Question

A mixture containing 0.9% hexane, 1.0% methane and 1.5% ethylene in air is exposed to a pressure of 3 bars and a temperature of 45 oC. Is this a hazardous condition.

Answer 1

FOR AN EXPLOSION OR FIRE TO OCCUR 3 CONDITIOS MUST BE MET SIMULTANEOUSLY FUEL AND AIR MUST BE IN CERTAIN RATION ALONG SIDE IGNITION SOURCE

THERE ARE LOWER EXPLOSIVE LIMITS (LEL) AND UPPER EXPLOSIVE LIMITS.(UEL).

LEL - MINIMUM QUANTITY OF COMBUSTIBLE SUBSTANCE RQUIRED NECCESSARY TO SUPPORT COMBUSTION IN AIR

UEL - MAXIMUM QUANTITY OF COMBUSTIBLE SUBSTANCE RQUIRED NECCESSARY TO SUPPORT COMBUSTION IN AIR

BELOW LEL GASES ARE TOO THINTO BURN AND ABOVE UEL GASES ARE TOO THICK TO BURN. BETWEEN LEL AND UEL IS THE FLAMAMBLE RANGE.

LEL AND UEL AT C AND ATMOSPHERIC PRESSURE

HEXANE -1.2 :7.4

METHANE- 5 :17

ETHYLENE- 2.7:34

AS TEMPERATURE DIAMETER AND PRESSURE INCREASES FLAMAMBILITY RANGE INCREASES

SO THIS CONDITION CAN BE HAZARDOUS IF THEY ARE ABOVE LEL VALUE AND BELOW UEL VALUE