General Many factors need to be considered in order to achieve the desired tank cleaning result. Planning a tank cleaning operation is the key to success. Planning should be carried out by qualified people only. Planning the cleaning operation should be kept in mind even before loading the cargo, to avoid potential adverse effects from adjacent cargoes.
A good preparation of the cleaning operation will avoid tank rejections as well as incidents during the operation. In general the tankcleaning procedure can be determined from the product properties of the product to be cleaned, the surrounding conditions, the available equipment and last but not least the requirements of the product to be loaded (Next Cargo).
Required cleanliness standard of the next cargo
Although not officially defined in chemical shipping two major cleanliness standards should be distinguished:
Water White Standard means visually clean, dry and odour-free. Wall wash not required.
High Purity Standard is required for very sensitive cargoes to be loaded such as products applied in food processing (Food Grade) or in pharma production (USP), where any contamination is a potentially high risk for the application. Another category of product that typically requires high purity standard are all active solvents, such as chlorinated hydrocarbons, glycol ethers, light alcohols (e.g. methanol), ketones (e.g. acetone) and many hydrocarbons (e.g. hexene). These chemicals tend to dissolve all remaining impurities resulting in potential contamination of the substance.
Sometimes chemical companies require High Purity Standard because the application of the product in chemical processing is very sensitive to contamination (e.g. poisoning of catalyst) and is thus comparable with the requirements for food or pharma grade. In MIRACLE for every product the typical cleanliness standard is listed. Depending on companies and their quality requirements those standards might deviate from the usual cleanliness requirement.