VesselDesignTool is a P&T computer tool for the design and rating of L/L, G/L and G/L/L separator vessels. It is based on the design rules mentioned in the latest DEP 31.22.05.11-Gen (2015) and DEP 31.22.05.12-Gen (2012). It is meant to assist on the following vessel designs: 1. Horizontal GLL Separator with Water Boot 2. Horizontal GLL Separator with Double Weir 3. Horizontal GLL Separator with Single Weir 4. Horizontal GL Separator 5. Horizontal LL Separator 6. Vertical GLL Separator with Plate Pack 7. Vertical GLL Separator with Horizontal Plate 8. Vertical GL Separator 9. Vertical GL Separator with Vane Pack 10. Vertical GL Separator with Swirl Tubes 11. Vertical GLL with downpipes 12. Twin Flange Coalescer