By Tony Millward

It’s possibly the most talked-about topic on board an installation vessel. It can disrupt the best-laid plans of even the most experienced contractor. And hundreds or even thousands of hours go into guessing what it’s going to do next. It’s the weather, of course!

Weather or not?

Say “offshore” – particularly in the waters of Northern Europe, and many might picture scenes of hardworking, sea-sprayed men struggling bravely against the elements, soaked through despite brightly coloured wet weather gear, their faces twisted but determined.

In actual fact, offshore weather in any particular year brings a bit of everything with it – rain, sunshine, gentle breezes, freezing cold, even hurricanes. You just can’t be sure what challenges or opportunities the conditions will present for installation tasks.

But what exactly is the impact of the weather on installation? And how does an installation contractor like A2SEA deal with the uncertainties?

Highs and lows

Take the summer of 2013, for example. At least from a Northern European offshore wind perspective, it was one of the best. A2SEA’s installations ran like clockwork, achieving higher production rates than ever before thanks to long, favourable weather windows.

Then came autumn – no better or worse than you’d expect in the Irish Sea. The winter that followed was mild, yet windy – not the kind of weather preferred by installation contractors. And the period from the beginning of December to mid-January was something we’d rather just forget happened.

Over a 12-month period, these varied conditions simply balanced each other out. And that’s a pretty good description of how practically any year of installation weather ends up. The trick then, is to work optimally no matter what we encounter.

Working out the weather

For each project, an installation contractor receives metocean reports and uses these to estimate the weather during planned installation months. The reports show expected wave heights and winds for various periods.

To jack up or down, a six-hour weather window is necessary. Using a spreadsheet we can calculate, for example, that the likelihood of such a window on any one day in, say, January might be 50 percent, while it may be as much as 95 percent in June.

Blade installation, on the other hand, requires suitable wind speeds and will have a different window estimate. We compare the spreadsheet result against our ‘gut feeling’ then discuss any variation. Of course, you can’t rely on the final estimate but, at the end of the day, the weather is what it is, and you just have to ensure you’re ready for anything that comes.

Contract conditions

Installation contracts almost always include buffers to make room for a range of potential delay factors, including the weather.

Contract style is up to the client, ranging, for example, from agreements where the installation contractor assumes the risk of delay up to the limit of the metocean data predictions, through charter-only contracts where the client assumes all weather risks, to less common, fixed-price contracts where the installation contractor takes on all the risk itself.

Just do it

Obviously, wind speed is a key factor when you’re lifting big, comparatively lightweight structures such as blades, which are specially designed to capture every bit of wind. So instead of windy, mild winters like that of 2013-14, we prefer colder, clear and calm conditions.

But whatever the weather, what’s important is that we are sitting in position as often as possible, ready to use even the smallest windows. After all, you don’t install by sitting in the harbour. If you can get out there, you do.

You might say we’re pragmatic – we like to get the job done no matter what the weather is. And the weather is what it is. If you get into too much detail, the returns on the analysis are pretty limited. So we don’t want to spend too much time over-analyzing it.

Ready for anything

Of course, any developer or installer planning team should be prepared for the worst. It’s also vital for the contractor to be fully prepared, as any delay may have repercussions for the vessel’s ability to arrive at the next project on time.

Contingency planning is almost always in place to make sure that, if things are far behind schedule, additional resources can be brought in to meet the deadline.

That said, the weather doesn’t normally delay a project as the no. 1 cause, but it can complicate any other problems that may show up. However, if installation windows have been properly exploited, then everything is usually be on track.

So the focus is really on good planning, good procedures, good working relationships so when the windows are there you can get as much done as possible.

 

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