Introduction to Chemical Tanks
1) A Brief Historical Account
The tanks were invented to transport large amounts of fuel and supplies efficiently in order to meet the demands during wartime. In the 1950s, the American military employed the first tanks in order to store large amounts of gas. The tanks were proved to be very efficient, as it can be repeatedly used and transported to any place. In early 1960s, the tanks were first employed for business transportation of consumer goods, including wine, hard liquor, petrochemical products, fuel, etc. The frame of the very first tank (40 feet long, 4.25 feet high) and the two cigar-shaped tubes together form the so called “Cigar Box.” Such tanks were used in the 1960s by manufacturing companies to transport wine and sherry from Spain and Portugal to Northern Europe. In the past 50-60 years, the “Cigar Box” has evolved into the modern tanks we see today. Its benefits are limitless, transporting and storing massive loads of liquids, gases, powder, and granules safely over long distances, with small costs and no additional expenditure needed for barrels and drums.
2) The Petrochemical Products Carried by the Tanks
These include the products listed under levels 3, 5, 6, 8, and 9 of the 9 types of hazardous objects categorized by the IMDG, published by the IMO. In addition, the tanks can also carry the seeds, oil, and food grade products regulated by the FOSFA.
3) Hazardous Products Classification Criteria
The classification of hazardous objects is based on the chemical substances contained. The IMDG Code published by the United Nations describes clear and detailed guidelines for the classification, as seen in the pictures below:
4) Minimum/Maximum Load Limit Required for IMO / IMDG Shipping
The general practice can be roughly divided into the following transportation guidelines (This calculation ignores the relationship between temperature and the coefficient of expansion):
Dangerous Goods: The maximum is 95% of the volume of the tank, and the minimum is 80% of the volume of the tank.
Non-dangerous Goods: The maximum is 97% of the volume of the tank, and the minimum is 75% of the volume of the tank.
As examples, the maximum and minimum for phenol (dangerous) and lubricant (non-dangerous) can be calculated as follows (the corresponding tank has volume 24,000 liters):
- Phenol; SG:1.06; Un Number:2312; Class:6.1
(tank volume＊weight of goods)＊95%=maximum (24,000L*1.06M(KGS)/V(L))*95%=24,168KGS
(tank volume＊weight of Goods)＊80%=minimum (24,000L*1.06M(KGS)/V(L))*80%=20,352KGS - Lubricant;SG:0.78; Un Number:NONE; Class:NONE
(tank volume＊weight of goods)＊97%=maximum (24,000L*0.78M(KGS)/V(L))*97%=18,158KGS
(tank volume＊weight goods)＊75%=minimum (24,000L*0.78M(KGS)/V(L))*75%=14,040KGS
5) Why Consider the Maximum and Minimum Load Requirements?
The tanks are pressure containers that are sealed and mobile. Due to the liquid nature and inertia of the products, carrying a load below the minimum requirements can result in severe accidents during road and rail transportation processes. Similarly, carrying a load above the maximum requirements can result in overflowing due to the change in dimensions in response to temporal and environmental changes.
6) Stainless Steel
American Iron And Steel Institute uses a "three figures" method to mark a variety of standard stainless steel taking into account of the level of stainlessness, corrosion resistance, chemical composition of the steel itself, interactions between the substances, environmental conditions, etc. Currently, the common Tank Container is mostly made of Austenitic 300, especially the AISI 304/AISI304L and AISI316/AISI316L.
7) Tank Types and Classification
With the exceptions of grades 4.1 and 5.2 using Type T23 and grade 2 (gas) using Type T50 (non-frozen, pressurized, liquefied gases) and Type T75 (frozen, pressurized, liquefied gases), the IMDG code uses the “four conditions” to distinguish tank types. These four conditions include: minimum tank-shell test pressure, minimum tank-shell thickness, depressurization valve requirements, and whether the bottom valve is classified as T1 to T22. Our company provides tanks that comply with this classification process.
8) The United Nations Assignment of Dangerous Goods to Responsible Organizations
One of United Nations’ jurisdictions is to ensure and constantly improve the safety of transportation of dangerous substances. For this purpose, the United Nations General Assembly established the “Economic & Social Council” (ECOSOC). Under the auspices of the ECOSOC, each type of transportation has its responsible organization, as listed below:
The tanks are used in 4 of the transportation types listed above, thus their designs must comply with the safety restrictions set forth by each of the corresponding organizations.
9) IMO (International Maritime Organization)
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In 1948, The United Nations formally established the Inter-Governmental Maritime Consultative Organization (IMCO), which officially started operating in 1958. In 1982, its name was changed to International Maritime Organization (IMO). In terms of maritime safety and marine environmental protection, the IMO had passed the relevant treaties, agreements, and protocols below:
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The IMO is made of an Assembly, a Council, a sub-committee, and a working group. The Maritime Safety Council and the Maritime Environmental Protection Committee under the Council are responsible for vessel security and environmental protection, respectively. The Maritime Safety Council makes many suggestions to its responsible working groups on coordination and organization to improve and amend the IMDG Code. The Maritime Environmental Protection Committee functions in a similar way, aiming to amend MARPOL73/78.
10) The IMDG Code
The International Maritime Dangerous Goods Code (IMDG) is a statutory publication by IMO that provides guidelines on operating with dangerous goods in maritime transports. It contains detailed explanations on the classification of dangerous substances, the definition of dangerous goods, the packaging structure and the safety concerns regarding standard transport operations. The publication combined SOLAS1974 with MARPOL73/78 and relevant regulations and is updated every two years in response to more recent needs.
