GB2572536A

GB2572536A - Gas cylinder flow monitoring

Info

Publication number: GB2572536A
Application number: GB1803729.1A
Authority: GB
Inventors: Reid Dennis; Jacobsen Brian; Perez De Alejo Rigoberto
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2018-03-08
Filing date: 2018-03-08
Publication date: 2019-10-09
Also published as: WO2019170289A1; GB201803729D0

Abstract

The present invention provides a gas flow monitoring system 1 for use with a gas cylinder 10, comprising a valve body 12 associated with the gas cylinder, having a flow control valve 14 operable from a first position to allow the flow of gas from or to said cylinder and a second position to prevent the flow of gas from or to said cylinder; a vibration sensor 16 attached to or in physical association with the valve body 12 for detecting vibrations of the valve body, creating a vibration signal, and transmitting the vibration signal; a processor 18, connected to the vibration sensor 16, for receiving and processing the vibration signal from the vibration sensor and a memory 19, connected to the processor 18 pre-loaded with a calibrated lookup table 19a relating vibration signals from the vibration sensor with flow-rates of flows of gas through the valve body. Such a system is able to compare the vibration signal received with data from the look-up table thereby to determine the flow-rate of the flow of gas through the valve body 12. Methods of determining the volume or pressure of gas in the cylinder using the apparatus are also claimed. A method of checking a measurement of the volume or pressure in the cylinder comprises comparing the determination with a determination made using the temperature of the body of the valve.

Description

GAS CYLINDER FLOW MONITORING

The present invention relates to a gas flow monitoring system, in particular to a gas flow monitoring system for use with gas cylinders for supplying clinical gasses such as, for example, oxygen, argon, nitrous oxide, xenon, nitric oxide, helium and mixtures thereof to patients, and for supplying industrial gases such as oxygen, nitrogen, carbon dioxide and argon and mixtures thereof.

Known gas cylinders include mechanical valves to control the flow of gas from the cylinder. The valve typically includes a mechanical pressure gauge to display the pressure of the gas in the cylinder. It is important, particularly when supplying clinical gases, that the cylinder does not run out of gas. Whilst the pressure gauge displays the pressure of gas remaining, human intervention is required in order to read the pressure gauge and from this work out the amount of gas remaining, and some users find it difficult to interpret the information supplied and may thus make incorrect determinations of important data such as the total time of gas supply remaining.

In an attempt to overcome the above problem, mechanical valves have been replaced by socalled intelligent valves which incorporate an electronic monitoring system to process the gas pressure to determine information which is more pertinent, for example, the time remaining before the gas in the cylinder either runs out or reaches a pre-determined threshold. The electronic monitoring system can also wirelessly transmit the gas pressure to a remote computer which includes a management system which not only enables analysis of the gas pressure, but can identify gas cylinders which require replacing due to having low gas content. Hospitals will typically have many gas cylinders at different locations, and therefore it is beneficial to be able to manage the contents of those gas cylinders via a remote computer.

Whilst the use of intelligent valves eliminates the need for human intervention to check the gas contents, and enables remote management, the majority of gas cylinders used in hospitals still employ mechanical valves.

The managing of the gas contents of cylinders in hospitals which use cylinders with mechanical valves and intelligent valves is a particular problem because it is only the cylinders with intelligent valves that can communicate with and be managed by the remote computer, leaving those cylinders with mechanical valves at greater risk of running out of gas.

Whilst it would be possible to identify cylinders with mechanical valves and replace them with intelligent valves, this is not always practical, and can be prohibited by cost.

It would be desirable to be able to better manage the contents of gas cylinders which retain mechanical valves.

Thus, in an aspect there is provided a gas flow monitoring system as claimed in claim 1.

The present applicants have realised that when a gas flows through a body, such as a pipe, or more particularly as in the circumstances of a gas cylinder valve, there is an associated vibration. In some instances this vibration is in the auditory range and can, for example, be heard as a ‘hiss’ as gas flows out from a cylinder through the valve body. At different gas flow rates, there are different vibrations. This effect can be exploited when a gas flows from a cylinder and through a valve body by detecting these vibrations by use of a suitable vibration sensor, and monitoring and processing the resultant vibration signals produced by the sensor. A calibrated look-up table may be provided in a memory connected to a processor, where any particular flow-rate of a flow of gas through the valve body is associated with a particular vibration pattern in that particular type of valve. The flow-rate of a flow of gas through the valve can then be determined at any time there is a flow of gas through the valve. Additionally, an absence of any particular known vibration pattern, present in calibrated data, will indicate that there is no flow of gas through the valve. Further, the pressure change in a cylinder and the quantity of remaining gas can also be determined by calculation from the flow-rate of the flow of gas and the time data associated with a particular flow rate. From the flow-rate it is possible to calculate the change in volume in the gas cylinder over the time the valve was opened, and from that volume change it is possible to calculate the remaining volume and thus pressure, based on knowing the initial or last recorded and stored pressure and/or volume. The processor or the memory can be provided with the initial pressure and/or volume of gas in the cylinder upon installation. Thus, knowing the volume change enables the remaining volume and pressure of gas in a cylinder to be calculated. It is then possible to know or predict when a given cylinder needs to be changed or refilled.

As noted, the valve calibration data, which may be in a first look-up table, enables a relationship between a particular vibration frequency and/or amplitude and an associated flow-rate of a flow of gas through a valve to be established. This is then used to determine the actual flowrate when the valve is in operation and gas is flowing through it. It will be appreciated that for any given flow-rate of a flow of gas through the valve, there may be more than one frequency and/or amplitude of vibration associated with that flow-rate, and the calibration data will contain at least as much of this information as is necessary to identify a given flow-rate.

Insofar as it relates to flow-rates, the valve calibration data is established for a particular valve type by measuring the vibration frequency (or frequencies) and/or amplitude (or amplitudes) in controlled conditions, and recording the vibration frequency(ies) and/or amplitude(s) for different flow-rates of flows of gas through that particular valve type.

By repeating the calibration exercise for valves with different characteristics, such as size and material type, it is possible, upon installation of a gas cylinder, or upon installation of a valve to a gas cylinder, to select the appropriate calibration data, and therefore the relationships between the vibrations and flow-rates (and thus volume change, remaining volume and remaining pressure in a cylinder), relating to that valve when the monitoring system is subsequently used with that valve.

Calibration data may also be established for different cylinder properties and initial fill pressures of cylinders.

It is important to identify when the valve opens and closes so that the system is appropriately activated, or data from the system is appropriately recorded and/or processed. The processor may determine that the valve is open at any time when a vibration signal is received from the vibration sensor that, by reference to the calibration data, indicates that there is a flow of gas through the valve at a particular flow rate. When there is no such vibration signal received, there is no flow of gas.

In an embodiment, the vibration sensor comprises one or more of: a microphone; a MEMS microphone; a passive ultrasonic transducer, or an accelerometer. It will be appreciated that the vibrations associated with any particular flow-rate of a flow of gas through a valve may comprises a number of different frequencies and amplitudes, and there may thus be a requirement for different types of vibration sensor in order to pick up the full range of vibrations that may be associated with a particular flow-rate. In some instances there may be a requirement to provide more than one particular type of sensor in order to pick up the range of vibrations produced by a particular valve type. A vibration sensor may thus in fact be one, two or more sensors, such as a combination of a MEMS microphone and an ultrasonic sensor. An ultrasonic sensor may be a micro-machined ultrasonic transducer (MUT). Advantageously a

MEMS microphone and a MUT, if used in combination, may be fabricated together on the same silicon substrate.

In an embodiment, the monitoring system further comprises a display for displaying data associated with the flow of gas. The data can be data from the processor or the memory. This data may include one or more of the presence or absence of a flow of gas, the flow-rate of a flow of gas, the time for which a flow of gas has been flowing through the valve, the volume of gas that has passed through the valve over a period of time, the change in volume or pressure of gas in the associated cylinder, the remaining volume or pressure of gas in the cylinder, vibration data, data from the calibrated look-up table, valve type or identity data, cylinder type or identity data, and location data. The display may be mounted locally on the valve or may be a remote display. It may be directly connected to the processor or may be remotely connected to the processor.

In an embodiment, the gas flow monitoring system can include a transmitter for transmitting data associated with the flow of gas to a remote device comprising a receiver for receiving transmitted data associated with the flow of gas. The transmitter and receiver may be a wireless transmitter and receiver and may use Wi-Fi® or Bluetooth®. The remote device may be a hand-held unit, may be a vehicle-mounted device, or may be a remote monitoring system, such as the remote computer noted earlier. The remote device, monitoring system or computer may be a system in, for example, a hospital or may belong to a service provider to the hospital. The transmitted data can be data from the processor or the memory. This data may include one or more of the presence or absence of a flow of gas, the flow-rate of a flow of gas, the time for which a flow of gas has been flowing through the valve, the volume of gas that has passed through the valve over a period of time, the change in volume or pressure of gas in the associated cylinder, the remaining volume or pressure of gas in the cylinder, vibration data, data from the calibrated look-up table, valve type or identity data, cylinder type or identity data, and location data. The transmission of such data to a remote device enables management of the gas cylinder contents.

Data transmission can be from the processor via the transmitter directly to the remote device, or can be via one or more hubs which are themselves connected to the remote device. The inclusion of a wireless transmitter in the device offers the advantage that mechanical valves incorporating the monitoring system, and intelligent valves, both of which will typically be present in, for example, a hospital, may both communicate, and be jointly managed by the remote device, which may be the remote or a central computer of the hospital.

In an embodiment, the remote device comprises a remote display. Where the remote device is a hand-held device, vehicle mounted device, or other remote monitoring system such as a remote computer system, it is advantageous for an operator to be able to see any of the data associated with a flow of gas through the valve or any of the other derived data or data otherwise noted as associated with the valve or cylinder as available from the processor or memory.

In an embodiment, the elements of the monitoring system that are local to the valve and cylinder are as small and/or simple as possible and thus comprise a vibration sensing means and a transmission means and either an absolute minimum of or no processing means. In such an embodiment, vibrations are picked up by the vibration sensing means and turned into a vibration signal that is transmitted either directly or after minimal processing to the remote device (potentially via hubs as noted), where recording of vibration data, determination of flowrates of flows of gas (and thus volumes, pressures and so on as discussed elsewhere herein) by reference to calibration tables, and any other necessary or desirable processing, is performed. The connections between the processor, the vibration sensor, and/or the memory may thus be via the transmitter and receiver. The remote device can also make a determination as to when a valve has been opened or closed by processing of the ‘raw’ or little-processed vibration data received from the monitoring device. In this manner, the power requirements of the monitoring device may be made as low as possible, thus maximising the time a device can remain in situ before needing to be replaced, moved, have its battery replaced or recharged, or otherwise serviced. This minimises the time and cost associated with maintenance of the device.

In an embodiment, the vibration sensor of the monitoring system is releasably attachable to the valve body of the gas cylinder enabling it to be used with different gas cylinders. Alternatively, where a guard is provided which is attached to the valve body, the vibration sensor is releasably attachable to the guard (valve guard). It will be understood that so long as there is an undamped physical connection between the guard and the valve body, vibrations of the valve will travel through the guard and will thus be able to be picked up by the vibration sensor.

In an embodiment, the vibration sensor is releasably attached by a collar or clamp. A collar or clamp is an understood mechanical means of attaching a device to an object. Any arrangement which ensures that the vibration sensor engages with, or is in undamped physical connection with, the valve body, or a valve guard, is desirable. A biasing means to bias the vibration sensor into engagement with the valve body may be provided.

In an embodiment, the gas flow monitoring system may further comprise a controllable outlet valve operable from a first open position to allow the flow of gas from the cylinder and a second closed position to prevent the flow of gas from the cylinder and having a plurality of intermediate positions therebetween so as to regulate the flow of gas from the cylinder, wherein the processor is operable to receive an indication of the controllable outlet valve position and the memory is pre-loaded with a second look-up table relating controllable outlet valve positions to flow rates of gas through the valve body, whereby the processor compares the vibration signal received with data from the look-up table thereby to determine the flow rate of a flow of gas through the valve body and compares the determined flow rate of the flow of gas with data from the second look-up table, thereby to determine if the flow rate of the flow of gas is consistent with the indicated controllable outlet valve position.

It will be understood that gas cylinder valves can be provided with both a flow control valve that is intended to act primarily as a main ‘on-off’ valve and also a controllable outlet valve such as a Maxiflow® valve for more accurate and/or finer control of the flow of gas from a cylinder. This controllable outlet valve may be used, for example, when a gas cylinder is situated for use at a point where a particular maximum flow rate is desired to be set. A second look-up table of calibrated data can be created which correlates a flow-rate of a flow of gas through the valve body, and the associated vibrations, with positions of the controllable outlet valve. For example, a controllable outlet valve may have settings of from 0.25 to 25 litres per minute, and for each setting the associated vibrations may be calibrated. Upon installation of a cylinder, the setting of the controllable outlet valve may be input to the processor so that an expected flow-rate of a flow of gas is thus set, from the second look-up table, for when the cylinder is in use. Upon the drawing of a flow of gas, the processor determines the flow-rate of the flow of gas from the first look-up table of calibrated date in accordance with the procedures described earlier herein. This flow-rate is then compared to the expected flow-rate derived from the controllable outlet valve setting. If there is a variance, this may indicate any one of a number of undesirable situations, such as: an incomplete opening of the main on-off valve (flow control valve); an unexpected loss of pressure in the gas cylinder; a leak; or a problem with the controllable outlet valve. The processor may then be programmed to send an error signal via the transmitter to the remote device. It may also display an error message on a display, either local to the valve or remote as described herein. This will allow management of the situation by an operator. It will be understood that, in this document, whilst for convenience and to aid understanding the terms ‘first look-up table’ and ‘second look-up table’ have been used in relation to different sets of calibrated data, all the calibrated data might in fact be represented by a single table and/or may be stored in some other form of array, common in the art of memory storage, for which the word ‘table’ is a general term.

In an aspect, there is provided a method of determining a flow-rate of a flow of gas through a valve body of a gas cylinder, the method comprising the steps of providing a gas cylinder monitoring system as described herein, measuring vibrations associated with the flow of gas through the valve body with the vibration sensor and transmitting a vibration signal to the processor, and processing the vibration signal in relation to the calibration data in the memory to determine the flow-rate of the flow of gas through the valve body.

In an aspect, there is provided a method of determining the volume and/or pressure of gas in a gas cylinder, the method comprising the steps of providing a gas cylinder monitoring system as described herein, determining an initial volume and/or pressure of gas in the cylinder, measuring vibrations associated with a flow of gas through the valve body with the vibration sensor and transmitting a vibration signal to the processor, processing the vibration signal in relation to the calibration data in the memory to determine the flow-rate of the flow of gas through the valve body, processing flow rate data over time to calculate a change in volume of gas in the cylinder, and determining the remaining volume and/or pressure in the gas cylinder by processing the change in volume in relation to the initial volume I pressure determination.

In an aspect, there is provided a method of checking a measurement of the volume and/or pressure of gas in a gas cylinder comprising the steps of determining the volume and/or pressure of gas in the cylinder by the method of the previous aspect, and comparing the determination of volume and/or pressure of gas in the cylinder with a determination obtained by a different method. It can be seen that aspects and embodiments of the present invention provide a ready method of determining the contents of a gas cylinder, particularly where the gas cylinder is fitted with an mechanical valve. It is known that other, different methods of determining the contents exist, and so it is an aim of this aspect that where a determination of the contents of a cylinder has been obtained by such a different method, the present invention provides a means of checking or correlating that determination.

In an embodiment, the different method noted in the previous aspect comprises the steps of determining an initial volume and/or pressure of gas in the cylinder, measuring an ambient temperature, measuring the temperature of the body of the valve, processing the difference between the ambient and valve body temperature to determine the flow rate of the flow of gas through the valve body, processing the flow rate of gas over time to calculate a change in volume of gas in the cylinder, and determining the remaining volume and/or pressure in the gas cylinder by processing the change in volume in relation to the initial volume I pressure determination. Such a method is disclosed in GB patent application 1622194.7.

The invention will now be described by way of example only with reference to the accompanying drawings, in which:

Figure 1 is a schematic view of a gas flow monitoring system as applied to a gas cylinder, according to an embodiment of the present invention.

Figure 2 is a perspective view of an mechanical valve including a gas flow monitoring system according to an embodiment of the present invention.

Figure 3 is a schematic view of a memory provided with look-up tables in accordance with an embodiment of the invention.

In Figures 1 and 2, there is shown a gas cylinder monitoring system 1 comprising a valve body 12 and a casing 17 in engagement with the valve body 12.

Figure 2 additionally shows a handle 14a for the operation of flow control valve 14, and a handle 214a with a scale 214b for the operation of controllable outlet valve 214.

Figure 3 shows a memory 19 as described in the present application, which is loaded with a first look-up table 19a and a second look-up table 19b.

Figure 1 further shows a gas cylinder 10 to which valve/valve body 12 is fluidly connected. Valve body 12 has a flow control valve in the form of a primary on-off valve 14 and a controllable outlet valve 214 which is a flow-regulator valve.

The gas cylinder is further provided with a guard 11, directly mechanically connected to the valve body 12.

The gas cylinder monitoring system 1 has a vibration sensor 16 within the casing 17. The vibration sensor is a MEMS microphone. Also within the casing 17 is a processor 18 connected to the vibration sensor 16 and a memory 19 in turn connected to the processor 18. Figure 1 shows that the vibration sensor 16 is pressed up against the valve body 12. A fixing means (not shown) is provided to enable the casing 17 and its contents (16, 18, 19) to be releasably attachable to the valve body 12. Any suitable fixing means is envisaged such as a strap or a clamp, the requirement for the fixing means and the casing being that the vibration sensor 16 engages with the valve body 12 when the casing 17 is attached to the valve body 12. The memory 19 is provided with first and second look-up tables 19a and 19b, the first look-up table 19a comprising calibrated data relating vibration signals from the vibration sensor with flowrates of flows of gas through the valve body 12, and the second look-up table 19b comprising calibrated data relating positions of the controllable outlet valve 214 (as indicated by the scale 214b on the handle 214a) to flow-rates of flows of gas through the valve body 12.

The memory 19 or the processor 18 can further store reference data associated with the gas cylinder 10 and or the valve I valve body 12. The look-up tables of calibrated data may contain calibrated data for a number of combinations of gas cylinder, gas, and valve body, and upon installation the specific set of calibration data may be selected according to the particular valve body, cylinder, and gas used, as well as the initial fill pressure of the cylinder. In the present example, when the gas cylinder was installed, the information regarding the gas, cylinder type, valve type and initial fill pressure had been pre-loaded into the memory alongside the first and second look-up tables.

The gas cylinder monitoring system of Figure 1 further has a display 13 and Wi-Fi transmitter 15, which are connected to processor 18 by means of wires (not shown). Advantageously the display 13 and Wi-Fi transmitter 15 are shown as being attached to the guard 11, which allows easy viewing of the display 13 by an operator and maximises the broadcasting ability of the Wi-Fi transmitter 15.

The casing 17 also contains a battery (not shown) to power the processor 18, and transmitter 15. The display 13 contains its own battery (not shown) and the display 13 may be removed from the guard 11 for changing of its own battery or for removal in the case that it is decided by the operator that it is not necessary in the particular installation.

The transmitter 15 can transmit data, including the cylinder details and the remaining volume left in the cylinder 10 to the receiver 22 of remote device 20 to make the operator (not shown) of the remote device 20 aware if the cylinder needs changing. The remote device 20 here has a remote display 24 which can show a visible alarm or other notification to indicate when the contents of the gas cylinder 10 reach a pre-determined lower threshold. The same visible alarm or notification simultaneously shows on the display 13 that is attached to the cylinder guard 11. The remote device 20 and/or the processor 18 or the casing 17 can also include an audible alarm to indicate the contents of the cylinder 10 reaching the lower threshold.

In the above embodiment, the processor 18 constantly monitors the vibration signal from the vibration sensor 16 and compares it with the calibrated data in the first look-up table that is relevant to the particular cylinder 10 and valve/valve body 12 to which it is attached. When a vibration signal corresponds to a flow-rate of a flow of gas as indicated by the table, the processor measures for how long gas is flowing at that flow-rate and then processes the flowrate and time data to calculate the volume of gas that has left the cylinder, and further, by reference to data on the initial pressure and/or volume of the cylinder, calculates the remaining gas content and sends that information to the remote device 20. In an alternative embodiment, the flow-rate and time data can be sent directly to, and processed by, the remote device, i.e. there is no need for any processing to be done at the valve/cylinder location. The remote device can be a hand-held unit or a central computer or a mobile computer on a service vehicle.

The flow-rate data, or the time or gas content remaining is sent via Wi-Fi® directly to the remote device 20 in the above embodiments. Alternatively, the system transmitter 15 can transmit the data using Bluetooth® to hubs (not shown) positioned in key locations such as a ward, surgery, filling station, storage station and transportation when the transmitter is within range of those hubs. The hubs can then communicate with the remote device 20 using wireless transmission protocols more suitable for longer distances, such as Wi-Fi®.

The gas flow monitoring system 1 operates as follows:

Firstly, valve calibration data is created for each of the different valve types, cylinder types, gasses, and initial filling pressures, and stored in the memory 19 of processor 18 as follows:

For calibration purposes, the actual pressure and flow-rate data is required. This could be achieved by using an intelligent valve which can measure the pressure and flow-rate to high degrees of accuracy.

The valve calibration data is established for different flow-rates by measuring the vibration frequencies at various flow rates, and establishing the relationship between different flow-rates of gas through the valve and the associated vibration frequencies. Then, when the valve is in operation, a flow-rate of a flow of gas can be determined from measured vibration frequencies, and hence, over time, volumes of gas which have left the cylinder.

The valve calibration data is stored in the system on the memory 19.

Further calibration data is established by measuring the vibration frequencies at different flow rates which differ according to a setting of the controllable outlet valve 214, and thus a relationship determined between a maximum flow rate possible at any setting of the controllable outlet valve 214 and that setting of the controllable outlet valve 214. Then, when the valve is in operation, it is possible to determine if a flow rate of a flow of gas is not as high as might be expected for a given controllable outlet valve setting (in which case there may be a leak or the cylinder might unexpectedly be running low on gas), or if the flow rate of a flow of gas is higher than should be possible for a given controllable outlet valve setting, in which case the controllable outlet valve may be faulty.

This further calibration data is stored in the system on the memory 19.

When installed, the relevant set or sets of calibration data may be selectable, via for example a button or keypad (not shown) or via instruction from the remote device, according to the cylinder and valve type upon which the system is mounted.

Once the system has been calibrated, it is used with the gas cylinder as follows:

The correct calibration data is selected according to the valve and/or cylinder type and the initial pressure and/or volume of the gas in the cylinder is recorded to the memory or the processor, and the cylinder is installed with the flow control valve 14 fully open and the controllable outlet valve 214 set at a flow-rate consistent with the maximum expected safe rate of use of the gas depending on the purpose. For example, in a medical application a typical flow rate might be anything from 0.25 to 25 litres per minute, depending on application, whereas in an industrial setting such as welding it might be 4 to 15 litres per minute. The controllable outlet valve setting is also selected for the system and stored on the memory or in the processor.

Gas then flows through the valve body 12 for a period of time, and the processor records the associated vibrations and the period of time and processes these to determine a volume of gas that has left the cylinder - a change in the volume of gas.

From the determined volume change, a corresponding pressure change can be calculated based on the initial or previous pressure and/or volume, at least one of which are known. Cumulative pressure and volume changes are stored in the processor or memory for subsequent pressure and volume calculations.

Once the volume changes have been calculated, the volume remaining in the cylinder can be determined based on the previous volume, and transmitted to the remote device 20. The volume remaining can also be displayed on display 13 or remote display 24.

If the calculated volume remaining in the cylinder is below a pre-determined threshold then an alarm can be activated either at the cylinder itself, by means of a visual alarm on display 13 or on the remote display 24 of the remote device 20; optionally there may be provided an audible alarm device at the cylinder, for example within or on casing 17, or attached to the guard 11, or part of the display 13, or an audible alarm may be provided at the remote device 20.

In the above embodiment, if the processor detects that the flow-rate of the flow of gas through the valve/valve body 12 exceeds the maximum flow-rate consistent with the setting of the controllable outlet valve 214 as recorded on the processor or memory, an alarm can likewise be activated at the cylinder location itself or at the remote device.

It will be understood that the system of the present invention enables information about the contents of the gas cylinder to be obtained in real-time by monitoring and processing vibrations of the valve body. More specifically, the estimated flow-rate of a flow of gas is obtained by processing time and vibration data and comparing it with valve calibration data. From that estimated flow-rate of a flow of gas it is possible to calculate the volume change and hence the volume and pressure remaining in the cylinder.

It will further be understood that the system can readily be adapted so that a plurality of gas cylinders can be monitored by the system, provided that each gas cylinder is fitted as a minimum with a valve body with a vibration sensor attached and a transmitter capable of transmitting a vibration signal and an identity. A receiver, processor, memory and display can all be provided as or as part of a remote device, and appropriate calibration and initial state data for the plurality of gas cylinders can likewise be uploaded to the remote device so that the remote device can determine flow rates and volumes and pressures for each cylinder by processing vibration signals received which are associated with an identity of that cylinder.

It will also be understood that the system can be easily retrofitted to conventional mechanical valves without the need to interfere with the high pressure components of the gas cylinder. By retrofitting, the system enables mechanical valves to operate in a similar way to intelligent 5 valves, by firstly displaying more pertinent cylinder data such as remaining volume, and also by being able to communicate with a central computer for easier management of gas contents, particularly when both retrofitted mechanical valves and intelligent valves are used in the same location.

Claims

1. A gas flow monitoring system (1) for use with a gas cylinder (10), comprising:

a. a valve body (12) associated with the gas cylinder, comprising a flow control valve (14) operable from a first position to allow the flow of gas from or to said cylinder and a second position to prevent the flow of gas from or to said cylinder;

b. a vibration sensor (16) attached to or in physical association with the valve body (12) for detecting vibrations of the valve body, creating a vibration signal, and transmitting the vibration signal;

c. a processor (18), connected to the vibration sensor (16), for receiving and processing the vibration signal from the vibration sensor;

d. a memory (19), connected to the processor (18), pre-loaded with a calibrated lookup table (19a) relating vibration signals from the vibration sensor with flow-rates of flows of gas through the valve body;

whereby the processor (18) compares the vibration signal received with data from the lookup table, thereby to determine the flow-rate of the flow of gas through the valve body (12).

2. A gas flow monitoring system (1) as claimed in claim 1 wherein said vibration sensor (16) comprises one or more of: a microphone; a MEMS microphone; a passive ultrasonic transducer; or an accelerometer.

3. A gas flow monitoring system as claimed in claim 1 or claim 2, further comprising a display (13) for displaying data associated with the flow of gas.

4. A gas flow monitoring system as claimed in claim 1, claim 2 or claim 3, further comprising a transmitter (15) for transmitting data associated with the flow of gas to a remote device (20) comprising a receiver (22) for receiving transmitted data associated with the flow of gas.

5. A gas flow monitoring system as claimed in claim 4, wherein said remote device (20) further comprises a remote display (24).

6. A gas flow monitoring system as claimed in claim 4 or claim 5, wherein said remote device (20) comprises one or more of a hand-held device and a remote monitoring system.

7. A gas flow monitoring system as claimed in any of claims 1 to 6, further comprising a guard attached to the valve body, wherein the vibration sensor is releasably attached to the valve or to the guard.

8. A gas flow monitoring system as claimed in claim 7, wherein the vibration sensor is releasably attached by a collar or a clamp.

9. A gas flow monitoring system as claimed in either of claim 7 or claim 8, further comprising a casing (17), wherein the vibration sensor (16) is mounted on or within the casing and one or more of the following are also mounted on or within the casing: the processor (18); the memory (19); the display (13); and the transmitter (15).

10. A gas flow monitoring system as claimed in any of claims 1 to 8, further comprising a controllable outlet valve (214) operable from a first open position to allow the flow of gas from the cylinder and a second closed position to prevent the flow of gas from the cylinder and having a plurality of intermediate positions therebetween so as to regulate the flow of gas from the cylinder, wherein the processor (18) is operable to receive an indication (214b) of the controllable outlet valve (214) position and the memory (19) is pre-loaded with a second look-up table (19b) relating controllable outlet valve positions to flow rates of gas through the valve body, whereby the processor (18) compares the vibration signal received with data from the look-up table (19a) thereby to determine the flow rate of a flow of gas through the valve body and compares the determined flow rate of the flow of gas with data from the second look-up table (19b), thereby to determine if the flow rate of the flow of gas is consistent with the indicated controllable outlet valve position.

11. A method of determining a flow-rate of a flow of gas through a valve body of a gas cylinder, the method comprising the steps:

providing a gas cylinder monitoring system as claimed in any of claims 1 to 10; measuring vibrations associated with a flow-rate of a flow of gas through the valve body (12) with the vibration sensor (16) and transmitting a vibration signal to the processor (18);

processing the vibration signal in relation to the calibration data (19a) in the memory (19) to determine the flow-rate of the flow of gas through the valve body.

12. A method of determining the volume and/or pressure of gas in a gas cylinder, the method comprising the steps:

Providing a gas cylinder monitoring system as claimed in any of claims 1 to 10; determining an initial volume and/or pressure of gas in the cylinder;

measuring vibrations associated with a flow-rate of a flow of gas through the valve body (12) with the vibration sensor (16) and transmitting a vibration signal to the processor (18);

processing the vibration signal in relation to the calibration data (19a) in the memory (19) to determine the flow-rate of the flow of gas through the valve body; processing flow rate data over time to calculate a change in volume of gas in the cylinder;

determining the remaining volume and/or pressure in the gas cylinder by processing the change in volume in relation to the initial volume I pressure determination.

13. A method of checking a measurement of the volume and/or pressure of gas in a gas cylinder comprising the steps;

determining the volume and/or pressure of gas in the cylinder by the method of claim 12;

comparing the determination of volume and/or pressure of gas in the cylinder with a determination obtained by a different method.

14. A method of checking a measurement of the volume and/or pressure of gas in a gas cylinder as claimed in claim 14 wherein the different method comprises the steps:

determining an initial volume and/or pressure of gas in the cylinder; measuring an ambient temperature;

measuring the temperature of the body of the valve;

processing the difference between the ambient and valve body temperature to determine the flow rate of the flow of gas through the valve body;

processing the flow rate of gas over time to calculate a change in volume of gas in the cylinder;