Page 1 Illustrated guide to 13 common leaks

The Institute of Refrigeration, working with the Carbon Trust, brings you REAL Zero – Refrigerant Emission and Loss Zero. The aim of this project is in the title – zero refrigerant loss. The project offers practical assistance to everyone involved in purchasing, designing, installing, servicing, maintaining and owning refrigeration equipment to help them reduce leaks.

Refrigeration and air conditioning service and maintenance engineers can have a significant impact on refrigerant leakage.

• Good service and maintenance reduces current leaks and leakage potential. • Inadequate service and maintenance can increase the risk of leakage and hence increase the environmental impact of RAC systems.

To make your service and maintenance more effective in reducing leaks it helps to know the common leak points – here are the top 13. The causes of leaks at each point are explained as is, more importantly, how they can be avoided. For more details about leakage reduction, see the Guide to good leak testing from www.realzero.org.uk

1. Shut-off and ball valves Page 3 2. Schrader valves Page 3 3. Flare joints Page 3 4. Mechanical joints and flanges Page 4 5. Pressure relief valves and fusible plugs Page 4 6. Shaft seals Page 5 7. Condensers Page 5 8. Line tap valves Page 6 9. Pressure switches Page 7 10. O rings Page 7 11. Capillary tubes Page 8 12. Return bends on evaporators and condensers Page 8 13. Condensate tray pipework Page 9

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Leak point Likely causes Solutions

1. Shut-off and ball valves • Wear of the • Ensure that the gland packing gland is tightened. between the • Wrap the valve with a valve body and damp rag while spindle shaft as brazing. it becomes compacted with age and use. • Overheating during installation. Always cap valves – most • Caps not fitted. leaks occur at uncapped valves.

2. Schrader valves Likely causes Solutions • Valve cores • Remove the core when damaged brazing the fitting in; during brazing. ensure the valve body • The cores not has cooled before tightened replacing the core. correctly during • Use the correct tool to replacement. replace / tighten the • Deterioration of core. internal seals • Ensure the cap is fitted over time. and has a seal (in good • Caps not fitted condition) in place. or have no O- ring seal.

3. Flare joints Likely causes Solutions • Loosening of Where possible, avoid the flare nut using flare connections. If due to thermal they cannot be avoided: expansion / • Use flare solder contraction due adaptors (factory to a wide produce flares). Ensure temperature the copper seal is variation, located correctly. especially • If you have to make a where those at flare, cut the pipe work the outlet of with a pipe cutter and expansion de-burr using the valves. correct tool. Use an • Poor joint eccentric flaring tool preparation and ensure the correct (causing amount of pipe is

leakage from protruding through your initial flaring block.

Page 3 Flare joints continued.. installation). • Check the flare size • Over tightening, and that it does not foul leading to the flare nut on the damage at the pipe. copper flare • Lubricate the flare and face and the nut face with a small flare nut. amount of refrigeration • Under grade oil. tightening of the • Don’t over or under flare. tighten the flare nut – use a torque wrench to the setting provided by the equipment manufacturer.

4. Mechanical joints and flanges Likely causes Solutions There are a variety joints and flanges • Incorrectly • Avoid using PTFE on on a system e.g. drier core lids etc. prepared joint HFC refrigerants - use Not replacing an appropriate thread gaskets. sealant • Uneven • Replace gaskets on tightening of flanges and remove all flanges. the old gasket material • Incorrectly before applying the torque used for new one. tightening bolts. • Tighten flanges down evenly applying the ‘opposites’ rule until the flange is seated correctly. • Use a torque wrench to carry out the final tensioning of flange bolts.

5. Pressure relief valves (PRVs) Likely causes Solutions and fusible plugs (over-pressure • Fusible plugs Fusible plugs protection) – wide • Where possible, avoid

temperature using fusible plugs. If and / or possible, replace them pressure with a PRV. variations weaken the • Always leak test bond between fusible plugs. the solder core and the plug. • PRVs - do not PRVs reseat when the • Always leak test the pressure drops outlet of PRVs. after release and often leak • If a PRV is leaking across the PRV replace it with an

Page 4 seat during equivalent rated PRVs continued normal device. operation. • Do not cap the PRV if it is leaking. • Use dual PRVs with a change over valve where possible. • Use a bursting disc in conjunction with the PRV where possible. It forms part of the PRV assembly and often has a tell tale gauge to indicate rupture.

6. Shaft seals (open type Likely causes Solutions compressors) • General wear • Regular observation of over time, oil leakage rate into indicated by an shaft seal collection increased oil vessel to check oil loss loss from the does not increase. shaft seal or • Leak testing of the refrigerant shaft seal with the leakage. compressor switched • Lubrication off. failure. • Using the correct type • Incorrect fitting of shaft seal and of a new shaft following the proper seal. procedure when replacing the shaft • Incorrect shaft seal. alignment. • Excessive crankshaft end float or bearing damage.

7. Condensers Likely causes Solutions Shell and tube Shell and tube

condensers condensers • Ensure adequate • Corrosion of the corrosion prevention copper and mild scheme is in place e.g. steel if the chemical dosing. water circulating in • Regular inspection to the tubes is not monitor potential treated corrosion level. correctly. Leaks • Regular maintenance can be and monitoring. Where particularly hard a leak has occurred in to locate, as the tube bundle it is they cannot be often false economy to

Page 5 seen – replace one tube, as condensers continued refrigerant the rest of the tubes might be are probably in a detected in the similar condition and water, but will fail. usually the leak is only detected by carrying out a full pressure test of the system.

Air-cooled condensers Air cooled condensers

• Always position • Corrosion due condensers on a level to aggressive base. air. • Repair or replace out • Impact damage of balance fans. due to foreign • Check the fin block for bodies in the air signs of oil. stream. • When replacing a • Vibration condenser, select it causing carefully, especially if it premature is going into an failure of the aggressive tube bundle. environment e.g. on the coast.

8. Line tap valves Likely causes Solutions • Poor fitting of • Ensure the correct size the line tap onto of tap valve is being the pipe, or used and read the being fitted to instructions for its badly formed or installation. flattened pipe • Fit a line tap to access work. a system, and then • Use of the braze a Schrader wrong size line connector to replace it tap – do not leave the line tap valve on the • Loosening of system. the line tap valve due to • Leak test any line taps movement and found fitted and vibration. replace them if possible.

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Leak point Likely causes Solutions

9. Pressure switches • Vibration • Use flexible pressure causing the couplers where pressure possible (stainless coupler to split steel braided type offer or damage to a high degree of the pressure strength and switch. mechanical • The pressure protection). coupler chafing. • Make sure pressure • Rupture of the couplers do not rub or switch bellows chafe on other pipes or due to vibration vibrating surfaces. or liquid • Ensure the switch is hydraulic correctly supported / action. fixed. • Failure of the • Use flare solder flare connection adaptors on the switch onto the switch. where copper pipe is • Poorly being used. supported or • Use dual bellows fixed switch switches where body. possible. • Connect the switches to minimise the transfer of vibration into the switch. • Always leak test inside switches (be aware of the risk of electric shock).

10. O-rings • Wear, • Check (for roundness O-rings are widely used in hardening or and flexibility) and components such as sight glasses, flattening, change seals rather solenoid valves and shaft seals. especially when than re-using the subjected to existing ones, extremes of especially during a temperature. refrigerant retrofit. • Leakage after • Oil seals before fitting retrofitting them. because of a • Ensure the different replacement seal is reaction to the suitable for the system new oil. oil and refrigerant.

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Leak point Likely causes Solutions

11. Capillary tubes (pressure • Chafing due to • Check capillary tubes couplers and expansion devices) insecure fixing. are firmly located and cannot chafe – correct • Leakage where if necessary. a capillary tube expansion device enters / exits the suction line.

12. Return bends on evaporators Likely cause Solutions and condensers • Leak test return bends • Corrosion due carefully, especially if to chemical the atmosphere is action on the aggressive (e.g. in return bends on food factories where coolers or air salad is washed in cooled chlorine-treated water; condensers. where vinegar Since the products are made; copper used in close to the sea). these heat exchangers is • If evaporators and thinner than condensers that are normal copper prone to leaks from pipe work, a return bends are to be surface pinhole replaced, specify is likely to result materials which are in a leak in a less susceptible to relatively short damage such as period of time. coated or electro Aggressive plated heat fin blocks. environments • When chemical (such as a salty cleaners are used or acidic ensure they are totally atmosphere) washed off. accelerate damage and hence leakage.

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Leak point Likely causes Solutions

13. Condensate tray pipe work • Corrosion of the • Always leak test discharge line in the vaporiser because of tray and check contact with air the condition of and water. the pipe work. If it is corroded, replace the pipe work before it fails. • Where possible, replace the pipe work with a plastic coated type as this extends the life dramatically.

The Institute of Refrigeration accepts no liability or errors or omissions Published January 2009

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