Stand Out from the Crowd
A competitive advantage for any company is the ability to keep production going. Learn how a custom-engineered seal solution for a German geothermal plant provides reliability in extreme conditions.
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For the past decade, as oil prices continue to rise around the world, Germany is one of many countries that has been racing to develop cleaner, more environmentally friendly sources of power. One method that is finding favor in Germany is geothermal energy.
When Flowserve was asked to provide a deep-well submersible pump and motor to a Germany-based geothermal power plant, the Flowserve team reviewed the requirements and knew the pump would have to be customized so that it would be robust and reliable enough to handle high temperatures and an installation depth of more than 700 m (2,300 ft).
Face to Face - The Sealing Technology Magazine
Discover how your company can stand out from the crowd and rise above the rest by using Flowserve engineered solutions to solve tough challenges.
Such a long shaft is bound to shift with movement, and the pump’s seals generally can take a one-time axial shift of about 0.381 mm (0.015 in). However, in this geothermal application, Flowserve needed to design a seal that could accommodate +/- 5 mm (0.197 in) of axial movement.
“Thermal expansion causes axial movement of the shaft, as well as motor thrusting during start-up and shutdown,” says Ryan Kremer, product development special projects senior engineer, Flowserve.
“Just like any seal, if the axial movement is greater than the seal’s capability, the faces could be overloaded, and a catastrophic failure could occur,” he adds. The geothermal plant also required that the seals for the vertical pump and motor could leak oil no more than 3.79 l/hr (1 gal/hr), and could not leak any water into the system. This was necessary because the motor can only hold so much oil, and it will overheat and fail once that oil is gone. The motor also would fail if any water were to contaminate the oil.
Most seals rely on high-pressure differential to keep the leakage rate low. In this case, a low-pressure differential, ranging from 0 to 1.03 bar (0 to 15 psi), required Flowserve engineers to further customize its solution.
“One way to combat leakage is to increase the spring load. But the higher the spring load, the higher the start-up torque, which can lead to seal face damage,” Kremer explains.
Determined to find a solution, Kremer and the Flowserve engineered solutions team added a diamond coating to the rotating faces to enhance seal face life and reliability in hostile environments. The diamond coating also would eliminate potential damage caused by the increased spring load.
Going Above and Beyond
To increase seal pressure and help prevent water from leaking into the motor, a pumping screw was added near the inner diameter of the product side seal faces. Because motor oil lubricates this seal face, the pumping screw will help direct leakage outward and prevent water from entering the system. A dual-seal configuration provides additional security in the event the inboard seal side were to fail.
Keeping maintenance in mind, Flowserve engineers designed the seal cartridge to be easy to install, and Kremer says operators who’ve tested the seal are pleased with its ease of installation.
To make sure the pump and seal work in the most extreme operating conditions, Flowserve runs its designs through extensive testing. If problems arise during testing, the team goes back to the drawing board until the pump and seal pass all requirements. In this case, the seal has met its leakage requirements and is undergoing further validation testing before the user installs it.
No Challenge Too Big
This geothermal plant application is just one example of how Flowserve can fully engineer and design a product to suit any application.
For more information, visit www.flowserve.com/Industries/Power-Generation/Geothermal
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