What Is An Offshore Container?
Everything you needed to know about offshore containers, and how to choose the best DNV offshore container for your needs
Offshore containers are specially manufactured shipping containers that are used to transport equipment and materials to offshore structures such as oil rigs and wind farms. They are different to ‘regular’ containers because they can be transfered from ship to ship, or ship to platform and can withstand the force of banging against structures during transfer.
Offshore containers are also known as ‘DNV containers’ due to their certification standard.
DNV Offshore vs ISO-Certified Containers
DNV offshore containers are significantly tougher than their ISO-certified counterparts. Offshore boxes are designed to be stacked on deck, exposed to the most extreme weather that nature can hurl at them – 24/7/365.
They’re certified to DNV 2.7-1, an extremely rigorous set of standards that governs their design, manufacture, testing, marking and inspection regimes. So they will remain strong and safe for repeated use…year after year…for at least a decade, and potentially up to a quarter of a century.
Offshore containers are built to withstand the unrelenting punishment inflicted by storm-force winds, heavy seas, huge rogue waves and mercilessly corrosive sea spray. If ocean waves are powerful enough to swamp the bows and deck cargo of a 400-metre long boxship displacing 230,000 gross tonnes, think how robust and watertight the 23,000+ TEU containers it’s carrying need to be.
Find out more here about the difference between a DNV container and an ISO container.
So, How Tough is a DNV 2.7-1 Offshore Container?
Tough as hell. They don’t come any tougher. Seriously.
But then they need to be. If any proof were needed, in November 2020 the ONE Apus lost more than 1,800 of her boxes en route from Yantian, China to Long Beach, the USA’s second-biggest container port.
The Japanese-flagged Apus rolled heavily in a storm some 1,600 nautical miles north-west of Hawaii. Hundreds of containers either plunged into the sea or suffered damage. It was the second biggest container cargo loss in history after the MOL Comfort hogged and broke in two in June 2013.
Transoceanic shipping is punishing enough but DNV containers must also be able to survive the added dangers of the offshore industry: oil and gas exploration (and increasingly now wind farms).
Every offshore container must be capable of withstanding temperatures as low as -20°C, temperatures so low that exposed skin will stick to metal.
They are manufactured from weathering steel (best known as US Steel’s trademarked COR-TEN® steel). Weathering steel alloys are designed to resist the seemingly inevitable corrosion caused by rain, snow, ice and fog.
When exposed to these conditions, COR-TEN® forms a dark brown oxidation to help protect it against deeper corrosion. In theory, this removes or reduces the need for protective paint. If left unpainted, COR-TEN® would go from bright orange (after two weeks) to a dark black/brown after 40 years. But DNV offshore containers are painted anyway for added protection. You can paint COR-TEN® just like normal steel.
In short, COR-TEN® is way more weather resistant than ordinary steel; four-to-eight times more corrosion-resistant (depending on the product grade). Why is it so effective? With less carbon in its metallurgical makeup, it is less vulnerable to corrosion. This tried-and-trusted self-protecting steel alloy is a winning formula that includes:
- silicon (a stabiliser for improved oxidation resistance)
- manganese (for improved strength and hardenability)
- phosphorous (for added strength)
- sulphur (for improved machinability, without compromising longitudinal mechanical properties)
- copper (improves corrosion resistance)
- nickel (for superior weldability)
- chromium (increases wear and corrosion resistance).
Put simply, COR-TEN® works. That’s why they built countless bridges and the Angel of the North from it.
What Does the DNV Standard Mean?
DNV is an abbreviation of Det Norske Veritas, the international accredited registration and classification society headquartered in Høvik, just 20 minutes’ drive west of Oslo, Norway.
DNV was created from the 2013 merger of risk management company Det Norske Veritas (“the Norwegian truth”, founded 1864) and Germanischer Lloyd SE, a classification society based in Hamburg.
DNV is the world’s largest classification society, covering some 13,175 vessels and mobile offshore units (MOUs) equating to 265.4 million gross tonnes. That is 21% of the global market. Furthermore, 65% of the world’s offshore pipelines are designed and installed to DNV standards.
That alone should tell you these guys are serious when it comes to setting the global standard for shipping containers. If it doesn’t, we suggest you peruse DNV’s standard for 2.7-1 offshore containers. The August 2017 edition is 106 pages long. That’s an increase of 18 pages on the 2013 edition and nearly twice as long as the 2006 edition.
The 2.7-1 standard goes into meticulous detail on approval and certification procedures, materials (steel, aluminium, non-metals), design, welding, structural strength, production, inspection, certification, marking, data plates, lifting sets, testing and repairs.
Spoiler alert: for project managers and engineers, the DNV 2,7-1 2017 edition is reassuringly detailed. But for mere mortals, it is not light reading (especially not the load formulae for forklift pockets and for slings on pad eyes).
How Waterproof is an Offshore Container?
Testing for the weather tightness of a offshore container starts at the prototype and production stage, in accordance with the ISO 1496-1 standard. And that testing continues: it is required for 10% of all production.
The remaining 90% of containers undergo a light test. Here’s how it works: an inspector enters the container and is given three minutes to allow his or her eyes to become accustomed to the darkness. Then a powerful light is shone on all external surfaces and the inspector checks for light ingress. Simple but effective.
It’s tempting to think of protection from water ingress in binary terms: something either is or isn’t waterproof. But that is a dangerous and potentially expensive over-simplification.
Take IP (and their US equivalent NEMA) ratings, for example. They detail a wide range of ingress protection levels. IP ratings go from drip- and splash-proof to immersion-proof (to a defined depth/pressure)…right up to protection from high pressure jets or steam cleaning.
Don’t believe us? Pity the poor guy who took his expensive dive watch into a hot tub. He assumed (wrongly) that a glorified bathtub was no match for a watch that could withstand seawater up to 200m deep. He reckoned without the hot tub’s high pressure water jets. His watch was a write-off.
Moral of the story? Never underestimate the destructive power of water under pressure. Do not assume that a basic container will be ‘just fine because it’s watertight’ if your project involves people and kit heading offshore or cargo crossing one of the world’s great oceans.
Just because a container is sitting on a deck (in a stack), just because it’s well away from sea level, just because it’s ‘waterproof’…does not mean it’s invulnerable. That container has to survive massive storms, bow-engulfing waves and the often-underestimated force of sea spray.
So don’t compromise. Don’t chance it. If in doubt, specify DNV offshore containers – not their lesser counterparts.
Which DNV Containers Should I Choose for My Offshore Project?
The standard size for a DNV 2.7-1 offshore container is between 10ft and 40ft but custom sizes and weights are also available.
- Offshore cargo carrying units (CCUs) – closed, open top, double door (for flexible access), container frames (skids), hazardous goods containers, bottle racks, waste skips and intermediate bulk containers (IBCs).
- Offshore reefers (refrigerated) for perishable goods such as meat, fruit and vegetables. We are the only company that offers twin-room, dual voltage reefers.
- Offshore half-heights – open-topped for crane-loadable goods. They can be stacked with their slings still attached for easy loading and unloading.
- Offshore tank containers – 2,500L to 20,000L.
- Offshore baskets – including 4ft goods baskets with/without a side door, 8ft offshore cargo baskets, 14ft drum baskets, 21ft and 34ft open-top baskets, 45ft pipe/tool carriers and 47ft basket risers for long equipment.
- Offshore workshop/rigging loft containers and waste skips.
Need modified containers? Watch this short (1 min 29 sec) video to find out more about specifying DNV offshore containers customised to your exact requirements. Options include:
- crew-ready office units – with flooring, insulation, lighting and power (voltage-specified), desks, workbenches, extra doors and windows
- workshops and mud labs – with tool shelving, workbenches, electrics and additional technology
- modified reefers with additional shelving and lighting
- custom hazardous goods containers with bunded floors and chemical spillage kits for safety.
Why Cargostore for DNV Offshore Containers?
Cargostore is one of the world’s leading suppliers of DNV 2.7-1 and ISO CCUs for shipping, offshore and onshore projects. Benefit from:
- expert technical advice and fast quotes from our highly experienced team
- seamless transition to a smooth and efficient finance team – fast credit checks and paperwork
- excellent operational aftercare – proactive assistance for unit repairs and troubleshooting
- offices in London (HQ) and Abu Dhabi, a local representative in Holland and depots worldwide.
Get Expert Advice on DNV and ISO Containers
Contact Cargostore now in London, Abu Dhabi or Holland to discuss your shipping and/or offshore project requirements.
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Cargostore Worldwide exhibitted at Wind Energy Hamburg and showcased our range of DNV 2.7-1 certified containers for offshore wind.