What are different types of gas measuring equipments used on ships ?

  1. The explosimeter:

The explosimeter is an instrument which is specifically designed for measuring the lower flammable limit (LFL). It will only function correctly if the filament has an explosive mixture in contact with it.

When in use, the sample tube is lowered into the tank and a sample of the atmosphere is drawn up into the instrument by several depressions of the rubber aspirator bulb. If the sample contains an explosive mixture the resistance of the catalytic filament will change due to the generated heat.

An imbalance of the wheat-stone bridge is detected by the ohm meter which tells the operator that hydrocarbon gas is present in the tank in sufficient quantity to support combustion.

The graduations on the meter are a per cent of the lower explosive limit (LEL) reading between 0% and 100%. A deflection of the meter between 0% and 100% shows how close the atmosphere being tested approaches the minimum concentration required for explosion. When a test is made with the explosimeter, and a deflection to the extreme right-hand side of the scale is noted and remains there, then the atmosphere under test is explosive.

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