Most seafood plants, breweries and cold stores in Vietnam run ammonia screw and reciprocating compressors, and many of them use CPI oil supplied by Hop Tien. This page sets out six things the operating engineer should demand of the oil in his system, with the TDS data of CPI oils for each point, the standard fill-and-drain procedure, and the systems already converted. At the end of the page: how to send your make-up oil figures for a Hop Tien engineer to read.
Ammonia refrigeration systems use naphthenic mineral oil, hydrotreated mineral oil or synthetic PAO; they do not use POE oil as HFC systems do. The base oil only tells you whether an oil can be used with NH₃, not how it will perform: two oils of the same base and the same ISO VG 68 still differ in volatility (make-up oil per month), actual pour point, oxidation stability, additives and batch-to-batch consistency. Hop Tien supplies Lubrizol's CPI oils for ammonia systems: CPI-1009-68 (hydrotreated mineral, pour point −43 °C, water below 50 ppm) for evaporators down to about −35 °C; CPI-4600-68 (PAO, pour point −57 °C) for colder systems (IQF, −40 °C and below) or where a long drain interval is wanted. The engineer fixes the grade by the lowest evaporating temperature of the system and the pour point in the TDS. The first system in the list at the end of the page: four NH₃ screw compressors with 11,400–49,100 hours in Dong Thap, converted during one maintenance shutdown in 2016 without dismantling the machines.
Hop Tien is the authorized distributor of Lubrizol Fluid Engineering (LFE) in Vietnam for CPI oils (certificate); every batch comes with a batch CoA, SDS and supplementary label. The manufacturer's TDS (English) is sent automatically by email; SDS and batch CoA within 24 working hours. The table of converted systems at the end of the page lists systems whose data a Hop Tien engineer has confirmed.
In an HFC system, POE oil dissolves in the refrigerant and returns to the compressor with it. Ammonia is different: mineral oil and PAO are almost insoluble in liquid NH₃ and heavier than ammonia, so they settle at the bottom of receivers, liquid separators and evaporators. That oil has to be drained by hand or by an oil-return device; if it is not drained fully, the evaporator becomes "oil-logged", heat transfer drops, the compressor runs short of oil and the operator has to top up more and more. Oil leaves the compressor in two ways: as oil mist (which the oil separator retains) and as oil vapor (which the separator does not retain). The vapor fraction depends on the oil's volatility at discharge temperature; this is why two oils of the same ISO VG 68 can differ several-fold in the amount of make-up oil per month. The article Ammonia compressor oil carried over with the refrigerant explains the mechanism and how a plant measures it itself.
| Base oil | General characteristics of the base oil | Differences between products of the same base |
|---|---|---|
| Naphthenic mineral | Naturally low pour point, low cost, familiar to operators | The degree of refining decides volatility and oxidation stability: two naphthenic oils of the same viscosity grade can differ several-fold in make-up oil per month; look at the make-up figures and the color of the drained oil in your own system |
| Hydrotreated (isodewaxed) paraffinic mineral | Low volatility, better oxidation and thermal stability than naphthenic, pour point treated down to about −40 °C; moderate price | Actual pour point varies with the degree of treatment (isodewaxed or not): not every paraffinic oil can be drained from a −35 °C evaporator; antioxidant and water-separation additive packages differ between manufacturers |
| Synthetic PAO | Low volatility, very low pour point (per the TDS of each grade), long drain intervals, little make-up oil | Low-temperature viscosity, pour point and additive package differ between products; costs more than mineral oil; check seals when changing from mineral; rarely needed for a −20 °C cold store |
Characteristics are stated for the base oil type in general, not as comments on any specific product; for each product's figures see that manufacturer's TDS. POE oils (EMKARATE, SOLEST…) are for HFC/HFO refrigerants and are not used with ammonia. PAG oil is used only in direct-expansion (DX) ammonia systems as specified by the manufacturer (see the CPI oil table below). Alkylbenzene oils and blends are found in some older systems; when you meet one, ask an engineer before topping up.
Hop Tien distributes CPI oils for ammonia systems. CPI's (Lubrizol) document Ammonia Refrigeration Lubricant Solutions selects the oil by three questions: is the system direct expansion (DX); is it a heat pump; what is the lowest evaporating temperature of the system. The viscosity grade is confirmed against the compressor manufacturer's recommendation; the Hop Tien engineer fixes the grade by the lowest evaporating temperature of the system and the pour point in the TDS.
| System type | CPI oil | Base oil |
|---|---|---|
| Evaporators down to about −35 °C (cold stores, conventional freezing) | CPI-1009-68 (pour point −43 °C); CPI-1008-68 on the engineer's advice | Hydrotreated mineral (HTMO), low volatility |
| Colder (IQF, −40 °C and below), or a long drain interval wanted | CPI-4600-68 (pour point −57 °C); the CPI-4628 series where extra seal protection is needed (CPI-4628-100, pour point −58 °C); food plants: CPI-4614-68 F (CPI's food-grade series) | PAO |
| Direct-expansion (DX) ammonia systems | CPI-412-100 DX | PAG |
| Ammonia heat pumps | Icematic G 220A / G 220C | PAO |
Per CPI's document Ammonia Refrigeration Lubricant Solutions (NH3_22 0721). Product pages exist for CPI-1009-68, CPI-4600-68 and CPI-4628-100; for the other grades a Hop Tien engineer sends the manufacturer's TDS for each system.
"Also a mineral oil" or "also ISO VG 68" only says that the oil can be used with NH₃. The six points below are what decide how the system runs and what it costs. The "CPI oil" column gives data per the Lubrizol TDS published on the product pages; where the TDS does not publish a value, this is stated rather than inferred.
| What to demand | Why it matters | CPI oil (per TDS) | How to check it yourself |
|---|---|---|---|
| Degree of base-oil refining, volatility | The oil vapor that passes the separator at discharge temperature is the monthly make-up oil and the oil pooling in the evaporators | CPI-1009-68: hydrotreated (hydrogen-refined) mineral oil, viscosity index 111. CPI-4600-68: PAO, viscosity index 134. The TDS does not publish Noack volatility; compare by the system's actual make-up oil | Record the make-up oil and the oil drained at each point for 3 months with the current oil; after the change, compare the same way |
| Actual pour point | Whether oil pooled in a −35 °C evaporator or a low-pressure receiver still flows to the drain valve | CPI-1009-68: −43 °C. CPI-4600-68: −57 °C (TDS) | Compare the TDS pour point with the lowest evaporating temperature of the system; the Hop Tien engineer fixes the grade by these two figures |
| Oxidation and thermal stability | Oil life at the machine's discharge temperature, deposits in the separator, color and smell of the drained oil | CPI-1009-68: flash point 224 °C, acid number 0.04 mg KOH/g. CPI-4600-68: flash point 276 °C (TDS) | Sample the current oil as a baseline; after the change, sample at 500 hours and then periodically |
| Additive package and compatibility | Water separation, rust protection, behavior with seals; two oils of the same base are not necessarily miscible | CPI-1009-68: water content as delivered below 50 ppm. CPI-4600 series: PAO miscible with mineral oil per the PDS, still drained fully at changeover | Do not top up with a different oil; drain fully when changing; check seals if the system has run for many years |
| Batch-to-batch consistency and documents | Whether this year's result is repeated with next year's batch; TDS, SDS, batch CoA | Every batch Hop Tien delivers comes with a batch CoA, SDS and supplementary label (sent within 24 working hours); food plants ask the engineer about the CPI-4614 F series and its registration documents | Ask for the batch CoA and keep the batch number on file so that oil analysis results can be read |
| Service that comes with it | Who comes to the machine at changeover, who reads the analysis results, where stock is held when an urgent top-up is needed | Hop Tien engineers work with the maintenance team following the low-point drain procedure; periodic oil analysis; stock at Song Than, Ho Chi Minh City | Ask these three questions clearly before signing, and write them into the contract |
Because these points differ, the price per liter differs. The true cost of oil over a year is the oil price, the make-up volume, the number of drains and changes, machine downtime and the evaporator capacity lost when oil pools; comparing price per liter between two oils of the same base without make-up data is comparing two things in different units.
Oils of different bases are not miscible and require draining and flushing; the risk in an ammonia system lies in how the change is done. The mistakes below are common when oil is changed without measuring the system first.
Measure first. Record the monthly make-up oil of each compressor, the oil drained at each low point and the discharge temperature, and send one sample of the current oil for analysis; this is the baseline for judging the new oil by data rather than by impression.
Change correctly. The principle Hop Tien applies to every changeover: never fill new oil on top of old. Sequence for each machine while stopped: drain the old oil from the compressor unit and the oil separator; remove the oil filter, clean out the deposits and refit it; open the drain valves one by one at every low point of the receiver, liquid separator, evaporators and piping until the oil runs clear; only then pump in the new oil. Record machine hours and oil temperature and photograph the drained oil at each point for comparison at the next service.
Check afterwards. Sample the oil after 500 hours to confirm no old oil remains, and compare make-up and drained oil with the pre-change baseline after 3 months. The whole sequence is shown with photos in the case study at a pangasius processing plant in Dong Thap: four screw compressors with 11,400–49,100 hours were converted during one maintenance shutdown without dismantling.
Each row is a system Hop Tien converted or supplies with oil, anonymized by industry and province; data confirmed by the engineer.
| Industry, province | Year | Compressors | Machine hours at changeover | Previous oil | CPI oil |
|---|---|---|---|---|---|
| Seafood processing (pangasius), Dong Thap Read the case study → | 2016 | 4 NH₃ screw compressors (built 2007–2014) | 11,400–49,100 h | Other mineral oil | CPI-1009-68 |
Naphthenic mineral oil, hydrotreated paraffinic mineral oil or synthetic PAO with low volatility and a low pour point, usually ISO VG 68 (some machines use VG 46 or 100 per the manual). POE oil from HFC systems is not used.
Because oil is insoluble in ammonia and heavier, it settles at the low points; if it is not drained, the evaporator loses heat-transfer area and the compressor runs short of oil. The amount of oil that has to be drained and topped up is a direct measure of the volatility and oil separation of the oil in use.
The same base is not enough: two mineral oils of the same viscosity grade still differ in volatility, pour point, oxidation stability and additives, which shows in the make-up and drained oil. A change is possible if the system is measured first, every low point is drained fully, nothing is filled over old oil, and a sample is taken at 500 hours.
The risk lies in how it is done: filling over old oil, not draining every low point, changing to a different base oil without draining and flushing, a pour point that is not low enough, changing base oil without checking seals, no baseline. Measure first, change correctly, check afterwards, and it is ordinary maintenance; the draining follows the plant's ammonia safety procedure.
Not at a fixed number of hours. Sample the oil periodically per the machine manual (usually every 2,000–4,000 hours) for viscosity, acid number, water content and wear metals; change when a value exceeds its limit or when the oil drained at the low points is black and thick. Hydrotreated and PAO oils usually last longer than naphthenic oils under the same conditions.
Hydrotreated mineral oil such as CPI-1009-68 (pour point −43 °C per TDS) is used for evaporators down to about −35 °C. Systems at −40 °C and below (IQF, conveyor freezers), or where make-up oil is to be reduced: use PAO CPI-4600-68 (pour point −57 °C per TDS). The engineer decides by the lowest evaporating temperature of the system and the TDS pour point so that oil pooled in the evaporator can still be drained.
Yes. Hop Tien technicians work with the plant's maintenance team to drain the oil, clean the filters, drain the low points and fill the oil in the sequence above, with a photo record and a sampling schedule; the plant receives the manufacturer's TDS (English), SDS and batch CoA for its files within 24 working hours.
Per CPI's document Ammonia Refrigeration Lubricant Solutions: CPI-1009-68 (hydrotreated mineral, pour point −43 °C) for evaporators down to about −35 °C; CPI-4600-68 (PAO, pour point −57 °C) or the CPI-4628 series for colder systems (IQF, −40 °C and below) or where a long drain interval is wanted; CPI-4614-68 F (PAO, food-grade series) for food plants; CPI-412-100 DX (PAG) for direct-expansion systems. The viscosity grade is confirmed against the compressor manufacturer's recommendation; the engineer decides by the lowest evaporating temperature of the system and the TDS pour point.
Four NH₃ screw compressors with 11,400–49,100 hours: drain the compressor unit and separator, clean the filters, drain every low point until the oil runs clear, then pump in CPI oil; done during a maintenance shutdown, no dismantling.
KnowledgeSeven common signs, the oil-mist and oil-vapor mechanism, how a plant measures it itself before deciding.
KnowledgeViscosity, TAN, water, iron, copper, silicon: what each one says about your machine.
