Physical Properties

The physical properties listed below are deemed relevant for tank cleaning. These properties are displayed for each cargo in the MIRACLE database, provided the info is available.

Is the ratio of the mass of a volume of a product to the mass of an equal volume of fresh water (1.0). For a product with limited or no solubility in water, a specific gravity below 1.0 indicates that the product will float on the water, a specific gravity above 1.0 indicates that the product will sink in water. More details can be found here.

Water- soluble substances and water-miscible substances are easy to clean with water, and the solubility of the substances might increase at higher temperatures. The use of a cleaning detergent is only advisable for reduction of the cleaning time or for smell removal (e.g. Phenol)

These products should be washed at a temperature of 15-20º C above the melting point. During washing there should be no ballast water or cold cargoes adjacent to the tank to be cleaned. During cleaning special attention should be given to liquid and vapour line systems to avoid freezing/solidification at cold line segments. Washing as soon as possible after discharge is recommended.
Watch IBC chapter 17 column o (specific and operational requirements) for 16.2.9

These products should be washed at higher temperatures. In general the viscosity is closely related to the temperature and will decrease at higher temperatures. During washing there should be no ballast water or cold cargoes adjacent to the tank to be cleaned. Washing as soon as possible after discharge is recommended. The respective product characteristic of the individual product must be observed.
Exceptions are some highly viscous cargoes (e.g. certain lube additives or polyols) which need to be pre-cleaned with lower or moderate temperatures, because they tend to undesired reactions at higher temperatures.
Watch IBC chapter 17 column o (specific and operational requirements) for 16.2.6

Boiling point is the temperature at which a liquid changes to a gas (vapour) at normal atmospheric pressure. The boiling point of an element or a substance is the temperature at which the vapour pressure of the liquid equals the environmental pressure surrounding the liquid.

Products with a high vapour pressure (higher than some 50 mbar at 20º C) can be removed from the tank by evaporation. As always during ventilation, special care must be taken to prevent the risk of explosion (flammable products) and emission (toxic vapours). All safety precautions must be taken. Emission and Immission regulations must be considered and followed. Products with low vapour pressure, or products which leave residues or contain inhibitors should never be cleaned by evaporation (ventilation). The non-volatile matter (NVM) content in the specification of the product is a good indication to determine, whether a product will leave residues. Substances containing inhibitors, even if the quantities are low, must be washed thoroughly. Any inhibitor left in the tank is difficult to remove and nearly always has a negative influence on the wall wash and on the next product to be loaded. Product mixtures containing low vapour pressure components or crude products should never be cleaned by evaporation (ventilation).
Watch chapter 15.14 in the IBC code for cargoes (such as Propylene Oxide) having a vapour pressure greater than 1,013 bar @ 37.8°C

The pre-cleaning temperature must be well below (minimum 10°C) the flashpoint. If this is not possible, because the flash point is lower than the ambient temperature, there is the risk of a flammable mixture that could be ignited during the cleaning operation. Any ignition source must be eliminated under such circumstances! More information is available here.