GB2504280A

GB2504280A - Discharging refrigerant from a refrigeration system by means of a capillary tube

Info

Publication number: GB2504280A
Application number: GB201213078A
Authority: GB
Inventors: Klaus Wiemer; Alexander Selinger
Original assignee: IMI Cornelius UK Ltd
Current assignee: Marmon Foodservice Technologies UK Ltd
Priority date: 2012-07-23
Filing date: 2012-07-23
Publication date: 2014-01-29
Also published as: GB201213078D0

Abstract

A method of discharging refrigerant from a refrigeration system 1 and charging the system 1 with refrigerant by means of capillary tube assemblies 9, 19 connected to the system 1 is disclosed. When discharging the system 1, the rate of flow of gaseous refrigerant through a capillary tube 13 of the assembly 9 may be controlled to reduce an operating pressure of the refrigerant to a safe level before the refrigerant is released into the surrounding area. When charging the system 1, the rate of flow of liquid refrigerant through a capillary tube 20 of the assembly 19 may be controlled to allow the liquid refrigerant to boil off into a gaseous form within the system 1. When discharging the system 1, the capillary tube 13 may be connected to a high pressure region of the refrigeration system 1, for example the outlet side of a compressor 2 for the system 1. When charging the system 1, the capillary tube 20 may be connected to a low pressure region of the refrigeration system 1, for example the pipe work associated with an evaporator 8 of the system 1.

Description

REFRIGERATION SYSTEMS

The present invention relates to refrigeration systems. The invention has application to refrigeration systems used for the cooling of draught beverages and S in particular, but not exclusively, application to beverage coolers of the type in which operation of the refrigeration system causes a bank of frozen coolant, typically ice, to form on an evaporator of the refrigeration system that is submerged in a bath of the coolant to provide a thermal reserve for cooling beverages passing through the bath during periods of high cooling demand. More especially the invention concerns servicing and/or repair of refrigeration systems during which it is necessary to discharge and charge the system with refrigerant.

Global warming is a matter of great conccrn and stcps are being takcn on a worldwide scale to reduce or eliminate the use of substances which contribute to global warming. Refrigerants have long been known to cause ozone depletion and to increase global warming when released into the atmosphere when, for example, refrigeration equipment is serviced or scrapped or when used as a propellant in aerosol containers. This has led to several refrigerants being banned or scheduled for phasing out and stringent legislation rcquiring costly capturc and controlled destruction of waste and used refrigerant.

Hydrocarbon (HC) in the form of pure propane has proven to be a possible alternative refrigerant to the more common groups of refrigerants such as chlorofluorocarbon (CFC) hydrochlorofluorocarbon (HCFC) and hydrofluorocarbon (HFC), having a global warming potential (GWP) of 3 versus GWPs in the range 1300-4000. However, due to the highly flammable nature of propane, the risk of fire or explosion has hindered its adoption.

In view of the foregoing, carbon dioxide (C02) has gained in popularity as a refrigerant, having a GWP of only 1 and being non-flammable. In addition, there is generally no requirement to capture and destroy waste or used CO2. However, a major disadvantage of CO2 is its high operating pressure within the system, typically 90 bar versus 15 bar for alternative hydrocarbon type refrigerants mentioned above. This has required the development of compressors capable of working up to maximum pressures of 130 bar and the need for great care in the repair and service of systems where CO2 is used as a refrigerant.

This is relatively easy to control in an industrial environment where the refrigeration systems are manufactured but presents problems once equipment is installed and operational and where it is not practical to return the equipment to the manufacturer or service provider for repair.

The use of CO2 as a refrigerant in the beverage dispense trade is a particular case in point as coolers for draught beverages are often heavy and bulky, installed in inaccessible locations such as basements or cellars and have a great number of inlet and outlet connections such as beer, water, CO2 for carbonation, syrup and the like.

Removal of the cooling unit would require all connections to be uncoupled and the pipes drained and result in unacceptable waste and interruption to the dispense of beverages, the retailers of which expect a rapid resumption of normal trading. This requires that all repairs are carried out to the equipment in its operating location, including those which require discharging and recharging the refrigeration system with refrigerant.

Due to the high evaporating pressures within a CO2 refrigeration system, it is often the case that compressor life is reduced and refrigerant loss is more often experienced than with earlier refrigerants.

The main steps in refrigeration system repair are as follows:- 1. Vent the system and discharge refrigerant 2. Exchange any faulty components for good 3. Pressurise and leak test the system 4. De-pressurise and evacuate the system 5. Refill the system with refrigerant CO2 6. Test operation of the equipment The same steps apply to all refrigerants, but step I can present a safety hazard where the refrigerant is C02, due to the higher operating pressure within the system. Thus, when using standard refrigeration servicing equipment in the form of a combined tube piercing and needle valve, the valve is clamped to a suitable S pail of the copper refrigeration tubing which is pierced by the clamping action and the needle valve is then used to control the discharge of refrigerant from the copper tube. However, it is possible to pierce the copper tube with the needle valve fully open and, where the refrigerant is C02, this results in a sudden and violent release of CO2. often carrying with it oil from the compressor which may cause serious injury to personnel.

Step 5 can also present problems where the refrigerant is CO2 as it is introduced into the system in gaseous form and this requires the usc of two stage high pressure regulator valves to control the CO2 flow where, in fact, it is more desirable to control flow directly. Two stage pressure regulator valves for high pressure gases are not only expensive but they are vulnerable to mishandling, their gauges require periodic recalibration and they may be subject to regulations which require them to be replaced or refurbished at regular intervals.

Thc potential for injury and costs in providing extra equipment to service engineers combined with the perceived risk of more frequent repair/maintenance of CO2 refrigeration systems may outweigh the benefits of reduced Global Warming Potential.

It is an object of the present invention to address the problems aforementioned.

More especially, the invention seeks to provide a method of safely releasing refrigerant from a refrigeration system and recharging the system with refrigerant after making any necessary repairs or servicing. The invention also seeks to provide apparatus and a kit for use in carrying out the method. It is a preferred aim of the invention to provide such method, apparatus and kit that is suitable for use with refrigeration systems in which the refrigerant is CO2.

According to a first aspect of the invention, there is provided a method of discharging refrigerant from a refrigeration system and/or charging a refrigeration system with refrigerant by means of a capillary tube connected to the refrigeration syst em.

The capillary tube provides a restriction that controls the rate of flow of refrigerant S when discharging the system and when charging the system. The method may have particular benefits for repair or servicing of refrigeration systems in which the refrigerant is CO2.

Thus, when discharging gaseous CO2 from the system, the rate of flow of CO2 is controlled as it flows through the capillary tube to reduce the high operating pressure of the CO2 to a safe level before the CO2 is released into the surrounding area. In this way a sudden and violent release of CO2 often carrying with it oil from the compressor which may cause serious injury to personncl can be avoided.

Also, when charging the system from a supply of liquid C02, the rate of flow of CO2 is controlled as it flows through the capillary tube allowing the liquid CO2 to boil off into a gaseous form thereby preventing liquid CO2 from being drawn into the compressor which may result in damage to the compressor.

It may be that when discharging CO2 from the system, the capillary tube is connected to a high pressure region of the refrigeration system. For example the capillary tube may be connected to pipe work downstream of the compressor. In one form, the system may include a discharge tube to which the capillary tube can be connected, for example by a connector at one end of the capillary tube. In one form, the discharge tube is provided on the outlet side of the compressor, preferably between the compressor and a gas cooler.

The connector may be adapted to pierce the discharge tube when it is secured to the discharge tube. Alternatively, the connector may include a device to pierce the discharge tube once thc connector is seeurcd to the discharge tube. A shut-off valve may be provided to permit/prevent discharge of refrigerant. The shut-off valve may be incorporated in the connector or may be provided at the other end of the capillary tube.

It may be that when charging the system with CO2 the capillary tube is connected to a low pressure region of the refrigeration system. For example, the capillary tube may be connected to pipe work downstream of a pressure reducing device. In one form, the system may include a charging tube to which the capillary tube can be connected, for example by a connector at one end of the capillary tube. The other end of the capillary tubc may have a connector for connecting the capillary tube to a source of CO2 such as a cylinder, preferably a cylinder of liquid CO2. In one preferred form, the charging tube is associated with the evaporator, preferably at or near to the inlet of the evaporator.

The connector for attaching the capillary tube to the charging tube may be a coupler of any suitable type, for example a push fit or compression coupling, that preferably provides a fluid-tight connection between the charging tube and the capillary tube. It may be that the capillary tube is provided with a length of tube similar to the charging tube to facilitate connection of the capillary tube to the charging tube.

The connector for attaching the capillary tube to the source of liquid CO2 may be a coupler of any suitable type for connecting to the CO2 source. Thus, where the CO2 source is a cylinder having an outlet valve, the coupler may be adapted for connecting to the valve, preferably providing a fluid-tight connection between the capillary tube and the cylinder.

It may be that the amount of CO2 introduced when charging the system is controlled by monitoring change in weight of the CO2 source and closing the outlet valve when the required amount has been introduced. It may be that the compressor is operated if insufficient CO2 is added to assist introduction of CO2 when charging the system.

According to a second aspect of the invention, there is provided apparatus for usc when discharging refrigerant from a refrigeration system or when charging the refrigeration system with refrigerant, the apparatus including a capillary tube adapted for connection to the refrigeration system to control tiow of refrigerant when discharging refrigerant from the system or when charging the system with refrigerant.

The apparatus may be used when carrying out the method of the first aspect of the S invention and may have particular benefit when used for servicing or repairing refrigeration systems employing CO2 as the refrigerant. The apparatus may include separate capillary tubes for discharging CO2 from the system and for charging the system with CO2.

The capillary tube of thc apparatus for discharging CO2 from the system may be adapted for connection to pipe work of the refrigeration system. In one form the capillary tube may be connected to a high pressure region of the refrigeration system. The pipe work may include a discharge tube in the high pressure region and the capillary tube may have a connector at one end that may be adapted to pierce the discharge tube when it is secured to the discharge tube. Alternatively, the connector may include a device to pierce the discharge tube once the connector is secured to the discharge tube. The other end of the capillary tube may be open.

A shut-off valve may be provided to allow discharge of refrigerant to be further controlled. The shut-off valve may be incorporated in the connector or may be provided at the other end of the capillary tube.

The capillary tube of the apparatus for charging the system with CO2 may be provided with a connector at one end for connecting the capillary tube to pipe work of the refrigeration system and a further connector at the other end for connecting the capillary tube to a source of CO2 such as a cylinder, preferably a cylinder of liquid CO2 In one form the capillary tube may be connected to a low pressure region of the refrigeration system. The pipe work may include a charging tube in the low pressure region to which the capillary tube is connected.

According to a third aspect of the invention, there is provided a kit for use when servicing or repairing a refrigeration system, the kit including a capillary discharge tube for connecting to the refrigeration system when discharging refrigerant from the system and a capillary chargc tube for connecting to the rcfrigeration systcrn when charging the system with refrigerant.

The capillary discharge tube may connect to a high pressure region of the refrigeration systcm. For example, the system may have a process discharge tube to which the capillary discharge tube can be secured by a connector at one end of the capillary dischargc tube. The other end of the capillary discharge tube may be open. A shut-off valve may be incorporated in the connector or may be provided at the other end of the capillary tube. The connector may be adapted to pierce the process tube or provided with a device to pierce the process tube.

The capillary charge tube may connect to a low pressure region of the refrigeration system. For example the capillary discharge tube may have a connector at one end for connection to a process charge tube of the system and a further connector at the other end for connection to a source of refrigerant.

The kit may be used with refrigeration systems in which the refrigerant is CO2.

The kit may include a source of CO2 that can be used when charging the system.

The source may be a cylinder containing CO2. preferably liquid CO2.

These and other features, benefits and advantages of the invention in its various aspects will be apparent from the description of embodiments of the invention that now follows by way of example only with reference to the accompanying drawings in which: Figure 1 illustrates the main components of a refrigeration system embodying the S invention suitable for use in beverage cooling applications; Figure 2 illustrates in schematic form the refrigeration system of Figure 1; and Figure 3 shows a detail of the charging capillary tube assembly.

Referring to the drawings, a sealed refrigeration system 1 is shown containing CO2 refrigerant within a circuit including a compressor 2, a gas cooler 3, a pressure relief burst disc 4, a tube in tube heat exchanger 5, a strainer 6, a capillary tube 7 and an evaporator 8. A suitable refrigerant grade CO2 is available under the trade name R744. R744 is a high-purity gas with a nioisture content of less than 10 parts per million. It will be understood that we do not intend the invention to be limited to the use of R744 and that other refrigerant grade CO2 may be employed.

The refrigeration system 1 may be employed with a beverage cooler (not shown) for a beverage dispense system (not shown) where the evaporator 8 is located in a reservoir containing a liquid coolant, for example water, and product from a product source, for example a keg of beer, passes in a product line through the reservoir to cool the product by heat exchange with the coolant prior to passing to an outlet for dispense of the product into a glass or similar vessel.

Typically, the cooler is located remotely from the outlet, for example in a cellar, and chilled product passes from the cooler to the dispense location in readiness for dispense from the outlet via an insulated sleeve containing a bundle of tubes commonly referred to as a python.

Coolant in the reservoir may pass via a flow line contained within the python to the dispense location and return to the reservoir via a return line also contained within the python. The flow line, return line and product line(s) are preferably in thermal contact within the python to minimise the warming effect of ambient conditions upon the product within the python. The coolant may be circulated by a pump driven by a motor. The pump motor may be a single speed, multi-speed or infinitely variable speed motor.

S During operation of the refrigeration system 1, coolant contained within the reservoir freezes and forms a bank of frozen coolant upon the evaporatorS. During operation of the dispense system, coolant in the reservoir is warmed up by heat exchange with warmer product passing through the cooler from the product source to the outlet and by mixing with warmer coolant returning to the reservoir from the python.

Heat from the product and from the return flow of coolant is conducted to the bank of frozen coolant causing it to erode and the refrigeration system may be controlled to maintain the thickness of the frozen coolant between upper and lower limits for maintaining a stable, even coolant temperature in the reservoir. Heat transfer may be enhanced by circulating the coolant within the reservoir by means of an agitator.

The agitator may be combined with the pump and driven by a common motor.

Alternatively the agitator motor may be separate from the pump and driven by a separate motor. Such separate agitator motor may be a single spced, multi-speed or infinitely variable speed motor.

The coolant may be water that forms an icc bank on the evaporator S. The water may include an additive that suppresses the freezing point of the water. For example, the coolant may be a water/glycol mixture, a water/alcohol mixture or a water/salt (brine) mixture. Other additives such as corrosion inhibitors may also be provided in the coolant.

In operation of the refrigeration system 1 during the ice building phase of the beverage cooler described above, CO2 refrigerant is circulated around the refrigeration system 1 by compressor 2, typically raising the pressure to around 90 bar. From the compressor 2, the CO2 refrigerant passes through gas cooler 3, typically reducing its temperature from around 120°C to around 45°C. From the gas cooler 3, the CO2 refrigerant passes through heat exchanger 5 where further CO2 cooling takes place by heat exchange with cold gas returning from evaporator 8. From the heat exchanger 5, the CO2 refrigerant passes through strainer 6 where any particles of debris are removed and held. Thc CO2 refrigerant then travels through a fine capillary tube 7 which provides a restriction that enables the compressor 2 to generate its high discharge pressure. The sudden release of pressure that occurs when the CO2 refrigerant leaves the capillary tube 7 causes drastic cooling of the gas which then passes through the evaporator 8 and typically cools the evaporator 8 to around minus 10°C whereupon the coolant in the reservoir of the beverage cooler forms the bank of frozen coolant on the surface of evaporator 8 which serves as a thermal reserve for beverage cooling applications as described above. The low pressure CO2 refrigerant leaving the evaporator 8 is drawn into the suction side of the compressor 2 via heat exchanger 5 where it serves to further cool high pressure CO2 refrigerant flowing from the gas cooler 3 to the evaporator 8 as described previously. The cycle continues as long as cooling is required for beverage cooling applications as described above.

When it is required to service or repair the refrigeration system 1 on location (i.e. where the system is installed), the main steps involved are as follows:- 1. Vent and discharge refrigerant from the system 2. Exchange any faulty components for good 3. Pressurise and leak test the system 4. De-pressurise and evacuate the system 5. Refill the system with refrigerant CO2 6. Test operation of the equipment The present invention is concerned with a method, apparatus and kit for carrying out steps I and 5. The remaining steps are conventional and are not described in detail herein as they will be familiar to those skilled in the art.

When carrying out step 1 to discharge CO2 refrigerant from the refrigeration system 1, for example when servicing or repairing the system 1, a capillary tube assembly 9 is secured to a process discharge tube 10 which is incorporated into the high pressure pipe work of the system 1. In this embodiment, the discharge tube 10 is located downstream of the compressor 2 between the compressor 2 and the gas cooler 3 although this may not be essential and other locations of the discharge tube 10 in the high pressure pipe work may be employed. The outermost end 12 of the process tube 10 is closed and sealed, for example by crimping and soldering.

S

The capillary tube assembly 9 includes a length of capillary tube 13, typically 0.8mm inside diameter x 3000mm long, having a connector 14 at one end that is preferably clamped to the process tube 10. The connector 14 may be adapted to pierce the process tube 10 to allow CO2 refrigerant to escape via the capillary tube 10. The connector 14 may pierce the tube 10 automatically as it is clamped to the tube or it may be provided with a device that is operable to pierce the tube once it is clamped to the tube During the discharging operation, the rate of flow of CO2 from the system I is controlled by the restriction of the capillary tube 13 such that the flow rate of escaping gas is greatly restricted and rendered safe. The internal diameter and/or length of the capillary tube 13 may be chosen to provide any required restriction for controlling flow of CO2 from the system 1 when discharging the system 1 and it will be understood the dimensions providcd are exemplary only and arc not intended to be limiting on the scope of the invention. A capillary tube having a substantially uniform internal diameter may be employed but this may not be essential and in a modification (not shown), the internal diameter may be non-uniform. It may be that the capillary tubc can be replaced by a tubc in which flow is restricted at at least one and preferably several positions along the length of the tube for controlling flow of CO2 from the system.

Connector 14 may have incorporated into it a shut-off valve 15 or, alternatively, the shut-off valve 15 may be connected to the free end of the capillary tube 13 for instances where it is desired to shut-off gas flow before the system is empty. For example, where a system had been accidentally ovcrcharged with refiigcranl.

When carrying out step 5 to charge the refrigeration system 1 with CO2 refrigerant, a portable CO2 cylinder 16 may be used which may be of the type having a dip tube extending within it from an outlet valve 17 and terminating at the bottom of the interior of the cylinder 16. CO2 refrigerant may be contained in the cylinder 16 under sufficient pressure to maintain it in liquid form and thus, opening valve 17 will discharge liquid CO2. If a cylinder with internal dip tube is not readily available, a regular cylinder may be used in an inverted position to ensure that S liquid CO2 is discharged, as shown in Figure 2.

The shut-off valve 17 of the CO2 cylinder 16 is connected to a charging process tube 18 which is incorporated into the low pressure pipe work of the refrigeration system 1 downstream of the capillary tube 7 by means of a capillary tube assembly 19. In this embodiment, the charging process tube 18 is provided at the inlet to the evaporator 8 but this may not be essential and other locations of the charging process tube 18 in the low pressure pipe work may be employed.

Thc capillary tube assembly 19 includes a length of capillary tube 20, typically 1.2mm internal diameter by 2000mm long, having a connector 21 at one end for attaching to the shut-off valve 17 and a short length of copper tube 22 at the other end, preferably of thc same outside diamctcr as the process tube 18, to enable a leaktight joint to be made using a standard straight coupler 23 which may be of the compression type. As best shown in Figure 3, the connector 21 includes a threaded union nut 24, nipple 25 and seal 26 for releasable connection to the shut-off valve 17.

When charging the refrigeration system 1 with CO2 refrigerant after leak testing has been carried out following any servicing or repairs, the CO2 cylinder 16 is connected to the charging process tube 18 by the capillary tube assembly 19 and the coupler 23. At this point, shut-off valve 17 remains closed and the CO2 cylinder 16 should be disposed to discharge liquid CO2 as described earlier and supported by a suitable accurate means of weighing such as scales 27.

Thc refrigeration system 1, including capillary tube assembly 19 is now ready to be evacuated and vacuum connections sealed after removal of the vacuum pump. This is standard refrigeration practice and will not be described further.

By opening shut-off valve 17 on CO2 cylinder 16, liquid CO2 is introduced into the refrigeration system 1 via the capillary tube assembly 19 and process tubc 18, assisted by the aforementioned vacuum in the system 1, until flow stops as pressure within the system 1 and CO, cylinder 16 equalise or the correct charge has been introduced, as indicated by the difference in the weight of the CO2 cylinder 16 by the scales 27, whichever is the sooner.

If insufficient CO2 has been introduced into the system I when the flow stops as a result of pressure equalisation, the compressor 2 may be operated and the resulting drop in pressure within the system downstream of the charging process tube 18 will allow further CO2 to flow into the system 1 until the specified charge weight is achieved.

During the charging operation, the rate of flow of CO2 into the evaporator S is controlled by the restriction of the capillary tube 20, allowing the liquid CO2 to boil off into gaseous form thereby preventing liquid CO2 from being drawn into the compressor 2 which may rcsult in damage to the comprcssor 2. The internal diameter and/or length of the capillary tube 20 may be chosen to provide any rcquircd rcstriction for controlling flow of CO2 into the system 1 whcn charging the system I and it will be understood the dimensions provided are exemplary only and are not intended to be limiting on the scope of the invention. A capillary tube having a substantially uniform internal diameter may be employed but this may not be essential and in a modification (not shown), the internal diameter may be non-uniform. It may be that the capillary tube can be replaced by a tube in which flow is restricted at at least one and preferably several positions along the length of the tube for controlling flow of C02 from the system.

After charging, sealing of process tube 18 by crimping and soldering, system leak detection and cooler testing are standard practice and will not be described further.

It can be seen from the above description that the present invention provides means of safely discharging high pressure CO2 refrigerant from a refrigeration system and recharging same by using capillary tubes to control flow, reducing the possibility of personal injury and the need for expensive pressure regulators which may be subject to abuse and inconvenient and costly maintenance procedures.

Furthermore, controlling flow of CO, when charging a system rather than pressure is preferable as it requires no adjustment to account for pressure variation in the CO2 supply or system duc to ambicnt conditions.

The use of a capillary tube to control fill rate also has the benefit of allowing the refrigeration system compressor to draw in additional CO2 to make up the charge weight without risking damage to the compressor by the ingress of liquid CO2.

It will be understood that the invention is not limited to the embodiment above-described and that various modifications and improvements can be made without departing from the principles and concepts of the invention as described herein.

Thus, while the invention has been described with reference to refrigeration systems employed for beverage cooling, it extends to and includes refrigeration systems for other applications and uses. Moreover, while the invention has particular benefit when used with refrigeration systems in which the refrigerant is C02, it may have wider application to include refrigeration systems in which other types of refrigerants are employed.

Claims

CLAIMS1. A method of discharging refrigerant from a refrigeration system and/or charging a refrigeration system with refrigerant by means of a capillary tube connected to the refrigeration system.
2. The method of claim 1 wherein the refrigerant is CO2.
3. The method of claim 2 wherein, when discharguig gaseous CO2 from the system, the rate of flow of CO2 is controlled as it flows through the capillary tube to reduce an operating pressure of the CO2 to a safe level before the CO2 is released into the surrounding area.
4. The method of claim 2 or claim 3 wherein, when charging the system from a supply of liquid CU2, the rate of flow of CO2 is controlled as it flows through the capillary tube allowing the liquid CO2 to boil off into a gaseous form.
5. The method of any of claims 2 to 4 wherein, when discharging CO2 from the system, the capillary tube is connected to a high pressure region of the refrigeration system.
6. The method of claim 5 wherein, the capillary tube is connected on the outlet side of a compressor for the system.
7. The method according to claim 5 or claim 6 wherein, a connector for the capillary tube is adapted to pierce pipe work of the system to which it is connected.
8. The method according to claim 7 wherein the connector includes a shut-off valve
9. The method according to claim 7 wherein a shut-off valve is provided at the end of the capillary tube remote from the connector.
10. The method of any of claims 2 to 9 wherein, when charging the system with CO2. the capillary tube is connected to a low pressure region of the refrigeration system.S
II. The method of claim 10 wherein the capillary tube is connected to pipe work associated with an evaporator of the system.
12. The method of claim 10 or claim 11 wherein the capillary tube is connected to the pipe work by a connector at one end of the capillary tube and the other end of the capillary tube has a connector for connecting the capillary tube to a source of CO2.
13. The method of claim 12 wherein the source is a cylinder of liquid CO2.
14. The method of claim 12 or claim 13 wherein the amount of CO2 introduced when charging the system is controlled by monitoring change in weight of the CO2 source.
15. The method of any preceding claim wherein separate capillary tubes are used to discharge and charge the refrigerant.
16. Apparatus for use when discharging refrigerant from a refrigeration system or when charging the refrigeration system with refrigerant, the apparatus including a capillary tube adapted for connection to the refrigeration system to control flow of refrigerant when discharging refrigerant from the system or when charging the system with refrigerant.
17. Apparatus according to claim 16, for use with systems containing CO2 as the refrigerant.
18. Apparatus according to claim 17 wherein the capillary tube for discharging CO2 from the system is adapted for connection to a high pressure region of the system.
19. Apparatus according to claim 17 or claim 18 wherein the capillary tube has a connector at one end for connection to pipe work of the system.
20. Apparatus according to claim 19 wherein the connector is adapted to pierce the discharge tube
21. Apparatus according to claim 19 or claim 20 wherein the connector includes a shut-off valve.
22. Apparatus according to claim 19 or claim 20 wherein a shut-off valve is provided at the end of the capillary tube remote from the connector.
23. Apparatus according to any of claims 17 to 22 whercin the capillary tube for charging the systcm with CO2 is adapted for connection to a low pressure region of the system.
24. Apparatus according to any of claims 17 to 23 wherein the capillary tube for charging the system with CO2 is provided with a connector at one end for connecting the capillary tube to pipc work of the system and a further connector at the other end for connecting the capillary tube to a source of CO2.
25. A kit for use when servicing or repairing a refrigeration system, the kit including a capillary discharge tube for connccting to the refrigcration system when discharging refrigerant from the system and a capillary charge tube for connecting to the refrigeration system when charging the system with refrigerant.
26. A kit according to claim 25 wherein the capillary discharge tube connects to a high pressure region of a system.
27. A kit according to claim 25 or claim 26 wherein the capillary charge tube connects to a low pressure region of the system.
28. A kit according to any of claims 25 to 27 wherein the kit is adapted to be used with refrigeration systems in which the refrigerant is CO2.
29. A kit according to claim 28 further including a source of CO2 that can be used when charging the system.
30. A kit according to claim 29 wherein the source is a cylinder containing liquid CO2.