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Mass spectrometer leak testing

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article image Cincinnati’s mass spectrometer.

CINCINNATI Test Systems mass spectrometer leak testing units have been highly beneficial in the air charge cooler business for heavy off road vehicle industry.

Diesel engines produce a significant amount of NOx emissions resulting in smog; therefore a pollution control system regulated by the EPA is utilised to reduce the NOx emissions for diesel engines.

Cincinnati’s mass spectrometer leak systems are advantageous in testing the heat exchangers and piping for these systems.

The standards for the NOx emissions have decreased steadily from initial levels of 16g/bnp-hr in 1970 to 5g/bnp-hr in 1991 to less than 3g/bnp-hr in 2002 to less than 1g/bnp-hr in 2007.

In 2010 it will be reduce further to 0.2g/bnp-hr. These stringent regulations set by the EPA require the off road vehicle industry to consistently improve their pollution control technologies as well as their test methods for the heat exchangers and piping of these systems.

Severely high combustion temperatures cause NOx production and so its production can be reduced by lowering the combustion temperature. Two methods to reduce combustion temperature are: retard ignition timing or reduce oxygen levels in the cylinder.

Retarding the ignition timing starts the combustion process at a less than optimal point that reduces efficiency of combustion, reduces fuel economy and performance, and increases soot production.

The second method is to reduce the oxygen levels at combustions. This is accomplished by re-circulating exhaust gas (EGR - Exhaust Gas Recirculation) into the cylinder. Since the objective of this process is to reduce the temperature at combustion, it is beneficial to cool the hot exhaust gas before recirculating it back into the combustion process.

When the engine combustion temperature rises, the engine control computer opens the EGR valve and a turbocharger forces exhaust gases through an EGR cooler. EGR gases are cooled by the engine cooling system circulating through the EGR cooler. Cooled exhaust gases are then transferred to the intake manifold.

The leak rates on the water cavities typically range from 0.5 to 15.0 sccm and air cavities have similar rates.

Because of the welding processes involved in manufacturing these heat exchanger parts, the proximity to the manufacturing process and the cycle times, these parts are usually tested with either helium accumulation or helium vacuum mass spectrometer systems.

Cincinnati Test Systems is represented in Australia by MPW Australia .

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