REPURPOSING THE VESSEL EXPERIENCE FACTOR AS A STATISTICAL PROCESS CONTROL TOOL FOR TANKER CARGO MEASUREMENT

Abstract

Accurate reconciliation of cargo quantities measured on board a tanker with those declared by shore terminals is central to reliable tanker operations and to the prevention of commercial disputes. The Vessel Experience Factor (VEF), provides a historical, vessel-specific relationship between shipboard and shore measurements and is traditionally used as a cargo-reconciliation and loss-control tool. This paper investigates whether the same historical VEF population can additionally support the statistical quality control of the ship/shore measurement process itself. A case study was carried out using operational data from 23 consecutive loading operations of a medium-range product/chemical tanker, covering nine cargo grades and fifteen terminals. For each voyage, the Ship/Shore Ratio was computed and compared with unity, with the vessel's historical VEF and with a ±0.3% tolerance band reinterpreted as Shewhart-type control limits. Descriptive statistics, a normality check and an individuals control chart were used to assess the stability of the measurement process and to identify voyages departing from the vessel's established behaviour. The historical VEF was 0.99947 (n = 20 qualified voyages), all 23 ratios remained inside the ±0.3% band, and a five-voyage window (voyages 241-246) revealed two short downward runs separated by a partial recovery - a pattern invisible to a simple per-voyage tolerance check. The results show that VEF data, already collected for commercial reasons, can be repurposed at no additional cost into a vessel-specific quality-control indicator that complements, rather than replaces, conventional cargo reconciliation.