The latest wind turbine generators (WTGs) are colossal. The offshore Vestas V236 has a rotor diameter of 236m and the nacelle housing the hub is at least 150m above the sea. Access is needed for inspection and maintenance, so service lifts are fitted inside the mast; few technicians could undertake a boat transfer then climb a 1,000-step staircase, and helicopter access is rarely practical. But these have risks.
HSE published a bulletin in August entitled ‘Wind turbine generator service lifts: risk of serious injury’, which warned that the design of landing gates and guarding did not eliminate or reduce access to dangerous moving parts of the lift car as it operated with external one-touch controls (www.is.gd/owiwig). An earlier letter stated: “During a routine servicing procedure…the service technician was able to place his hand into an aperture while sending the lift down using the external controls. This resulted in serious injuries to his fingers as they became trapped between fixed and moving parts”.
The bulletin recommends that operators follow the standard BS EN 81-44 ‘Safety rules for the construction and installation of lifts: Lifting appliances in wind turbines’, which it says, “sets the benchmark for the safe design of service lifts and associated safeguards”.
Practically, it adds, “Given risks involved from any retrofit programme on a WTG, it may not be appropriate to replace access gates and/or landing guards, but operators must assess and adopt suitable hierarchical control measures”.
Unfortunately, the final version of EN 81-44 Part 44, which should have been published this November, is not out yet. It is being overseen by CEN (The European Committee for Standardisation) and approval is now scheduled for January 2024.
HSE says EN 81-44 “offers a table to determine the correct level of safeguarding required depending on the access to dangerous moving parts and the distance to them, from, for example, a closed gate. Had this been adopted, then either a full-height gate would have been applicable or a lower gate with additional safeguards such as a light curtain or sensors to prevent movement if reaching in”.
HSE added, “The failures identified mirror key concerns… identified at the Safe by Design workshop”. This 2016 event, organised by offshore safety body G+, resulted in an excellent follow-up document in 2020 which examined how best practice is applied in reality (see also www.is.gd/okoxin).
That document starts broadly: “Notified Bodies generally insisted that it remains the responsibility of the lift system manufacturer to ensure… a product… is fully compliant with relevant directives… contrast this to the anticipated practical reality, where a lift system manufacturer may commonly not be involved in the integration and/or commissioning of their systems”.
It cites the recommendations for use document (RFU) issued by the EC’s Machinery Directive Working Group, which previews the requirements of EN 81-44, such as:
To prevent impact and trap risks at the stops; if the distance from the platform to the ladder is less than 0.5m, both the bottom and top of the platform must be provided with a safety feature The stops must be provided with doors or fencing, complemented by the impact and trap risk safety feature. If the distance from the platform to the stop is greater than 0.5m, fencing only will suffice It must be possible to use additional facilities to open the barriers for when the ladder is used (if provided) when the platform is not there It must not be possible to open the platform door between the floor levels Due to lack of space and the risk of falling objects, usually a full enclosure of the carrier is necessary Measures must be taken to evacuate the users in an emergency.Technicians who were surveyed said that ladder climb-assist systems should be used as a back-up; and half of those that had used one preferred it to using a lift. These systems use a smart winch and harness to take most of the weight as the user climbs a ladder. ‘Next generation’ systems add fall prevention, rescue, workpiece lifting and battery back-up.
One recommendation was to “leverage the knowledge, skills, experience and capability of technicians to rationalise and prioritise pre-use checklists”. This advice could apply to almost any type of machinery:
Make checks more concise, focusing on safety-critical features Use more images/diagrams to replace ‘long wordage’ Where checklists have been created from the manufacturers’ manual, ensure nothing has been lost in the transfer Design smart machines where the results of pre-use checks must be entered (and within specifications) for the machine to operate.It’s worth saying that wind turbine operations are not especially dangerous: there was one fatality at an onshore construction site in 2022 (and none onshore in 2020-21), and there have been none offshore since at least 2016. This must be largely due to the approach of the industry, under what the HSE calls the “leadership from SafetyOn and G+”.
The Energy Institute, G+ and SafetyOn – organising safety
Martin Maeso directs the technical and innovation team at the Energy Institute, a professional membership body for the power industry: “We’re there to effectively support the industry and accelerate that transition towards net zero,” he says.
The Institute works with G+ (the global health and safety organisation for the offshore wind sector) and SafetyON, the UK equivalent for onshore wind. Both carry out incident reporting, run safety workshops and produce good practice guidance. G+ says: “Through sharing and analysis of incident data… an evidence-based understanding of the risks encountered during the development, construction and operational phases of an offshore wind farm project has been developed.”
“We facilitate that collaboration,” says Maeso. “We’re not a trade body that’s trying to lobby, and that’s really key – the regulators find it easy to work with us, because they know that we’re going to be talking about technical issues.”
One of the results of the Institute’s collaboration is Toolbox – a collection of incident reports and definitive safety information presented in clear, usable form and as easily-digested videos, accessible via a web browser (www.is.gd/edidac) or a free app. This usability is no accident, says Maeso, who says that it used PhD research to develop the app.