example consist of sintered metal, sintered or otherwise produced ceramic or glass.

[17] The gas sensors of the first and the second sensor arrangement can advantageously be formed by semiconductor sensors. Such semiconductor sensors have a gas-sensitive semiconductor layer, which is usually formed from a metal oxide. The semiconductor sensors are energized. Under a certain gas influence, the conductivity of the semiconductor sensor changes and leads to a change in resistance, which forms the basis for the measurement signal supplied by the semiconductor sensor. The use of the semiconductor sensors is advantageous in that they are relatively inexpensive to obtain and their energy consumption is relatively low. The latter characteristic makes them particularly suitable for use in autonomously operated gas detection devices where the power supply of the device is disposed within the device.

[18] As an alternative to the use of semiconductor sensors as gas sensors, the gas sensors of the first and the second sensor arrangement can also be formed by optical sensors. In this case, it is preferably provided that the measuring chambers of the two sensor arrangements are arranged between a light source in the form of a tunable laser radiation source operating according to the TDSL principle (TDLS = Tunable Diode Laser Spectroscopy) or an infrared light source and a detector detecting the light intensity, which an optical signal, such as an infrared radiation, converted into an electrical signal. Starting from the light source, light rays are transmitted through the measurement space, using light rays whose wavelength is specifically absorbed by the gas to be detected. This is detected by the detector and further processed into a measuring signal in conjunction with an electronics connected downstream of the detector. The detector may be a photodetector utilizing the internal or external photoelectric effect or, in the case of using an infrared light source, a thermal detector, e.g. a pyroelectric detector or Thermopilede- act detector which converts the heat energy of the infrared radiation into an electrical or mechanical signal.

[19] More preferably, each of the two sensor arrangements has at least one second gas sensor. These second gas sensors of the two sensor arrangements form a redundancy to the two first gas sensors of the sensor arrangements and thus capture the same gas as the first gas sensors. The second gas sensors of the first and second sensor arrangement are expediently designed to be identical and are preferably in each case in connection with a measuring space which is closed by means of a gas-selective membrane wherein the membrane of the first sensor arrangement forms a liquid-tight barrier directly to the outside environment of the device and the membrane of the second sensor arrangement forms a liquid-tight barrier to the buffer space. Advantageously, the configuration of the second gas sensors and the measurement spaces associated therewith can be completely identical to the configuration of the first gas sensors and the measurement spaces associated therewith. In addition, the first gas sensors and the second gas sensors of the two sensor arrangement can each also be connected to the same measuring space.

[20] As noted above, the device of the present invention is primarily intended to inspect underwater installations for offshore exploration and offshore oil and gas exploration, thereby providing early detection of leaks in the underwater exploration and production facilities which are initially noticeable by an increased content of hydrocarbon gases in the immediate water environment of these facilities. According to a further advantageous development of the invention, therefore, the gas sensors are designed for the selective detection of hydrocarbon gases.

For example, if only the concentration of a specific gas to be determined with the device according to the invention, wherein the gas sensor used for this purpose does not have the appropriate selectivity, it is advantageous if the gas sensor comes into contact with only this special gas. This ensures a further advantageous development of the invention, according to which at least on the input side of the gas sensors of the first sensor arrangement in each case a filter is arranged, which is permeable only for a particular gas. If the gas sensors are designed for the selective detection of hydrocarbon gases, the filter can, for example, be designed such that it only a particular hydrocarbon gas such. B. lets methane through to the gas sensor. In the preferred embodiment, in which the gas sensors are in connection with a sealed by a gas-permeable membrane measuring chamber, it is preferably provided that the filter is formed by a corresponding layer which is mounted on the membrane.

If no corresponding filter is arranged on the membrane, it is also possible for oxygen present in the liquid to pass through diffusion into the measuring space communicating with the gas sensors of the first sensor arrangement. Since greatly varying oxygen concentrations in the measurement spaces may influence the measured values of the gas sensors of the two sensor arrangements intended for detecting a gas other than oxygen, it makes sense to consider the oxygen in the measurement space when determining the concentration of the gas actually to be detected , According to a further preferred embodiment, therefore, each of the two sensor arrangements additionally has a gas sensor for the selective detection of oxygen.

[23] The absolute humidity in the measuring chambers in connection with the gas sensors of the two sensor arrangements also affects the measured values of the gas sensors. So z. As an increased absolute humidity in the measuring chambers in the use of semiconductor sensors an increase in the conductivity of the semiconductor sensor and, consequently, a distortion of the measured value result. In this respect, there is basically an interest in determining the absolute humidity in the measuring chambers and in determining the concentration of the gas to be detected. In this respect, according to a further preferred embodiment, a sensor for determining the absolute humidity in the measuring space is arranged in the measuring space of the two sensor arrangements. In order to be able to keep the absolute humidity in the measuring chambers constant, a temperature sensor and a heater are advantageously arranged in the measuring space of the two sensor arrangements, wherein a temperature control device is provided, which regulates the temperature in the measuring space to a constant value.

[25] Furthermore, when determining the concentration of the gas to be detected, it is also necessary to have knowledge of the gas pressure in the measuring chambers of the two sensor arrangements. In this context, it is preferably provided that a gas pressure sensor is arranged in the measuring space of the two sensor arrangements. This gas pressure sensor is advantageously signal-connected to the electronic evaluation unit for determining the concentration of the gas to be detected.

In addition, it is also useful to include in the determination of the concentration of the gas to be detected, the conductivity, the temperature and the pressure of the ambient liquid of the device according to the invention. The invention takes this into account by preferably providing a sensor which detects the conductivity of the ambient liquid of the device, more preferably a sensor detecting the temperature of the ambient liquid of the device, and furthermore providing a sensor detecting the pressure of the ambient liquid of the device. These mentioned sensors are also advantageously signal-connected to the electronic evaluation unit for determining the concentration of the gas to be detected.

[27] The invention is explained in more detail below with reference to exemplary embodiments illustrated in the drawing. In the drawing shows schematically simplified and partly in different scales: 1 is a sectional view of a device for detecting

Gas in a liquid,

2 shows possible application scenarios of the device according to FIG. 1, FIG.

FIG. 3 shows a gas sensor of the device according to FIG. 1 according to a first embodiment, FIG.

4 shows a gas sensor of the device according to FIG. 1 according to a second embodiment and FIG

5 shows a cable-guided underwater vehicle shown in FIG. 2. The device 2 shown in detail in FIG. 1 is intended for underwater assessment of offshore installations for the extraction and transport of crude oil and natural gas located below the water surface and serves to detect any hydrocarbon gases exiting there. Related possible use scenarios of the device 2 are shown in FIG.

[29] Fig. 2 shows an offshore installation arranged in a body of water for the extraction of crude oil. In addition to an offshore platform 6, which is arranged largely above a water surface 4, this offshore installation also has a number of conveyors arranged below the water surface 4. In this context, an underwater structure 10 arranged on the bottom 8 of the water is illustrated in FIG. 2 with conveying lines 12 and 14 extending therefrom, wherein a so-called sub-tree 1 6 adjoins one end of the conveying line 14. If leaks occur at the conveyors arranged below the water surface 4, which are manifested by hydrocarbon gases 20 exiting into the water 18, the device 2 serves to locate these leaks by transferring the hydrocarbon gases then exiting at the leakage point into the water 18 20 detected.

[31] In order to be able to position the device 2 in the vicinity of a possible leakage point, it can be arranged in or on an underwater vehicle. As shown in Fig. 2, the underwater vehicle may be a cable-guided underwater vehicle 22 (ROV) or an autonomous underwater vehicle 24 (AUV). While the autonomous underwater vehicle 24 operates substantially autonomously, in the present case the cable-guided underwater vehicle 22 is remotely controlled by a surface ship 26. For this purpose, the underwater vehicle 22 is connected via a cable 28 to the overwater vessel 26. The cable 28 serves in addition to the power supply of the underwater tool 22 for the transmission of control signals from the surface ship 26 to the underwater vehicle 22 and for data exchange between the device 2 and devices communicating therewith on the surface ship 26.

[32] Furthermore, it is possible to monitor the individual components of the conveyors arranged below the water surface 4 by means of devices 2 which are arranged in a stationary manner in direct proximity to the monitored object. In this context, a long-term monitoring station 30 equipped with two devices 2 is shown in FIG. 2, with which the subsea tree 1 6 is monitored.

[33] In the following, detailed reference is made to FIG. The device 2 shown there has a housing 32. In view of a possible use of the device 2 in large water depths, the housing 32 is pressure-resistant and non-pressure-resistant components of the device 2 are flameproof encapsulated in the housing 32. The housing 32 has a base body 34 which forms a hollow body open after two directly opposite sides. An interior 36 of the main body 34 is closed by two pressure-resistant walls 38 and 40, which are arranged in the interior of the base body 34 slightly offset from the open ends of the base body 34. At both open ends of the main body 34 of the housing 32 in each case a shoulder 42 is formed in the interior of the main body 34. On each of these paragraphs 42 is a plate 44. The plates 44 are each gas-permeable and pressure-resistant formed as sintered parts of metal or other materials.

On the plate 44, which is disposed immediately outside the wall 38, is located on the side facing away from the wall 38 side of the plate 44 a likewise engaging in the shoulder 42 membrane 46. The membrane 46 is permeable to gas, but not formed liquid permeable. With its side facing away from the plate 44, the membrane 46 terminates flush with the end of the main body 34. By means of a fastening ring 48 which is screwed to the base body 34 of the housing 32, the membrane 46 and the plate 44 in the shoulder 42 of the Grundköpers 34 are positively and optionally fixed non-positively.

[35] Between the plate 44 and the wall 38 there is a free space, which is referred to below as measuring space 50. If the device 2 is in use, no water 18 can enter the measuring space 50 due to the liquid-impermeable formation of the membrane 46. The situation is different with gases present in the water 18, such as hydrocarbon gases 20 exiting primarily at a leakage point, which diffuse through the membrane 46. and thus pass over the likewise gas-permeable plate 44 in the measuring chamber 50. The diffusion of the gas continues until a thermodynamic equilibrium between the hydrocarbon gas 20 and the water 18 is established. The molar concentration of the carbon gas 20 dissolved in the water 18 is then in thermodynamic equilibrium with the partial pressure of the hydrocarbon 20 in the gas phase in the measuring space 50.

[36] In the measuring space 50, a first sensor arrangement 52 of the device 2 is arranged. The sensor arrangement 52 includes a first gas sensor 54 for determining the hydrocarbon gas concentration in the measurement space 50, a second gas sensor 56 forming a redundancy to the first gas sensor 54, a gas sensor 58 for determining the oxygen concentration in the measurement space 50, a sensor 60 for determining the absolute humidity in the measuring space 50, a temperature sensor 62 for determining the gas temperature in the measuring space 50 and a pressure sensor 64 for determining the gas pressure in the measuring space 50.

[37] In addition to the first sensor arrangement 52, a heating 66 is also arranged in the measuring space 50. The heater 66, together with the temperature sensor 62 and a temperature control device not explicitly shown in the drawing, serves to keep the temperature in the measuring space 50 constant.

[38] All sensors of the first sensor arrangement are connected by means of lines to an electronic module 68, which is arranged in the interior 36 of the main body 34 of the housing 32. The electronic module 68 serves to supply electrical energy to all electrical or electronic devices of the device 2 and to evaluate the measurement signals supplied by the sensors of the device 2. For self-sufficient power supply of the device 2, the electronic module 68 is equipped with an accumulator 70, which has a La deregier 72 with a charging port 74 is in communication. The evaluation of the measurement signals provided by the sensors of the device 2 takes place in an evaluation device 76 of the electronic module 68. Furthermore, the electronic module 68 has a data memory 78, which via a data input and output unit 80 and a data line 80 with a peripheral device (not shown). is connectable.

[39] On the plate 44, which is arranged directly on the outside of the wall 40, a membrane 84 engaging in the shoulder 42 rests on the side of the plate 44 facing away from the wall 40. Like the membrane 46, the membrane 84 is gas permeable but not liquid permeable. With its side facing away from the plate 44, the membrane 84 terminates flush with the end of the main body 34. By means of an element 86, which is screwed to the main body 34 of the housing 32, the membrane 84 and the plate 44 in the shoulder 42 are fixed in a form-fitting manner and optionally also non-positively.

[40] As between the plate 44 and the wall 38 is also between the plate 44, against which the membrane 84 is applied, and the wall 40, a free space, which is hereinafter referred to as the measuring chamber 88. In this measuring space 88, a second sensor arrangement 90 of the device 2 is arranged. This second sensor arrangement 90 has, in addition to a first gas sensor 92, which is identical to the gas sensor 54 of the first sensor arrangement 52, a second gas sensor 94 which is identical to the second gas sensor 56 of the first sensor arrangement 52 and a redundancy to the first gas sensor 92 second sensor arrangement 90 forms. Furthermore, the second sensor arrangement 90 includes a gas sensor 96 for determining the oxygen concentration in the measuring chamber 88, which is identical to the gas sensor 58 of the first sensor arrangement 52, a sensor 98 for determining the absolute humidity in the measuring chamber 88, which is identical to the sensor 60 of the first sensor assembly 52, a temperature sensor 100 for determining the gas temperature in the measuring chamber 88, which is identical to the temperature sensor 62 of the first sensor assembly 52 and a pressure sensor 102 for determining the gas pressure in the measuring space 88, which is identical to the pressure sensor 64 of the first sensor arrangement 52. All sensors of the second sensor arrangement 90 are likewise connected via lines to the evaluation device 76 of the electronic module 68. In addition to the second sensor arrangement 90, a heating 104 is also arranged in the measuring space 88, which, together with the temperature sensor 100 and a temperature control device not explicitly shown in the drawing, serves to keep the temperature in the measuring space 88 constant at the temperature value of the measuring space 50. [41] The element 86, which is screwed to the base body 34 of the housing 32 and fixes the membrane 84 and the plate 44 in the shoulder 42 of the base body 34 in a form-fitting and optionally non-positive manner, is cup-shaped and forms a cavity 106 which is open to the membrane 84. On a parallel to the diaphragm 84 aligned end plate 108 of the element 86, a hole is formed in which one end of a multi-helical wound pipe 1 10 engages.

[42] Together with the cavity 106 of the element 86, the tube 1 10 forms a buffer space 1 12 for receiving water 18, which from the environment of the device 2 via the open end of the tube 1 10 formed in the tube 1 10 and there in the cavity 106 of the element 86 can flow. In particular, the length and inner cross-sectional dimensions of the tube 110 hereby ensure that gases present in the water 18, at least during the use of the device 2, do not reach the vicinity of the membrane 84 and from there into the measuring chamber. reach 88, while the other environmental conditions of the measuring chamber 88 and arranged therein second sensor array 90 with the environmental conditions of the measuring chamber 50 and the first sensor array arranged therein 52 match. Changes in the measurement signals of the gas sensors 92, 94 and 96 of the second sensor arrangement 90 are therefore due only to a measurement signal drift of these gas sensors 92, 94 and 96, which coincides with the measurement signal drift of the gas sensors 54, 56 and 58 of the first sensor arrangement 52. This circumstance is used in the evaluation device 76 of the electronic module 68 in order to eliminate the drift-related components of the measurement signal variations of the gas sensors 54, 56 and 58 of the first sensor arrangement 52 used for detecting hydrocarbon gases 20 and oxygen.

[43] The adjusted measurement signals of the gas sensors 54, 56 and 58 of the first sensor arrangement 52 form the basis for the calculation of a carbon gas concentration in the water 18 in the environment of the device 2 in the evaluation device 76 of the electronic module 68. However, it is necessary to calculate this carbon gas concentration also required to have knowledge of the temperature, pressure and conductivity of the water 18 in the vicinity of the device 2. Therefore, in addition to the sensors of the first sensor arrangement 52 and the sensors of the second sensor arrangement 90, the device 2 also has a temperature sensor 1 14 directly connected to the outside environment of the device 2, a pressure sensor 1 in direct communication with the outside environment of the device 2 16 as well as also with the outside environment of the device 2 directly communicating conductivity sensor 1 18.

[44] The gas sensors 54, 56 and 58 of the first sensor arrangement 52 and the gas sensors 92, 94 and 96 of the second sensor arrangement 90 may be formed as semiconductor sensors. Such a semiconductor Sensor 120 is shown in Fig. 3 schematically greatly simplified. The semiconductor sensor 120 has a main body 122 on which a sensor layer 124 made of a semiconductor material is arranged. Via contacts 126 and 128, an electrical voltage is applied to the sensor layer 124. The semiconductor material of the sensor layer 124 is selected so that when it comes in contact with a particular gas 130, it reacts thereto in the form of a change in the electrical conductivity of the sensor layer. In order for a good intrinsic conductivity of the sensor layer 124 to be used at all, this must be heated to a specific temperature. For this purpose, a heating element 132 is arranged in the main body 122 of the semiconductor sensor 120.

[45] As an alternative to the use of semiconductor sensors as gas sensors, the gas sensors 54, 56 and 58 of the first sensor arrangement 52 and the gas sensors 92, 94 and 96 of the second sensor arrangement 90 can also be formed by optical sensors. Such an optical sensor 134 is shown in FIG. 4 in a schematic diagram. This sensor 134 has a light source 138 controlled by an electronic module 136. The light source 138 may be a tunable laser, a tunable laser diode, or an infrared light source. In the beam path of the light source 138 is a light intensity detecting detector 140, which is spaced from the light source 138 is arranged. If a particular gas 130 is present in the gap 142 between the light source 138 and the detector 140, typical wavelengths of the light emitted by the light source 138 are absorbed by the gas 130 for this gas 130, which is detected by the detector 140. A signal-connected to the detector 140 electronic signal processing device 144 then generates a corresponding measurement signal in the form of an electrical voltage value. [46] As already noted in connection with FIG. 2, the device 2 may be used in conjunction with a cable-guided underwater vehicle 22 (ROV). Fig. 5 shows the underwater vehicle 22 shown in Fig. 2 in an enlarged single drawing. The underwater vehicle 22 has an upper part 146, to which a substructure 148 adjoins. While the upper part 146 contains the buoyancy bodies of the underwater vehicle 146, the device 2 is arranged in its substructure 148, wherein the end region of the device 2, in which the first sensor arrangement 52 is arranged, projects out of the substructure 148. At this end of the device 2 projecting from the substructure 148, a housing 150 is arranged on the outside of the fastening ring 48. The housing 150 is designed to be open to the fastening ring 48, the cross section of an inner space 152 of the housing 150 corresponding to the inner cross section of the fastening ring 48. On the housing 150, a hole is formed at its side facing away from the mounting ring 48 side into which a hose 154 engages. At the end remote from the housing 150 of the tubing 154 a funnel 156 is formed. By means of an underwater pump 158 integrated in the hose line 154, water 18 from the environment of the underwater vehicle 22 is conveyed via the funnel 156 and the hose line 154 into the interior 152 of the housing 150. There, the water 18 comes into contact with the membrane 46, through which any hydrocarbon gas 20 present in the water 18 diffuses into the measuring space 50 of the first sensor arrangement 52, so that the concentration of hydrocarbon gas 20 in the apparatus 2 in the manner already described can be determined. While the underwater pump is operating, excess water 18 may exit the interior 152 of the housing 150 via two outlets 160 formed on the housing 150. In order to be able to align the funnel 156 precisely to a possible leakage point, the underwater vehicle 22 has a multi-articulated maneuvering device. low in pulp 162. At this manipulator arm 162, the hose 154 is attached in the region of the funnel 156.

reference numeral

2 device

4 water surface

6 offshore platform

8 body of water

10 Underwater structure

12 support line

14 support line

16 subsea tree

18 water

20 hydrocarbon gas

22 Submersible water

24 underwater vehicle

26 overwater ship

28 cables

30 long-term monitoring station

32 housing

34 basic body

36 interior

38 wall

40 wall

42 paragraph

44 plate

46 membrane

48 fixing ring

50 measuring room

52 sensor arrangement

54 gas sensor

56 gas sensor

58 gas sensor

60 sensor 62 temperature sensor

64 pressure sensor

66 heating

68 electronic module

70 accumulator

72 charge controllers

74 charging port

76 evaluation device

78 data memory

80 data input and output unit

82 data line

84 membrane

86 element

88 measuring room

90 sensor arrangement

92 gas sensor

94 gas sensor

96 gas sensor

98 sensor

100 - temperature sensor

102 - Pressure sensor

104 - Heating

106 - cavity

108 - end plate

1 10 - pipe

1 12 - buffer space

1 14 - Temperature sensor

1 1 6 - Pressure sensor

1 18 - Conductivity sensor

120 - semiconductor sensor

122 - basic body

124 - sensor layer 126 - contact

128 - contact

130 - gas

132 - heating element

134 - Sensor

136 - Electronic module

138 - light source

140 - detector

142 - gap

144 - Signal processing device

146 - top

148 - substructure

150 - housing

152 - interior

154 - Hose line

156 - funnels

158 - Underwater pump

1 60 - outlet

Claims

claims

1 . Device (2) for detecting gas (130) in a liquid, having a first sensor arrangement (52) which has at least one gas sensor (54) and is in communication with the environment of the device (2), and with a second sensor arrangement ( 90), which has a with the gas sensor (54) of the first sensor arrangement (52) identical gas sensor (92) and with the environment of the device (2) via a buffer space (1 12) in communication.

Device (2) according to claim 1, in which the buffer space (1 12) is open towards the liquid surrounding the device (2).

Device (2) according to claim 1, in which the buffer space (1 12) is closed towards the liquid surrounding the device (2) by an elastic membrane.

4. Device (2) according to one of the preceding claims, wherein the buffer space (1 12) is at least partially formed by a multi-threaded tube (1 10).

Device (2) according to one of the preceding claims, in which the two sensor arrangements (52, 90) are in each case in communication with a measuring space which is closed by means of a gas-permeable membrane (46, 84), which in conjunction with the first sensor arrangement (52) stationary measuring chamber (50) occluding membrane (46) forms a liquid-tight barrier directly to the external environment of the device (2) and the in connection with the second sensor arrangement (90) ste- henden measuring chamber (88) occluding membrane (84) forms a liquid-tight barrier to the buffer space (1 12).

6. Device (2) according to one of the preceding claims, in which the gas sensors (54, 56, 92, 94) of the first (52) and the second (90) sensor arrangement of semiconductor sensors (120) are formed.

Apparatus (2) according to any one of claims 1 to 5, wherein the gas sensors (54, 56, 92, 94) of the first (52) and second (90) sensor arrays are formed by optical sensors (134).

8. Device (2) according to one of the preceding claims, wherein the gas sensors (54, 56, 92, 94) for the selective detection of hydrocarbon gases (20) are formed.

9. Device (2) according to one of the preceding claims, characterized in that each of the two sensor arrangements (52, 90) additionally comprises a gas sensor (58, 96) for the selective detection of oxygen.

10. Device (2) according to one of claims 5 to 9, wherein in the measuring space (50, 88) of the two sensor arrangements (52, 90) a sensor (60, 98) for determining the absolute humidity in the measuring space (50, 88) is arranged.

1 1. Device (2) according to one of claims 5 to 10, wherein in the measuring space (50, 88) of the two sensor arrangements (52, 90) a temperature sensor (62, 100) and a heater (66, 104) are arranged, wherein a Temperature control device provided is, which regulates the temperature in the measuring chamber (50, 88) to a constant value.

Device (2) according to one of claims 5 to 11, in which a gas pressure sensor (64, 102) is arranged in the measuring space (50, 88) of the two sensor arrangements (52, 90).

Device (2) according to one of the preceding claims, in which a sensor (1 18) detecting the conductivity of the ambient fluid of the device (2) is provided.

Device (2) according to one of the preceding claims, in which a sensor (1 14) detecting the temperature of the ambient fluid of the device (2) is provided.

15. Device (2) according to one of the preceding claims, in which a pressure of the surrounding liquid of the device (2) detecting sensor (1 1 6) is provided.