ISO 6521-3:2019 pdf free.Lubricants, industrial oils and related products (Class L)一Family D (compressors)一 Part 3: Specifications of categories DRA, DRB, DRC, DRD, DRE, DRF and DRG (lubricants for refrigerating compressors).
4 Sampling
Sampling of compressor oils for the purpose of this document, unless otherwise specified, shall be carried out in accordance with the relevant procedure described in Iso 3170. The sample shall be evaluated on a representative portion. Any drum, barrel, tanker compartment or any type of container delivered to the end user may be sampled and analysed, at the discretion of the purchaser.
5 Requirements for oils operating in refrigerating compressors
5.1 General
The lubricant chosen for a refrigerating system shall be
— suitable to effectively lubricate the mechanical parts of the compressor, and
— compatible with the refrigerant.
The compatibility covers the following aspects:
— chemical compatibility at high temperatures;
— miscibility and solubility characteristics.
Additionally, the lubricant should be as dry as possible.
5.2 Compatibility with the refrigerant
The compression of the refrigerant warms up not only the refrigerant itself, but also the oil. The final compression temperature might increase, leading to thermal stress for the oil. At these temperatures, the lubricant should not chemically react with the refrigerant.
5.3 Miscibility with the refrigerant
This characteristic is important at the evaporator level of the refrigerating circuit. The lubricant carried over from the compressor into the evaporator shall be sufficiently miscible with the refrigerant at the evaporator temperature so that the mixture of oil and refrigerant stays monophasic after expansion in the evaporator. If the lubricant separates in the evaporator due to poor miscibility with the refrigerant, fluid may get trapped in the evaporator, leading to loss of cooling capacity/efficiency and insufficient oil return to the compressor. Miscibility curves are established for oil/refrigerant pairs; they are used to ensure that the selected lubricant matches the solubility requirements for the application.
5.4 Solubility with the refrigerant
This characteristic is important to ensure that the lubricant having absorbed the gaseous refrigerant under the temperature/pressure conditions at the compressor keeps sufficient viscosity to correctly lubricate the compressor. Viscosity/Pressure/Temperature (VPT) diagrams are established for the various oil/refrigerant combinations. The oil/refrigerant mixture viscosity should match the compressor manufacturer requirement.
5.5 Water content
The specified values are maximum permissible values for fresh oils. The water contents specified depend on the chemical nature of the lubricating oil; polyalkylene glycols are much more hygroscopic than polyol esters, themselves more than hydrocarbon type oils. Refrigerating oils are normally delivered in gas-tight metal packages, designed to avoid any moisture ingress, even after long periods of storage. Partly used containers should be always resealed and used as rapidly as possible. Good handling and storage practices are of utmost importance. Before filling a compressor, the lubricant should be dried and degassed under vacuum.
6 Specifications
6.1 General
All categories mentioned below are defined in accordance with ISO 6743-3. All Specification tables are available in Annex A.
6.2 Specifications for ISO-L-DRA refrigerating compressor oils
ISO – L – DRA are refrigerating compressor oils that are not miscible with ammonia (R717 refrigerant). ISO – L – DRA are typically highly refined mineral oils, naphthenic or paraffinic, poly a-olefins or alkyl benzenes.These lubricants shall be in accordance with specifications given in Table A.1.
6.3 Specifications for ISO-L-DRB refrigerating compressor oils
ISO – L – DRB are refrigerating compressor oils that are miscible with ammonia (R717 refrigerant).
ISO – L – DRB are typically polyalkylene glycols.These lubricants shall be in accordance with specifications given in Table A.2.
6.4 Specifications for ISO-L-DRC refrigerating compressor oils
ISO – L – DRC are refrigerating compressor oils that are not miscible with hydrofluorocarbons.
ISO – L – DRC are typically highly refined mineral oils, naphthenic or paraffinic, poly cz-olefins or alkyl benzenes.These lubricants shall be in accordance with specifications given in Table A.3.
6.5 Specifications for ISO-L-DRD refrigerating compressor oils
ISO – L – DRD are refrigerating compressor oils that are miscible with hydrofluorocarbons (HFC).
ISO- L – DRD are typically polyol esters, poly-vinyl ethers, polyalkylene glycols.These lubricants shall be in accordance with specifications given in Table A.4.ISO 6521-3 pdf download.