BS 2000-40:1992 pdf free download.Determination of oxidation stability of gasoline nduction period method.
1. SCOPE
1.1 This method describes a procedure for determining the stability under accelerated oxidation conditions of aviation and motor gasoline in their finished form only.
CAUTION: ThLc method is not intended for determining the stability of gasoline components particularly those with a high percentage of low boiling unsaturated compounds as these may cause explosive conditions within the apparatus. However, because of the unknown nature of certain samples the bomb assembly shall include a safety burst disk in order to safeguard the operator.
NOTE 1: For measurement of oxidation stability of gasoline by measurement of potential gum. refer to method ASTM D873—IP 138. Test for Oxidation Stability of Avialion Fuels (Potential Residue Method).
NOTE 2: The accepted unit of pressure is the bar for IP methods. The ASTM uses the pascal (Pa) for pressure measurement. Unit conversion factors are as follows:
1 psi — 6.894757x I0 Pa
I psi — 0.06894757 bar
I bar— lO Pa.
2. SUMMARY OF METHOD
2.1. The sample is oxidized in a bomb initially filled at 15 to 25°C with oxygen at 7.0 bar and heated at a temperature between 98 and 102°C. The pressure is read at stated intervals or recorded continuously until the break point is reached. The time required for the sample to reach this point is the observed induction period at the temperature of test, from which the induction period at 100°C may be calculated.
3. SIGNIFICANCE
3.1. The induction period may be used as an indication of the tendency of motor gasoline to form gum on storage. It should be recognised, however, that its correlation with the formation of gum in storage may vary markedly under different storage conditions and with different gasolines.
4. DEFINITIONS
4.1. Break Point is the point in the pressure-time curve that is preceded by a pressure drop of exactly 0.14 bar within 15 mm and succeeded by a drop of not less than 0.14 bar in 15 mm.
4.2. Induction Period is the time elapsed between the placing of the bomb in the bath and the break point at 100°C.
5. APPARATUS
5.1. Oxidation Bomb, Glass Sample Container and Cover, Accessories, Pressure Gauge, and Oxidation Bath, as described in the Annex.
5.2. Thermometer — having a range shown below and conforming to the requirements as prescribed in ASTM specifications El or the Specifications for IP Standard Thermometers Appendix A.
6. MATERIALS
6.1. Gum Solvent — A mixture of equal volumes of toluene and acetone.
CAUTION: Toluene is a toxic, volatile hydrocarbon which Is absorbed by inhaling the vapour or through the skin by contact with the liquid. Use in adequate ventilation and avoid skin contact.
7. PREPARATION OF APPARATUS
7.1. Wash the glass sample container with gum solvent until free from gum, rinse thoroughly with water and immerse the sample container and cover in hot detergent cleaning solution. Remove from the cleaning solution by means of corrosion-resistant steel forceps and handle only with forceps thereafter. Wash thoroughly, first with tap water, then distilled water, and dry in an oven at 100 to 150°C for at least
lh.
detergent cleaning shall be a matching of quality of that obtained with chromic acid cleaning solution on used sample containers and covers (fresh chromic acid, 6 h soaking penod. rinsing with distilled water and drying). For this comparison visual appearance and weight loss on heating the glassware under test conditions may be used.
Detergent cleaning avoids the potential hazards and inconveniences related to handling chromic acid solutions. The btter remains as the reference cleaning practice and as such may function as an alternitive to the preferred procedure — cleaning with detergent solutions.
CAUTION: Chromic acid is pot enisally hazardous in contact with organic materials and I, toxic and highly corrosive. If used, wear approved full face -shield. andfull-length protective clothing mcludin.g gloves (ES 2092/2 .tpeclfies protective gloves).
7.2. Drain any gasoline from the bomb and wipe the inside of the bomb and lid, first with a clean cloth moistened with gum solvent and then with a clean dry cloth. Remove the filler rod from the stem and carefully clean any gum or gasoline from both stem and rod with gum solvent. Clean the needle valve, the quick release air coupling and all lines leading to the bomb. The bomb, the valve and all connecting lines shall be thoroughly dry before each test is started.
CAUTION: Volatile peroxides which may have formed during a previous test may accumulate in the equipment producing a potentially explosive environment.
8. PROCEDURE
8.1. Bring the bomb and the gasoline to be tested to a temperature of 15 to 25°C. Place the glass sample container in the bomb and add 50± 1 mL of sample. Cover the sample container, close the bomb, and using the quick release air-coupling introduce oxygen until a gauge pressure of 6.89 to 7.03 bar is attained. Allow the gas in the bomb to escape slowly in order to flush out the air originally present. (CAUTION:
Release the pressure through the needle valve at a rate not to exceed 3.5 bar per minute.) Introduce oxygen again until a gauge pressure of 6.89 to 7.03 bar is attained and observe for leaks, ignoring an initial rapid drop in pressure (generally not over 0.4 bar) which may be observed because of the solution of oxygen in the sample. If the rate of pressure drop does not exceed 0.07 bar in 10 mm, assume the absence of leaks and proceed with the test without repressunng.
8.2. Place the charged bomb in the vigorously boiling water bath, being careful to avoid shaking, and record the time of immersion as the starting time. Maintain the temperature of the water bath between 98 and 102°C. Observe the temperature to the nearest
0.1°C at intervals during the test, and record the average temperature to the nearest 0.1°C as the temperature of the test. Make a continuous record of the pressures in the bomb, or if an indicating pressure gauge is used. taking pressure readings at 15 mm intervals or less. If, during the initial 30 mm of the test, a leak develops (as indicated by a steady drop in pressure considerably in excess of 0.14 bar in 15 mm) discard the test. Continue the test until a point is reached which is that noint oreceded by a oressure
drop of exactly 0.14 bar in 15 mm and succeeded by a drop of not less than 0.14 bar in 15mm.
NOTE: if the test is made in a region where the atmospheric pressure is consistently below normal 1013 m bar (760mm Hg), it is permissible to add a higher boiling liquid such as ethylene glycol to the water in order to maintain the operating temperature of the bath in the neighbourhood of 100°C.
8.3. Cool the bomb then record the number of minutes from the time the bomb is placed in the bath until the break pOint2 has been reached as the observed induction period at the temperature of the test.
8.4. Release the pressure from the bomb slowly and wash the bomb and sample container in preparation for the next test.
CAUTiON: Release the pressure through the needle valve at a rate not to exceed 3.5 bar per minute.
9. CALCULATIONS AND REPORTING
9.1. If the test temperature is above 100°C calculate the induction period at 100°C from the observed induction period at the temperature of the test by means of the following equation:
Induction period at 100°C = (IP,)(l +O.lOiAt) where:
IP, induction period at the temperature of the test, and
= algebraic difference between the test temperature and 100°C.
9.2. If the test temperature is below 100°C, calculate the induction period at 100°C by means of the foHowing equation:
IP
Induction period at 100°C = (1 +0.10 t)
9.3. Report the results as induction period at — 100°C, IP 40’.
10. PRECISION
10.1. Results should not differ from the mean by more than the following amounts:
Repeatability Reproducibility
(one operator and (I)iflerent operators and
apparatus) apparatus)
5percent lOpercent
NOTE: The precision reported was determined using equipment not incorporating a burst disk. However safety considerations now demand the inclusion of such a disk without waiting to determine ha influence on precision. From a design point of view any effect is expected to be minimal.