Determination of the density of oil and oil products with a hydrometer is carried out in accordance with GOST 3900-85.

The essence of the method consists in immersing the hydrometer in the product under test, taking readings on the hydrometer scale at the determination temperature and converting the results to density at a temperature of 20 °C.

Equipment

To carry out the work you need:

Preparation for analysis

The oil sample is brought to the test temperature or maintained at a temperature environment until this temperature is reached.

Conducting an analysis

A sample of the product to be tested is poured into a cylinder set on a level surface at the same temperature as the sample. The cylinder should be filled with the sample no more than 2/3 of the volume. Air bubbles that form on the surface are removed with filter paper.

The temperature of the test sample is measured before and after the density measurement. The temperature is maintained constant with an error of not more than 0.2 °C.

Rice. 1.2. Hydrometer Fig. 1.3. Taking readings

The clean and dry hydrometer (Figure 1.2) is slowly and carefully lowered into the cylinder containing the product to be tested. The hydrometer is supported by the upper end, preventing wetting of the part of the rod located above the immersion level of the hydrometer. When the oscillations of the hydrometer stop, read the readings along the upper edge of the meniscus. In this case, the eye should be at the level of the meniscus (Fig. 1.3).

The reading on the hydrometer scale corresponds to the density of the oil product at the test temperature (g/cm3).

Results processing

The measured test temperature is rounded off to the nearest temperature value given in Table. 1.5.

Table 1.5

Conversion of density at test temperature to density at 20 °C

According to the density value determined using a hydrometer and the rounded temperature value, the density of the test product at a temperature of 20 ° C is found according to Table. 1.5.

The arithmetic mean of the two determinations is taken as the test result.

State Scientific Metrological Center
Federal State Unitary Enterprise "All-Russian Research Institute of Metrology
them. DI. Mendeleev"
(GNMTs FSUE "VNIIM named after D.I. Mendeleev")
Gosstandart of Russia

State system ensuring the uniformity of measurements

OIL DENSITY
Requirements for methods for performing measurements with a hydrometer
in accounting transactions

MI 2153-2004

ST. PETERSBURG 2003

2.8 Tanks for taking and transferring oil samples.

2.9 Gasoline solvent according to TU 38.401-67-108.

2.11 Distilled water of single distillation according to GOST 6709.

It is allowed to use other measuring instruments and materials that provide density measurements in accordance with this recommendation.

3 Measurement method

3.1 The methodology described in this recommendation is used when determining the mass of oil by the indirect method of dynamic and static measurements in case of absence or failure of the in-line density transducer (in-line PT) and to control the in-line PT.

3.2 The essence of the method consists in immersing the hydrometer in the tested oil sample, taking readings on the hydrometer scale at the test temperature and recalculating the hydrometer readings to the temperature and pressure at which the volume of oil is determined. When monitoring in-line PP, the hydrometer readings are recalculated to the temperature and pressure of oil in the density meter at the time of sampling for control.

4 Safety, environmental and operator qualification requirements

When measuring the density of oil, the following safety requirements are observed:

4.1 Room for oil density measurements according to fire hazard belong to category A. It meets the requirements of the "Rules fire safety for industrial enterprises”, approved by the Main Directorate fire brigade Ministry of Internal Affairs of Russia.

4.2 The room is equipped with devices supply and exhaust ventilation and fume hoods. Persons performing measurements are provided with personal protective equipment.

4.3 Flammable testing and flushing liquids are placed in metal canisters for storing petroleum products. Canisters are placed in rooms specially designed for storing petroleum products or metal cabinets.

4.4 Persons at least 18 years of age who have been instructed in safety precautions and have studied the operational documentation for the measuring instruments used and this recommendation are allowed to perform measurements.

5 Measurement conditions and preparation for measurement

5.1 All used measuring instruments are verified, have valid verification certificates or impressions of verification marks.

5.2 Measurements are carried out in the block for measuring oil quality parameters (BIK) or in the premises of the testing (analytical) laboratory.

5.3 When performing measurements, observe following conditions:

5.4 If the temperature of the oil sample before filling the measuring cylinder differs from the ambient air temperature by more than 3 °C, use a heat-insulated, temperature-controlled or built-in pipeline cylinder.

5.6 Filling the measuring cylinder or other container during sampling, packaging and testing is carried out in a closed way using a tube lowered to the bottom.

5.7 Before measurements, the oil sample in the sample receiver or other vessel is mixed without leaking (the capacity of the container and the volume of the sample taken allow for uniform mixing).

5.8 Hydrometers, cylinders, sample receiver and other equipment used are washed with nefras or hot water and air dry.

6 Taking measurements

7.6 The result of oil density measurements is taken as the value calculated in accordance with paragraph . Numbers are recorded and rounded to four significant digits.

State Scientific Metrological Center
Federal State Unitary Enterprise "All-Russian Research Institute of Metrology
them. DI. Mendeleev"
(GNMTs FSUE "VNIIM named after D.I. Mendeleev")
Gosstandart of Russia

State system for ensuring the uniformity of measurements

OIL DENSITY
Requirements for methods for performing measurements with a hydrometer
in accounting transactions

MI 2153-2004

ST. PETERSBURG 2003

2.8 Tanks for taking and transferring oil samples.

2.9 Gasoline solvent according to TU 38.401-67-108.

2.11 Distilled water of single distillation according to GOST 6709.

It is allowed to use other measuring instruments and materials that provide density measurements in accordance with this recommendation.

3 Measurement method

3.1 The methodology outlined in this recommendation is used when determining the mass of oil by the indirect method of dynamic and static measurements in the absence or failure of the in-line density transducer (in-line DP) and to control in-line PP.

3.2 The essence of the method consists in immersing the hydrometer in the tested oil sample, taking readings on the hydrometer scale at the test temperature and recalculating the hydrometer readings to the temperature and pressure at which the volume of oil is determined. When monitoring in-line PP, the hydrometer readings are recalculated to the temperature and pressure of oil in the density meter at the time of sampling for control.

4 Safety, environmental and operator qualification requirements

When measuring the density of oil, the following safety requirements are observed:

4.1 The room for measuring the density of oil in terms of fire danger is classified as category A. It meets the requirements of the "Fire Safety Rules for Industrial Enterprises" approved by the Main Directorate of Fire Protection of the Ministry of Internal Affairs of Russia.

4.2 The room is equipped with supply and exhaust ventilation devices and fume hoods. Persons performing measurements are provided with personal protective equipment.

4.3 Flammable testing and flushing liquids are placed in metal canisters for storing petroleum products. Canisters are placed in rooms specially designed for storing petroleum products or metal cabinets.

4.4 Persons at least 18 years of age who have been instructed in safety precautions and have studied the operational documentation for the measuring instruments used and this recommendation are allowed to perform measurements.

5 Measurement conditions and preparation for measurement

5.1 All used measuring instruments are verified, have valid verification certificates or impressions of verification marks.

5.2 Measurements are carried out in the block for measuring oil quality parameters (BIK) or in the premises of the testing (analytical) laboratory.

5.3 When performing measurements, the following conditions are observed:

5.4 If the temperature of the oil sample before filling the measuring cylinder differs from the ambient air temperature by more than 3 °C, use a heat-insulated, temperature-controlled or built-in pipeline cylinder.

5.6 Filling the measuring cylinder or other container during sampling, packaging and testing is carried out in a closed way using a tube lowered to the bottom.

5.7 Before measurements, the oil sample in the sample receiver or other vessel is mixed without leaking (the capacity of the container and the volume of the sample taken allow for uniform mixing).

5.8 Hydrometers, cylinders, sample receiver and other equipment used are washed with nefras or hot water and dried in air.

6 Taking measurements

7.6 The result of oil density measurements is taken as the value calculated in accordance with paragraph . Numbers are recorded and rounded to four significant digits.

Density called the mass of a unit volume of a substance (oil, oil product). The SI unit of density is kg/m 3 .

In research practice, the relative density is determined.

Relative density is the ratio of the density (mass) of oil or oil product at 20ºС to the density (mass of the same volume) of distilled water (reference substance) at 4ºС. The relative density is denoted by ρ 20 4 . Multiplying the value of the relative density by 1000, we get the density in kg / m 3.

The density of oil and oil products depends on temperature. As the temperature rises, their density decreases. Density versus temperature based on the linear law:

ρ t 4 \u003d ρ 20 4 - γ (t-20),

This dependence is valid for the temperature range of 0 ... 50ºС and for oils (petroleum products) that do not contain a large number solid paraffin and aromatic hydrocarbons.

Methods for determining density oil products:

1.density determination pycnometer(GOST 3900-85);

2.density determination hydrometer(oil density meter).

Density determination with a pycnometer(GOST 3900-85):

Instruments, reagents, materials: pycnometer, thermostat, chromium mixture, distilled water, ethyl alcohol, pipette, filter paper.

The standard temperature at which the density of oil and oil products is determined is 20ºС. To determine the density, glass pycnometers (decanters with a lid) with a label and a capillary tube are used. different capacity. Each specific pycnometer is characterized by " water number”, i.e. mass of water in the volume of this pycnometer at 20ºС. Before determining the water number, the pycnometer is washed successively with a chromium mixture, distilled water, ethyl alcohol and dried. A clean and dry pycnometer is weighed to the nearest 0.0001 g. Using a pipette, fill the pycnometer with distilled, freshly boiled and cooled to room temperature water (pycnometers with a mark are above the mark, and capillary ones are up to the top). Then the pycnometer with water is thermostated at (20±0.1)ºС for 30 min, keeping the pycnometer in the thermostat on a cork float. When the water level in the neck of the pycnometer stops changing, take the excess water with a pipette or filter paper, wipe the neck of the pycnometer inside and close with a cork. The water level in the pycnometer is set at the top of the meniscus. In capillary pycnometers, excess water is taken from the capillary with filter paper. The pycnometer with the water level set at (20 ± 0.1) ° C is thoroughly wiped from the outside and weighed to the nearest 0.0001 g.

« water number» m pycnometer is calculated by the formula:

m \u003d m 2 - m 1,

where m 2, m 1 are the masses of pycnometers, respectively, with water and empty, g.

The "water number" of the pycnometer must be checked after 20 determinations of the density of the oil (oil product).

oil density (oil product) with viscosity at 50ºС no more than 75 mm 2 /s determine pycnometer in the following way:

A dry and clean pycnometer is filled with a pipette with the analyzed oil (petroleum product) at 18 ... 20ºС ( pycnometer with label- slightly above the mark, and capillary- to the top), trying not to cover the walls of the pycnometer. Then the pycnometer with oil (oil product) is closed with a stopper and thermostated at (20 ± 0.1) ºС until the level of oil (oil product) stops changing. Excess oil (petroleum product) is taken with a pipette or filter paper. The level of oil (petroleum product) in the pycnometer is set along the upper edge of the meniscus. The pycnometer with the level set is removed from the thermostat, thoroughly wiped and weighed to the nearest 0.0001 g.

« Visible» density ρ"

ρ" \u003d (m 3 - m 1) / m,

where m 3 is the mass of the pycnometer with oil (oil product), g; m 1 - mass of an empty pycnometer, g; m is the "water number" of the pycnometer, g.

"Visible" density is converted to at 20ºС by the formula:

ρ 20 4 \u003d (0.99823-0.0012) ρ "+ 0.0012 \u003d 0.99703ρ" + 0.0012,

where 0.99823 is the value of water density at 20ºС; 0.0012 - the value of air density at 20ºС and a pressure of 0.1 MPa (760 mm Hg).

The corrections to the “apparent” density calculated using this formula are summarized in the table “Corrections to the “apparent” density”. To obtain the relative density ρ 20 4 at 20ºС of the analyzed oil (petroleum product), the correction is subtracted from the values ​​of the “apparent” density. discrepancy 0,0004 .

oil density (oil product) with viscosity at 50ºС more than 75 mm 2 /s and solid petroleum products at room temperature are determined pycnometer with label. A dry and clean pycnometer is filled about halfway with oil (petroleum product) so as not to smear its walls. When filling the pycnometer with a very viscous oil product, the latter is preheated to 50 ... 60ºС. After filling the pycnometer by about half, it is heated in a thermostat to 80 ... 100ºС (depending on the viscosity of the oil product) for 20 ... 30 minutes to remove air bubbles and then cooled to 20ºС.

If the oil product is in a solid state at room temperature (for example, residual or oxidized bitumen), the pycnometer is filled to about half with small pieces of oil product and then thermostated at a temperature of 10 ° C above its melting point, but not lower than 100 ° C, to remove air and complete melting. Then the pycnometer is cooled to 20ºС, wiped and weighed to the nearest 0.0001 g.

After that, the pycnometer with the oil product is filled with distilled water and thermostated at (20±0.1)ºС until the water level stops changing. Excess water is taken with a pipette or filter paper and the neck of the pycnometer is wiped inside. The water level in the pycnometer is set at the top of the meniscus. The pycnometer is removed from the thermostat, thoroughly wiped from the outside and weighed to the nearest 0.0001 g.

« Visible» density ρ" analyzed oil (oil product) is calculated by the formula:

ρ" \u003d (m 3 - m 1) /,

where m 4 is the mass of the pycnometer with oil and water, g; m 3 - mass of the pycnometer with oil, g; m 1 - mass of an empty pycnometer, g; m - "water number" of the pycnometer, g.

The obtained value of the "apparent" density is converted into relative density ρ 20 4 at 20ºС. discrepancy between parallel density determinations should not exceed 0,0008 .

The results of density determination are distorted if the initial oil (oil product) sample contains water and mechanical impurities.

Determination of density with a hydrometer (oil densimeter):

Instruments, reagents: hydrometer; a glass or metal cylinder with a diameter of at least 5 cm; kerosene.

A hydrometer determines the density of oils, light and dark petroleum products and oils having viscosity at 50ºС no more than 200 mm 2 /s, as well as more viscous petroleum products that do not precipitate when diluted. Determining the density of volatile petroleum products (eg petroleum ether, gas condensate) with a hydrometer is not recommended.

Hydrometers are selected in such a way that, when immersed in the analyzed oil (petroleum products), they do not sink and do not float above the part where the density calibration scale is applied. Determination of density by a hydrometer is based on the law of Archimedes.

Before determining the density, the analyzed sample of oil (petroleum product) is kept at ambient temperature so that the sample assumes this temperature.

oil density(petroleum) with viscosity at 50ºС no more than 200 mm 2 /s determine hydrometer in the following way:

Oil (petroleum) is carefully poured into a clean dry glass (or metal) cylinder with a diameter of at least 5 cm, mounted on a solid stand, along the wall or over a glass rod so that when the hydrometer is immersed, the analyzed sample does not overflow over the edges of the cylinder. Then a clean and dry hydrometer is slowly and carefully lowered into the oil (petroleum), holding it by the upper end. After the hydrometer is established and its oscillations stop, the density value is read along the upper edge of the meniscus. In this case, the researcher's eye should be at the level of the meniscus. At the same time, the temperature of the oil (petroleum product) is determined using a hydrometer thermometer or an additional thermometer (hydrometers come with a thermometer and without a thermometer).

Reading on the hydrometer scale gives the density of oil (petroleum product) at the temperature of analysis. To bring the found density to a relative density ρ 20 4 at normal temperature(20ºС) use the formula:

ρ t 4 \u003d ρ 20 4 - γ (t-20),

where ρ t 4 is the relative density at the analysis temperature; ρ 20 4 - relative density at 20ºС; γ - average temperature correction of density per 1ºС (according to the table: "Average temperature corrections of density per 1ºС for oils and oil products"); t is the temperature at which the analysis is carried out, ºС.

discrepancy between parallel density determinations should not exceed 0,001…0,002 .

For determining density high viscosity oils and petroleum products having viscosity at at 50ºС more than 200 mm 2 /s, they must first be diluted with kerosene. Viscous oils (petroleum products) are diluted with an equal (exactly) volume of kerosene with a known density. If the density of kerosene is unknown, it can be determined with the same hydrometer.

The density of the analyzed viscous oil (petroleum product) is calculated by the formula:

ρ = 2ρ 1 – ρ 2 ,

where ρ 1 is the density of the mixture; ρ 2 is the density of kerosene.

Depending on the type of hydrometer discrepancy between parallel determinations of the density of viscous oils and petroleum products should not exceed 0,004…0,008 .

The essence of the method. The essence of the method consists in immersing the hydrometer in the product under test, taking readings on the hydrometer scale at the determination temperature and converting the results to density at a temperature of 20ºС.

Equipment and materials:

Set of hydrometers;

Cylinder for hydrometer glass;

Mercury glass thermometer;

Funnel glass;

Paper napkins.

Working process:

The cylinder for hydrometers is installed on flat surface. A sample of the product to be tested is poured into a cylinder. Air bubbles that form on the surface are removed with filter paper or a napkin.

The temperature of the test sample is measured before and after the thermometer density measurement.

A clean and dry hydrometer is slowly and carefully lowered into the cylinder with the product to be tested, supporting the hydrometer by the upper end, preventing wetting of the part of the rod located above the immersion level of the hydrometer.

When the hydrometer is established and its oscillations stop, the readings are taken along the upper edge of the meniscus, while the eye is at the level of the meniscus. The reading on the hydrometer scale corresponds to the density of the oil product at the test temperature ρ t .

The measured test temperature is rounded up to the nearest temperature value given in the annex table.

According to the rounded value of temperature and density ρ t, determined on the scale of the hydrometer, find the density of the test product at 20 ° C according to the application table.

The test result is taken as the arithmetic mean of the two density determinations.

For oil and oil products intended for export, recalculate the measured density to the density at 15ºС (60 ºF), and when recalculating the mass of oil and oil products in mass units (tons) by volume (barrels), an amendment is made in accordance with GOST R 8.599-2003 " Density and volume of oil. Tables of density and mass conversion factors”.

By density and according to the GOST 51858-2002 standard, we determine the type of this batch of oil.

Density Conversion at Density Test Temperature

at a temperature of 20ºС, GOST 3900-85.

The application table shows the density values ​​​​(in g / cm 3) at a temperature of 20ºС.

Example.

The density of the oil product at a temperature of 27.5ºС is 0.6448 g/cm 3 .

To convert the density of a product measured at 27.5ºС to density at 20ºС, it is necessary:

a. round the measured density up to the second significant digit, for example up to 0.640 or up to 0.650 g/cm 3 ;

b. according to the table in the horizontal column “Density on the hydrometer scale, g / cm 3”, find the rounded density value, for example, 0.640;

in. in the column "Test temperature, ºС" find the value of the test temperature - 27.5ºС;

g. according to the table, find the density of the product at 20ºС - 0.647 g / cm 3 (at the intersection of the column and row). Since, when rounding the measured density, the density value was actually reduced by 0.6448 - 0.640 \u003d 0.0048 g / cm 3, it is necessary to add this value to the density value found in the table at 20ºС, that is, (0.647 + 0.0048) g / cm 3 \u003d 0.6518 g / cm 3.

Thus, the density of the product at 20ºС is 0.6518 g/cm 3 .

If the measured density is rounded up to 0.650 g/cm 3 , the actual density increase is 0.650 - 0.6448 = 0.0052 g/cm 3 . Therefore, from the density value at 20ºС, found from the table (0.6569 g / cm 3), it is necessary to subtract 0.0052 g / cm 3, that is, 0.657 - 0.0052 \u003d 0.6518 g / cm 3.

The density of the product at 20ºС is 0.6518 g/cm 3 .

D is the difference between and the taken density value on the hydrometer scale of the GOST 3900-85 table.

Using table 2, we determine the type of oil:

0 - extra light;

1 - light;

2 - medium;

3 - heavy;

4 - bituminous.

table 2

III. Questions for self-control

1. Methods for determining the density of oil and oil products.

2. Which of the methods for determining the density of oil and oil products is the most accurate, which one is the fastest?

3. Areometric method.

4. Dimension of density.

5. Dependence of density of oil products on temperature.

6. Dependence of the density of oil and oil products on the hydrocarbon composition.

7. Practical use density of oil and oil products during acceptance operations in determining the type of oil.

8. For which oil products is density a standardized indicator?

9. GOST 3900-85, procedure for performing calculations.

10. Determine the relative density of a mixture consisting of three components:

V 1 \u003d 0.05 m 3, relative density

V 2 \u003d 820 l, relative density

M 3 = 25 kg, relative density

11. Relative density of the oil product at 20ºС () 0.825. Using the Manovyan formula, determine the relative density of the oil product at 55ºС ().

12. Relative density of the oil product at 20ºС () 0.750. Using the Mendeleev formula, determine the relative density of the oil product at 32ºС ().

Appendix

Density conversion table at test temperature in

density at 20 ºС

Lab #3

Oil viscosity