D525_10 (12a)

Bring the pressure vessel and the gasoline to be tested to a temperature of 15 to 25 degrees Celsius. Place the glass sample container in the pressure vessel and add 50 plus or minus 1 milliliter of test specimen. Alternatively, transfer 50 plus or minus 1 milliliter of the test specimen into the glass sample container first before placing the glass sample container into the pressure vessel. Cover the sample container. Close the pressure vessel. And using a quick release air coupling, introduce oxygen until a pressure of 690 to 705 kilopascals is attained. Allow the gas in the bomb to escape slowly in order to flush out the air originally present. Release the pressure at a slow uniform rate through the needle valve at a rate not to exceed 345 kilopascals per minute. Introduce oxygen again until a pressure of 690 to 705 kilopascals is attained, and observe for leaks, ignoring an initial rapid drop in pressure, generally not over 40 kilopascals, which may be observed because of the solution of oxygen in the sample. When the rate of pressure drop does not exceed 7 kilopascals in 10 minutes, assume the absence of leaks and proceed with the test without repressuring. Place the charged pressure vessel in the vigorously boiling water bath or appropriate liquid bath equipped with mechanical stirring, being careful to avoid shaking, and record the time of immersion as the starting time. Maintain the temperature of the liquid bath between 98 and 102 degrees Celsius. Observe the temperature to the nearest 0.1 degree Celsius at intervals during the test. And record the average temperature to the near 0.1 degree Celsius as the temperature of the test. Make a continuous record of the pressures in the pressure vessel. Or if an indicating pressure gauge is used, take pressure readings at 15-minute intervals or less. If during the initial 30 minutes of the test a leak develops, as indicated by a steady drop in pressure considerably in excess of 14 kilopascals in 15 minutes, discard the test. Continue the test until reaching a point preceded by a pressure drop of exactly 14 kilopascals in 15 minutes and succeeded by a drop of not less than 14 kilopascals in 15 minutes or until the induction period exceeds the product specification. If no breakpoint is observed at the termination of the test, refer to section 12 of the written standard for reporting the result. Warning-- if a boiling water bath is used and the test is made in a region where the atmospheric pressure is consistently below normal, 101.3 kilopascals, it is permissible to add a liquid with higher boiling point, such as ethylene glycol, to the water in order to maintain the operating temperature of the bath in the neighborhood of 100 degrees Celsius. If a liquid other than water is used, be sure the liquid is compatible with the seals in the pressure vessel. Record the number of minutes from the time the pressure vessel is placed in the bath until the break point has been reached as the observed induction period at the temperature of the test. Cool the pressure vessel to approximately room temperature within 30 minutes after removal from the bath using ambient air or water less than or equal to 35 degrees Celsius before releasing the pressure slowly from the pressure vessel through the needle valve at a rate not exceeding 345 kilopascal per minute. Wash the pressure vessel and sample container in preparation for the next test.