Returning a cargo tank back to a water-white standard is, or should be, the default tank cleaning operation following the discharge of any product on a chemical tanker.
From that default position and depending on the next product to be loaded, additional cleaning can take place to suit the supplied product specifications.
Should the specifications of the next product not have been advised, then cleaning should be carried out to the highest known specification for that particular product.
Of course, if the next product to be loaded is know, then tank cleaning from one product directly to the next can be conducted, however that cleaning process will always pass through the water-white standard.
So what is a water-white standard?
Back in the days of yore, the major chemical tanker owners, Stolt, Odfjell etc, developed their own water-white standard which was widely followed by the industry, and served well for some decades.
The basic premise of a water-white standard may be defined as:
A water-white standard may be defined as that standard where if fresh water is inserted into a cargo tank, then that water will not materially change in terms of chemical composition, odour and colour.
However, with the advent of compulsory double hull construction resulting in many more owners trying their hand in the chemical game, these cleaning standards became somewhat inconsistent, with the final result being the promulgation of a Cargo Tank Cleanliness Standard by Intertanko in 2017.
Both the old and new standard are given below, your choice.
The old standard:
- The following items are considered to be part of a water-white standard in respect to a cargo tanks and its associated lines and systems.
- No traces of previous cargoes in cargo tanks and the associated systems.
- No odour.
- No suspendables (floating or other visible particles.
- No discolouration from previous cargoes or from tank cleaning.
- No free water in the cargo pump well, tank bottom, tank bulkheads, tank overhead and the associated lines.
- No loose scale or blisters which may entrap cargo residues in the tank coating.
- Heating coils are clean and bright.
- Cargo pump is clean and bright.
- Tank packing’s are clean and free of odour.
The Intertanko standard:
The full Intertanko publication may be downloaded above.