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Title:
A METHOD OF DETECTING A LEAK IN A CLOSED SYSTEM
Document Type and Number:
WIPO Patent Application WO/2019/162207
Kind Code:
A1
Abstract:
A leak detector kit for detecting a leak in a closed system is provided. The leak detector kit comprises a dispenser with a tracer fluid for dispensing the tracer fluid into the closed system, and a detector for detecting any tracer fluid leaking from the closed system. The dispenser has a container storing tracer fluid, a second inlet constituting a container inlet, and a container outlet connectable to the first inlet. The container inlet and container outlet being fluidly communicating with each other via said container. The dispenser being adapted for cooperating with an injector having a dilution fluid for admitting said dilution fluid into said container via said container inlet for propelling said tracer fluid with said dilution fluid out of said container via said outlet and into said closed system.

Inventors:
QUAADE, Ulrich (Gammelmosevej 331, 2880 Bagsværd, 2880, DK)
Application Number:
EP2019/053835
Publication Date:
August 29, 2019
Filing Date:
February 15, 2019
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
INNOVIRIUM APS (Gammelmosevej 331, 2880 Bagsværd, 2880, DK)
International Classes:
G01M3/22; A46B11/00
Domestic Patent References:
WO1992014109A11992-08-20
Foreign References:
US20110247399A12011-10-13
EP1544613A12005-06-22
US4822743A1989-04-18
Other References:
J. MATER. CHEM. A, vol. 3, 2015, pages 5642 - 5647
"Sensor + Test Conferences", SENSOR PROCEEDINGS, 2011, pages 652
JOURNAL OF THE AIR POLLUTION CONTROL ASSOCIATION, vol. 15, no. 10, pages 481 - 484
PROCEDIA ENGINEERING, vol. 168, 2016, pages 1237 - 1240
"Sensors and Actuators B: Chemical", RSC ADV., vol. 253, no. 7, December 2017 (2017-12-01), pages 846 - 851
Attorney, Agent or Firm:
BUDDE SCHOU A/S (Hausergade 3, 1128 Copenhagen K, 1128, DK)
Download PDF:
Claims:
CLAIMS

1. A dispenser for detecting a leak in a closed system having a leak, a first inlet, and a wall defining an outer surface, said dispenser comprising: a container storing a tracer fluid,

a second inlet constituting a container inlet, and

a container outlet connectable to said first inlet for dispensing said tracer fluid into said closed system via said first inlet, said container inlet and said container outlet being fluidly communicating with each other via said container, said dispenser being adapted for cooperating with an injector having a dilution fluid for admitting said dilution fluid into said container via said container inlet for propelling said tracer fluid with said dilution fluid out of said container via said container outlet and into said closed system via said first inlet, said container outlet being configured such that in use, said container outlet being connected through a gas tight connection to said closed system for pressurizing said tracer fluid with said dilution fluid into said closed volume, said tracer fluid being detectable at said outer surface by a detector for indicating a presence of any of said tracer fluid having leaked through said wall.

2. A leak detector kit for detecting a leak in a closed system having a leak, a first inlet, and a wall defining an outer surface, said leak detector kit comprising: a dispenser including a tracer fluid for dispensing said tracer fluid into said closed system via said first inlet, and

a detector for detecting said tracer fluid,

said dispenser comprising:

a container storing said tracer fluid,

a second inlet constituting a container inlet, and

a container outlet connectable to said first inlet for dispensing said tracer fluid into said closed system via said first inlet, said container inlet and said container outlet being fluidly communicating with each other via said container, said dispenser being adapted for cooperating with an injector having a dilution fluid for admitting said dilution fluid into said container via said container inlet for propelling said tracer fluid with said dilution fluid out of said container via said container outlet and into said closed system via said first inlet, said container outlet being configured such that in use, said container outlet being connected through a gas tight connection to said closed system for pressurizing said tracer fluid with said dilution fluid into said closed volume,

said detector comprising a detector material for reacting with said tracer fluid when said detector material contacting said tracer fluid for indicating a presence of any of said tracer fluid having leaked through said wall when applying said detector to said outer surface.

3. A dispenser for detecting a leak in a closed system having a leak, a first inlet, and a wall defining an outer surface, said dispenser comprising: a container storing a tracer fluid,

a second inlet constituting a container inlet, and

a container outlet connectable to said first inlet for dispensing said tracer fluid into said closed system via said first inlet, said container outlet comprising a connector for fluidly connecting said container outlet to said first inlet or to a tube extending between said container outlet and said first inlet, said container inlet and said container outlet being fluidly communicating with each other via said container, said dispenser being adapted for cooperating with an injector having a dilution fluid for admitting said dilution fluid into said container via said container inlet for propelling said tracer fluid with said dilution fluid out of said container via said container outlet, through said connector and into said closed system via said first inlet, said tracer fluid being detectable at said outer surface by a detector for indicating a presence of any of said tracer fluid having leaked through said wall.

4. The dispenser according to any of the preceding claims, said tracer fluid being incorporated in a sorption material for desorption of said tracer fluid.

5. The dispenser according to any of the preceding claims, said container outlet comprising a thread or a hose for connecting said container outlet to said first inlet.

6. The dispenser according to claim 4, said sorption material having an equilibrium pressure of said tracer fluid between 0.01 mbar and 1000 mbar at 20 °C.

7. The leak detector kit according to any of the preceding claims, said dilution fluid being air.

8. The leak detector kit according to any of the preceding claims, said detector being a litmus paper or an ammonia cloth.

9. The dispenser according to any of the preceding claims, having an inlet plug for closing said container inlet, and an outlet plug for closing said container outlet.

10. The dispenser according to any of the preceding claims, said container inlet having an inlet filter for containing said sorption material.

11. The dispenser according to any of the preceding claims, said container outlet having an outlet filter for containing said sorption material

12. The dispenser according to any of the preceding claims, said container inlet having an inlet valve constituting a one-way valve.

13. The leak detector kit according to any of the preceding claims, said injector including an injector outlet connectable to said container inlet for admitting said dilution fluid into said container.

14. The leak detector kit according to any of the preceding claims, said injector being a pump or a powerlet cartridge such as a C02 charger.

15. A method of detecting a leak in a closed system having a leak, a first inlet, and a wall defining an outer surface, said method comprising: providing a dispenser including:

a container storing a tracer fluid,

a second inlet constituting a container inlet, and

a container outlet connectable to said first inlet for dispensing said tracer fluid into said closed system via said first inlet, said container inlet and said container outlet being fluidly communicating with each other via said container, connecting said container outlet to said first inlet, providing a dilution fluid, and admitting said dilution fluid into said container via said container inlet for propelling said tracer fluid with said dilution fluid out of said container via said outlet and into said closed system via said first inlet, said method further comprising:

providing a detector including a detector material for reacting with said tracer fluid when said detector material contacting said tracer fluid for indicating said tracer fluid, and

applying said detector to said outer surface for indicating a presence of any of said tracer fluid having leaked through said wall to the outer surface.

Description:
A method of detecting a leak in a closed system

DESCRIPTION Many practical applications include a fluid, liquid or gas, pressurized or non-pressurized, confined in a closed system. Such closed systems can comprise tanks, tubes, hoses, bags and the like as well as mechanical components like pumps, valves etc.

Often, it is important for the function of the application that the fluid does not escape from the closed system. Leaks, i.e. channels or punctures where fluid can escape from the closed system can occur from production or assembly errors of the closed system or by wear and tear, i.e. a closed system is to be understood as a volume, which may comprise a valve for inletting fluid into the system. Thus, the system is closed in the sense that it does not have any leaks for example.

If a leak occurs, it is desirable in many situations to check such closed systems for leaks and identify the location of the leak.

Leak detection is a huge field with leak detection methods ranging from visual inspection to highly sophisticated chemical or physical detectors.

Here, a novel design for producing a diluted tracer gas such as ammonia gas for leak detection is disclosed. The advantages include compactness, easy handling, fast re- sponse and safe operation.

The above object and advantages together with numerous other objects and ad- vantages, which will be evident from the description of the present invention, are ac- cording to a first aspect of the present invention obtained by: A dispenser for detecting a leak in a closed system having a leak, a first inlet, and a wall defining an outer surface, said dispenser comprising: a container storing a tracer fluid,

a second inlet constituting a container inlet, and

a container outlet connectable to said first inlet for dispensing said tracer fluid into said closed system via said first inlet, said container inlet and said container outlet being fluidly communicating with each other via said container, said dispenser being adapted for cooperating with an injector having a dilution fluid for admitting said dilution fluid into said container via said container inlet for propelling said tracer fluid with said dilution fluid out of said container via said container outlet and into said closed system via said first inlet, said container outlet being configured such that in use, said container outlet being con- nected through a gas tight connection to said closed system for pressurizing said tracer fluid with said dilution fluid into said closed volume, said tracer fluid being detectable at said outer surface by a detector for indicating a presence of any of said tracer fluid having leaked through said wall.

A gas tight connection is to be understood as a connection allowing a fluid to flow therein, which may be substantially airtight understood in the sense that the connection is substantially hermitically sealed at both ends and along the path of the connection - the connection being from the container outlet to the first inlet of the closed system, so that the connection does not leak so much fluid that it defeats the purpose of the system, but may allow for minor leakage.

The connection may be direct in the sense that the container outlet is connected directly to the first inlet of the closed system or indirect in the sense that between the container outlet and the first inlet a hose or tube or similar is inserted with one distal end connected to the container outlet and the other distal end to the first inlet of the closed volume. In both cases, the function of the connection is to guide fluid from the container and into the closed volume.

The connections, either between the container outlet and the first inlet or between the first outlet and one distal end of a hose or tube or similar or between the other distal end of the hose or tube or similar and the first inlet of the closed volume, may be in the form of two mating parts, often a male and female, that cooperate to form an essentially gas- tight connection. In some cases, the mating parts forming the connection are secured by means of mechanically fixing the mating parts to each other. In some cases, the mating parts are simply pushed or held together for the time needed to inflate and pres- surize the closed volume.

Numerous connector designs exist: Threaded connectors, where for example a stud with an outer thread (male) is mated with a hollow cylindrical part with an inner thread (female), hose connectors, where a hose is pushed onto a stud, bicycle pump connect- ors, where a circular rubber gasket on the pump is pushed onto the valve, flange con- nectors, various types of quick connectors etc.

Historically different industrial areas have developed their own types of connectors op- timized for their specific uses and often, the type of connector is dictated by the type of apparatus that needs to be leak tested.

The injector can for example be in the form of a pump, a compressor, a pressurized gas cylinder etc. In some instances, it is advantageous to use a pump rather than a com- pressor or compressed air to pressurize the closed volume since the temperature in- crease related to compression of the air helps desorption of the tracer (e.g. ammonia) into the dilution gas.

The tracer fluid can be stored as a solid that by desorption or decomposition releases the tracer fluid. Alternatively, the tracer fluid can be dissolved in a liquid and released by evaporation.

In the following, the term sorption material is used to denote any material, solid or liquid, that can release the tracer fluid.

If the sorption material is liquid, it is advantageous in some instances to immobilize the liquid in a sponge, foam or other porous structure to help retaining the liquid in the con- tainer.

According to a second aspect of the present invention, the above objects and ad- vantages are obtained by:

A method of detecting a leak in a closed system having a leak, a first inlet, and a wall defining an outer surface, said method comprising: providing a dispenser including: a container storing a tracer fluid,

a second inlet constituting a container inlet, and

a container outlet connectable to said first inlet for dispensing said tracer fluid into said closed system via said first inlet, said container inlet and said container outlet being fluidly communicating with each other via said container, connecting said container outlet to said first inlet, providing a dilution fluid, and admitting said dilution fluid into said container via said container inlet for propelling said tracer fluid with said dilution fluid out of said container via said outlet and into said closed system via said first inlet, said method further comprising:

providing a detector including a detector material for reacting with said tracer fluid when said detector material contacting said tracer fluid for indicating said tracer fluid, and

applying said detector to said outer surface for indicating a presence of any of said tracer fluid having leaked through said wall to the outer surface.

According to a third aspect of the present invention, the above objects and advantages are obtained by: A leak detector kit for detecting a leak in a closed system having a leak, a first inlet, and a wall defining an outer surface, said leak detector kit comprising: a dispenser including a tracer fluid for dispensing said tracer fluid into said closed sys- tem via said first inlet, and

a detector for detecting said tracer fluid,

said dispenser comprising:

a container storing said tracer fluid,

a second inlet constituting a container inlet, and

a container outlet connectable to said first inlet for dispensing said tracer fluid into said closed system via said first inlet, said container inlet and said container outlet being fluidly communicating with each other via said container, said dispenser being adapted for cooperating with an injector having a dilution fluid for admitting said dilution fluid into said container via said container inlet for propelling said tracer fluid with said dilution fluid out of said container via said container outlet and into said closed system via said first inlet, said container outlet being configured such that in use, said container outlet being con- nected through a gas tight connection to said closed system for pressurizing said tracer fluid with said dilution fluid into said closed volume,

said detector comprising a detector material for reacting with said tracer fluid when said detector material contacting said tracer fluid for indicating a presence of any of said tracer fluid having leaked through said wall when applying said detector to said outer surface.

According to a fourth aspect of the present invention, the above objects and advantages are obtained by:

A dispenser for detecting a leak in a closed system having a leak, a first inlet, and a wall defining an outer surface, said dispenser comprising: a container storing a tracer fluid,

a second inlet constituting a container inlet, and

a container outlet connectable to said first inlet for dispensing said tracer fluid into said closed system via said first inlet, said container outlet comprising a connector for fluidly connecting said container outlet to said first inlet or to a tube extending between said container outlet and said first in- let, said container inlet and said container outlet being fluidly communicating with each other via said container, said dispenser being adapted for cooperating with an injector having a dilution fluid for admitting said dilution fluid into said container via said container inlet for propelling said tracer fluid with said dilution fluid out of said container via said container outlet, through said connector and into said closed system via said first inlet, said tracer fluid being detectable at said outer surface by a detector for indicating a presence of any of said tracer fluid having leaked through said wall.

A tube is to be understood as a hose or pipe, which generally comprises a passage enclosed by a wall, often a cylindrical, where the passage extends from one end to the other.

Fluidly connecting is to be understood as a connection allowing a fluid to flow therein. The connection may be substantially airtight understood in the sense that the connection is substantially hermitically sealed at both ends and along the path of the connection - the connection being from the container outlet to the inlet of the closed system, so that the connection does not leak so much fluid that it defeats the purpose of the system, but may allow for minor leakage.

According to a fifth aspect of the present invention, the above objects and advantages are obtained by: a leak detector kit for detecting a leak in a closed system having a leak, a first inlet, and a wall defining an outer surface, said leak detector kit comprising: a dispenser including a tracer fluid for dispensing said tracer fluid into said closed sys- tem via said first inlet, and

a detector for detecting said tracer fluid,

said dispenser comprising: a container storing a tracer fluid,

a second inlet constituting a container inlet, and

a container outlet connectable to said first inlet for dispensing said tracer fluid into said closed system via said first inlet, said container outlet comprising a connector for fluidly connecting said container outlet to said first inlet or to a tube extending between said container outlet and said first in- let, said container inlet and said container outlet being fluidly communicating with each other via said container, said dispenser being adapted for cooperating with an injector having a dilution fluid for admitting said dilution fluid into said container via said container inlet for propelling said tracer fluid with said dilution fluid out of said container via said container outlet, through said connector and into said closed system via said first inlet, said detector comprising a detector material for reacting with said tracer fluid when said detector material contacting said tracer fluid for indicating a presence of any of said tracer fluid having leaked through said wall when applying said detector to said outer surface. The invention will now be explained in more detail below by means of examples of em- bodiments with reference to the very schematic drawings, in which

FIG 1A shows the schematics of the diluted tracer fluid (e.g. ammonia gas) dispenser. FIG 1 B shows the dispenser used with optional one-way valves.

FIG 2 shows the diluted ammonia gas dispenser in a particular configuration for use of finding leaks on tires. FIG 3 shows the dispenser connected to a wheel valve.

FIG 4 is a schematic diagram illustrating an embodiment of a leak identification method, where a closed volume is pressurized with diluted tracer fluid (e.g. ammonia gas) intro- duced to the closed volume through the dispenser, where after the leaking diluted tracer gas (e.g. ammonia gas) is detected with a detector (e.g. an ammonia detector cloth).

FIG 5 shows a system for identifying leaks of closed volumes in a professional setting for use in workshops/garages, construction sites etc. for extensive and/or repeated use to identify the location of leaks. FIG 6 shows the dispenser of figure 1 further showing the connection to the closed vol- ume and the connection to the source of pressurized gas.

FIG 7 shows the dispenser of figure 6, further showing an optional gas channel inserted between the connectors of the gas outlet and the first inlet.

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in different forms and should not be con- strued as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout. Like elements will thus not be described in detail with respect to the description of each figure.

In the following, the description is presented with ammonia as an example of the tracer fluid. In general, the tracer fluid can be a reactive material that upon escaping through the leak can induce a clear signal on a detector to indicate the position of the leak. Other non-limiting examples of a tracer fluid include: inorganic substances such as CO, CO2, NO, NO2, H2S, HCI, H 2 0(g) or organic substances like ethylene.

In many applications, it is advantageous to use a detector surface as indicator, that by exposure to the tracer fluid on the side of the detector surface facing the leak gives a visible detectable signal also on the side pointing away from the leak for easy detection. Examples of such a detector surface could be a colorimetric detector material applied to a cloth or a piece of tissue such as the ammonia cloth. Examples of colorimetric de- tector materials are found in the references:

J. Mater. Chem. A, 2015,3, 5642-5647

“Colorimetric gas sensors for the detection of ammonia, nitrogen dioxide and carbon monoxide: current status and research trends”, Sensor + Test Conferences 201 1 - Sensor Proceedings, p. 652

Journal of the Air Pollution Control Association, 15:10, 481 -484

Procedia Engineering, Volume 168, 2016, Pages 1237-1240

Sensors and Actuators B: Chemical, Volume 253, December 2017, Pages 846-851

RSC Adv., 2017, 7, 26849

“Colorimetric gas sensors”, Fraunhofer Institute for Physical measurement Techniques. The dispenser comprises a volume/container with an inlet and an outlet. Means for re- taining the ammonia releasing material is applied, for example in the form of binding the material in a solid block or placing a filter before the outlet and optionally at the inlet. In some instances, the dispenser is formed in a way easy to screw onto a valve.

Yet another aspect of the invention relates to a method of using the diluted ammonia gas dispenser for identifying leaks of a closed volume. The diluted ammonia gas dis- penser is connected to the closed volume, optionally through a one-way valve. Pressur- ized air/gas from a compressor, pump or similar is supplied to the inlet of the diluted ammonia gas dispenser. The diluted ammonia gas is then pressurized into the closed volume to some overpressure. Overpressure is to be understood as a pressure higher than ambient pressure, where ambient pressure is whatever pressure happens to be normal around the place or location of the closed volume, i.e. the pressure on the out- side of the closed volume. Overpressure in the closed volume is essential to drive gas containing tracer fluid from inside the closed volume through the leak to the outer sur- face, where the tracer can be detected. The overpressure may be generated by the air/gas supplied from the compressor, pump or similar to propel gas through the con- tainer and into the closed volume such that the tracer fluid may enter into the closed volume and eventually leak out through a leak to the outer surface of the closed volume. A bicycle pump may be suitable for creating the overpressure.

If any leak is present, the diluted ammonia gas will leak out. By searching the surface of the closed volume with an ammonia detector cloth or similar, any leaks can be identified.

Previous art describes inserting an open bottle or container with an aqueous solution of ammonia in the closed system and pressurize the system with air to some pressure above ambient. Ammonia will then desorb into the pressurized air and form a diluted tracer gas in the closed volume that can be detected in the outside if a leak is present. Ammonia solution is highly corrosive, which makes aqueous ammonia solution less at- tractive. Use of pressurized gas premixed with traces of ammonia has the drawbacks of the need for a bulky pressure vessel with related pressure directive regulations and low capacity of gas compared to a solid. Many chemical substances can release ammonia by desorption or decomposition. De- pending on the substance, the ammonia equilibrium pressure can vary. In general, the equilibrium pressure depends on the temperature. Depending on the reaction enthalpy, the ammonia pressure can range from almost zero to above ambient pressure at room temperature. The solid material can be any material that can release ammonia like am- monium carbonate, ammonia bicarbonate, ammonium carbamate or absorbed ammo- nia in ammonia absorbing salts like calcium chloride, aluminium sulphate etc. or ammo- nia adsorbed in zeolites or other high surface-area materials.

By passing a gas or air flow across such a material, ammonia will desorb into the gas or air to a partial pressure limited by the equilibrium pressure and desorption kinetics of the ammonia releasing material.

Fig 1 shows the schematics of the diluted tracer gas (e.g. ammonia gas) dispenser. The container (101 ) has a gas/air inlet (103) and gas outlet (104). The container (101 ) con- tains the ammonia releasing material (102) and may have means for retaining the am- monia releasing material for example in the form of the outlet filter (106) and optionally the inlet filter (105). In use, the outlet (104) is connected through a gas tight connection to the closed volume for leak inspection. The inlet is connected to a source of pressur- ized gas or air in the form of for example a pump or compressor or a reservoir of corn- pressed gas or air such as compressed gas cylinder or a balloon. Optional seals (107) and (108) prevent loss of ammonia when the dispenser is not in use.

It is of particular importance to choose the right ammonia desorbing material. Many chemical substances can decompose and release ammonia. Depending on the sub- stance, the ammonia equilibrium pressure can vary. In general, the equilibrium pressure depends on temperature according to the Van’t Hoff equation:

dH dS_

ln K

RT R

where K eq is the equilibrium constant of the ammonia release reaction, dH is the reacton enthalpy, dS the entropy change, R the gas constant and T is the temperature in Kelvin. Depending on the reaction enthalpy, the ammonia pressure can range from close to zero to above ambient pressure at room temperature. The solid material can be any material that can release ammonia like ammonium carbonate, ammonium bicarbonate, ammonium carbamate or absorbed ammonia in ammonia absorbing salts like calcium chloride, aluminum sulphate etc. or ammonia adsorbed in e.g. zeolites or other high surface materials. The material can be mixed with an inert solid like e.g. sand or aluminum oxide in order to prevent agglomeration and clogging and help to have a uniform gas flow through the material to give efficient ammonia desorption. It is advantageous to have the material in a high surface area form like a powder or granulate in order to have fast desorption kinetics.

For maximum sensitivity in leak detection efficiency a high partial pressure of ammonia is desirable. However, in order not to loosing ammonia when the apparatus is not in use and to avoid excessive smell of ammonia or even irritating or harmful ammonia levels, the ammonia amount should be limited. It can be limited, either by absolute amount, by the release kinetics, or by equilibrium pressure of the ammonia desorbing material.

In one embodiment, the total amount of material in the container (101 ) is limited to an equivalent amount of ammonia of 5 gram, 1 gram, 0.1 gram, 10 mg or 1 mg. However, in order to detect the ammonia, the concentration C inside the closed volume must ex ceed 2 ppm, 10 ppm, preferably 100 ppm or even more preferably 1000 ppm or 1 %. Given the volume, V, of the closed volume and the pressure, p, in the closed volume, the minimum molar amount of ammonia n amount is given by n=V p C/(R T), where R is the gas constant and T the temperature. If for example V is 2 Liter (or 2 10 3 m 3 ), p is 2 bar (or 2 x 101300 Pa), T is 300 Kelvin and the desired concentration, C, is 1000 ppm, the needed amount of ammonia is: n=0.00016 Mol. If the ammonia comes from disso- ciation of ammonium carbonate:

(NH 4 ) 2 C0 3 -> NH 3 + NH 4 HC0 3

Accordingly, 0.00016 Mol of ammonium carbonate is needed corresponding to 0.015 gram.

In another embodiment, the ammonia pressure is limited by the equilibrium pressure. In this situation, it is assumed that ammonia desorb sufficiently fast to give a partial pres- sure in the gas that is within a factor of ten of the ammonia equilibrium pressure of the ammonia desorbing material. It is desirable to choose a material with partial pressure of 0.01 mbar, 0.1 mbar, 1 mbar, or 10 mbar at ambient temperature which leads to con- centrations of 10 ppm, preferably 100 ppm or even more preferably 1000 ppm or 1 % respectively if the gas pressure is 1 bar. If the pressure is higher, the chosen partial pressure and corresponding concentration should increase proportionally. In all embodiments, the ammonia equilibrium pressure at 50 °C should not exceed 3 bar, preferably 2 bar, even more preferably 1 bar. Ammonium carbonate has an equilib- rium pressure of 1 bar at 58 °C and correspondingly below 1 bar at 50 °C.

The desorption speed can be increased by preparing the ammonia desorbing material in a highly porous form with high surface area or as a powder that gas can easily flow through. Optionally, the ammonia desorbing material can be mixed with another porous and/or powder material to facilitate gas permeability.

Mechanical designs of the diluted ammonia gas dispenser.

Depending on the application, it can be advantageous to have the diluted ammonia gas dispenser in either a one-time (or limited number of times) use version or extensive/mul- tiple time use version.

One embodiment is associated with a diluted ammonia gas dispenser that is made small and compact for one-time (or limited number of times) use and loaded with an amount of ammonia desorbing material that desorbs essentially all the ammonia and where the amount is adjusted to the intended use as in the example above. The advantages of this embodiment are that the diluted ammonia gas dispenser is compact, can be sealed in a one-time fashion, can be made of cheap materials and is easy to carry. An example of use for this embodiment is to identify tire leaks and fixing punctures in the field. If the tire is a bicycle tire with a volume of 2 Liters and the desired ammonia concentration is 1000 ppm the diluted ammonia gas dispenser should be loaded with 0.0028 gram of ammonia carbonate as an example. In this embodiment, the seals (107) and (108) can be of one-time use type.

Another embodiment is associated with extended use or multiple use. Here, the con- tainer is larger and carries material for multiple uses. For this embodiment, it is advan- tageous that the material is not depleted in a single use or few uses and the ammonia release is advantageously chosen to be limited by the partial pressure of the ammonia releasing material. An example of use can be inspection of tubes and fittings for leaks after installation. For such applications, it is desirable that the equipment can be used over and over again with little or no maintenance. In this embodiment, means for sealing the inlet and outlet is needed to prevent ammonia from escaping the dispenser between uses. In this embodiment, the seals (107) and (108) are preferably of multiple use type like e.g. valves or plugs.

In yet another embodiment, the ammonia concentration is limited by the equilibrium pressure of the ammonia releasing material, but the dispenser is intended for only a limited number of uses. This is advantageous if the intended use is leak detection and repair over a limited time period with several leak tests.

To keep the volume pressurized during leak testing, it is advantageous to install a one- way valve at the inlet (1 10), the outlet (109) or both the inlet and the outlet of the diluted ammonia gas dispenser. It is even more advantageous to use one-way valves that that are sealing when there is low (below 1 bar, 0.5 bar, 0.2 bar, 0.1 bar) or no pressure difference across in which case the one-way valves also act as means for sealing (107) and (108).

The diluted ammonia gas dispenser can be made of any material that is chemically inert and leak resistant to diluted ammonia gas. Non-limiting examples are metals like alumi- num or stainless steel or polymers like nylon or polypropylene, natural rubber or ceram- ics.

Depending on the choice of material, the diluted ammonia gas dispenser can be pro- duced using standard production methods like machining, hot or cold forming, die cast- ing, injection molding etc.

In one embodiment, the ammonia gas dispenser is produced by die casting or injection molding, where the die also holds the structure of the filters (105) and/or (106) in which case the filters become an integrated part of the dispenser.

A particular embodiment is intended for leak detection of tires and tubes. Here, it is advantageous that the diluted ammonia gas dispenser is compact and easy to use. Fig- ure 2 shows a symmetric design of the diluted ammonia gas dispenser, that can easily be attached/screwed on to the valve of the tire or tube.“A” is sideview and“B” is top view. It is advantageous for this particular embodiment to be essentially rotational sym- metric to facilitate easy on- and un-screwing of the diluted ammonia dispenser to the valve of the closed volume. (201 ) is the symmetric housing, (202) is the ammonia de- sorbing material, (203) is the inlet, (204) and (205) are filters. The thread of the outlet (206) should match the thread of the valve.

The connector (203) should match the means for pressurized air as for example a bicy- cle pump or another standard fitting for pressurized air. Commonly used valves are Presta, Schrader or Woods valves. Optionally, the inlet (203) is formed with a thread.

In some cases, the location of the leak can be found without removing the tube from the wheel and in the case of tubeless tires the location of the leak must be found before removing the tire. Figure 3 shows the diluted ammonia gas dispenser (301 ) attached to the valve (302) of a wheel (303).

Desorption of ammonia from the ammonia desorbing material is enhanced at elevated temperature. In some embodiments the diluted ammonia gas dispenser comprises means for heating. This can be external heating in form of a heater element or internal heating, where a flow restriction is incorporated in the dispenser to provide friction be- tween the gas and the dispenser and/or provide an approximate adiabatic compression during pumping that also results in increasing temperature. Another embodiment concerns a compact system for occasional leak detection in e.g. the field, or other circumstances where easy use is desired.

Figure 4 shows a system for leak detection of for example a bicycle tube. It comprises as example a tube (402) with a leak, a valve (403), a diluted ammonia dispenser (405), a piece of ammonia detector cloth (401 ) and a pump (404) to inflate the tube through the diluted ammonia gas dispenser. To identify the position of the leak, the diluted am- monia gas dispenser is screwed onto the valve. The tube is the inflated through the diluted ammonia gas dispenser to fill the tube to slight overpressure with air containing traces of ammonia. The air with diluted ammonia will escape through the leak. By searching the surface of the tube with the ammonia detector cloth, the position of the leak is revealed by green coloration of the ammonia detection cloth. This embodiment is particularly useful for identifying leaks on the road if a vehicle like e.g. a bicycle expe- riences a puncture during a ride. Yet another embodiment concerns a system for extensive or professional use. Figure 5 shows a system intended for repeated use as in e.g. a workshop, garage of construction site. It comprises a closed volume e.g. an automobile tube or similar (502) with a valve (503), hoses (506) attached between the valve and diluted ammonia gas dispenser (507) and between the diluted ammonia gas dispenser (503) and the pump (504). Alternative to the pump, a compressor or compressed air or gas could be used. T o identify the position of the leak, the diluted ammonia gas dispenser is attached to the valve through the hose. The tube is then inflated through the diluted ammonia gas dis penser to fill the tube to slight overpressure with air containing traces of ammonia. The air with diluted ammonia will escape through the leak. By searching the surface of the tube with the ammonia cloth, the position of the leak is revealed by green coloration of the ammonia detection cloth.

With sufficient size of the diluted ammonia gas dispenser, there is capacity for many repeated uses before the dispenser is depleted.

In this system the diluted ammonia gas dispenser may be larger and may be for multiple use. This system is particularly useful for use in a garage, workshop or repair shop, where several puncture repairs are anticipated, or at construction sites, where tubes or hoses are installed and need to be checked for leaks.

Figure 6 shows the dispenser of Figure 1 including a connector (1 1 1 ) of the dispenser outlet and a mating connector (1 12) of the closed volume (1 13). The figure also high- lights the outer surface (1 14), the leak (120) and the detector (130). The dilution fluid is provided from the source (150) at pressure a Pi. The resulting pressure of the closed volume (1 13) is indicated by P 2 . The ambient pressure is indicated by P ambient . The rela- tion Pi > P 2 > P ambient must be fulfilled in order for the source of the dilution fluid to propel dilution fluid through the container to obtain diluted tracer fluid, further propelling said diluted tracer fluid through the container outlet and the connector into the closed volume to a pressure above ambient to provide for the leakage of diluted tracer fluid from the closed volume through the leak to ambient for subsequent detection of the tracer fluid at the outer surface of the closed volume. The container inlet (103) may be equipped with an essentially gas tight connector (140) that mates with a corresponding connector on the source (150). The connector pairs (1 1 1/1 12) and (140/150) may be similar or different. Optionally, the oneway valves (109, 1 10) and/or the seals (107,108) may be inserted or integrated in, before or after the connectors (1 11 ) and (140).

Figure 7 shows the embodiment of Figure 6, where an optional gas channel is inserted between the connectors of the gas outlet and the first inlet. The figure shows the optional configuration, where an essentially gastight gas channel (115) with connectors (1 16) and (117) is inserted between the connectors (1 11 ) and (112). The gas channel may for example be a tube or hose. In this configuration, the connector pairs (1 11 )/(116) and (112)/(1 17) may be similar or of different type.

The embodiments can be used for leak detection of any closed volume. They are par- ticularly useful for leak detection of smaller items like inflated tubes, hoses, balls, toys, air mattresses and the like. The embodiments can also be used for identification of leaks of pressure vessels, tube or hose systems in metal, rubber, plastic or other synthetic materials.

A method for leak detection comprising the following steps:

1. Providing a diluted tracer gas (e.g. ammonia) dispenser described above.

2. Attaching the dispenser to the suspected leaking volume, V.

3. Inflating or pressurizing the volume, V through the dispenser.

4. Providing means for detecting diluted tracer gas (e.g. ammonia) leaking from the volume, V.

5. Searching the surface of the volume, V with said means for detecting leaking diluted ammonia gas to identify the leak.

The means for detecting leaking diluted ammonia gas can be electronic ammonia de- tectors, litmus paper, ammonia detector cloth or the like. Ammonia detector cloth as described in patent application US4822743A or“ammonia leak detection cloth” as sup- plied from Precision Laboratories is especially advantageous as it is flexible, has distinct color change and the color change is easily visible on both sides of the cloth.

Also spraying the surface with a liquid solution of ammonia detection material will reveal the position of the leak by reacting with the escaping ammonia.

Even searching the surface by spraying with CO2WNI reveal the leak since ammonia and CO2 gas react to form a mist that is easily detected. EXAMPLES

Example 1a: Diluted ammonia dispenser In this example, the diluted ammonia dispenser is made from Nylon 6.6 in a geometry similar to Figure 2. The dimensions are: overall length 50 mm, outer diameter 8 mm, inner diameter 4 mm. The thread to attach to a valve is unc 12-24 iso. The starting point is a 50 mm, 08 mm Nylon rod. From one end a hole, 03.5 mm is drilled to a depth of 1.6 mm and the unc 12-24 iso thread is cut. From the other end a hole 04 mm is drilled to a depth such that the holes from each end are separated by 1 mm Nylon. The top 4 mm is increased in diameter to 05 mm to form a recess with a 5 mm drill. The two holes are then connected by drilling a small hole 01.5 mm through the remaining 1 mm Nylon to leave a constriction between the two holes. A piece of rockwool 6 mm x 6 mm is inserted on the hole without thread and pushed to and compacted against the constriction. This is the outlet filter. The hole without thread is then filled with ammonium carbonate up to

5 mm from the edge. Another piece of rockwool (6 mm x 6 mm) is inserted and corn- pressed against the top of the ammonium carbonate. This is the inlet filter. Finally, a Nylon tube OD 5mm, ID 1.5 mm, length 8 mm is inserted with a press fit to the bottom of the 5 mm recess. This both holds the inlet filter and extends to form the stud, where a pump can be applied.

The ammonia dispenser was filled with 263 mg ammonium carbonate. Several tests showed that after inflating a bicycle tube 700 x 25-35c to a diameter of 2.5 cm, 6-9 mg ammonium carbonate was released from the diluted ammonia dispenser each time.

When not in use, the inlet and outlet is sealed with aluminum tape to prevent loss of ammonia.

Example 1 b:

Other prototypes have been prepared with filters consisting of compacted glass wool. Both work well. Samples with filters made from felt pads similar to pads mounted under furniture to protect the floor from scratches work even better as they provide more flow resistance and larger pressure increase and hence temperature rise during pumping. The temperature increase causes a higher ammonia concentration that makes the leak more easily detectable. In another instance, the ammonia dispenser was filled with 140 mg CaCl 2 :8NH 3 . By in- flating a bicycle tube 700 x 25-35c to a diameter of 2.5 cm, 9-13 mg ammonia was released from the dispenser as was shown in several tests.

Prototypes in aluminum, iron and steel have been prepared with similar dimensions and work equally well.

One sample with inner diameter 2 cm and length 7 cm also works well and can be used many more times before depletion.

Example 2: System for“in-field” leak detection on a bicycle tube.

The system comprises a small diluted ammonia gas dispenser, an ammonia detector and a pump/compressor, and is used together with a leaking part.

In this particular example, the leaking part is a bicycle rubber tube. The ammonia detec- tor is a piece of ammonia cloth 5 cm by 10 cm from Precision Laboratories. The diluted ammonia gas dispenser is made from Nylon 6.6 and filled with -250 mg ammonium carbonate as in Example 1 a. The pump is a standard bicycle pump.

Example 3: System for identifying leaks for use in a professional setting like a garage or construction site.

The system comprises a diluted ammonia gas dispenser intended for extended multiple use, an ammonia detector and a pump/compressor, and is used together with a leaking part.

In this example, the diluted ammonia gas dispenser has a volume of 400 mL and is made of stainless steel SAE 304. It consists of a straight tube OD=60 mm, wall thickness 2 mm with welded Kloebber form end-caps. Each end-cap has a centered opening with a 3/8-inch thread for attaching fittings. In this example, a filter disk of glass wool match- ing the inner diameter is placed in one of the endcaps before welding the straight tube and the endcaps together. A ball valve with hose fitting is screwed onto the endcap containing the filter disk. This end will be the outlet. The other endcap (the inlet) is welded to the other end of the straight tube. The diluted ammonia gas dispenser is filled 90% with ammonium carbonate through the opening in the inlet endcap and flexible filter material (glass wool) is presses to fill the last 10%. Finally, a ball valve with hose barb is screwed onto the inlet. For operation, the inlet is connected with a hose to a pressur- ized air supply or a pump and the outlet is connected to the part to be leak tested through another hose. When the part to be leak tested is inflated, both ball valves are opened. When the de- sired overpressure is reached, one or both ball valves are closed.

When the diluted ammonia gas dispenser is not used, both ball valves are closed to prevent loss of ammonia.

The ammonia detector is a piece of ammonia cloth 10 cm by 20 cm from Precision Laboratories.

The system is used with a leaking part, e.g. a leaking hose or tube, air mattress or other inflatable items, tube systems of metals, plastics or composites or any combination thereof.

Example 4: Method of detecting leaks in a rubber tube.

A leaking bicycle tube is provided. A diluted ammonia gas dispenser similar to example 1 a is provided and is screwed onto the valve of the bicycle tube. The leaking bicycle tube is inflated using an standard bicycle pump through the diluted ammonia gas dis penser to slight overpressure. An ammonia detector cloth 5 cm by 10 cm from Precision Laboratories is provided. The surface of the tube is searched with the ammonia detector cloth until change of color from yellow to green indicates the position of the leak. A few pump strokes can be applied through the diluted ammonia dispenser when necessary during searching to maintain the overpressure until the leak is localized.