Cost-efficient transformer repair

Reducing cost of ownership

Repairing the transformer is a cost-efficient solution, compared to exchanging the damaged unit. In most cases with leaking transformers, we are able to repair the transformer, using our specialized welding repair method. Our method is designed to reduce both downtime and cost of ownership, and thereby maximizing the availability and performance of your assets.

We have many years of experience within the field of welding repair sol

utions and hundreds of transformers still operating today. Our skilled employees are highly trained to carry out the procedure, making sure that the transformers can continue to operate without leakages and without the need for replacement.


The repairing process is smooth and fast and is performed without any drainage of the transformer. Depending on the leaks, the timeframe of the repair is typically 2-5 days, from inspecti- on of the transformer to completion of the final documentation.

The process

1. Detection & inspection
The leaks are typically detected during an inspection, which leads to further inspections to identify and map the leaks. The process is fully documented.

2. Repairing process
Repairing the leaks, using special developed on-site welding methods, thus reducing both downtime and costs significantly.

3. Testing & documentation
Pressure testing and documentation to ensure that the transformer is sealed. The welding repair of the transformer is completed and documented.

Contact us for more information about the repair method. Find our contact info right here

Local presence, local support: UK team of highly trained inspectors

Our UK based NDT & Inspection team, led by Stephen Chambers, carry out major on and offshore inspection methods for aging turbines or turbines that are new in service. Our catalogue of inspection methods ranges far and wide, and among others we can mention: 
𝗘𝗱𝗱𝘆 𝗰𝘂𝗿𝗿𝗲𝗻𝘁 𝘁𝗲𝘀𝘁𝗶𝗻𝗴 (𝗘𝗧)

A method performed on mainframes and turbine towers that makes us capable of testing issues without the need to remove paint to identify flaws in metal surfaces and welds. 

𝗠𝗮𝗴𝗻𝗲𝘁𝗶𝗰 𝘁𝗲𝘀𝘁𝗶𝗻𝗴 (𝗠𝗧)

Non-destructive testing which can detect surface and subsurface defects of the welds, used post ET if any indications found with the latter method. 

𝗨𝗹𝘁𝗿𝗮𝘀𝗼𝗻𝗶𝗰 𝗧𝗲𝘀𝘁𝗶𝗻𝗴 (𝗨𝗧): 

By sending ultrasonic waves through a structure or material, we can detect potential flaws in key safety points in e.g., ladder welds and platforms. 
𝗣𝗵𝗮𝘀𝗲𝗱 𝗔𝗿𝗿𝗮𝘆 𝗨𝗹𝘁𝗿𝗮𝘀𝗼𝗻𝗶𝗰 𝗧𝗲𝘀𝘁𝗶𝗻𝗴 (𝗣𝗔𝗨𝗧)

An advanced NDT technique that detects defects in metal and composites and provides us with accurate and detailed information about the depth, size, and severity of the defect. 
𝗢𝘃𝗲𝗿𝗮𝗹𝗹 𝘃𝗶𝘀𝘂𝗮𝗹 𝗶𝗻𝘀𝗽𝗲𝗰𝘁𝗶𝗼𝗻

The inspection is performed on both aging turbines and turbines that are new in service, using rope access or drones to inspect e.g., the blades of the turbine, main structures, and internal frames. If flaws are detected, further inspections and solutions can be implemented to prevent down time of assets. 
Do not hesitate to contact us if you would like to know more about our advanced NDT and inspection methods and how we support both locally and globally. Contact info right here.

The life-extending outcome of reinforcing wind turbine structures 


As the first commercial models of wind turbines that are still standing today, are reaching 30 years of service, turbine owners begin to face the challenge of either continuing to maintain and optimize these older wind turbines or dismantle them. There comes a certain point where expenses to maintain the wind turbine might overdue the turnover from energy production. Some of the critical components that often require attention within wind turbines, are among others the mainframe, flanges, bolts and yaw rings. Traditionally, damages to some of these components on older turbines has led to the consideration of dismantling, if the turbines have outlived their designed lifetime and the guarantee-period from the developer is expired. This is where we at 3WIS offer our conceptual repair solutions, a proactive procedure that reinforces bearing steel structures, where deterioration appears. Wind turbine owners hereby can extend the lifetime of their assets with up to 10 years, hereby achieving increased return on their investment while reducing the environmental impact from decommissioning or installing new turbines.  

What to consider when prolonging the lifetime of your assets

Taking all scenarios into account, here are some key figures that turbine owner should make when considering extending the life of their assets:

Calculating TOC is relative for each turbine, depending on wind site affecting the average AEP (Annual Energy Production), general condition of the other components on the turbine, potential local tariffs, and more.

The Impact of Reinforcing Solutions

Deterioration of exposed structures in older wind turbines or new turbines in general can be a quite concerning issue for turbine owners. In the past, damages to crucial components often meant extended repair and downtime, involving removement of the nacelle with heavy lifting equipment (among others) and replacing the damaged components. Hereby resulting in significant financial losses and contributing to environmental waste as well. However, by investing in reinforcing solutions, owners can now significantly extend the lifetime of their assets.

Preventive maintenance through Core Integrity Testing

One of the solutions we provide at 3WIS is a preventive maintenance-based multipoint inspection of exposed areas, at an early stage. Preventive maintenance through on-going NDT inspections, may also be a solution that helps service companies as part of their core integrity checks, as well as turbine owners, in maintaining quality- & safety demands from their insurance companies. Adopting a procedure that reinforces the mainframe aligns with regulatory standards and certification requirements. he turbine in peak condition and in compliance with safety guidelines, enhancing the credibility within the wind energy sector.

Maximizing Return on Investment:

The implementation of the proactive procedure for reinforcing exposed structures allows wind turbine owners to protect their investments and increase their return on invest over more years. By addressing deterioration at an early stage, operators can prevent further damage, costly repairs, and unplanned downtime, through a cost-friendly and fast reinforcement procedure. If other mechanical or electrical parts of the turbine is in good condition, reinforcement of exposed structures is a cost-friendly and highly beneficial solution. 

Environmental Benefits:

Sustainable development requires the optimization of existing resources and minimizing waste. Extending the life of older wind turbines through reinforcement of the mainframe is a solution that contributes to a significant reduction in the environmental impact associated with producing new turbine. The mainframe is a highly exposed steel structure of the wind turbine, that most turbines experience within their designed lifetime. By keeping functional turbines in operation, the industry can decrease the amount of waste that the industry produces, through manufacturing processes, and energy consumption involved in building new units.


Wind turbine owners face the dual challenge of either keeping their turbines running or dismantling them when they have reached their designed lifetime and that service and repair expenses exceed turnover from energy production. The implementation of a procedure such as reinforcing exposed steel structures, when deterioration appears, represents a significant step towards keeping older turbines running. By extending the life of older wind turbines by up to 10 years, operators can continue to generate more renewable energy and therefore improving total cost of ownership while simultaneously reducing the environmental impact of installing new turbines. Embracing these reinforcing solutions underscores the wind industry's commitment to sustainability, safety, and responsibility of resources, paving the way for a greener and more resilient exploitation of wind power. 

Feasibility studies: Investing in cost-efficient and validated project execution! 

Feasibility and validation studies makes us able to test and develop various repair methods before implementing them on-site, thus providing validated and documented repair solutions that mitigate the risk of technical, financial, and operational aspects. 

The method is typically applied in more complex repair projects and is designed to determine: 

  1. best suitable repair method, AND
  2. to identify potential issues that could arise during the repair process. 

Recently we completed a test and validation project to document a repair concept we have been working on for one of our clients. 

The study 

After detecting welding flaws, compromising the strength of the weld of the bottom flange of the wind turbine towers, our client reached out to get answers on the following questions:  

  1. Is it possible to repair and perform NDT on the detected welding flaws?
  2. AND is it possible to repair the welding flaws from the outside of the wind turbine tower, without removing the stud bolts? 

With the project scope defined, we manufactured a mock-up of a tower, simulating the welding defects and thereafter tested the validity of the repair concept. The aim was to create a validated, and documented repair solution to our clients before the actual repair campaign on-site which not only solve the technical issue, but also mitigate on the overall complexity and HSE related concerns. On this basis we concluded on the repair method which is applicable for the actual situation on-site. 

Learn more about our engineering competencies right here Or reach out to Daniel Stenstrup Rasmussen at or tel. +45 20 277 951.  

Danish welding specialists are ready to offer global repair solutions

According to WindEurope's latest analysis, Europe currently has 255 GW of wind energy installed, of which 19 GW are newly established facilities from 2022. WindEurope's expectations for the future are that an additional 129 GW will be established in Europe between 2023-2027. To meet the 2030 climate goals, the expansion is expected to especially speed up from 2025 to 2027. Based on these predictions, the Danish company, 3WIS has expanded its portfolio of repair solutions to include engineering consulting. 

3WIS is highly specialized in complex repairs of steel structures on wind turbines and offshore foundations and has accelerated the development of the company by establishing an engineering department. The new department is built on the foundations of in-house expertise and knowledge, accumulated over the years with highly specialized and complex welding repairs of wind turbines. This includes up-tower and –on-site welding repairs, as well as feasibility studies, root cause analysis, and initial validation of repair solutions in our facilities in Denmark.  

Therefore, 3WIS can now bridge the gap between practical problem-solving and consulting before repair and planning, and thus service their clients in all aspects of maintenance and repair, from execution to consulting on future maintenance. By supporting a larger scope of the supply chain, wind park owners are ensured an extended lifetime of their turbines, fewer downtime hours, and significant savings on repair work. 

"All analyses indicate that the capacity of wind energy in Europe will grow significantly towards 2030, and we want to be part of that development. We see a great need to increase the quality and speed of delivery in the market, which is why the development of our Engineering department is our highest priority right now. We are well-known trough out the industry for responding very fast and solving technical complex tasks related to welding repair of steel structures and wind turbines and it is quite natural to add an additional dimension to our business, offering OEMs and developers a complete repair solution that also includes engineering. It is a natural step when we are already deeply involved in these projects. We can simplify complex tasks by combining practical solutions with engineering when it comes to welding and repairing steel structures. Based on great expertise, we can create solutions already from receiving the first inquiry. 

In short, we can simplify a complex project into a feasibility study. In the study we can create a mock-up solution, simulating the problem and finding the right solution, thus combining theory and practice to mitigate the risk of the problem and therefore also the costs”, explains Daniel Stenstrup Rasmussen, Chief Operating Officer at 3WIS. 

The consulting especially targets site managers, park owners, and operators on new projects and older parks facing challenges and complex problems that require specialist welding repair. 

Full-functioning project department 

The new project department is fully functional, and the organization consists of both engineering and project management. Employees are located at 3WIS' two locations in Denmark, Esbjerg, and Munkebo. In addition, 3WIS has 20 Service Technicians solving tasks around the world. 

"We have managed to create an environment with room for professional immersion in welding. In practice, this means that our employees can go deep into their expertise in welding, structures, loads, dynamics, and unique solutions. In short, we can turn theory into practice on site," says Simon Øland, owner and CEO of 3WIS. 


Global solutions 

The company is founded on strong competencies within welding and steel structures while being specialized in traditional NDT inspections, advanced NDT and QA/QC services towards OEMs and developers and their welding repair-specific projects. Over the last  few years, 3WIS has managed to expand into several industries, whereas they have their strongest competencies in on- and offshore wind. 


With most projects executed in Europe, 3WIS has also completed more complex tasks in the U.S., Japan, and Mexico. Their knowledge and experience from the last 12 years are part of the extensive know-how that has been developed in the Danish wind industry. Here Denmark is known as the country in the world running the most on wind energy, where 55% of all energy in Denmark comes from wind turbines. 


Simon Øland is very positive towards the initiation of a new project management department in 3WIS. 

We have already initiated the next step in the development of 3WIS generating great value for our clients. By merging the executing competencies of our business, our service technicians, and the solutions solved by our project- & engineering department. Hereby we can make great benefit of our great on-site experience”, explains Simon Øland.