Prod. Characteristics

The initial wash of products that tend to polymerise should be carried out with cold (ambient) water. Washing with hot water may result in polymeric residues being left in tanks and lines, which are very difficult to remove. To avoid any polymerisation by loss of inhibitor-protection it is also recommended that tanks be washed immediately after discharge.
MIRACLE indicates products that are liable to polymerisation in the Product Description, in the Safety Remarks, in the Info for cleaning after discharge section. In addition there is an indication in the IBC section special requirements in chapter 15.13 , if the cargo requires an inhibitor. More info about polymerization

Cargoes consisting of mixtures with different vapour pressures should neither be cleaned by evaporation nor prewashed hot. The evaporation of the light substances from a mixture could result in low boiling residues or non-volatile residues, which are very difficult to remove.

Isocyanates must never come into contact with water, not even the residues because the reaction product and insoluble urethane (plus CO2) are very difficult to remove. Such products must be washed with a suitable solvent, that does not contain any water.
MIRACLE indicates products that may react with water in the Product Description, in the Safety Remarks, in the Info for cleaning after discharge section. In addition there is an indication in the IBC section special requirements in chapter 15.16.2 were water shall not be allowed to contaminate this cargo.
More information about the reaction with water is available here.

(Drying Products) Drying and semi-drying vegetable and animal oils react with oxygen to form a varnish-like polymeric film. This is very difficult to remove from the bulkheads etc. Heat increases the reaction speed. Therefore the initial washing of these products must be done with water at ambient temperature without any delay after unloading the cargo.
Heated cargoes in adjacent tanks should be avoided. In case of doubt as to whether a vegetable or animal oil is non-drying or drying, always use water with ambient temperature first.

Water hardness is formed by the calcium and magnesium content of the water. Seawater contains a large amount of calcium and magnesium and therefore has a very high water hardness. Some products like fatty acids and vegetable oils with a high free fatty acid content will form white sticky residues (calcium and magnesium soaps) if they are cleaned with water of high water hardness (e.g. seawater). Heat increases these reactions, therefore if seawater must be used the initial wash must be done at a temperature of 20º C above the melting point of the product.
Note: 10º C increase in temperature doubles the chemical reaction rate.
The best method to pre-clean this kind of product is to prepare the required amount of freshwater for the pre-cleaning in a separate and clean tank and to add a suitable water hardness remover.
If seawater or untreated freshwater must be used for cleaning the formation of white residues or a white powdery film cannot be avoided.
For the removal of white residues see cleaning suggestion for Fatty Acids.
The second example of a reaction with water hardness compounds is Sodium Silicate Solution. Sodium Silicate Solution will form calcium and magnesium silicates, which are very hard to remove. Sodium Silicate Solution should be therefore washed with freshwater only and never with seawater

Acid soluble cargo residues like calcium carbonate slurry or magnesium hydroxide slurry can be solved by a solution of Nitric Acid in freshwater. Nitric Acid together with Calcium or Magnesium will form the salts Calcium-Nitrate or Magnesium-Nitrate which are both water soluble.

Carbonate residues which could be formed by caustic soda solutions (white powder) can be removed with a solution of phosphoric acid in freshwater or an acid cleaner based on Phosphoric Acid.

Iron Oxide residues (rust) coming from carbon steel shore tanks and shore lines can be removed with an acid cleaner based on Phosphoric Acid.
If the tanks have been a long time under Nitrogen condition there will be a formation of Iron 3 which will cause a dark black layer on the bulkheads. This dark black layer can be as well solved with a solution of phosphoric acid in freshwater or an acid cleaner based on phosphoric acid.

To avoid any damage to the stainless steel the use of freshwater is mandatory if acid solutions or acid cleaners are used for cleaning.

Cargo residues which are saponifiable like vegetable and animal oils can be cleaned by using an alkaline cleaner based on sodium- or potassium hydroxide. the saponification product beside glycerin will be a hard soap if sodium hydroxide is used and a soft soap if potassium hydroxide is used. Soft soaps (green soap) have a quicker water solubility than hard soaps and can be easier washed out of the tank thus potassium hydroxide based cleaners are preferable.

A negative side effect during the saponification is the possible concurrently formation of calcium and magnesium soaps which are non water soluble soaps forming the typical white powdery or sticky residues (see also water hardness).
To avoid this undesired reaction the use of freshwater with a low water hardness is mandatory. Most alkaline cleaners contain so-called water hardness stabiliser which will prevent the formation of calcium and magnesium soaps in freshwater.

Seawater contains a large amount of calcium and magnesium and therefore has a very high water hardness. The water hardness stabiliser in an alkaline cleaner is not able to deal with such a high water hardness thus seawater should never be used during the saponification process.
It is of utmost importance to remove the seawater residues by flushing the tanks with fresh water before any re-circulation cleaning with an alkaline cleaner (saponification) is performed.

Minor residues of a smell-producing cargo left in lines, valves and pumps (including pump cofferdams) can contaminate a sensitive cargo.

To neutralise the smell of some chemicals (e.g. Acrylate, Nitrobenzene or Pygas) the use of a smell remover may be recommended. Special attention should be given to gaskets in the tank and cleaning hatches. If the next cargo is a sensitive cargo the gaskets should be cleaned or renewed.
A smell killer/remover should preferably be used in combination with an emulsifier. The tanks should be cleaned by recirculation to guarantee that every drop of the smell-producing cargo inside cargo lines, stripping lines, pumps and valve seats are removed.

Any of several natural oils which, when exposed to the air, oxidise to form a tough, elastic film. The oil dries through oxidation, a chemical reaction between the oxygen in the air and the oil, and not through evaporation. This oxidation process creates a remarkably durable and flexible paint film.
Classification of oils

Most animal and vegetable oils undergo decomposition over time.
Putrefaction (rottening) is a biochemical process that decomposes these oils partly under generation of noxious vapours and depletion of oxygen in the tank.
Attention: Putrefaction generates carbon monoxide.