A screwr is used in combination with refrigerated oil and less than 10 minutes after start-up, the pressure rises, the electric heat alerts, and finally the axle is completely disabled — the cost of the maintenance sheet is too high to breathe。
It's not uncommon in the industry。
Refrigerated oil replacement operations appear to be a simple “lay, add and replace” operation, which is in fact a high-risk operation involving the life and death of the central air conditioner “heart”。
The real professional oil exchange is not just the replacement of old oil, but the reshaping of the life cycle of a system。
Many do not realize until the compressor is in trouble: refrigerated oil is not a simple lubricant, but carries multiple functions such as sealing, heat dispersion, noise abatement, and protection of electrical insulation。
Once the wrong oil, mixed oil, water or residues were not cleared, the entire compressor system was placed into a time bomb。
To avoid such lessons, it is necessary to start at source — precise oil selection, complete draining, vacuuming, synchronized replacement, commissioning, with standards, details and scientific logic at every step。
*accurate oil selection is the starting point for the life of the refrigeration system。
The current refrigerant environment has changed and the r22 system, which was used in the past, has been able to use mineral oil, but the new type uses r134a or r410a and must be accompanied by pee-type oil。
By 2026, low gwp refrigerants, such as r32, r454b, are dominant in the new generation of a2l refrigerants。
They have higher requirements for oil, and some of the manufacturers have even recommended a special version of poe or the use of pve oil。
Pve is less humid, more hydrolytic, less chronic acid corrosive and suitable for environmentally friendly refrigerants。
If on-site technicians do not check the tags, do not look at the original factory manual and refuel with experience, chemical mismatches can easily occur。
Refinery data indicate that there are additive formulations that vary from brand to brand, even if the oil is the same as poe, and that when mixed, sedimentation or even blocking of oil routes can be detected。
Professional teams typically search the database according to the machine number, and then prioritize stable synthetic oil against the latest energy efficiency standards (e. G. Gb 19577)。
Large enterprises also conduct half-yearly oil sample spectral analyses to detect mechanical wear and tear at an early stage by detecting concentrations of iron, copper and aluminium particles。
* a complete emptiness is a real test of the technical credentials。
Gravity discharges appear to be clean, leaving only about 70 per cent of the old oil, while the remaining 30 per cent is hidden at the corner of the pipeline, at the bottom of the heater and at the end of the oil separators。
If it's not cleaned, the new oil will be contaminated。
The correct approach is first to recover the refrigerant, remove the system pressure, and then clean it repeatedly with dry nitrogen。
For systems that used to burn electric power or to blacken oil, the rinsing agent is also to be recycled until the back flow colour is transparent。
The new regulations introduced in 2025 (db44/t 2718-2025) have explicitly provided for the replacement of oil filters, refrigerated oils and refrigerant dry cores at least once a year。
The standard used in the field is that nitrogen is pressured to 4. 0 mpa for 24 hours; then the vacuum is pumped to -100. 7kpa and the pressure is not increased for an hour。
Both met the standards to indicate that the moisture and gas impurities had been removed。
If high acid values are detected, dry filters must be replaced simultaneously, in particular with models of activated aluminium oxide or molecular sifting material that can adsorb acid and moisture to prevent ice congestion。
* vacuum observation is the last line of defence against system “oxidation”。
Many of the aircraft have acid corrosive and electric insulation, which is rooted in the mixing of air and water during refuelling。
The standard process requires a vacuum pump to pump the system to less than 500 μm, with a decomposition test, which is only eligible if the vacuum does not rise significantly for an hour。
At this point, new oil is inhaled through pressure differentials and exposed throughout the course。
More rigorous operations involve multiple cycles of nitrogen gas pressure and vacuum destruction that completely push potential moisture out。
This is a slow but significant increase in the life of the oil。
In particular, oils of the poe type can be exposed to air for a few minutes to inhale into water vapour and generate acid, which cannot be completely removed once in the system。
Some high-end service teams also use drying pipes throughout the process and record vacuum values for each operation, which has become the new recommended practice。
* synchronize the refilling of filter cores and seals to protect new oils from old problems。
Many of the workers at the scene were able to save themselves by changing the oil without changing the cores and returning to work in a few months。
Leach core jams cause constant stress variations, impede the oil cycle, and compressors rub up temperature。
The oil separators elements of the screwrs are recommended for replacement once a year or 8,000 hours, which reduces the risk of carrying the oil into the cooling circuit。
The centrifuge focuses on the examination and calibration of the oil table in the gear tank, where noise and wear occur when the pressure varies。
An old leak in the seal is equally dangerous, and if the oil is replaced without inspection of the sealed material and the electrostatic field, the light leaks and the weight causes combustion。
All operating records should be kept, including oil sample tests, alarm records, replacement dates, not only as a warrant for protection, but also as a requirement for special equipment security regulations。
* the commissioning phase is the time to test whether the protection is actually meeting the standards。
The refuelled air conditioning system, which is not finished, leaves。
The professional operator monitors the level of oil on a case-by-case basis between 1/2 and 2/3 of the lens and the oil pressure differential between 1. 4 and 3. 5 bar。
The bearings and the electrical state are being tested with vibrations and acoustic collectors。
Semi-annual detection of changes in metal particles in oil samples results in early detection of abnormal wear。
The environmental protection code (aim act) from 2026 also included refrigerant leakage rates in the performance appraisal, after which leakage detection and energy consumption data must be recorded。
A particular detail reveals the level of service: experienced engineers will keep a batch number, vacuum values, field photographs, which are used for late-stage energy efficiency audits and warranty disputes。
In summary, the replacement of refrigerated oil should be considered as a system-level “heart surgery”, both in terms of technical standards and economics。
It connects the compressors, the electrics and the refrigerant cycle, and an oversight could cause millions of losses。
Current industry trends are also shifting — in the past, relying on empirical judgement, more and more enterprises are beginning to use data to speak, to analyse oil samples, to monitor vibrations in advance of risk, and to apply regulations and standards to protect quality。
In my view, it is not the maintenance workers, but the equipment managers, who should be the most alert。
Because of the consequences of poor or mixed refrigeration, it is almost always the business that ultimately pays。
A truly smart approach would be to obtain the authorization of the manufacturer prior to protection, to establish an annual oil exchange file and to use forecasting maintenance。
Oil and refrigerants are moving in the direction of low gwps and the process is being upgraded, a trend that will not be bypassed by each room in the next three years。
The refuelling of the central air conditioner is by no means a fluid line of work, more like a precision surgery。
Professionals are the least expensive。
Those who think that “more oil is fine” are actually laying mines in advance for future failures。
Would you like to give a million worth of equipment to a single master
