In one application, an energy services company switched from a traditional keyed coupling to a custom, torsionally rigid disc coupling with a shrink disc. This latter component overcame several challenges related to design and material construction — minimizing maintenance, saving costs, and improving installation service life within the wind turbine.
Overcoming Nylon Coupling Failure
This application originally involved a keyed, torque-limiting coupling. Installed on the drive end of the shaft was the sprocket, which also mated with a nylon base inside the coupler hub. The hub then mounted to the generator. This nylon ring, however, was a point of frequent failure in the installation, causing the energy company to pursue another, more durable coupling option.
The solution was a custom-engineered, torsionally rigid disc coupling with a shrink disc that excelled in the wind turbine for the following reasons:
Metal construction improved installation lifespan. In place of the failure-prone nylon ring, engineers delivered a rigid disc coupling constructed entirely from steel. This rugged component achieved a nominal torque capacity of 12,650 Newton-meters and avoided premature failure—all while withstanding harsh environmental conditions. In fact, engineers designed the first wind turbine rigid disc couplings in 2008—and 13 years later, no modifications have been necessary.
Electrical isolation prevents unwanted arcing. Despite the steel construction, engineers had to ensure the new coupling couldn’t transfer electricity. Because the installation included bearings on either side of the coupling, an all-metal unit could transfer current, leading to dangerous arcing. Arcing could easily burn out the bearings, driving up maintenance costs and reducing the lifespan of the installation.
To overcome this challenge, instead of incorporating solid metal spacers into the coupling, engineers designed a pressed-fit glass composite spacer between the two metal flange ends to break up the continuous metal chain. This design disrupted the end-to-end electrical connection, effectively preventing arcing between the bearing.
Keyless design facilitates installation and removal. Since being integrated into the wind turbine, the rigid disc couplings paired with a shrink disc have sped up the installation and removal of the generators, as no additional alignment is required to install the drive-end. The rigid disc coupling mounts to the generator and slides over the splines of the high-speed pinion (drive-end). Eliminating keyways via the use of the shrink discs eliminates the need to align keys and keyways during installation in a potentially challenging environment.
The rigid disc coupling’s keyless design is beneficial for several other reasons as well. For one, it offers an even distribution of locking forces compared to keyways, which tend to concentrate stresses around the key. In addition, the keyless connection:
Reduces maintenance
Improves energy savings
Increases equipment efficiency
Boosts component value
Reduces potential for flexing of disc packs extending coupling life
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