GB2617378A

GB2617378A - A method of commissioning or decommissioning a fuel gas installation

Info

Publication number: GB2617378A
Application number: GB2205077.7A
Authority: GB
Inventors: John Ryan Nicholas; Scott Roberts Sebastian
Original assignee: Steer Energy Solutions Ltd
Current assignee: Steer Energy Solutions Ltd
Priority date: 2022-04-07
Filing date: 2022-04-07
Publication date: 2023-10-11
Also published as: GB202205077D0

Abstract

A fuel gas installation assembly includes a fuel gas installation (120 Fig. 13) and an acoustic instrument 1, and the fuel gas installation includes a fuel gas combustion appliance and/or a fuel gas transmission system, such as pipework from a main supply (123 Fig. 13 via a gas network (121 Fig. 13) of branched pipes (121a Fig. 13) that connect to buildings (122 Fig. 13). The acoustic instrument can be in the form of a whistle 1, such as a pellet whistle, and during commissioning, air in the transmission system can be purged by fuel gas, and during decommissioning fuel gas can be purged by air. During commissioning or decommissioning the acoustic instrument produces a sound with a pitch that is dependent on the composition of the fuel gas/air mixture flow, and thus can indicate when the fuel gas/air in the pipework installation has been substantially purged. Other forms of acoustic instrument can include a fipple, and the acoustic instrument may be housed in a shroud (40 Fig. 7) or a flexible bladder (50 Fig. 8). The arrangement can provide a simple and accurate way to demonstrate completion of a purge event during either commissioning or decommissioning of a fuel gas installation.

Description

A METHOD OF COMMISSIONING OR DECOMISSIONING A FUEL GAS INSTALLATION

Field of the Invention

The present invention relates to a method of commissioning or decommissioning a fuel gas installation. The present invention also relates to a fuel gas installation that has been commissioned or decommissioned according to the method. The present invention also relates to an acoustic instrument assembly. The present invention also relates to a fuel gas installation assembly comprising a fuel gas installation and an acoustic instrument.

Background of the Invention

Buildings are supplied with a fuel gas to provide an energy source to the building. In this respect, such buildings comprise a fuel gas system that comprises one or more fuel gas combustion appliances (such as a gas fire, cooker and/or boiler, etc) that are typically connected, by a network of pipes, to an inlet emergency control valve (ECV).

The inlet emergency control valve (ECV) is connected to a national fuel gas transmission system or to a local fuel gas supply (e.g. a bottled supply of fuel gas), so as to supply the fuel gas system of the building with fuel gas.

The fuel gas system of the building and of the national/local transmission system are formed by one more fuel gas installations. In this respect, a fuel gas installation is an installed system, or piece of equipment, for transmitting, storing and/or combusting a fuel gas. For example a fuel gas installation may be a fuel gas system of a building (i.e. downstream of an inlet emergency control valve (ECV) of a fuel gas system of a building) which may comprise a fuel gas transmission system connected to one or more fuel gas combustion appliances (such as a gas fire, cooker and/or boiler, etc.).

As a further example, a fuel gas installation may be a national/local fuel gas transmission network (i.e. upstream of an inlet emergency control valve (ECV) of a fuel gas system of a building). -2 -

Furthermore, a fuel gas installation may be a part of the above described installations, for example it may be fuel gas combustion appliance, a network or conduit for transmitting fuel gas, a container for storing fuel gas, etc. The flammability of fuel gases means that steps must be taken to prevent mixtures of fuel gas and air in a fuel gas installation. Because of this the process of commissioning or decommissioning a fuel gas installation (i.e. putting the installation into/out of service respectively) includes a purging process where the contents of the fuel gas installation are changed from air to fuel gas or vice versa, respectively.

In this respect, during the commissioning of a fuel gas installation, the purging process changes the gas inside the installation from air to fuel gas. The purging process is typically carried out by opening an upstream valve (e.g. an emergency control valve ([CV)) to connect the installation to a supply of fuel gas. As the fuel gas enters the installation, air in the installation is displaced from the installation through an outlet.

The fuel gas is allowed to flow until fuel gas is detected at the outlet, or preferably until a measured volume of fuel gas is released. Where the installation has multiple branches, the purging process is carried out for each branch of the installation. Ideally the purging process is carried out until all of the air has been removed from the installation. During the purging process, the gas emitted from the outlet starts as pure air, then transitions to fuel gas over a period of time. If the purging process is stopped as soon as fuel gas is detected at the outlet then the installation will still contain a mixture of air and fuel gas. If the fuel is natural gas then this may not pose a significant problem as the upper flammable limit for natural gas is 17% volume of gas in air therefore the mixture inside the system is not likely to be flammable. However, if the fuel gas is hydrogen where the upper flammable limit is 75% volume of gas in air then it is very likely that unless all of the air is purged from the installation, the mixture remaining in the installation will be flammable and potentially explosive.

It is possible to increase the length of time that the purging process is carried out, to increase the likelihood of a complete purge however this will result in larger volumes of fuel gas being released into a building containing the installation. There is therefore a desire to have a simple and accurate way of demonstrating a complete purge of air during the -3 -commissioning of a fuel gas installation, whilst limiting the amount of fuel gas released during the purging process.

There is also a desire to have a simple and accurate way of demonstrating a complete purge of fuel gas during decommissioning of a fuel gas installation.

The present invention seeks to address or mitigate at least some of the above mentioned problems. Alternatively, or additionally, the present invention seeks to provide an improved method of commissioning or decommissioning a fuel gas installation. Alternatively, or additionally, the present invention seeks to provide an improved fuel gas installation that has been commissioned or decommissioned. Alternatively, or additionally, the present invention seeks to provide an improved acoustic instrument assembly.

Summary of the Invention

According to a first aspect of the invention there is provided a method of commissioning or decommissioning a fuel gas installation, wherein: at least part of a fuel gas installation contains a first gas, and wherein the method comprises: using a purging process to purge the first gas from the at least part of the installation such that the first gas is substantially replaced by a second gas; where the method is a method of commissioning, the first gas being air and the second gas being a fuel gas and where the method is a method of decommissioning, the first gas being a fuel gas and the second gas being air; and wherein the method comprises, during the purging process, passing gas from the at least part of the installation to an acoustic instrument such that the acoustic instrument is sounded by the gas and produces a sound with a pitch that is dependent on the composition of the gas; and indicating when the first gas has been substantially replaced by the second gas, by the pitch of the sound produced by the acoustic instrument. -4 -

The above method may provide a method of commissioning or decommissioning a fuel gas installation, using a purging process, where the point in time in which the purging process is completed is accurately indicated. During commissioning, this may minimise the amount of fuel gas released into the surroundings. During decommissioning, this may reduce the overall time of the purging process. Furthermore, this is done using relatively easy to use and inexpensive equipment (using an acoustic instrument).

In embodiments of the invention the method comprises indicating when the first gas has been substantially replaced by the second gas, in the at least part of the installation, by the pitch of the sound produced by the acoustic instrument.

Optionally said indication is provided by the acoustic instrument producing a sound with a substantially constant pitch. Optionally said indication is provided by the acoustic instrument producing a sound that changes to a substantially constant pitch.

Optionally said indication is provided by the sound produced by the acoustic instrument changing from a first substantially constant pitch to a second substantially constant pitch. This change may be gradual, for example via a gradually changing pitch from the first substantially constant pitch to the second substantially constant pitch.

Where the method is a method of commissioning, the second substantially constant pitch may be higher than the first substantially constant pitch. Where the method is a method of decommissioning, the second substantially constant pitch may be lower than the first substantially constant pitch.

Optionally a completion step of the purging process is performed in dependence on said indication. Optionally the completion step is performed when said indication occurs.

Optionally the purging process comprises connecting an inlet of the at least part of the installation to a supply of the second gas such that the second gas passes into the at least part of the installation, with the first gas being displaced, by the second gas, through an outlet of the at least part of the installation and wherein the completion step comprises: -5 -a) closing the outlet; and/ or b) disconnecting the supply of the second gas from the inlet such that the second gas is prevented from passing into the at least part of the installation.

In embodiments of the invention, the second gas is supplied at a pressure that is sufficient to displace the first gas from the at least part of the installation.

In embodiments of the invention an inlet of the acoustic instrument is in fluid connection with the at least part of the installation such that gas passes from the at least part of the installation to the inlet of the acoustic instrument. The inlet of the acoustic instrument may be in fluid connection with said outlet. Alternatively, the inlet of the acoustic instrument may be in fluid connection with a different outlet. In this case, the displaced first gas may pass out of the at least part of the installation through first and second outlets and wherein the inlet of the acoustic instrument is in fluid connection with (only) one of the outlets.

The inlet of the acoustic instrument may, for example be connected to a pressure test port of the at least part of the installation. The inlet of the acoustic instrument may, for example, be connected to a conduit of the at least part of the installation, which may be to an open end of the conduit.

Optionally the method is a method of commissioning a fuel gas installation and wherein the completion step comprises closing the outlet and wherein the first gas is air and the second gas is a fuel gas.

Optionally the method is a method of decommissioning a fuel gas installation and wherein the completion step comprises disconnecting the supply of the second gas from the inlet such that the second gas is prevented from passing into the at least part of the installation and wherein the first gas is a fuel gas and the second gas is air.

Optionally the acoustic instrument is configured such that at least part of the gas that passes to the acoustic instrument is caused to vibrate such that said sound is produced. Optionally the acoustic instrument is configured such that the gas that passes to the acoustic -6 -instrument causes the instrument to vibrate such that said sound is produced. The acoustic instrument is blown by said gas, to produce said sound.

Optionally the acoustic instrument comprises a resonance chamber configured such that the gas that passes to the acoustic instrument passes into the resonance chamber and vibrates within the resonance chamber such that said sound is produced. In this respect, the resonance chamber may be configured such that acoustic waves within the gas in the resonance chamber are reflected in the resonance chamber to produce a standing wave that results in said sound. The acoustic instrument may have an inlet that directs gas into the resonance chamber. The acoustic instrument may comprise a means of vibrating the gas in, or passing into, the resonance chamber to produce said sound. Said means of vibrating may comprise an edge, aperture or vibrating reed, for example.

Optionally the acoustic instrument is an aerophone. In this respect, the acoustic instrument may produce sound by causing a body of the gas passed to it to vibrate, without the use of strings or membranes. This may be without the vibration of the instrument itself adding considerably to the sound.

The acoustic instrument may be a non-free aerophone. In this respect, it may contain a column of gas that vibrates when played. This may advantageously produce a substantially pure note that enables accurate determine of its pitch and therefore enables an accurate determination of when purging is complete.

Optionally the acoustic instrument comprises a resonance chamber and an edge configured such that the gas that passes to the acoustic instrument is divided by the edge, with a portion of the gas passing into the resonance chamber such that gas within the resonance chamber vibrates such that said sound is produced.

Optionally the acoustic instrument comprises a duct configured to direct gas blown into the duct onto said edge.

In this respect, the gas blown instrument may be a fipple flute. The fipple flute may be a whistle. Optionally the whistle a is pellet-less whistle. Alternatively, the whistle may be a pellet whistle. -7 -

Alternatively, the fipple flute may be a recorder or organ pipe, for example.

The fipple flute may be open ended. Alternatively, the fipple flute may be closed ended.

Optionally the acoustic instrument comprises an inlet duct that directs the gas passing to the acoustic instrument onto said edge.

Optionally the resonance chamber extends from a first end, provided with said edge, to a second end that is closed. This may advantageously produce a lower note for a given size of resonance chamber of the instrument.

In embodiments of the invention an inlet of the acoustic instrument is connected to an outlet of the at least part of the installation such that gas from the at least part of the installation passes to the inlet of the acoustic instrument.

The gas passing into the resonance chamber of the acoustic instrument is at a pressure such that the acoustic instrument is sounded by the gas. In this respect, the outlet of the at least part of the installation, that the inlet of the acoustic instrument is connected to, and/or the inlet of the acoustic instrument may be sized such that the gas passing into the resonance chamber of the acoustic instrument is at a pressure such that the acoustic instrument is sounded by the gas. This may be by air passing to the resonance chamber and by fuel gas passing to the resonance chamber.

The outlet of the at least part of the installation, that the inlet of the acoustic instrument is connected to may be a pressure test port or an open end of a pipe, for example.

The second gas is supplied into the at least part of the installation at a system pressure such that the gas from the at least part of the installation passes to the acoustic instrument such that the acoustic instrument is sounded by the gas to produce said sound. Where the second gas is natural gas, the system pressure may be 21 mbar. Where the second gas is propane, the system pressure may be 37 mbar.

The second gas is supplied into the at least part of the installation at a pressure such that the first gas is displaced, by the second gas, through said outlet. The inlet of the acoustic -8 -instrument and/or an aperture upstream of the inlet of the acoustic instrument may be sized such that the acoustic instrument is sounded by the gas passing to the acoustic instrument at the pressure that that gas is pressurised at, due to the pressure of the second gas. In this respect, this may be such that the acoustic instrument is sounded by the first gas passing to the acoustic instrument, due to the pressure of the second gas, and by the second gas passing to the acoustic instrument, due to the pressure of the second gas.

Optionally the inlet of the acoustic instrument has substantially the same sized cross sectional area as the outlet of the pressure test port.

Optionally an air barrier substantially prevents external air from being entrained in the gas passing into the resonance chamber.

Optionally the acoustic instrument is provided in a housing that provides said air barrier.

Optionally the housing is flexible such that it is at least partially inflated by gas passing from the acoustic instrument into the housing.

Optionally an outlet conduit is connected to the housing such that gas within the housing is vented out of the housing, through the outlet conduit. This may allow for gas in the housing to be vented to a more desirable location, e.g. out of a building. Optionally the fuel gas installation is located in a building and the outlet conduit has an outlet located outside of the building.

Optionally the at least part of the installation comprises a pressure test port and wherein the gas is passed through the pressure test port to the acoustic instrument.

Optionally the acoustic instrument is mounted to the pressure test port. Optionallythe resonance chamber is located adjacent, and extends substantially parallel, to a conduit of the fuel gas transmission system.

Optionally a valve member is configured with the pressure test port such that the pressure test port is operable between: -9 - * an open configuration in which an outlet of the at least part of the installation is open such that gas can flow from the outlet to an inlet of the acoustic instrument; and * a closed configuration in which the outlet is closed.

Optionally an inlet of the acoustic instrument is connected to the pressure test port, between the outlet of the at least part of the installation and an outlet of the pressure test port.

Optionally the at least part of the installation is a first part of the installation and the method is repeated for a second part of the installation.

Optionally the supply of the second gas is connected to an inlet of the installation and wherein the second part of the installation is closer to the inlet of the installation than the first part of the installation.

Optionally the installation contains the first gas. Optionally the purging process purges the first gas from the installation such that the first gas is substantially replaced by the second 15 gas.

Optionally an inlet of the acoustic instrument is connected to an open end of a conduit of the installation and wherein the inlet of the acoustic instrument is sized such that the acoustic instrument sounds in both air and in the fuel gas when driven by the system pressure for the particular fuel gas.

Optionally a restriction to the flow of gas is provided in the installation such that the acoustic instrument sounds in both air and in the fuel gas.

Optionally the completion step is performed by a human operator. The operator may be listening to the sound produced by the acoustic instrument to deduce when to do this. For example, when the human operator hears said indication (e.g. the acoustic instrument producing a sound with a substantially constant pitch), they may perform said completion step.

-10 -Alternatively, or additionally, the operator may use a pitch measurement device to measure the pitch of the note produced by the acoustic instrument, so as to deduce when to perform the completion step. This may, for example, be musical instrument tuner or a suitable application on a smart phone or a computer program.

Optionally the method comprises the step of opening the outlet of the at least part of the installation. Optionally the method comprises the step of connecting an inlet of the acoustic instrument to the at least part of the installation. Optionally the method comprises the step of connecting an inlet of the acoustic instrument to the outlet at least part of the installation.

According to a second aspect of the invention there is provided an acoustic instrument assembly comprising, an acoustic instrument having in inlet for connection to an outlet of at least part of a fuel gas installation such that gas may pass from the outlet to the inlet of the acoustic instrument; wherein the acoustic instrument comprises a resonance chamber arranged with the inlet such that gas passing to the inlet passes to the resonance chamber and vibrates within the resonance chamber such that a sound is produced with a pitch that is dependent on the composition of the gas; and wherein the assembly further comprises an air barrier configured to substantially prevent external air from being entrained in the gas passing into the resonance chamber.

Optionally the assembly comprises a housing and wherein the acoustic instrument is provided in the housing such that said air barrier is provided by the housing.

Optionally the housing is flexible such that it is at least partially inflatable by gas passes from the acoustic instrument into the housing.

Optionally an outlet conduit is connected to the housing such that, in use, gas is vented out of the housing, through the outlet conduit.

-11 -Optionally the acoustic instrument comprises an edge configured such that the gas that passes to the acoustic instrument is divided by the edge, with a portion of the gas passing into the resonance chamber such that gas within the resonance chamber vibrates such that said sound is produced and wherein the resonance chamber extends from a first end, provided with said edge, to a second end that is closed.

According to a third aspect of the invention there is provided a fuel gas installation that has been corn missioned or decommissioned according to the method of the first aspect of the invention.

According to a fourth aspect of the invention there is provided a fuel gas installation assembly comprising: a fuel gas installation, and an acoustic instrument; wherein the fuel gas installation forms: a) at least part of a fuel gas system that comprises at least one fuel gas combustion appliance; and/or b) at least part of a fuel gas transmission system configured to transmit fuel gas to at least one fuel gas system that comprises at least one fuel gas combustion appliance; and wherein the acoustic instrument is in fluid communication, or selective fluid communication, with at least part of the fuel gas installation and is configured such that when gas passes to the acoustic instrument, from the at least part of the installation, the acoustic instrument is sounded by the gas and produces a sound with a pitch that is dependent on the composition of the gas.

Optionally the fuel gas installation and the acoustic instrument has any of the features of the fuel gas installation or acoustic instrument in the method of the first aspect of the invention or of the acoustic instrument assembly of the second aspect of the invention.

-12 -According to a fifth aspect of the invention there is provided a method of commissioning a fuel gas installation, wherein: at least part of a fuel gas installation contains air, and wherein the method comprises: using a purging process to purge the air from the at least part of the installation such that the air is substantially replaced by a fuel gas; and wherein the method comprises, during the purging process, passing gas from the at least part of the installation to an acoustic instrument such that the acoustic instrument is sounded by the gas and produces a sound with a pitch that is dependent on the composition of the gas; and indicating when the air has been substantially replaced by the fuel gas, by the pitch of the sound produced by the acoustic instrument.

According to a sixth aspect of the invention there is provided a method of decommissioning a fuel gas installation, wherein: at least part of a fuel gas installation contains a fuel gas, and wherein the method comprises: using a purging process to purge the fuel gas from the at least part of the installation such that the fuel gas is substantially replaced by air; and wherein the method comprises, during the purging process, passing gas from the at least part of the installation to an acoustic instrument such that the acoustic instrument is sounded by the gas and produces a sound with a pitch that is dependent on the composition of the gas; and indicating when the fuel gas has been substantially replaced by the air, by the pitch of the sound produced by the acoustic instrument.

-13 -According to a seventh aspect of the invention there is provided a method of purging a gas from at least part of a fuel gas installation, wherein: at least part of a fuel gas installation contains a first gas, and wherein the method comprises: using a purging process to purge the first gas from the at least part of the installation such that the first gas is substantially replaced by a second gas; the first or second gas being a fuel gas; and wherein the method comprises, during the purging process, passing gas from the at least part of the installation to an acoustic instrument such that the acoustic instrument is sounded by the gas and produces a sound with a pitch that is dependent on the composition of the gas; and indicating when the first gas has been substantially replaced by the second gas, by the pitch of the sound produced by the acoustic instrument.

Optionally the other of the first or second gas is air.

According to an eighth aspect of the invention there is provided method of commissioning a fuel gas installation comprising purging a gas from at least part of a fuel gas installation according to the method of the seventh aspect of the invention, wherein the first gas is air and the second gas is a fuel gas.

According to a ninth aspect of the invention there is provided method of decommissioning a fuel gas installation comprising purging a gas from at least part of a fuel gas installation according to the method of the seventh aspect of the invention wherein the first gas is a fuel gas and the second gas is air.

-14 -The features of any of the above aspects of the invention may be combined with one or more features of any of the other aspects of the invention, in any combination.

Other preferred and advantageous features of the invention will be apparent from the following description.

Description of the Drawings

A specific embodiment of the invention will now be described with reference to the description and drawings.

Figure 1 shows a perspective view of an acoustic instrument, in the form of a whistle, according to a first embodiment of the invention; Figure 2 shows a view corresponding to that of Figure 1, but where a side of the whistle has been cut away for illustrative purposes; Figure 3 shows a perspective view of an acoustic instrument, in the form of a whistle, according to a second embodiment of the invention; Figure 4 shows a schematic view of a fuel gas installation according to a further embodiment of the invention, in selective connection with a mains fuel gas supply, where the installation is to be commissioned; Figure 5 shows a perspective view of a pressure test port of the fuel gas installation shown in Figure 4, where a side of the pressure test port has been cut away for illustrative purposes; Figure 6 shows a perspective view of the whistle of Figure 1 connected to the pressure test port of Figure 5; Figure 7 shows a view corresponding to that of Figure 6, but where the whistle is housed within a shroud; Figure 8 shows a view corresponding to that of Figure 6, but where the whistle is housed within a flexible bladder; -15 -Figure 9 shows a perspective view of an alternative version of the pressure test port of Figure 5, where the whistle of the first embodiment is integrated with the pressure test port; Figure 10 shows a schematic view of the whistle of the first embodiment and an acoustic pitch detector; Figure 11 shows a view corresponding to that of Figure 4, but where the installation is in selective connection with a supply or air, where the installation is to be decommissioned; Figure 12 shows a view corresponding to that of Figure 1, but there an inlet of the whistle is connected into an open end of a pipe of the installation in Figure 4, and Figure 13 shows a schematic view of a fuel gas installation according to a further embodiment of the invention.

Detailed Description

Referring to Figures 1 and 2, there is shown an acoustic instrument 1, in the form of a whistle 1, according to a first embodiment of the invention. The whistle 1 comprises an inlet duct 2 and a resonance chamber 3 attached to an end of the duct 2.

The inlet duct 2 comprises a ducted conduit 10 (see Figure 2) that extends from an duct inlet 4 to a duct outlet 5. The duct inlet 4 forms an inlet of the whistle 1. The resonance chamber 3 has the general shape of a hollow cylinder and extends from a first open end, provided with a labium lip 6, to a second end 7 that is closed. A whistle 1 with a closed end 7 may advantageously produce a lower note for a given size of the resonance chamber 3.

The inlet duct 2 and the labium lip 6 together form a fipple. In this respect, the inlet duct 2 is configured to direct gas blown through the inlet 4, out of the duct outlet 5 and onto an edge 8 of the labium lip 6, such that gas blown onto the edge 8 is split, with a portion of the split gas passing into the resonance chamber 3 causing gas within the resonance chamber 3 to vibrate such that sound is produced. In this respect, acoustic waves within the gas in the resonance chamber 3 are reflected in the resonance chamber 3 to produce a standing wave that results in an audible sound being produced.

-16 -The resonant frequency of a system comprising an excitation source (the gas blown into the acoustic instrument), the resonant length (determined by the length of the resonance chamber, which is constant), and the transmission medium (the gas passing to the whistle 1), is a function of the resonant length and the speed of sound of the gas in the in the resonance chamber 3. Accordingly, as the composition of the gas passing to the whistle 1 changes, the composition of the gas in the resonance chamber 3 changes, thereby changing the density of the gas in the resonance chamber. This changes the speed of sound in the gas in the resonance chamber 3 and so the resonant frequency of the system changes. Therefore the pitch of the sound produced by the whistle 1 varies depending on the composition of the gas passing to the whistle 1.

It will be appreciated that this effect is not limited to whistles and will occur with any acoustic instrument that is configured such that the gas that passes to the acoustic instrument is caused to vibrate such that a sound is produced, and so other types of acoustic instrument may be used in place of the whistle 1.

Referring to Figure 3 there is shown a whistle 101 according to a second embodiment of the invention. The whistle 101 of the second embodiment is substantially the same as the whistle 1 of the first embodiment except for the differences described below. Corresponding features are given corresponding reference numerals, but incremented by 100.

The whistle 101 of the second embodiment is substantially the same as the whistle 1 except in that the second end of the resonance chamber 103 is an open end, provided with a circular opening 109, through which gas passes out of the resonance chamber 103. It will be appreciated that the whistle 101 may be used in place of the whistle 1 in any of the described embodiments.

Referring to Figure 4, there is shown a schematic view of a fuel gas installation 20 according to a further embodiment of the invention. In the currently described embodiment the fuel gas installation 20 is a fuel gas system of a domestic building. However it will be appreciated that the invention is not limited to use with a fuel gas system of a domestic building and may be used with any fuel gas installation, including a fuel gas installation of an -17 -industrial, commercial or academic building and/or a fuel gas installation of a mains fuel gas supply network (see below), or of a local fuel gas supply system, for example.

The fuel gas installation 20 comprises a fuel gas transmission system 30, comprising a plurality of pipes 30', and a plurality of fuel gas combustion appliances, in the form of first and second gas fires 26, 26', a gas cooker 27 and a gas boiler 28, connected to respective pipes 30' of the fuel gas transmission system 30. In this respect, each appliance is connected to a respective branch of the fuel gas transmission system 30.

The fuel gas installation 20 further comprises a fuel gas inlet emergency control valve (ECV) 21, that selectively fluidly connects (and disconnects) the fuel gas installation 20 to a mains fuel gas supply 22 via a (national) mains fuel gas supply network 23.

In the currently described embodiment the fuel gas is natural gas. However, it will be appreciated that any fuel gas may be used. In this respect, a fuel gas is any type of gas that is for use as a fuel, i.e. that can be combusted to produce energy (e.g. heat and/or light). The fuel gas may, for example, be a manufactured fuel gas or a natural fuel gas. The fuel gas may be natural gas, coal gas, propane or hydrogen, for example. The fuel gas may, for example, be any of the fuel gases in the three families of fuel gas as defined by the Wobbe index, i.e. family 1 -town gas/syngas; family 2 -natural gas; family 3 Liquified Petroleum Gas (LPG). Alternatively the fuel gas may be hydrogen, for example.

A pressure regulator 24 is connected to a downstream side of the emergency control valve 21, which sets the pressure in the fuel installation to a system pressure of 21 mbar. A gas meter 25 is connected to a downstream side of the pressure regulator 24. The gas meter 25 measures the volume of gas used in the building. A domestic system pressure is typically in the range 19 to 22 mbar and a supply system pressure is typically up to 75mbar. Where the fuel gas is propane, the system pressure may, for example, be set to 37 mbar. However, it will be appreciated that any suitable system pressure may be used and it is not limited to any of the above.

The fuel gas combustion appliances 26, 26', 27, 28 are connected, via the respective pipes 30', to the downstream side of the gas meter 25.

-18 -A plurality of pressure test ports 31 are provided in the fuel gas installation 20, with a respective pressure test port 31, 31', 31" located adjacent to and upstream of each appliance 26, 26', 27, 28. In normal use, each pressure test port is used to test the pressure in that part of the installation, by connecting a pressure measurement device to the pressure test port.

With reference to Figure 5, each pressure test port 31, 31', 31" comprises an outlet pipe 32 that connects to a pipe 30' of the fuel gas transmission system 30 and extends along a longitudinal axis that is generally perpendicular to the longitudinal axis of the pipe 30'. An outlet aperture 39 passes through the thickness of a cylindrical wall of the pipe 30', with the outlet aperture 39 opening into the interior of the outlet pipe 32 of the pressure test port 31, 31', 31".

An end of the outlet pipe 32, that is distal to the pipe 30', is open and forms an outlet aperture 33, of the pressure test port, at said end of the pipe 32. The section of the outlet pipe 32 proximal the outlet aperture 33 is provided with an internal screw thread 34.

Each pressure test port 31, 31', 31" is provided with a sealing plug 35 that forms a valve that can be used to selectively open and close the outlet aperture 39 (and the outlet aperture 33). The plug 35 has a circular disc shaped head 38 and a central stem 36 that protrudes axially from the head 38. The head 38 has a diameter greater than that of the outlet aperture 33 such that it closes the outlet aperture 33.

The stem 36 comprises an externally threaded section 70, extending from the head 38, a middle section 71 extending from the externally threaded section 70 and a valve member section 72 extending from the middle section 71. The externally threaded section 70 is of reduced diameter relative to the head 38, the middle section 71 is of reduced diameter relative to the externally threaded section 70 and the valve member section 72 is of reduced diameter relative to the middle section 71.

The externally threaded section 70 is configured for screw engagement (and disengagement) with the internal screw thread 34 of the outlet pipe 32 of the pressure test port 31, 31', 31". When the plug 35 is screwed into the outlet pipe 32, into a closed position, the valve member section 72 of the stem 36 is received in, and closes, the outlet aperture 39 -19 -in the pipe 30' of the fuel gas transmission system 30 (as well as the outlet aperture 33). Conversely, the plug 35 may be unscrewed from the outlet pipe 32, to an open position, in which the outlet aperture 39 is open (and in which the outlet aperture 33 is open).

The fuel gas installation 20, as shown in Figure 4, has not yet been commissioned (and so is not in service). In this respect, the ECV 21 has been physically connected to the mains gas supply network 23, but the ECV 21 has not yet been opened. As the ECV 21 has not yet been opened, to connect the fuel gas supply 22 to the fuel gas installation 20, the pipes 30' of the fuel gas transmission system 30 contain air. A method of commissioning the fuel gas installation 20, according to a further embodiment of the invention, will now be described.

In order to commission the fuel gas installation 20, the plug 35 of the pressure test port 31" furthest from the emergency control valve 21 is unscrewed from the outlet pipe 32 (and removed from the outlet pipe 32) to open both the outlet aperture 39 in the pipe 30' of the fuel gas transmission system 30 and the outlet aperture 33 in the outlet pipe 32 of the pressure test port 31".

As shown in Figure 6, the inlet 4 of the whistle 1 is then connected to the outlet pipe 32, of the pressure test port 31" by a tubular connector 36 that fits around the outlet pipe 32 and the inlet duct 2 of the whistle 1, to form a collar that provides a gas-tight connection. In the currently described embodiment the tubular connector 36 is made of rubber. However, it will be appreciated that any suitable material may be used.

The ECV 21 is then opened and fuel gas from the mains supply 22 (via the supply network 23) enters the fuel gas installation 20, through the ECV 21, regulator 24 and gas meter 25 and through the various branches of pipes 30' to each gas combusting appliances 26, 26', 27, 28. This raises the system pressure of the installation 20 to said system pressure of 21 mbar.

As the fuel gas passes through the pipe 30' connected to the pressure test port 31", air in the pipe 30' is displaced from the pipe 30' and out through the outlet aperture 39 in the pressure test port 31", to the inlet 4 of the whistle 1.

-20 -Initially the gas passing to the whistle 1, is pure air and so a sound with a first, substantially constant, pitch is produced. As the gas passing out of the outlet aperture 39, to the whistle 1, transitions to the fuel gas, the pitch gradually changes (as a mixture of air and fuel gas are passing to the whistle 1). Once all the air has been purged from the pipe 30', pure fuel gas (in this case natural gas) passes out of the outlet aperture 39 and into the inlet 4 of the whistle 1 and so a sound with a second, substantially constant pitch, is produced. This signals to a human operator, who is carrying out the purging, that all of the air has been purged from that branch of the fuel gas transmission system 30. Accordingly, when the human operator hears this, they remove the whistle 1 from the outlet pipe 32 of the pressure test port 31" and close the pressure test port 31" with the plug 35.

The applicant has identified that the pitch corresponding to air and different fuel gases can be recognised by human operators, thus enabling determination of whether the gas passing through the whistle 1 is air or a particular fuel gas. For example, where the fuel gas is hydrogen, the pitch is approximately one octave higher when hydrogen is passing through the whistle 1 compared to when air is passing through the whistle 1.

In this respect, in the currently described embodiment, when pure air passes through the whistle 1, the frequency of the sound produced by the whistle 1 is 1380 Hz. As the gas passing to the whistle 1 changes to methane the pitch of the whistle 1 rises, settling after a short time to a substantially constant frequency of 1740 Hz. If hydrogen is used as the fuel gas instead of methane, the pitch of the whistle 1 rises to a substantially constant frequency of 4240Hz.

In the currently described embodiment the outlet aperture 39 in the pipe 30' has a diameter of lmm. At the system pressure of the fuel gas of 21 mbar, this provides a flow rate and pressure of gas into the inlet of the whistle 1 that sounds the whistle 1 both then fuel gas is passing through the whistle land when air is passing through the whistle (as well as when a mixture of the two is passing to the whistle 1).

The above method is then repeated for each branch of the fuel gas transmission system 30, working back towards the branch closest to the ECV 21, such that substantially all of the air is purged from the entire fuel gas installation 20. The pipes 30' are then entirely filled -21 -with fuel gas only and so the fuel gas installation 20 is put into service, i.e. the fuel gas installation 20 has been commissioned. The completed purge may then be confirmed by lighting each appliance 26, 26', 27, 28 in turn and ensuring a stable flame is maintained at that appliance.

As the time of completion of the purging is accurately identified by the whistle 1, the pressure test port 31" is closed as soon as the purging process is complete. Accordingly, the amount of fuel gas released into the surroundings is minimised. Furthermore, this is done using relatively easy to use and inexpensive equipment (using an acoustic instrument).

In order to decommission the fuel gas installation 20, the ECV 21 is disconnected from the fuel gas supply network 23 and is instead connected to a supply of pressurised air 123, for example using a low pressure air blower or bottled air (see Figure 11).

As with the method of commissioning, the pressure test port 31" is opened and the inlet 4 of the whistle 1 connected to the pressure test port 31", in fluid communication with the outlet aperture 39 in the pipe 30'.

The ECV 21 is then opened and air passes from the supply 123 into the fuel gas installation 20. As the air passes through the pipe 30' connected to the pressure test port 31", fuel gas in the pipe 30' is displaced from the pipe 30' and out through the pressure test port 31" to the inlet 4 of the whistle 1. In this respect, the whistle 1 is blown by the gas passing to it.

Initially the gas passing to the whistle 1 is pure fuel gas and so a sound with a first, substantially constant, pitch is produced. As the gas passing out of the outlet aperture 39, to the whistle 1 transitions to the air, the pitch changes. Once all the fuel gas has been purged from the pipe 30', pure air then passes from the test port 31" to the whistle 1 and so a sound with a second, substantially constant pitch, is produced. This signals to a person performing the purging that all of the fuel gas has been purged from that branch of the fuel gas transmission system 30, who then fluidly disconnects the supply of air 123 from the ECV 21. The whistle 1 is then removed from the pressure test port 31" and the pressure test port 31" closed with the plug 35.

-22 -This method is then repeated for each branch of the fuel gas transmission system 30, working back towards the branch closest to the inlet of the fuel gas transmission system 30, such that substantially all of the fuel gas is purged from the entire fuel gas installation 20. The pipes 30' are then entirely filled with air only and so the fuel gas installation 20 is decommissioned and safe for disposal.

The inlet of the whistle 1 is sized such that the whistle 1 is sounded by the pressure of the air passing to the whistle 1 and by the fuel gas passing to the whistle 1, driven by the pressurised air.

As the time of completion of the purging is accurately identified by the whistle, this may reduce the overall time of the purging process. Furthermore, this is done using relatively easy to use and inexpensive equipment (using an acoustic instrument).

The applicant has identified that the whistle should be designed to sound across the range of gases passed to it at the system pressure. The flow through the whistle is determined by the system pressure and the size of the outlet aperture 39 in the test port 31. Conveniently the ducted channel of the indicator whistle 1 is sized to provide a similar cross-sectional area to the test port 31. This results in a similar flow in the whistle when driven from gas at system pressure. The whistle can therefore be optimised to sound at the flows determined by system pressure, independent of the placement of the whistle 1, be it on a test port or on an open ended pipe so long as a relatively leak free connection is made.

Referring to Figure 7, there is shown a view corresponding to that of Figure 6, but where the whistle 1 is housed within a shroud 40. The shroud 40 forms an air barrier that substantially prevents external air from being entrained in the gas passing into the resonance chamber 3 (from the whistle inlet 4) through the open end of the resonance chamber 3. In this respect, the shroud 40 covers the open end of the resonance chamber 3. This ensures that a relatively accurate and repeatable pitch is produced by the whistle 1, for a given fuel gas.

This allows the whistle 1 to accurately indicate when the purging process is complete.

In this respect, when pure air passes through the whistle 1 in the shroud 40, the frequency of the sound produced emitted out of the shroud was 1380 Hz. As the gas passing -23 -to the whistle 1 changed to methane the pitch of the sound rose, settling after a short time to a substantially constant frequency of 1780 Hz. Where hydrogen was used a fuel gas instead of methane, the pitch of the sound rose to a substantially constant frequency of 5200Hz.

A flexible hose 41 is connected to the shroud 40 such that gas is vented out of the shroud 40, through the hose 41. The hose 41 extends out of the building that contains the fuel gas installation 20 (the boundary of the building is shown schematically as the dashed line labeller 300 in Figure 7) so that the gas is vented outside of the building. This is important where purging standards require venting of purges to be outside.

Referring to Figure 8, there is shown a view corresponding to that of Figure 6, but where the whistle 1 is housed within a flexible bladder SO. The bladder SO also acts as an air barrier, in the same way as the shroud 40. Also, as with the shroud 40, a flexible hose 51 is connected to the bladder 50 such that gas is vented out of the bladder 50, through the hose 51, out of the building.

In addition, the bladder 50 is flexible such that it inflates as gas passes out of the open end of the resonance chamber of the whistle land into the bladder 50. This provides a visible indication that the purging process is occurring. The bladder 50 has a thin wall that allows the sound from the whistle 1 to pass through it. In the currently described embodiment the flexible bladder SO is made from PVC or polyurethane. However, it will be appreciated that any suitable flexible material may be used.

Referring to Figure 9, there is shown an alternative version of a pressure test port 231, where the whistle 1 according to the first embodiment of the invention is integrated with the pressure test port 231.

The pressure test port 231 is substantially the same as the pressure test ports 31, 31', 31" described above except for the differences described below. Corresponding features are given corresponding reference numerals, but incremented by 200.

In this respect, an aperture 280 extends through the thickness of the side wall of the outlet pipe 232. The inlet duct 2 of the whistle 1 is mounted within the aperture 280 (and seals against the walls that define the aperture), such that the inlet 4 of the duct 2 is located in the -24 -interior of the outlet pipe 232, between the outlet aperture 233 of the outlet pipe 232 and the outlet aperture 39 in the wall of the pipe 30' of the fuel gas transmission system 30.

When the plug 235 is unscrewed to its open position, in which the aperture 39 is open, gas can flow from the pipe 30' to the inlet 4 of the whistle 1, but is prevented from passing out of the outlet 233 of the pressure test port due to the inlet end of the whistle 1 extending across and closing the internal conduit of the pipe 32 of the pressure test port.

In the currently described embodiment the resonance chamber 3 of the whistle 1 is located adjacent, and extending substantially parallel, to the pipe 30' of the fuel gas transmission system 30. Integrating the whistle 1 with the pressure test port provides for a relatively compact and neat arrangement.

As a further alternative, the whistle 1, may be connected to an open end 30a of a pipe 30' of the fuel gas transmission system 30 by inserting the inlet duct of the whistle 1 directly into the open end 30a of the pipe 30' (as shown in Figure 12) or, alternatively, via a suitable connector, for example a rubber connector. In this case the flow through the whistle 1 is determined by the cross-sectional area of the whistle inlet 4. The inlet 4 has a smaller cross-sectional area that that of the open end 30a of the pipe 30 and so provides a restriction.

In this respect, the inlet of the whistle 1 is sized such that the whistle 1 is sounded by the gas passing to the whistle 1 at the system pressure. In this respect, the inlet of the whistle 1 is sized such that the whistle 1 is sounded by the air gas passing to the whistle 1, at the system pressure (of 21 mbar), and by the fuel gas passing to the whistle 1, at the system pressure.

Alternatively, the indicator whistle can be mounted onto an outlet of a said gas combusting appliance, such as a cooker hob fitting with a suitable rubber attachment.

Referring to Figure 10, there is shown a schematic view of the whistle 1 of the first embodiment and an acoustic pitch measurement device 90 arranged to measure the pitch of the sound produced by the whistle 1. This may allow the operator to accurately determine the pitch of the sound produced by the whistle 1, to accurately determine when the purging -25 -process is complete. The pitch measurement device 90 may, for example, be a musical instrument tuner or a suitable application on a smart phone or a computer program.

Referring to Figure 13 there is shown a schematic view of a fuel gas installation 120 in the form of a national fuel gas transmission system 120. The fuel gas transmission system 120 comprises a network 121 of pipes 121a that connect a plurality of fuel gas systems 122 of buildings (which each correspond to the fuel gas installation 20 described above and have at least one fuel gas combustion appliance) to a fuel gas supply 123. The inlet 4, 104 of the whistle 1, 101 (according to any of the above described embodiments) is connected to an end of the fuel gas transmission system 120.

A restriction 200, in the form of a pipe 200 of smaller diameter than an upstream pipe 121a that it is connected to, is provided at the end of the system 120. The restriction is sized so as to provide a desired flow rate and pressure of gas to the whistle 1, namely such that the whistle 1 is sounded by the pressure of the air passing to the whistle 1 and by the fuel gas passing to the whistle 1, driven by the pressurised fuel gas/air, during commissioning and decommissioning.

The above described methods of commissioning and decommissioning of the fuel gas installation 20 are used to commission and decommission the fuel gas transmission system 120 by connecting the system 120 to the fuel gas supply 123 or an air supply respectively (at location 123) to purge air or fuel gas from the system respectively, through an outlet 125, and using the whistle 1, 101 to indicate then the purging process is complete, as described above (for the installation 20). The operator closes the outlet 125 and/or disconnects the supply of the purging gas, when the whistle indicates that the purging process is complete, as described above.

It will be appreciated that any of the above described embodiments of the whistle and test port may be used with the above described methods of commissioning and decommissioning.

The above described methods and apparatus may advantageously provide a method of commissioning or decommissioning a fuel gas installation, using a purging process, where -26 -the point in time in which the purging process is completed may be accurately indicated. During commissioning, this may minimise the amount of fuel gas released into the surroundings. During decommissioning, this may reduce the overall time of the purging process. Furthermore, this is done using relatively easy to use and inexpensive equipment (using an acoustic instrument).

It will be appreciated that numerous modifications to the above described design may be made without departing from the scope of the invention as defined in the appended claims.

For example, in the currently described embodiments the acoustic instrument is a whistle. However, any suitable acoustic instrument may be used, for example any type of aerophone (i.e. a wind instrument), in particular a non-free aerophone. In this respect, the acoustic instrument may, for example, be a fipple flute. The fipple flute may be a whistle. The whistle may be pellet-less whistle. Alternatively, the whistle may be a pellet whistle. Alternatively, the fipple flute may be a recorder or organ pipe, for example.

The method may be used with any type of fuel gas installation, for example any system, or piece of equipment, for transmitting, storing and/or combusting a fuel gas. In this respect, a fuel gas installation may be a fuel gas system of a building (i.e. downstream of an inlet emergency control valve ([CV) of a fuel gas system of a building) which may comprise a fuel gas transmission system connected to one or more fuel gas combustion appliances (such as a gas fire, cooker and/or boiler, etc.). As a further example, a fuel gas installation may be a national/local fuel gas transmission network (e.g. where fuel gas is supplied from a bottle to the gas system) (i.e. upstream of an inlet emergency control valve ([CV) of a fuel gas system of a building). Furthermore, a fuel gas installation may be a part of the above described installations, for example it may be fuel gas combustion appliance, a network or conduit for transmitting fuel gas, a container for storing fuel gas, etc. The fuel gas installation (or each branch of the installation) may have first and second outlets, where the first gas (i.e. the purged gas) passes out of the installation through the first and second outlets and wherein the inlet of the acoustic instrument is connected to (only) one of the outlets.

-27 -The purging process may instead be effected by sucking the first gas from the at least part of the installation such that the first gas is substantially replaced by the second gas, for example by using a venturi.

In the described embodiments a human operator performs the purging completion step(s) in dependence on the pitch of the sound produced by the acoustic instrument.

Alternatively, an automated apparatus may be used, for example that comprises an actuator connected to a controller that is connected to a pitch measurement device such that the actuator performs the purging completion step(s) in dependence on the pitch of the sound produced by the acoustic instrument.

Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims.

Claims

-28 -Claims 1. A method of commissioning or decommissioning a fuel gas installation, wherein: at least part of a fuel gas installation contains a first gas, and wherein the method comprises: using a purging process to purge the first gas from the at least part of the installation such that the first gas is substantially replaced by a second gas; where the method is a method of commissioning, the first gas being air and the second gas being a fuel gas and where the method is a method of decommissioning, the first gas being a fuel gas and the second gas being air; and wherein the method comprises, during the purging process, passing gas from the at least part of the installation to an acoustic instrument such that the acoustic instrument is sounded by the gas and produces a sound with a pitch that is dependent on the composition of the gas; and indicating when the first gas has been substantially replaced by the second gas, by the pitch of the sound produced by the acoustic instrument.
2. A method according to claim 1 wherein said indication is provided by the acoustic instrument producing a sound with a substantially constant pitch.
3. A method according to claim 2 wherein said indication is provided by the sound produced by the acoustic instrument changing from a first substantially constant pitch to a second substantially constant pitch.
4. A method according to any preceding claim wherein a completion step of the purging process is performed in dependence on said indication.
-29 - 5. A method according to any preceding claim wherein the purging process comprises connecting an inlet of the at least part of the installation to a supply of the second gas such that the second gas passes into the at least part of the installation, with the first gas being displaced, by the second gas, through an outlet of the at least part of the installation and wherein the completion step comprises: a) closing the outlet; and/ or b) disconnecting the supply of the second gas from the inlet such that the second gas is prevented from passing into the at least part of the installation.
6. A method according to claim 5 wherein the method is a method of commissioning a fuel gas installation and wherein the completion step comprises closing the outlet and wherein the first gas is air and the second gas is a fuel gas.
7. A method according to claim 5 wherein the method is a method of decommissioning a fuel gas installation and wherein the completion step comprises disconnecting the supply of the second gas from the inlet such that the second gas is prevented from passing into the at least part of the installation and wherein the first gas is a fuel gas and the second gas is air.
8. A method according to any preceding claim wherein the acoustic instrument is configured such that at least part of the gas that passes to the acoustic instrument is caused to vibrate such that said sound is produced.
9. A method according to claim 8 wherein the acoustic instrument comprises a resonance chamber and an edge configured such that the gas that passes to the acoustic instrument is divided by the edge, with a portion of the gas passing into the resonance chamber such that gas within the resonance chamber vibrates such that said sound is produced.
-30 - 10. A method according to claim 9 wherein the acoustic instrument comprises an inlet duct that directs the gas passing to the acoustic instrument onto said edge.
11. A method according to either of claims 9 or 10 wherein the resonance chamber extends from a first end, provided with said edge, to a second end that is closed.
12. A method according to any of claims 9 to 11 wherein an air barrier substantially prevents external air from being entrained in the gas passing into the resonance chamber.
13. A method according to claim 12 wherein the acoustic instrument is provided in a housing that provides said air barrier.
14. A method according to claim 13 wherein the housing is flexible such that it is at least partially inflated by gas passing from the acoustic instrument into the housing.
15. A method according to either of claims 13 or 14 wherein an outlet conduit is connected to the housing such that gas within the housing is vented out of the housing, through the outlet conduit.
16. A method according to any preceding claim wherein the at least part of the installation comprises a pressure test port and wherein the gas is passed through the pressure test port to the acoustic instrument.
17. A method according to claim 16 wherein the acoustic instrument is mounted to the pressure test port.
18. A method according to any preceding claim wherein the at least part of the installation is a first part of the installation and the method is repeated for a second part of the installation.
-31 - 19. A method according to claim 18 wherein the supply of the second gas is connected to an inlet of the installation and wherein the second part of the installation is closer to the inlet of the installation than the first part of the installation.
20. A method according to any preceding claim wherein an inlet of the acoustic instrument is connected to an open end of a conduit of the installation and wherein the inlet of the acoustic instrument is sized such that the acoustic instrument sounds in both the air and in the fuel gas.
21. A method according to any preceding claim wherein a restriction to the flow of gas is provided in the installation such that the acoustic instrument sounds in both the air and in the fuel gas.
22. An acoustic instrument assembly comprising, an acoustic instrument having in inlet for connection to an outlet of at least part of a fuel gas installation such that gas may pass from the outlet to the inlet of the acoustic instrument; wherein the acoustic instrument comprises a resonance chamber arranged with the inlet such that gas passing to the inlet passes to the resonance chamber and vibrates within the resonance chamber such that a sound is produced with a pitch that is dependent on the composition of the gas; and wherein the assembly further comprises an air barrier configured to substantially prevent external air from being entrained in the gas passing into the resonance chamber.
23. An acoustic instrument assembly according to claim 22 wherein the assembly comprises a housing and wherein the acoustic instrument is provided in the housing such that said air barrier is provided by the housing.
-32 - 24. An acoustic instrument assembly according to claim 23 wherein the housing is flexible such that it is at least partially inflatable by gas passes from the acoustic instrument into the housing.
25. An acoustic instrument assembly according to either of claims 23 or 24 wherein an outlet conduit is connected to the housing such that, in use, gas is vented out of the housing, through the outlet conduit.
26. An acoustic instrument assembly according to any of claims 22 to 25 wherein the acoustic instrument comprises an edge configured such that the gas that passes to the acoustic instrument is divided by the edge, with a portion of the gas passing into the resonance chamber such that gas within the resonance chamber vibrates such that said sound is produced and wherein the resonance chamber extends from a first end, provided with said edge, to a second end that is closed.
27. A fuel gas installation that has been commissioned or decommissioned according to the method of any of claims 1 to 21.
28. A fuel gas installation assembly comprising: a fuel gas installation, and an acoustic instrument; wherein the fuel gas installation forms: a) at least part of a fuel gas system that comprises at least one fuel gas combustion appliance; and/or b) at least part of a fuel gas transmission system configured to transmit fuel gas to at least one fuel gas system that comprises at least one fuel gas combustion appliance; -33 -and wherein the acoustic instrument is in fluid communication, or selective fluid communication, with at least part of the fuel gas installation and is configured such that when gas passes to the acoustic instrument, from the at least part of the installation, the acoustic instrument is sounded by the gas and produces a sound with a pitch that is dependent on the composition of the gas.
29. A fuel gas installation assembly according to claim 28 wherein the fuel gas installation and the acoustic instrument has any of the features of the fuel gas installation or acoustic instrument in the method of any of claims 1 to 21 or of the acoustic instrument assembly in any of claims 22 to 26.