Prewash Requirement Check (Annex II Reg 13)

Decision support for whether a prewash is required after discharging a Category X/Y cargo.

Chemical tankerPrewash

Cargo categoryViscosity at unloading TmPa·sMelting point°C

High-viscosity (> 25 mPa·s at unloading T): Yes

Solidifying (MP > 15 °C): No

Prewash requirement: Required (high-viscosity or solidifying Y)

Changing the inputs requires JavaScript. The calculator above shows its default inputs and result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

\text{Prewash} = \text{CatX} \lor (\text{CatY} \land (\text{HV} \lor \text{Solidifying}))

Symbol	Meaning	Unit
$HV$	High viscosity, > 25 mPa·s at unloading T	boolean
$Solidifying$	Melting point > 15 °C	boolean

Source: MARPOL Annex II Reg 13

In short

Decision support for whether a prewash is required after discharging a Category X/Y cargo.

Learn the theory Marine Tank Cleaning and Crude Oil Washing