10 February 2010
Dr Dave Merchant

In the last 20 years, the wind turbine generator (WTG) has grown from something nailed to the roof of an organic commune to a major component in the world energy supply system and an equally major presence in our landscape.

The new wind farms being installed both onshore and far offshore are some of the biggest civil engineering projects the UK has seen since the coming of the railways, and make oil and gas platforms look like small beer. A 200 megawatt (MW) offshore site with perhaps 15 turbines can employ more than 1000 people during construction, and need more than 100 specialist vessels to get everything out there and keep it running. And we are going to have hundreds of these sites (see box below).

All these numbers mean one thing: wind turbines are going to loom large in the civil and utilities construction sectors for decades. Last year, more than 50% of the new power capacity built in Europe was renewables, and the vast majority of that was wind. The trade body the British Wind Energy Association (BWEA) estimates the industry’s UK workforce will grow from 5000 to 60,000 in the next 10 years.

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Wind scale

Worldwide, wind turbine generators have about 130 gigawatts (GW) of capacity — about 1% of the globe’s electricity demand — and the UK has both the largest offshore capacity at 600 megawatts (MW) and the largest average turbine
size (1.47MW).

The reason for all the effort is simple: we’re committed to generating about 10% of the UK’s total demand from renewables by 2010, and up to 30% by 2020, which equates to around 13GW, with most coming from wind. Right now we have 2700 turbines delivering 4GW capacity, so we need a lot more.

There’s another 1.7GW in construction, or due to start this year, and the offshore sites recently allocated in Round Three of the Government’s renewable energy plan should be able to deliver 25GW from massive farms far out in the North and Irish seas, since unless it’s always windy you never get full capacity, hence the need to build far more than your demand requires.

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It’s not just the job of sticking a big tube in a field or into the seabed; we need to rebuild entire sections of the electrical grid to connect the barren, windy places to where we live, and reengineer the switching and load-balancing systems to shuffle all this power around when the wind changes. A “smart supergrid” is on the cards, where not only can we share capacity with Europe and beyond, but where each one of you can stick a turbine on your roof and send the power back to the mains.

Wind power is a force for good, but I believe discussion of the safety aspects of WTG construction and maintenance is inadequate, given the particular combination of hazards, the youth of the industry and the massive expansion that’s coming.

When accidents happen we may see something mid-page in a local newspaper, but the wider health and safety community rarely notices. The anti-wind lobby talks a lot about danger, but it means danger to the country views and property prices, not to workers.

The HSE doesn’t separate out accidents on renewable energy projects notified under the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations, so incidents involving renewable sources generally and turbines in particular may be spread across sectors including construction and utilities.

Ardent anti-wind lobby group, the Caithness Wind Farm Forum has some limited statistics on safety incidents in the global wind industry culled from news reports. It says there were 106 serious incidents worldwide involving turbines in 2009 (not all caused injuries) and four fatalities, and 112 (and nine deaths) in 2008. As the Caithness group notes, this is probably the tip of the iceberg.

No fit and forget

Safety difficulties with turbines start at the manufacturing stage. There’s a standard for wind turbine safety systems, for example — EN50308 — but many makers don’t comply with it; nor do they consider the national peculiarities of their customers. So safety auditing installations we regularly find turbines in the UK with German or Danish equipment and safety signs that don’t comply with UK laws and training methods.

Operators often take the paperwork for their new machines at face value, so their risk assessments can be photocopies of something that only made sense to a German factory worker in 1995.

The industry is working to fill in the gaps for commercial-scale farms and turbines, but to keep the rapidly-increasing workforce and public safe, we need to do a lot more, as do the HSE and the emergency services.

When it’s behaving, a wind turbine is relatively benign. It can catch fire — it’s generating several hundred kilowatts of waste heat inside a fibreglass box the size of a caravan, so if the cooling system falters, you can guess the result. It can also get hit by lightning, and WTGs have no sprinklers or fire suppression.

They can sometimes fall over or lose a blade, and blade fragments can travel several hundred metres. That’s one of the reasons wind farms are in the countryside. They can drop chunks of ice metres long. At the extremes, joyriders can even bring them down with burning cars (and have done). But people are far enough away, most of the time, not to worry.

When they go wrong, WTGs will usually send an error messages to a website; but the fault won’t be sorted remotely, it’ll need hands on attention. And they do go wrong.

New models are better behaved, but most wind farms have one or two dead turbines at any one time, as they’re designed to be very skittish. Sensors monitor temperature, wind speed, vibration, oil and coolant levels, shutting the turbine down if anything looks unusual.

Repair work is in addition to the routine maintenance of what is in effect a small power station on a stick. Engineers need to change filters, grease bearings and replace oil, brake pads and brushes regularly, and turbines can have major overhauls (changing bearings, gearboxes and so on) several times in their 20-plus year lives.

A decade ago, many turbines were little more than prototypes; nobody knew how long the parts would last, or even how to replace them. In the UK we have a huge fleet of sub-megawatt turbines that are at that stage in life when, if they were cars, you’d be on first-name terms with the man in the garage.

It means that most farms have permanent staff on site, beavering away with hydraulics, high voltages, rotating shafts, thousands of gallons of transformer oil, and very long ladders.

There may be a few hundred engineers working on WTGs in the UK during any day, but on any one site there are just two or three, so far in the middle of nowhere they had to build their own road. The chance of an HSE inspector dropping by is as remote as the locations.

Auditing the safety of turbines for UK operators, on more than 20 farms from Orkney to Cornwall I have yet to find a single WTG that didn’t fail on something. Mostly it’s missing signs, an inspection that’s overdue, or eye-bolts mistakenly marked as anchor points that would be unlikely to hold an operator’s weight if they fell.

Ladders are deformed where they have been hit by equipment hoisted up the tower; in some older ones the rungs are even corroded.  At a good quarter of sites I’ve visited I’ve found things that would scare you stiff; the sort of failing that prompts a report to the operator with a paragraph in red headed “immediate danger to life”.

You’ve all seen photos of shoddy scaffolding or someone hanging off a building, but none of you have seen a video of someone climbing 60m of ladders in a wind turbine without any fall protection; not because it doesn’t happen, but because there’s nobody in there filming.

As you’ve probably never been in one, allow me to take you on a tour.

Round the tower

Almost all turbines in the UK are mounted on tubular steel towers. When you go in the door at the bottom, you find a control panel and the start of a fixed ladder, heading up past a series of platforms. Before you climb, the turbine is switched into “service mode”, so the blades stop spinning, electrical generation  ceases and the motors are turned off.

In many turbines, the base of the tower also holds a transformer, either in a basement or behind a cage. Some have it outside in a little hut. This steps up the generator output (690V AC) and sends it to the wind farm substation through buried cables, where it’s stepped up again for connection to the grid.

Turbines taller than 80m often have an elevator, which runs on wires or climbs the ladder. Typically, it has enough room inside for two people, if they don’t mind getting cozy. Smaller turbines just have the ladder, which if you’re lucky you climb with your back to the wall.

There are platforms every 10m to 30m, or if there’s a big gap you get little fold-down foot rests. Many of the smaller 400kW to 600kW turbines, with a 25m to 40m tower, have staggered ladders that change sides at each platform; but have no fall protection on them; none at all.

If you have a single run of ladder — anything from 25m to 150m — it will have a fall-arrest wire or rail system, though some are home-made things with no certification. As I hinted, the unlucky people have to climb facing the wall, which may not sound too hideous until you look at a turbine — it’s a tapering tube, so the ladder leans backwards.

At the end of the climb you arrive at the yaw platform at the top of the tower, where the part housing the generator (the nacelle) is attached to the bearing that allows it to rotate (yaw) to face the wind. The bearing runs around the edge of the tower wall, and has a set of disc brakes and a drive motor. It’s locked before anyone climbs, because it has the ability to cause serious injury if it moves.

As the nacelle yaws, you might be wondering what happens to the electrical cables. We can’t have slip-rings (too much power) so the cables run in a bunch up the centre of the tower, hanging from a bracket on the nacelle. As the WTG yaws, the bundle is twisted; so it eventually has to be untwisted. When that happens, the turbine yaws round and round at speed until it’s back to normal.

On small turbines, you have to open the nacelle roof, otherwise there’s not enough room to fit a human inside. Getting into the nacelle from the yaw platform involves some combination of ladder, cable tray, chassis or pipework you can wriggle and climb through, and you pop up underneath the main shaft, and into the nacelle.

On a sub-megawatt turbine, this is about 2m wide and 5m long, just big enough to contain the drive train and generator. Modern multi-megawatt nacelles are the size of a Portakabin, but they are equally cramped as they have much more equipment in them.

The dominant elements are the gearbox and generator, though on large turbines there can be just as much space for cooling systems, transformers and hydraulics. If the turbine isn’t completely turned off, there’s still a risk of electrocution, entrapment and lots of potential for twisted ankles — there isn’t really a floor so much as some flat parts here and there.

In some maintenance jobs, getting caught up in rotating shafts has tragically been demonstrated as a significant risk if very detailed safety procedures aren’t followed, and a “nobody’s watching” mentality often figures in accidents like that.

Access onto the roof of large nacelles is common for many reasons, including repairs to the wind sensors and when you arrive via helicopter to an offshore turbine. The views are great, but anchor points for fall arrest systems are not. Some turbines have them, some don’t, but the chance of finding a CE mark and inspection label is small.

The blades of most wind turbines are pitch-controlled; they twist to vary the angle of attack, adapting for wind speeds and also braking themselves to a standstill. This pitch system uses another bearing at the end of each blade, like the one on the yaw platform, but this time bolted to the hub: the hollow casting in the middle of the rotor, from the back of which comes the main driveshaft.

A hub on a 400kW turbine is less than a metre wide, but on bigger turbines it has room inside for a few people; and they’ll need to get inside, because there’s a heap of hydraulics, batteries, control panels and gears that need servicing. People also work inside the blades themselves; there can be few more extreme confined spaces.

In the hub

To access the hub, we lock the blades in a Y-pattern using steel pins, and either climb through a hatch in the front of the nacelle, or go back up onto the roof, and shimmy down over the front of the hub using intrepid systems of rope and prayer, to a hatch on the front. Climb through that and you’re in the hub.

At this point, if we break a finger, or trap a toe in a pinion, our mate, who is sitting in the nacelle, is our only hope. He has a rescue kit, with a winch, a rope and a sling or three, and a first aid badge that wouldn’t extend, for instance, to putting someone in a stretcher. And there might be no-one else to do that either since many emergency services staff who might answer a call will be working to rules that forbid them climbing up the tower.

If the county has a line rescue team who are trained to deal with this kind of height, the chances they are within half an hour’s striking distance of a remote windfarm is slim.

Wind turbine numbers are growing exponentially, getting bigger, and are sited in ever-more-remote locations. The oil and gas industry had to learn the hard way that remote, hazardous work required them to invest in extensive, expensive training, on-site medics, rescue teams and equipment.

An offshore wind farm might have three workers including the casualty, a boat that spends most days taking people out fishing, a first-aid kit and a couple of fire extinguishers; plus a pack of cards and two toilet rolls in the emergency survival box.

Industry bodies, such as the BWEA (soon to be renamed RenewableUK), do issue health and safety guidance notes to their members and run a limited training syllabus — and many operators do a good job of sending everyone on “a course”; but there are major discrepancies between policy and practice and we’re increasingly seeing issues crop up because of the unique mix of hazards in a turbine.

Which climb-assist devices are safe with which fall arrest systems, when there’s no EN standard to work to? If you arrive by helicopter but leave by boat, what type of lifejacket should you wear? Can someone with a basic first-aid certificate move a spinal patient through a hatch not much larger than a cat flap? Is a training course of any value if it doesn’t take you inside a real turbine? Who exactly is supposed to rescue that worker with the trapped foot?

Industry propaganda suggests a lot of it is already addressed, but in my experience, not enough of it is.

Work to do

We need wind turbines, and a lot more of them, in our energy portfolio. But it’s a high-hazard sector, and one that has neither the resources, nor the pressure of enforcement at present to bring in the same levels of provision as oil rigs.

The industry needs to do a lot more to close the gap, as many operators and manufacturers don’t even know how big that gap is. Some don’t give their workers any rescue training, as they assume a 999 call will solve anything.

Site owners also have to do more to ensure the workforce does what it should already be doing — I’ve seen too many cases of people not bothering to use harnesses, using out-of-date elevators or unsafe anchor points.

The emergency services have to deal with the gap as well; they are expected to respond to that 999 call, but often have no idea how to, or that they even should. Very few line rescue teams have ever been inside a turbine, neither have the new Hazardous Area Response Team paramedics in health trusts, and none of them have the equipment needed to access one safely. There have been a few carefully-staged pick-offs using helicopters, but only as a proof-of-concept and from the easiest locations in the best weather.

One thing I often hear from the industry is that if the emergency services got the chance to practice realistic incidents, they’d make a mess of it and HSE would wake up and take notice. I think it’s time to do it anyway, as someday soon it won’t be a practice.

Dr Dave Merchant is a consultant in height safety and rescue, instructing business and fire services and has developed height safety training content for companies in the UK and overseas.

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The trade body’s response

The British Wind Energy Association, the industry body whose members include turbine operators and manufacturers, says it disagrees fundamentally with Dave Merchant’s observations on the safety of UK wind farms and arrangements for rescue in this article.

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Categories:
Construction, Fire, Risk assessment, Work at height, Article, Features, Manufacturing / engineering, Electrical safety, Safe systems of work, Confined spaces

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