Monoethylene glycol fibregrade is a high specification, commonly carried cargo.
One of the critical parameters is that it must pass the UV light transmittance test. This is principally carried out at three wavelengths:
UV transmittance, 1cm cell, %
Cargo claims for failure of the UV test are exceedingly common and often costly, particularly when the MEG is downgraded to antifreeze, where there is often an absence of market. In recent years, there have been many claims simply based on bad science. Claimants have yet to fully appreciate that light transmittance at the 220 nm wavelength will deteriorate naturally over the course of the voyage simply as a result of oxygenation (circulation through pumps and lines and the cargo breathing through the PV valve). This can occur even where the tanks are purged with nitrogen prior to loading and the cargo blanketed with nitrogen throughout the voyage. This oxygenation process is of course elevated if transhipments occur. It is therefore essential to ascertain that the cargo on loading is well in excess of the 70% minimum if it is to survive the voyage. Owners should not be paying claims for a natural degradation occurring outside their control.
A further area of confusion is the propensity of cargo receivers to check UV transmittance on arrival “after reflux”. Reflux simply means that the samples are heated (boiled) prior to testing. The UV transmittance results are always lower after reflux. Given that the loadport samples (certificate of quality) did not “suffer” reflux prior to analysis, the effect of such a comparison is similar to comparing apples with pears and should not form the basis of any claim against owners.
Source of Information:
Russell Ridley, Sinclair Roche & Temperley