EMKA compression latches aid wind power from Nordex

24Feb

Onshore wind turbine specialist The Nordex Group’s decision to source its locking hardware from EMKA has resulted in the design of a unique compression latch, to secure vital access points where it must withstand forces of up to 331N. These locks are fitted to special floor plates which are required to prevent serious accidents.

The Nordex Group has over 35 years of experience in the onshore wind turbine business worldwide and seeks to set a benchmark for renewable energies. Since its foundation, it has installed wind turbines with more than 41GW of rated power. The company continuously optimises its development, production, project development and maintenance, including that of individual components inside the turbine.

This unique compression latch is used in the hub, on the rotor head of the turbine. The systems are sealed with special floor plates, to ensure that the technician can work safely, and not accidentally step into one of the hollow rotor blades. To gain access to the inner workings of the blades, the plates each have one or two inspection hatches; four compression latches ensure that these 15kg hatches are securely installed in the floor plate.

In the past, supply issues have been problematic, plus the generic housing used at the time was made of zinc die-cast, and the latch plate was made of unalloyed steel. This material combination was susceptible to corrosion and caused a decrease in strength over time. The component also indirectly added high service costs, because when checking the installed systems, it was not clear at first glance whether or not the component was in a locked position. The concern was that a technician might just possibly fail to close the hatches properly after maintenance. As a result, these hatches could become unhinged when the wind turbine rotated again. This meant that the wind turbine had to be shut down again in order to rectify the fault, so incurring unforeseen additional costs over the service life of the installation.

Since availability was a major concern, the responsible engineers at Nordex and the supplier of the floor plates decided in 2019 to replace the existing locking system inventory with a new lock. These unique designs were to identify the system’s open/locked position clearly. In addition, the new solution had to withstand high pressure and resist impurities, dust and lubricants. Because of these features alone, the locking systems would significantly increase the process reliability of the wind turbines.

Explained Peter Baars, Development Engineer in the rotor blade development department at the Nordex Group and responsible for the project, “EMKA stood out because of its good performance in the past, its large product range and, at the same time, its great disposition to approach the customer.”

To ensure that the floor hatches are securely mounted in the cut-outs, EMKA developed a new compression latch, made of stainless steel, to resist the forces and corrosive environment involved. This solution ensures that the cam not only closes the hatch firmly, but is also vibration-proof, due to its compression function. The lock can only be opened by turning it 180° with a square 8mm key with open/closed marking. When rotating the square 90°, the cam moves 6mm in the axial direction, releasing the compression. When rotating another 90°, the released cam rotates as well, and the hatch can now be lifted out. The actuation covers only half of the housing’s head, so that each position of the locking system shows either OPEN (red) or CLOSED (green). This visual aid allows the technician to see whether the locking system is closed or open, at a glance. The red/green markings are also smudge-tested according to DIN EN 62208 chap. 9.3 and DIN EN 61439-1 chap. 10.2.7.

In addition, EMKA had to consider the prevailing conditions in a wind turbine when developing the locking system, including, above all, the centrifugal forces, which have an increased effect on the turbine’s rotating hub. In the first step, therefore, the durability of dynamic loads of the latch cam combination had to be more than doubled – from the previous limit of 140N, to 337N. In order to prevent unintentional opening during operation, the locking system’s design is vibration-resistant and shock-proof, compliant with the European standard DIN EN 61373. In addition, the entire lock system is maintenance-free, so there are no conflicting schedules regarding the systems’ maintenance cycles.

There are now more than 850 plants equipped with EMKA compression locks – while Nordex is using its wind turbines to contribute to switching from fossil fuels to renewable energy sources. The design of this compression latch and its OPEN/CLOSED indicator enables EMKA to partner on this course.

More information on EMKA here.