Why choose Carbon Graphite for Hydropower Applications?
2021-04-26
Reduced leakage is vital for seals of all sizes in hydropower turbines. The durable nature of Morgan carbon results in reduced leakage over time while the split and segmented seal designs allow for easy installation.
The majority of hydropower turbines follow the Francis, Kaplan, or Pelton design with the Kaplan turbine design currently offering the best efficiency over a broader load range. These devices require gland rings that are tribologically reliable, are easy to install, and don’t damage the turbine shaft. To date, high-quality carbon has proven to be the optimal material and Morgan’s historic carbon grades have been developed in association with prominent turbine constructors globally. Morgan Seals & Bearings have supplied carbon glands for shaft diameters as large as 1350mm have been supplied. There are two main types of Seals for hydropower applications.
Tenon type seals
Carbon segments held together by a peripheral close-coiled tension or garter spring. Glands of this type are self-adjusting in that the segments move radially inwards under the force of the spring as wear takes place. To provide added protection against axial leakage, tenon rings are usually installed in series with the tenon joints between the upper and lower rings staggered. Although tenon rings are by far the most common, they are not recommended for shaft diameters above 500 mm and water pressures greater than 2 bar. At figures much in excess of these, disadvantages with the tongue joint structure becomes evident leading to higher leakage.
Wedge type seals
The wedge-type seal overcomes many of the disadvantages of the tenon design. Instead of having tongues and recesses, the ends of these segments are chamfered to present sliding surfaces to tapered wedge pieces, one of which is interposed between the ends of every pair of neighboring segments. In addition, a series of precise spring and pin layout creates a true pressurised on the shaft surface. Advantages over the Tenon design include Greater efficiency, Leakage is one-fifth that of the tenon gland, Less prone to damage at joints and Simpler shapes mean more hard-wearing carbon materials can be used and at higher pressures.
Morgan's high-performing approved grades for the market, Precision manufacturing capabilities, and application support to design seals for your specific setup make us the perfect fit to support your project. Learn more about our carbon grades below.