In monitoring the oil contents of ballast water being discharged from tankers, sample mixtures extracted from the effluent should be pumped up to oil content meters through the long piping system.
Two tankers, existing and newly constructed, are investigated about specifications of the piping systems both for sample mixtures and over board discharge. While, the effects of the specifications on the errors in measuring the oil contents are studied experimentally with a simulating apparatus of the systems.
The fluctuations in oil concentration at the outlet of the apparatus rise to 10-200% of the mean concentrations at the inlet especially for highly viscous oils. Measures to reduce the errors being caused by the fluctuations are shown as follows:
(1) Increase of the flow velocity through the piping system.
(2) Increase of the temperature of the sample mixture.
(3) Elimination of stagnant flow, such as that in large strainer, from the system and frequent flushing with fresh water.