GB2454879A

GB2454879A - Leakage test for refrigerant carrying pipe.

Info

Publication number: GB2454879A
Application number: GB0722734A
Authority: GB
Inventors: Thomas Ian Melling; Peter David Chitson
Original assignee: VULKAN IND Ltd
Current assignee: VULKAN IND Ltd
Priority date: 2007-11-20
Filing date: 2007-11-20
Publication date: 2009-05-27
Also published as: GB0722734D0

Abstract

Testing for a leak in a pipe for carrying refrigerant in a refrigeration unit or an air conditioning system of a building by introducing into the pipe a quantity of a detection gas comprising hydrogen and testing for the presence of hydrogen in the region of the external surface of the pipe.

Description

Detection Method The present invention relates to a method and kit for detecting leaks in pipes, in particular pipes used in cooling systems. In particular the present invention is able to detect leaks in pipes which carry a refrigerant.

A refrigerant is a material which is used in a heat cycle that undergoes a phase change from a gas to a liquid and back again. Refrigerants are commonly found in refrigeration and freezer units and in air conditioning systems.

Refrigerant compounds are typically halogeriated hydrocarbons. Previously chlorofluorocarbon materials were used but these are damaging to the ozone layer.

Small fluorinated molecules are now commonly used, for example 1,1,1,2-tetrafluoroethane and mixtures of difluoromethane and pentafluoromethane.

Before a refrigerant can be supplied to a pipe system, for example in a rerigeration unit or air conditioning system, the system must be tested to check if any leaks * are present. One common method of detecting leaks is to fill the pipes with a high pressure nitrogen system, leave **** *... 25 the pipes overnight and detect any drop in pressure. If a pressure drop is detected the source of the leak will then *.** have to be investigated. This is a very time consuming operation. S... * S S S. S

It is the aim of the present invention to provide an improved method of detecting a leak in pipes used to carry ref rigerants.

According to a first aspect of the present invention there is provided a method of testing for a leak in a pipe for carrying refrigerant in a refrigeration unit or an air conditioning system of a building, the method comprising: (a) introducing into the pipe a quantity of a detection gas comprising hydrogen; and (b) testing for the presence of hydrogen in the region of the external surface of the pipe.

Preferably the detection gas is not flammable, suitably as measured by 1S010156.

Preferably the detection gas comprises less than 7% hydrogen by volume, for example less than 6%, preferably less than 5.7%, more preferably less than 5.5%, for example less than 5.4%, preferably less than 5.3% and most preferably less than 5.2%. Suitably the detection gas comprises at least 0.5% hydrogen by volume, preferably at least 1%, more preferably at least 2%, for example at least 3%, preferably at least 4%, more preferably at least 4.5%, for example at least 4.7% and most preferably at least 4.8% by volume. * **

In addition to hydrogen, the detection gas suitably *S** comprises an inert gas, for example argon and/or nitrogen.

*.. Most preferably the detection gas consists essentially of **S.

* nitrogen and hydrogen.

****.* * S Suitably the detection gas comprises at least 80% *:*. 30 nitrogen by volume, preferably at least 85%, more preferably at least 90%, for example at least 92%, and most preferably it comprises at least 94% nitrogen by volume. It may comprise up to 99% nitrogen by volume, for example up to 98%, up to 97%, or up to 96%.

Preferably the detection gas is dry. It may suitably be dried by it passing through a desiccant prior to use.

Suitable desiccants include silica gel, activated alumina and molecular sieves.

The detection gas may be prepared by mixing very dry gases. Dry nitrogen and dry hydrogen are commercially available from BOC.

Suitably the detection gas comprises less than 100 ppm water, preferably less than 50 ppm water, most preferably less than 25 ppm water.

The method of the present invention may be used to test for a leak in a wide variety of refrigeration units and air conditioning systems. By refrigeration unit we mean to refer to a cooled chamber in which items, for example food stuffs, may be stored in a chilled environment. The chambers may be relatively small, for * example those found in domestic refrigerators and freezers. The present invention may also be used to detect *.*.

for leaks in pipes of larger commercial or industrial cooling chambers, for example walk-in cold rooms used for *S** * storage in supermarkets and the like. The method may be ***.** * used to test for leaks in pipes of both refrigerators and **** : freezers. *. *

* *. 30 S ** The method of the present invention is suitably used to test for leaks in an endless or closed-loop pipe system which when in normal use is filled with a refrigerant which circulates through the system. The present invention may be used to test for leaks in a closed-loop pipe system having a volume of between 0.2 dm3 and 100 dm3. For larger systems it may be necessary to isolate parts of the system and test one section at a time.

In some embodiments the method of the present invention may be used to test refrigeration units having an internal pipe volume of 2 dm3 or less, for example 1 dm3 or less or 0.5 dm3 or less. It may be used to test refrigeration units having an internal pipe volume of up to 10 dm3, for example up to 5 dm3 or up to 2.5 dm3.

The method of the present invention is suitable for testing air conditioning in buildings of any size. It may be used to test the pipes of small domestic or commercial units, including those comprising only a single room. It could also be used to test the pipes of very large buildings, for example large shopping complexes, hotels or office blocks.

The method of the present invention may be used to * test an air conditioning system of a small building, the system having an internal pipe volume of from 0.5 to 50 *...

dm3, for example 1 to 25 dm3, or 2.5 to 10 dm3. It may be **** used to test the air conditioning system of a large building in which the system has an internal pipe volume *S*...

* of up to 100 dm3, for example up to 80 dm3 or up to 60 dm3. S... * * * ** .

*** 30 Suitably in step (a) of the method of the present invention, the quantity of detection gas introduced into the pipe to be tested is sufficient to provide a pressure inside the pipe of between 0.1 and 3 MPa, preferably between 0.2 and 2 MPa, more preferably between 0.3 and 1.5 MPa, for example between 0.4 and 1 MPa.

The endless closed-loop pipe system to be tested will suitably include an access valve, provided for example by a T-shaped joint in the pipe. The present invention is suitably used to test for a leak in a pipe which has not yet been used and typically comprises air at atmospheric pressure. Inlet of the detection gas from a pressurised source may be controlled by use of an appropriate regulator.

Step (b) comprises testing for the presence of hydrogen in the region of the external surface of the pipe. This may be carried out by any suitable means. A hydrogen detector is suitably used, preferably a handheld device.

Suitably the hydrogen detector is passed along the length of the pipe of a closed-loop refrigeration or air conditioning system, in the region of the external surface thereof. As such the present invention will enable a * person carrying out the method to identify the location of a leak in such a system. **.. * *

*... 25 The detector should be positioned in the region of the *a..

external surface of the pipe. It is preferably held as * close to the external surface of the pipe as possible but it need not be held directly adjacent thereto. An advantage of the present invention is that due to the small size of hydrogen it is able to readily penetrate plaster and the like and so a leak could be detected in a pipe which has, for example, been plastered over.

The level of hydrogen that can be detected is limited by the accuracy of the detector. Suitably the method of the present invention may be used to detect levels of hydrogen of 100 ppm or less, preferably 50 ppm or less, for example 30 ppm, 20 ppm, 15 ppm, 10 ppm or 5 ppm.

Such low levels of hydrogen may be detected because the background levels of hydrogen present in the air are very low (about 0.5 ppm) . Thus the method of the present invention is highly sensitive.

The method of the present invention may be used to very small flaws in pipes. It may be used to detect flaws of less than 1 mm, those of less than 0.1 mm or those of less than 10 microns, for example less than 1 micron, or less than 0.1 microns, or less than 10 nm. In some cases, flaws of the order of magnitude of 1 nm may be detected.

A particular advantage of the present invention is the speed at which the method can be carried out. Suitably a refrigeration unit or air conditioning unit having a * volume of up to 10 dm3 can be tested for a leak in less than 2 hours, preferably less than 1 hour, or less than 30 * *** minutes. For example, an air conditioning unit suitable for carrying 3 to 4 kg of refrigerant can be tested for *S*.

* leaks in 15 minutes.

** S... * S S...

.. : Suitably after the detector has been passed along the 30 length of the pipe, the closed-loop system may be vented to air in order to release the detection gas. If a closed-loop pipe system has been found not to include leaks, it can then be filled with refrigerant. It is suitably vented to air and then evacuated to a pressure of about 0.01 MPa. Refrigerant is then delivered to the system.

According to a second aspect of the present invention there is provided a kit for use in the method of the first aspect, the kit comprising a source of detection gas and a detection device able to detect hydrogen.

Preferred aspects of the second aspect are as defined in relation to the first aspect.

Preferably the source of detection gas comprises a cylinder comprising said gas. The volume of the cylinder may vary according to the intended use thereof. If the kit is to be used to test small refrigeration units a cylinder of 1 to 4 dm3, for example 1.5 to 2.5 dm3 may suitably be used. If the kit is to be used to test larger systems, a cylinder size of S to 25, for example 5 to 15 or 8 to 12 dm3 may be provided. In some embodiments, very large cylinders holding up to 60 Kg of gas may be used.

Preferably the kit of the second aspect is readily portable. Preferably the detection gas is provided in a lightweight cylinder. Suitably the source of detection gas comprises an aluminium cylinder comprising said gas. * * S...

*.S...

* Suitably when full, a cylinder of detection gas has a pressure of between 1 and 50 MPa, preferably between 5 and ** 30 30 MPa, for example between 10 and 20 MPa, suitably about MPa.

Preferably the kit further comprises an adapter for connection to the cylinder to enable detection gas to be delivered to the pipe to be tested. A length of tubing may also be provided. The use of a non-flammable gas enables a standard adaptor to be used if desired. Preferably the apparatus includes a regulator to control the flow of detection gas.

The detection device may comprise any suitable hydrogen detector. Preferably it is a hand held device.

It suitably includes a sensor able to detect a change in hydrogen gas concentration. Most preferably it comprises a heated wire which changes resistance when in contact with hydrogen. Suitably the detection device comprises is electrical components able to convert the measurements taken by the sensor into a simple easy to read form. It may, for example be provided on a digital display.

Preferably however the device is provided with one or more indicators that signal whether the hydrogen is within a predetermined set level. Thus it may be provided with an audio alarm which sounds when an excess of hydrogen is present. Alternatively it may vibrate or be provided with **.. a light which illuminates or flashes when a predetermined *...

level is reached. In some embodiments, the device may be provided with more than one indicator. For example it may * * **** be provided with one indicator which signals when a slight ****** * excess of hydrogen is present and another indicator which *: signals when levels are significantly high. S. S

S SS * S.

In one especially preferred embodiment, the device includes three LED indicators. One is illuminated when the hydrogen level is acceptable, a second is illuminated when the level is marginally high and the third is illuminated when the hydrogen level is unacceptably high.

These lights may be colour coded, for example, green, amber, red, to provide a simple "traffic-light" indicator system. The levels may be adjusted by calibration of the detector to fit to desired requirements: the acceptable leak tolerance may vary for different systems and applications.

The present invention is highly advantageous. It provides a quick and efficient method of checking for leaks in a refrigeration unit or the air conditioning system of a building. It uses cheap, non- flammable detection gas which is not toxic and not harmful to the environment.

The invention will now be further described by way of the following non-limiting example.

A kit for detecting a leak was provided comprising a dm3 aluminium cylinder comprising a mixture of dry gas containing 5% hydrogen by volume and 95% nitrogen, at an initial pressure of 15 MPa. The kit also included a *..,. handheld hydrogen detector. The detector included a S...

.. 25 sensor comprising a heated wire which changed resistance *, upon contact with hydrogen. This change in resistance was * . *..

calibrated for hydrogen levels of 5 ppm, 10 ppm and 15 * ppm. The detector was designed to illuminate a green light a hydrogen levels of 5 ppm, an amber light at 30 hydrogen levels of 10 ppm, and a red light at hydrogen levels of 15 ppm or above.

The kit was lightweight and easily carried to a site for testing. Once at the site, the cylinder was fitted with a regulator, a hose and a female adaptor. The adaptor was connected to a corresponding male adaptor on the system to be tested.

In this case the system to be tested was a new air conditioning system of a building which had not yet been used but in which the system was expected to hold 3 to 4 dm3 of refrigerant. The detection gas was introduced into the system to provide a pressure in the system of 1 MPa.

This was controlled by use of the regulator.

The detection device was switched on and the sensor thereof passed along the external surface of the pipe.

The green light was illuminated at all times indicating that it was safe to introduce refrigerant into the pipe.

The detection gas cylinder was closed and disconnected from the system. The access valve was opened and the detection gas allowed to vent to the atmosphere. The system was then ready to be filled with refrigerant.

The kit of this example has also been used to test .... 25 for leaks in evaporator components prior to fitting the same in a domestic refrigerator. S.'

S

S..... * S

S * . . S. 4

S * S a c

Claims

Claims 1. A method of testing for a leak in a pipe for carrying refrigerant in a refrigeration unit or an air conditioning system of a building, the method comprising: (a) introducing into the pipe a quantity of a detection gas comprising hydrogen; and (b) testing for the presence of hydrogen in the region of the external surface of the pipe.
2. A method according to claim 1 wherein the detection gas comprises from 4 to 5.5% hydrogen by volume.
3. A method according to claim 1 or claim 2 which further comprises nitrogen.
4. A method according to any preceding claim wherein the detection gas comprises less than 50 ppm water.
5. A kit for use in the method of any preceding claim, the kit comprising a source of detection gas and a detection device able to detect hydrogen.
6. A kit according to claim 5 wherein the source of *.S.

2s detection gas comprises an aluminium cylinder comprising said gas. * * **..

*S***i * 1
7. A kit according to claim 5 or claim 6 wherein the detection device comprises a handheld hydrogen detector. S. * * S *

S I
8. A method or kit substantially as hereinbefore described with reference to the example.