1 / 32

Good Servicing Practices Do’s & Don’ts

Good Servicing Practices Do’s & Don’ts. Areas of Focus. Brazing Cleaning and Flushing Leak Testing Evacuation Measurement / holding of vacuum Charging of Refrigerant. Base Metal. Torch. Brazing Filler Rod. Essentials of Brazing. Brazing Filler Rod.

mackensie-hinton
Download Presentation

Good Servicing Practices Do’s & Don’ts

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Good Servicing PracticesDo’s & Don’ts Do's & Don'ts - 2008

  2. Areas of Focus • Brazing • Cleaning and Flushing • Leak Testing • Evacuation • Measurement / holding of vacuum • Charging of Refrigerant Do's & Don'ts - 2008

  3. BaseMetal Torch Brazing Filler Rod Essentials of Brazing Brazing Filler Rod • Melts at temperature lower than that of base metals • Rod should melt by contact with heated base metal • Melted Rod Material flows into clearance between walls of the two tubes through capillary action Do's & Don'ts - 2008

  4. Right brazing alloys; Right Flux • Right Joint preparation • Surface preparation • Joint clearances Right technique Right temperature Good Brazed Joints: Prerequisites Do's & Don'ts - 2008

  5. Suitability of Brazing Equipment • Oxy Acetylene: Best suited • Oxygen-LPG: Better suited than Air-LPG • Air-LPG: May be inadequate, but O.K. for Cu tubes up to 3/8” with Swirljet (or Cyclone) Torches • Kerosene Blow-lamp: Should be avoided Do's & Don'ts - 2008

  6. USE. Dry Nitrogen Trichloroethylene (for chemical cleaning) (ensure trichloroethylene vapourises and does not remain as liquid after cleaning, by application of gentle heat) DO NOT USE CTC (Being phased out) Air (Contains moisture, lubricant & other gases, detrimental to the system) Oxygen – not O.K. for compressor oil Petrol (has a lot of impurities which can destroy the compressor) Cleaning and Flushing Do's & Don'ts - 2008

  7. USE. Dry Nitrogen (after the system has been reassembled) Should have a dew point of at least -400C Commercial nitrogen with a drier (to reduce moisture content) DO NOT USE Compressed air (Contains moisture, lubricant & other gases, detrimental to the system) Refrigerant Leak Testing Do's & Don'ts - 2008

  8. Different types of N2 available For refrigeration service, following specification recommended : Purity : 99.995% Dew Point: -40 oC at least Approximate price: Rs. 325/- per cylinder of 7 m3 (with security deposit ranging from Rs. 5000/- to Rs. 10,000/-) Makes: Bombay Oxygen, Inox & others Dry Nitrogen Do's & Don'ts - 2008

  9. DO NOT USE Refrigeration System’s compressor Other Hermetic / Semi Hermetic / Open Refrigeration compressors May lead to compressor failure as: moisture gets deposited in compressor’s discharge chamber there can be loss of lubricant Equipment for Evacuation • Creates inadequate vacuum for moisture to boil and vacate the system Do's & Don'ts - 2008

  10. Why Vacuum Pump is needed Do's & Don'ts - 2008

  11. 3.0 3 CFM Pump (1/3 HP) 2.5 2 CFM Pump (1/4 HP) 2.0 ½ HP Compressor 1.0 10 100 1000 10,000 100,000 1,000,000 Vacuum in Microns of Hg Comparison of Vacuum Pump vs Compressor Do's & Don'ts - 2008

  12. Equipment for Evacuation(Cont) • Use specially designed vacuum pumps, capable of developing blank off pressure of 20 - 50 microns Hg • Micron gauge capable of reading pressures in 5 - 5000 Microns range • Most preferred: • Two stage, Rotary, multi-vane pump Do's & Don'ts - 2008

  13. Measuring Vacuum Accurately • Use Pirani / Thermocouple vacuum gauge having a range from 5-5000/10000 microns • Evacuate to about 500 microns or lower • Isolate the vacuum pump & observe the rise in the vacuum for 5-10 minutes • Repeat (a) & (b) till the vacuum in (b) stabilises at around 1500 microns or lower. The lower the stabilised vacuum the better. Do's & Don'ts - 2008

  14. If Micron Level Vacuum Gauge is not Used • If micron level vacuum gauges are not available • Bourdon type vacuum gauges cannot read vacuum in microns – hence actual vacuum reached cannot be known • In the absence of a micron vacuum gauge, the vacuum pump should be run at least half an hour after the Bourdon type vacuum gauge reading shows -30” / -760 mm / 0 millibar (at sea level). • Neither the vacuum level nor vacuum holding can be known from this. Therefore superior quality of evacuation & assurance using micron gauge will be absent in this case. Do's & Don'ts - 2008

  15. Charging • Charge the same weight of refrigerant in the system, as recommended by the appliance manufacturer instead of charging by feel(To ensure good cooling performance and low energy consumption) • Charging apparatus must provide for accurate weighing scales or calibrated charging cylinders(HFC-134a & HCs particularly are even more sensitive to charge quantity than CFC-12) Do's & Don'ts - 2008

  16. Use of Anti-Moist Don’t Use Anti-Moist • It has a harmful effect on compressor motor (Causes embrittlement of insulation leading to premature motor failure) • Strictly prohibited for HFC-134a systems Instead, evacuate system properly and use the appropriate drier Do's & Don'ts - 2008

  17. Contamination &Cross Contamination Contamination by : • Moisture • Non-condensables • Chemical residues • Dirt, dust metal particles • Organic contaminants Cross-Contamination through: • Import of contaminants from other systems or servicing equipment Contaminants: • Other refrigerants, other lub. Oils, chemical residues from other systems

  18. Cross-Contamination due to Refrigerant Mixing • Even at 10-20% of CFC-12 in HFC-134a & vice-versa, the azeotrope formed will have properties quite different from either • This will seriously affect appliance performance • Similar problems will arise with mixtures of CFC-12 & HCFC-22 or HCFC-22 & HFC-134a • As full data on HCs / CFC-12 or HCs / HFC-134a mixing is not available, it is better to avoid their mixing. CAUTION: Ensure that refrigerants do not mix.AVOID.

  19. Likely Sites for Refrigerant Cross-Contamination • Charging stills of E&C units, used for multiple refrigerants • Recovery & R&R machines used for multiple refrigerants • Recovery cylinders • Hoses & Manifolds • Old systems retrofitted with non-CFC refrigerants

  20. How to avoid Refrigerant Cross-Contamination (Cont) • Ensure that all traces of the previous refrigerants is removed from the charging still / recovery machine & the unit is evacuated to a deep vacuum (1000 microns) before switching to a new refrigerant • If possible use separate E&C & Recovery machines for each type of refrigerants • Use separate recovery cylinders for each refrigerant

  21. Gap is less than 2”, after some time wall will be hot Wrong Installation

  22. Wrong v/s. right Installation

  23. Wrong v/s. right Installation X √ U Trap is must for drains

  24. LET US INSIST ON GOOD SERVICE PRACTICES WITH PHD . THANKS!! Do's & Don'ts - 2008

  25. Contamination & Cross Contamination Contamination by : • Moisture • Non-condensables • Chemical residues • Dirt, dust metal particles • Organic contaminants Cross-Contamination through: • Import of contaminants from other systems or servicing equipment Contaminants: • Other refrigerants, other lub. Oils, chemical residues from other systems Do's & Don'ts - 2008

  26. Cross-Contamination due to Refrigerant Mixing • CFC-12 & HFC-134a when mixed, form high pressure azeotropes with pressure higher than either refrigerant • Even at 10-20% of CFC-12 in HFC-134a & vice-versa, the azeotrope formed will have properties quite different from either • This will seriously affect appliance performance • Similar problems will arise with mixtures of CFC-12 & HCFC-22 or HCFC-22 & HFC-134a • As full data on HCs / CFC-12 or HCs / HFC-134a mixing is not available, it is better to avoid their mixing. CAUTION: Ensure that refrigerants do not mix Do's & Don'ts - 2008

  27. Cross-Contamination due to Refrigerant Mixing Do's & Don'ts - 2008

  28. Likely Sites for Refrigerant Cross-Contamination • Charging stills of E&C units, used for multiple refrigerants • Recovery & R&R machines used for multiple refrigerants • Recovery cylinders • Hoses & Manifolds • Old systems retrofitted with non-CFC refrigerants Do's & Don'ts - 2008

  29. How to avoid Refrigerant Cross-Contamination (Cont) • Ensure that all traces of the previous refrigerants is removed from the charging still / recovery machine & the unit is evacuated to a deep vacuum (1000 microns) before switching to a new refrigerant • If possible use separate E&C & Recovery machines for each type of refrigerants • Use separate recovery cylinders for each refrigerant Do's & Don'ts - 2008

  30. Common Practices • Use of blow lamp • Brazing with Cu electrode for brazing Cu tubes Bundy/steel tubes • Flushing with air / refrigerant • Use of CTC / petrol for cleaning • Leak testing using air/refrigerant • Self-evacuation using system compressor or old / used compressor as vacuum pump • Improper assessment of vacuum achieved • Charging by feel (inaccurate) • Use of anti moist • Contamination / Cross Contamination of Refrigerants Do's & Don'ts - 2008

  31. Boundary locking layers (dotted) show metallurgical bond Filler material Tube hollow Outer tube end (swaged) Spigot (inner tube) Essentials of Brazing(Cont) Melted Filler Rod material wets base metal and penetrates surface & forms metallurgical bond. Do's & Don'ts - 2008

  32. 8150C 7050C 6000C 5900C Temperatures for Brazing Desired temperature range for Phos Cu Alloys Average temperature for Phos Cu Alloys Right temperature for Cu Ag alloys (Ag >35%) Do's & Don'ts - 2008

More Related