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Methods Of Water Content Determination In Petroleum Products

Technical Knowledge 2023-08-30 10:55:46
This article provides a comprehensive understanding of water content determination in petroleum products, including sources, forms, hazards, and methods of measurement. It emphasizes the importance of accurate water content analysis for ensuring product quality and preventing performance issues in various industries such as petroleum, chemicals, power, and more.

1. Sources of Water Content in Petroleum Products:

(1) Water Contamination during Storage and Transportation

Water can get mixed into petroleum products during storage, transportation, refueling, and usage due to various reasons. Residual moisture in containers, inadequate sealing of storage tanks, ingress of rain, snow, or frost during refueling, as well as condensation of water vapor, can all lead to the presence of water in petroleum products.


(2) Dissolved Moisture from Air

Petroleum products, especially light fuels, have a certain degree of water solubility. With increasing temperature, humidity in the air, and aromatic hydrocarbon content, the water solubility of light fuels also increases. Gasoline and kerosene do not readily mix with water but can contain up to 0.01% dissolved water.


2. Forms of Water Presence in Oil Products:

(1) Suspended Water

Water is suspended in the form of small droplets in the oil, forming cloudy emulsions or colloids. This phenomenon commonly occurs in high-viscosity heavy oils, with protective films formed by cyclic acids, colloidal substances, clays, and more. In such cases, water is difficult to separate by sedimentation and requires special dehydration methods. For example, air agitation and heating or vacuum drying methods are used to remove water from water-containing lubricating oils.


(2) Dissolved Water

Water is uniformly dispersed in molecular form among hydrocarbon molecules, known as dissolved water. The solubility of water in oil depends on the chemical composition of the oil and temperature. Alkanes, cycloalkanes, and olefins generally have weaker water solubility, while aromatics can dissolve more water. Higher temperatures result in greater dissolved water content in oil. In general, gasoline, kerosene, diesel, and some light lubricating oils have minimal dissolved water content, often below the detectable limit as per the "Method for Determining Water Content in Petroleum Products" GB/T260-1977 (1988).


(3) Free Water

Precipitated micro-water particles aggregate into larger droplets and settle out of the oil, resulting in an oil-water separation state. The term "water-free" in oil analysis generally refers to the absence of free and suspended water; dissolved water is difficult to remove.


3. Harms of Water Content in Petroleum Products:

(1) Impairment of Low-Temperature Flow Performance

Water in aviation fuels can elevate their freezing point, leading to filter or pipeline blockages and even fuel supply interruptions, causing accidents. Vehicle gasoline and diesel containing water can freeze in winter, obstructing fuel systems. Furthermore, water in fuel oil carries inorganic salts into cylinders, causing corrosion, increased carbon deposits, and heightened wear. Water in boiler fuel reduces combustion efficiency and increases corrosiveness.


(2) Degradation of Antioxidant Properties

Water in petroleum products can dissolve added antioxidants, accelerating the gum formation process in fuels like cracked gasoline and other unsaturated hydrocarbon-containing fuels. Water significantly affects the stability of stored fuel oils; gasoline stored with water forms gum faster than when water-free.


(3) Reduction of Oil Solubility

Solvent oils with water experience reduced solubility and efficiency.


(4) Diminution of Lubricating Properties

Water in lubricating oils can freeze into ice particles in winter, blocking fuel pipelines and filters, and increased component wear upon freezing in certain engine parts. Water presence also heightens lubricating oil corrosiveness and emulsification properties.


(5) Deterioration of Dielectric Properties

Water in electrical insulating oils lowers their dielectric properties and can lead to short circuits or even equipment damage.


4. Significance of Water Content Determination in Oil Products:

Water content is a crucial quality parameter for evaluating petroleum products. Determining water content holds the following significance:


Provides a basis for designing dehydration processes.

Evaluates oil product quality: Water content is an essential specification in various petroleum product standards and a primary control parameter for material in/out of oil production facilities.

Prevents the presence of water in petroleum products, except for specially treated water-containing fuels for energy saving and environmental protection.

Overview of Water Content Determination Methods:


Distillation Method: Involves distillation of a sample mixed with water-free solvent to determine water content as a percentage.

Karl Fischer Coulometric Titration Method: Utilizes the relationship between the number of water molecules and the charge according to electrolytic law for determining water content. This method is sensitive, precise, and suitable for trace analysis of low water content samples.


5. Overview of Water Content Determination Methods:


Distillation Method: Involves distillation of a sample mixed with water-free solvent to determine water content as a percentage.


LYD-260A Water Content Tester

Reference standards: GB/T260 Determination of Moisture in Petroleum Products, GB/T512 Determination of Moisture in Lubricating Grease


1. The gripper is designed reasonably. The installation and dismantlement are convenient.

2. The heating power is continuously adjustable. The voltmeter displays the power intuitionally. The temperature control is reasonable.

3. It can do parallel test for two samples. The working efficiency is high.



LYD-8929A Crude Oil Water Content Tester

Reference standard: GB/T8929 Determination of water content in crude oil


1. The instrument is a table-top structure and can test two samples at the same time.

2. The instrument is heated by an electric heating mantle, the heating power is continuously adjustable, and there is no open flame.

3. Parallel test can be done on two samples at the same time, with high work efficiency.


LYD-2122C Coulometric Karl Fischer Titrator

Reference standard: GB/T 11146 Determination of water content in crude oil Karl Fischer coulometric titration

SH/T0246 Determination of Water Content in Light Petroleum Products

GB/T 7600 "Determination of Moisture Content of Transformers in Operation (Coulometric Method)"

Principle: According to the law of electrolysis, the number of water molecules reacted is proportional to the number of charges, and the number of charges (coulombs) participating in the reaction detected by the instrument is automatically converted into the corresponding number of water molecules. Therefore, this method has high test accuracy, low test cost, high sensitivity, high precision, high reproducibility, low power consumption and energy saving design. Widely used in petroleum, chemical industry, electric power, quality inspection, scientific research, environmental protection, energy and other fields.



1. It can perform trace analysis on samples with low water content, with high sensitivity.

2. Equipped with an imported 0.5ul sample injector for calibration, the calibration of the instrument is fast and accurate.

3. It has test data storage space, which can store more than 20,000 test results, which is convenient for query and retrieval.

4. Adopt unique alternating balance isolation detection technology to make detection faster, more accurate and more stable.

5. The electrolytic circuit adopts PWM pulse width adjustment method, which is advanced in technology and greatly reduces the power consumption of the whole machine.

6. Adopt the touch screen human-computer interaction mode, and the man-machine dialogue interface is friendly, intuitive and friendly.

7. It has a real-time clock (year, month, day, hour, minute, second) display, and has a clock power-off hold function.

8. Embedded thermal printer, 36 characters, Chinese character output, printing is quieter, faster and clearer.

9. Convenient I/O technology, using program control, directly input numbers from the interface to adjust the stirring speed.

10. A variety of formula options, automatic replacement of display units (ug, mg/L, ppm, %) can be memorized.

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