🌫️ Cloud Point Temperature

Petrochemistry PN-EN ISO 3015

Overview

STATUS (as of 30.10.2026). PN-EN ISO 3015:2019-06 — Polish and English versions, implements EN ISO 3015:2019 and ISO 3015:2019 [IDT]; the Polish version was published on 02.12.2020 and replaced PN-ISO 3015:1997 (which implemented ISO 3015:1992 and EN 23015:1994). ISO 3015:2019 is the third edition of the standard, published on 25.04.2019 and confirmed by ISO on 12.09.2024.

SCOPE AND DEFINITION (clause 1, 3.1). Determination of the cloud point of petroleum products which are transparent in layers 40 mm in thickness and have a cloud point below 49 °C — amongst which are diesel fuels with up to 30 % (V/V) of fatty acid methyl ester (FAME), paraffinic diesel fuels with up to 7 % (V/V) FAME, 100 % FAME and lubricants. The cloud point is the temperature at which a cloud of wax crystals first appears in a liquid when it is cooled under specified conditions. According to the corresponding American standard ASTM D2500 (5.1), the cloud point is an index of the lowest temperature of a product's utility for certain applications.

EDITION (foreword). Compared with the 1992 edition, the scope was extended to diesel fuels with up to 30 % (V/V) FAME and to paraffinic diesel fuels, the digital contact thermometer was included, the normative references were updated, and the bath and sample temperature ranges were aligned with ASTM D2500 — the changes in bath temperatures and transfer points applied since 1992 have not shown a bias against results obtained with the former edition. The precision for “other products” was removed because data to support it could not be obtained for comparison, and a bibliography was added.

APPARATUS (clause 5). Test jar, cylindrical, of clear glass, flat-bottomed, 33.2 mm to 34.8 mm in outside diameter and 115 mm to 125 mm in height (inside diameter 30.0 mm to 32.4 mm, wall thickness not greater than 1.6 mm), with a line marking a sample height of (54 ± 3) mm above the inside bottom. Liquid-in-glass thermometer (A.2) or digital contact thermometer (A.1), and a cork bored centrally for the thermometer. Watertight, cylindrical, metal, flat-bottomed jacket, about 115 mm deep, with an inside diameter of 44.2 mm to 45.8 mm, projecting not more than 25 mm out of the cooling medium; at its bottom a disc of cork or felt 6 mm thick, and on the jar a ring gasket about 5 mm thick that prevents the jar from touching the jacket. Cooling baths maintained at the prescribed temperatures, with a firm support holding the jacket vertical, cooled by refrigeration or by cooling mixtures (recommended mixtures — Annex B).

HOW THE TEST IS PERFORMED (clause 7). The sample is brought to a temperature at least 14 °C above the approximate cloud point, but not above 49 °C, and any moisture is removed by a suitable method, for example by filtration through dry lint-less filter paper, until the sample is perfectly clear; it is then poured into the test jar to the level mark. With a liquid-in-glass thermometer, if the expected cloud point is above −36 °C the high cloud and pour point thermometer is used, otherwise the low one; the thermometer is checked immediately before the test — its ice point is to be 0 °C ± 1 °C. The jar is closed with the cork so that the thermometer and the jar are coaxial and the bulb or probe rests on the bottom. The disc and the jacket are placed in the cooling medium at least 10 min before the jar is inserted, the gasket is placed 25 mm from the bottom of the jar, and a jar is never placed directly into the cooling medium. The first bath is at 0 °C ± 1.5 °C. At each whole degree on the thermometer the jar is removed quickly from the jacket without disturbing the sample, inspected and replaced — the complete operation takes no more than 3 s. The jar (without the jacket) is transferred to the next bath when the sample, without a cloud, reaches the lowest temperature of the range of the current bath (Table 1): bath 1 — 0 °C, sample from the start to +9 °C; bath 2 — −18 °C, from +9 °C to −6 °C; bath 3 — −33 °C, from −6 °C to −24 °C; bath 4 — −51 °C, from −24 °C to −42 °C; bath 5 — −69 °C, from −42 °C to −60 °C (each ± 1.5 °C).

READING, WATER AND PRECISION (7.7, clauses 8–9). The cloud point is the temperature at which any cloud is observed at the bottom of the test jar, confirmed by continued cooling; it is reported to the nearest 1 °C. The wax cloud always appears first at the bottom, where the temperature is lowest; a slight haze throughout the entire sample, becoming more apparent as the temperature is lowered, is usually due to traces of water and generally does not interfere — filtration as in the sample preparation is usually sufficient. If the haze in a diesel fuel is very dense, a fresh portion is dried by shaking 100 ml of sample with 5 g of anhydrous sodium sulfate for at least 5 min and filtered through dry lint-less filter paper — always at a temperature at least 14 °C above the approximate cloud point, but not above 49 °C. Repeatability: the difference between two results exceeds 2 °C only in one case in 20; reproducibility — 4 °C; the precision data were obtained with liquid-in-glass thermometers to ASTM E1 or IP specifications.

WHAT WE DO NOT GIVE HERE. The requirements of the current edition for liquid-in-glass and digital thermometers (Annex A) and the cooling mixtures it recommends (Annex B) — they are outside the available text of the standard; in the apparatus list we give them according to the 1992 edition, labelled as such.

Method principle

The sample, brought to a temperature at least 14 °C above the approximate cloud point and freed of moisture, is cooled in a test jar placed in the jacket of successive baths at fixed temperatures and inspected at every whole degree.

The temperature at which a cloud of wax crystals is first seen at the bottom of the test jar, confirmed by continued cooling, is recorded as the cloud point (clause 4, 7.7).

Applications

• Diesel fuel, also with up to 30 % (V/V) FAME, and paraffinic diesel fuel with up to 7 % (V/V) FAME (clause 1)
• 100 % FAME (clause 1)
• Lubricants transparent in layers 40 mm in thickness, with a cloud point below 49 °C (clause 1)
• Diesel with improved low-temperature properties — the Polish regulation on quality requirements for liquid fuels (based on PN-EN 590:2022-08) requires a cloud point of at most −22 °C; for “standard” diesel it does not require one — in the summer, transitional and winter periods the cold filter plugging point (CFPP) of at most 0 °C, −10 °C and −20 °C applies (Dz.U. 2024 item 1018, Annex 3 No 19–20)

Key parameters

Standard

Standard number

PN-EN ISO 3015:2019-06

Title (PL)

Przetwory naftowe i produkty podobne pochodzenia naturalnego lub syntetycznego — Oznaczanie temperatury mętnienia

Title (EN)

Petroleum and related products from natural or synthetic sources — Determination of cloud point

Step-by-step procedure

1. Sample preparation

   Bring the sample to a temperature at least 14 °C above the approximate cloud point, but not above 49 °C; remove moisture, for example by filtration through dry lint-less filter paper, until the sample is perfectly clear (7.1).

2. Filling and thermometer

   Pour the sample to the level mark; select the thermometer (liquid-in-glass above −36 °C — high-range) and check its ice point (0 °C ± 1 °C); close the jar with the cork so that the thermometer and the jar are coaxial and the bulb or probe rests on the bottom (7.2–7.3).

3. Jacket

   Disc, gasket and inside of the jacket clean and dry; disc and jacket in the cooling medium at least 10 min beforehand; gasket 25 mm from the bottom of the jar; insert the jar into the jacket — never directly into the cooling medium (7.4).

4. Cooling and inspection

   First bath 0 °C ± 1.5 °C. At each whole degree remove the jar from the jacket without disturbing the sample, inspect the bottom and replace it — no more than 3 s (7.5–7.6).

5. Next baths

   When the sample reaches +9 °C without a cloud, transfer the jar (without the jacket) to the −18 °C bath; at −6 °C — to −33 °C; at −24 °C — to −51 °C; at −42 °C — to −69 °C (7.6, Table 1).

6. Reading

   Record to the nearest 1 °C the temperature at which any cloud is observed at the bottom, confirmed by continued cooling; with a dense water haze in diesel fuel test a fresh portion dried with sodium sulfate (7.7).

7. Test report

   Identification of the product, reference to ISO 3015:2019, result, deviations from the procedure and date of test (clause 10).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Use of the standard can involve hazardous materials, operations and equipment — safety measures are established by the user (warning of the standard)
• Cooling mixtures (Annex B; in the 1992 edition among others solid carbon dioxide with acetone or petroleum naphtha, prepared in a covered metal beaker) — precautions according to the safety data sheets of the substances used (4.7, note 1 of the 1992 edition)

Frequently asked questions