Retrofitting of Refrigeration Trainer

Colon, Edcel P.Francisco, Rome John S.Mabbayad, Jeffrey B.Viray, Maynard A.

Background of the Study

Refrigeration cycle in different forms finds applications in numerous

industrial and domestic situations throughout the world.

The components of a specific piece of refrigeration equipment have

been engineered

Issues arise from the use of inappropriate refrigeration equipment.

Retrofitting

Benefits of Retrofitting

Statement of the Problem

This study aims to provide mechanical

engineering students hands-on training of the principles

and systems of refrigeration, that is why we are

proposing for the retrofitting of the refrigeration trainer.

Objectives of the Study

General ObjectivesTo provide hands-on training to mechanical engineering

students about refrigeration and to develop

troubleshooting skills.

To determine the components to be replaced or fixed in

the refrigeration trainer and make it functional.

Specific ObjectivesTo help the mechanical engineering students to

familiarize the parts and functions that the refrigeration

trainer. 

To provide demonstration and better understanding on

the working principle of refrigeration cycle.

To develop fault finding techniques and assessment

procedures to build up diagnosis capability.

Assumption of the Study

The components to be replaced in the refrigeration

trainer are to be bought and some will be fabricated in

accordance with the specifications needed. Other

components that don’t need replacement are to be fixed

and adjusted.

Significance of the Study

The research study of retrofitting the refrigeration

trainer will provide hands-on training to mechanical

engineering students and better understanding of the

working principles of refrigeration. This will prepare

students to handle problems in refrigeration when

practicing the field Mechanical Engineering profession.

Scope and Delimitations

The scope of this study will be concentrated on

retrofitting of the refrigeration unit and to determine the

parts or components needed for replacement or to be

fixed.

Theoretical Framework

The concern of this research is to retrofit the

refrigeration trainer, to make it functional and operational

to provide hands-on training to mechanical engineering

students and understanding in the system of refrigeration.

Refrigeration Trainer

Retrofitting of the trainer

Functional and operational

Introduction of basic refrigeration

concepts

Provide hands-on-training

Research Methodology

Retrofitting procedures are being followed in the Code of

Practice for Refrigeration and Air Conditioning Manual.

The retrofitting of the trainer is guided and supervise by a

refrigeration technician.

Research Methodology

3.1 Retrofitting Procedures

Record the system performance data

Pump down the system

Recovered refrigerant must be stored

Knowing the recommended charge size

Ensure the prevention of refrigerant

emissions

Replace all equipment components and

accessories

Research Methodology

Research Methodology

Charge the system with new and correct

amount of alternative refrigerant oil

Reinstall the compressor

Run the system while performing the oil

change procedure

Research Methodology

Leak test the system

Evacuate system to at least 1000 microns

Monitor the system operation and

performance

Check remaining content of mineral oil

Follow the system and/or compressor

manufacturer recommendations

Label the system.

Research Methodology

3.2 Leak Testing MethodsMethod

Leak detection spray /soapy water

Electronic leak detector

Fluorescent additive(injected into the System with oil and detected usingan ultra violet lamp)

Leak Points Likely causes Solutions

1. Shut-off And ball valves

• Wear of the packing gland between the valve body and spindle shaft as it becomes compacted with age and use.• Overheating during installation.• Caps not fitted.

• Ensure that the gland is tightened.• Wrap the valve with a damp rag while brazing.

2. Schrader valves • Valve cores damaged during brazing.

• The cores not tightened correctly during replacement.• Deterioration of internal seals over time.• Caps not fitted or have no O-ring seal.

• Remove the core when brazing the fitting in; ensure the valve body has cooled before replacing the core.• Use the correct tool to replace / tighten the core.• Ensure the cap is fitted and has a seal in place.

3.  Flare joints • Loosening of the flare nut due to thermal expansion / contraction due to a wide temperature variation, especially where those at the outlet of expansion valves.• Poor joint preparation.• Over tightening, leading to damage at the copper flare face and the flare nut.• Under tightening of the flare.

• If possible, avoid using flare connections.

4. Mechanical joints and flanges • Incorrectly prepared joint

• Not replacing gaskets.• Uneven tightening of flanges.• Incorrect torque used for tightening bolts.

• Replace gaskets on flanges and remove all the old gasket material before applying the new one.• 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 and fusible plugs

• Fusible plugs – wide temperature and / or pressure variations weaken the bond between the solder core and the plug.• PRVs - do not reseat when the pressure drops after release and often leak across the PRV seat during normal operation.

Fusible plugs• Where possible, avoid using fusible plugs. If possible, replace them with a PRV.PRVs• Always leak test the outlet of PRVs.• If a PRV is leaking replace it with an equivalent rated device.• Do not cap the PRV if it is leaking.  

6. Shaftseals

• Lubrication failure.• Incorrect fitting of a new shaft seal.• Incorrect shaft alignment.• Excessive crankshaft end float or bearing damage.

• Leak testing of the shaft seal with the compressor switched off.• Using the correct type of shaft seal and following the proper procedure when replacing the shaft seal.

7. CondensersShell and tubecondensers• Corrosion of the copper and mild steel if the water circulating in the tubes is not treated correctly. Leaks can be particularly hard to locate, as they cannot be seen refrigerant might be detected in the water, but usually the leak is only detected by carrying out a full pressure test of the system.Air-cooledcondensers• Corrosion due to aggressive air.• Impact damage due to foreign bodies in the air stream.• Vibration causing premature failure of the tube bundle.

Shell and tube condensers• Regular inspection to monitor potential corrosion level.Air cooled condensers• Always position condensers on a level base.• Repair or replace out of balance fans.• Check the fin block for signs of oil.• When replacing a condenser, select it carefully, especially if it is going into an aggressive environment e.g. on the coast.

8. Line tap valves

• Poor fitting of the line tap onto the pipe, or being fitted to badly formed or flattened pipe work.• Use of the wrong size line tap• Loosening of the line tap valve due to movement and vibration.

• Ensure the correct size of tap valve is being used and read the instructions for its installation.• Leak test any line taps found fitted and replace them if possible.

9. Pressure switches

• Vibration causing the pressure coupler to split or damage to the pressure switch.• The pressure coupler chafing.

•Use flexible pressure couplers where possible.• Make sure pressure couplers do not rub or chafe on other pipes or vibrating surfaces.• Ensure the switch is correctly supported / fixed.

10. O-rings

• Wear, hardening or flattening, especially when subjected to extremes of temperature.• Leakage after retrofitting because of adifferent reaction to the new oil.

• Check and change seals rather than re-using the existing ones, especially during a refrigerant retrofit.• Oil seals before fitting them.• Ensure the replacement seal is suitable for the system oil and refrigerant.

13. Condensatetray pipe work

• Corrosion of the discharge line because of contact with air and water.

• Always leak test in the vaporizer tray and check thecondition of 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

11. Capillary tubes

• Chafing due to insecure fixing.• Leakage where a capillary tube expansion device enters / exits the suction line.

• Check capillary tubes are firmly located and cannot chafe – correct if necessary.

12. Return bends on evaporators andcondensers

• Corrosion due to chemical action on the return bends on coolers or air cooled condensers.

• Leak test return bends carefully, especially if the atmosphere is aggressive.• If evaporators and condensers that are prone to leaks from return bends are to be replaced, specify materials which are less susceptible to damage such as coated or electro plated heat fin blocks.