❄️ Pour Point Temperature

Petrochemistry PN-EN ISO 3016

Overview

STATUS (as of 30.10.2026). PN-EN ISO 3016:2019-06 — Polish and English versions, implements EN ISO 3016:2019 and ISO 3016:2019 [IDT]; the Polish version was published on 05.02.2021 and replaced PN-ISO 3016:2005 (which implemented ISO 3016:1994). ISO 3016:2019 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 pour point of petroleum products; the standard also describes a separate procedure for determining the lower pour point of fuel oils, heavy lubricant base stock and products containing residual fuel components. The procedure is not suitable for crude oils. Equipment using a similar automated procedure is available, but its precision has not been established (ISO is developing a separate standard for an automated test method). The pour point is the lowest temperature at which a sample of petroleum product will continue to flow when it is cooled under specified standard conditions. According to the corresponding American standard ASTM D97 (5.1), the pour point is an index of the lowest temperature of a product's utility for certain applications.

EDITION (foreword). Compared with the 1994 edition, the digital contact thermometer was included, the normative references were updated, chemicals and cooling mixtures were moved to Annex B (as in ISO 3015), and the bath and sample temperature ranges were aligned with ASTM D97 — the changes in bath temperatures and transfer points applied since 1994 have not shown a bias against results obtained with the former edition. The option of using automatic apparatus was removed — its use is at the discretion of the laboratory and the precision of the standard does not apply to it; sampling instructions were added (clause 6), the precision was aligned with ASTM D97, and Annex C and a bibliography were 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 at (54 ± 3) mm above the inside bottom representing 45 ml ± 1 ml. Digital contact thermometer (A.1) or partial-immersion liquid-in-glass thermometer (A.2) — checked immediately before the test, accurate within ± 1 °C, for example at the ice point; a cork bored centrally for the measuring device. Watertight, cylindrical, metal, flat-bottomed jacket, (115 ± 3) mm deep, with an inside diameter of 44.2 mm to 45.8 mm and a wall thickness of about 1 mm, projecting not more than 25 mm out of the cooling medium; a disc of cork or felt about 6 mm thick and a ring gasket about 5 mm thick that prevents the jar from touching the jacket. Cooling baths with a firm support holding the jacket vertical, cooled by refrigeration or by cooling mixtures (Annex B), and a timing device measuring up to 30 s with an accuracy of 0.2 s.

PREPARATION AND PRELIMINARY HEATING (7.1–7.6). The sample is poured into the test jar to the level mark, if necessary after heating it in a water bath until it is just sufficiently fluid to pour. If it had to be heated above 45 °C, if it has been heated above 45 °C during the preceding 24 h, or if its thermal history is not known, it is kept at room temperature for 24 h before testing. For pour points above 36 °C a higher-range device is used, for example an IP 63C or ASTM 61C thermometer, or a digital contact thermometer; the device is set coaxially with the jar — for a liquid-in-glass thermometer the beginning of the capillary 3 mm below the surface of the specimen, for a digital contact thermometer the end of the probe 10 mm to 15 mm below the surface. Samples with pour points above −33 °C are heated without stirring to 9 °C above the expected pour point in a bath at 12 °C above it, or to 45 °C in a bath at 48 °C, whichever is greater, and transferred to a bath at 24 °C ± 1.5 °C; observations start when the sample reaches 9 °C above the expected pour point (estimated as a multiple of 3 °C), and if the sample is still flowing at 27 °C, the jar is wiped on the outside and placed in the 0 °C bath. Samples with pour points of −33 °C and below are heated without stirring to 45 °C in a bath at 48 °C ± 1.5 °C, transferred to the 24 °C ± 1.5 °C bath, at 27 °C the high-range liquid-in-glass thermometer is replaced with the low-range one, and the jar is transferred to the cooling bath. The disc and the jacket are placed in the cooling medium at least 10 min before the jar is inserted, the gasket is placed about 25 mm from the bottom of the jar, and a test jar is never placed directly into the cooling medium.

OBSERVATIONS AND BATHS (7.7–7.9, Table 1). At each thermometer reading that is a multiple of 3 °C below the temperature of the first observation, the jar is removed from the bath or jacket and tilted just sufficiently to ascertain whether there is movement in the sample — the complete operation, including wiping and replacement, should typically not require more than 3 s. Once wax crystals form, the mass of the specimen must not be disturbed nor the thermometer shifted — disturbing the spongy network of wax crystals leads to low and erroneous results; condensed moisture is removed with a cloth moistened with wiping fluid (for example ethanol or methanol) close to the bath temperature. As soon as the sample does not flow when tilted, the jar is held in a horizontal position for 5 s, as measured by the timing device; if the sample shows any movement, the jar is replaced immediately and the observation repeated 3 °C lower, until a reading is reached at which the sample shows no movement when held horizontal for 5 s — this reading is recorded. Baths (Table 1): 1 — 12 °C above the expected pour point or 48 °C ± 1.5 °C, whichever is greater (preliminary heating); 2 — 24 °C, sample from the start to 27 °C; 3 — 0 °C, from 27 °C to 9 °C; 4 — −18 °C, from 9 °C to −6 °C; 5 — −33 °C, from −6 °C to −24 °C; 6 — −51 °C, from −24 °C to −42 °C; 7 — −69 °C, from −42 °C to −60 °C (baths 2–7 ± 1.5 °C). For obsolescent specifications with limits not divisible by 3 °C, observations start 9 °C above the limit, continue every 3 °C until the specification temperature and the result is reported as passing or failing.

RESULT, LOWER POUR POINT AND PRECISION — ACCORDING TO THE 1994 EDITION (ISO 3016:1994, in Poland PN-ISO 3016:2005; clauses 8–10 of the current edition are not known to us). 3 °C is added to the reading at which the sample held horizontal for 5 s remained motionless, and the result is reported as the pour point (clause 7). For fuel oils, heavy lubricant base stock and products containing residual fuel components, the result of the basic procedure is the upper (maximum) pour point; the lower (minimum) pour point is determined by heating the sample while stirring to 105 °C, pouring it into the jar and proceeding as in 6.2–6.8 (6.10). Repeatability 3 °C, reproducibility 6 °C — from tests of 10 new mineral oil-based lubricants (pour points from −48 °C to −6 °C) and 16 fuel oils (from −33 °C to +51 °C) by 12 co-operators (8.1–8.2, note 5). The 2019 edition gives the precision separately for lubricating oils and for middle distillate and residual fuels, aligned with ASTM D97, and an informative Annex C with derived values (foreword, table of contents).

WHAT WE DO NOT GIVE HERE. The expression of results, the lower pour point procedure and the precision values of the 2019 edition (clauses 8–9, Annex C), or the requirements of that edition for thermometers (Annex A) and cooling mixtures (Annex B) — they are outside the available text of the standard; we give them according to the 1994 edition, labelled as such.

Method principle

After preliminary heating, the sample is cooled at a specified rate and checked for flow every 3 °C (clause 4): the jar is tilted just sufficiently to ascertain movement, and when the sample does not flow when tilted, it is held horizontal for 5 s.

The pour point is the lowest temperature at which movement of the sample is observed; according to the 1994 edition it is obtained by adding 3 °C to the reading at which the sample held horizontal for 5 s remained motionless (clause 7 of the 1994 edition).

Applications

• Petroleum products (clause 1); the precision of the 2019 edition covers lubricating oils and middle distillate and residual fuels (9.2–9.3 according to the table of contents)
• Fuel oils, heavy lubricant base stock and products containing residual fuel components — separate lower pour point procedure (clause 1)
• Checking conformity with obsolescent specifications whose limits are not divisible by 3 °C — result “passing” or “failing” (7.9)
• Not applicable to crude oils — the procedure is not suitable for them (clause 1)

Key parameters

Standard

Standard number

PN-EN ISO 3016:2019-06

Title (PL)

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

Title (EN)

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

Step-by-step procedure

1. Filling and thermal history

   Pour the sample to the level mark, if necessary heating it in a water bath until it is just sufficiently fluid. If it had to be heated above 45 °C, if it has been heated above 45 °C during the preceding 24 h, or if its thermal history is not known — keep it at room temperature for 24 h before testing (7.1).

2. Measuring device

   Close the jar with the cork carrying the device set coaxially: a liquid-in-glass thermometer with the beginning of the capillary 3 mm below the surface of the specimen, a digital probe with its end 10–15 mm below the surface; above 36 °C a higher-range device (7.2).

3. Preliminary heating

   Pour point above −33 °C: without stirring to 9 °C above the expected one in a bath at 12 °C above it, or to 45 °C in a bath at 48 °C — whichever is greater; then the 24 °C ± 1.5 °C bath. Pour point of −33 °C and below: to 45 °C in a bath at 48 °C ± 1.5 °C, then the 24 °C bath; at 27 °C replace the liquid-in-glass thermometer with the low-range one (7.3–7.5).

4. Jacket and baths

   Disc and jacket in the cooling medium at least 10 min beforehand, gasket about 25 mm from the bottom; the jar never directly in the cooling medium. Transfer: at 27 °C to 0 °C, at 9 °C to −18 °C, at −6 °C to −33 °C, at −24 °C to −51 °C, at −42 °C to −69 °C (7.6, 7.8, Table 1).

5. Observations every 3 °C

   From 9 °C above the expected pour point, at each reading that is a multiple of 3 °C remove the jar and tilt it just sufficiently to ascertain movement — typically no more than 3 s in total; once wax crystals have formed, do not disturb the mass of the specimen or the thermometer (7.4.3, 7.7.1–7.7.2).

6. Horizontal check

   When the sample does not flow when tilted, hold the jar horizontal for 5 s by the timing device; at any movement replace it and repeat 3 °C lower; record the reading at which the sample remained motionless (7.7.3–7.7.4).

7. Result

   1994 edition (clause 7): add 3 °C to the recorded reading and report it as the pour point or lower pour point; the expression of results according to the 2019 edition (clause 8) is not known to us.

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 1994 edition among others solid carbon dioxide with acetone, methanol or petroleum naphtha, prepared in a covered metal beaker) — precautions according to the safety data sheets of the substances used (5.7, note 3 of the 1994 edition)

Frequently asked questions