VPS has developed an in-house method for the measurement of WAT for VLSFOs.
The technique is based on ASTM D5773 and involves direct detection of light scattered by wax crystals using the same technology that has been used to measure the WAT of crude oil for some years. Significant work has been carried out to modify the equipment instrumentation and optimise experimental conditions for VLSFO fuel types. It is sensitive, precise and reasonably quick in delivering results.
The method has been validated by correlating results of a series of distillate samples with an existing method and repeatability has been assessed on several VLSFO samples across a wide temperature range (10°C to 65°C). The WAT of many VLSFO samples bunkered over the past months has been measured and graphed. The wide variation of these results indicates the importance of measuring this parameter to mitigate cold-flow operability problems for VLSFOs.