According to the International Organization for Standardization (ISO) Container Technical Committee (ISO/TC104), the container shall meet the following conditions:
- has sufficient strength, can be used repeatedly for a long time;
- Applicable to one or more modes of transport, transshipment on the way, the goods in the box do not need to be replaced;
- Suitable for particular fast loading and unloading and handling devices, easy to convert from one mode of transport to another;
- Easy to fill and empty the goods;
- the volume is not less than 1㎡
With the rapid development of marine engineering, offshore containers as supporting equipment have also developed rapidly, and offshore containers are gradually evolving from standard containers.
Standard container refers to 20 feet, 40 feet container, the maximum total mass of 30480kg, generally made of steel, used for the shipment of general goods.
Offshore containers are mobile units capable of transporting and operating in the 6m sea area with a total mass of no more than 25 t. The team is frequently used for the transportation and lifting of cargo or equipment between fixed or floating facilities and ships at sea.
1 Use Environment And Lifting Method
Standard containers are generally transported via container liners to port.
If the standard container is placed in the liner compartment, the box guideposts in the cabin can be used to prevent the movement of the box;
If a standard container is placed on a deck and needs to be stacked in several layers, the upper and lower containers should be connected by stacking fixings, and the corners of the container are tightened with the tie rings on the deck via a tie rod.
In port terminals, standard container hoisting usually adopts shore container cranes or field station container cranes, using the crane twist lock device and four top corners of the container after vertical lifting.
Due to its generally mild climate and no collision when standard containers are hoisted, the environment is relatively safe to use.
Offshore containers are often placed on the decks of supply vessels in the offshore oil industry without bundling and exposed to the marine environment.
Offshore containers are all single-point lifting, often hoisted on the oil platform under harsh sea conditions. Each box part suffers a more significant impact, easy to collide with adjacent containers or hulls. Hence, the structural strength requirements of offshore containers are higher, generally will be permanently assembled on the box, and to Seeking to be equipped with a particular protection device.
Offshore containers usually do not have corner pieces, and even if they do, they are not allowed to be used for offshore lifting operations. In addition, offshore containers cannot be stacked on ships during transport, only on offshore and onshore facilities and generally no more than two floors.
2 Certification And Production
Compared with standard containers, there are strict requirements for the certification and production of offshore containers.
In response to IMO Maritime Safety Committee Circular 860, which requires explicitly design calculations and physical verification to be taken into account when certifying offshore containers, it specifies six items to be considered in the design of offshore containers and four tests to be performed.
Offshore container certification takes the following three steps.
- evaluation and certification: according to the standards of offshore container structure drawings calculation, audit, assessment of its box material, cargo carrying, box lifting, container cargo fastening, and other details.
- Manufacturing process inspection: certified inspectors certify and test raw materials to ensure that welder qualification, welding processes, and NDT work meets the requirements.
- sample box test: including four-point lifting, two-point lifting, inclination test, and drop test.
In the production process of offshore containers, the lug and the fillet weld are required to be fully fused, and 100% ultrasonic flaw detection is carried out;
The main structure, such as bearing structure beam, fork groove, and bottom beam welding, should be fully fused. Then, certified inspectors can, according to 20% requirements for ultrasonic or radiometric testing.
At the same time, the material of the main structure must be tracked throughout the production process.
Standard containers and offshore containers are different in certification and production based on other functions, operating environments, and lifting methods. Therefore, containers’ procurement, design, display, and operation must be differentiated and identified to carry out offshore container business better.