The Leader in the Industry for Over 50 Years
John S. Sohre, P.E., pioneered research and led the way in understanding the murky area of stray shaft currents. Until John published his research on shaft current damage, there was no satisfactory explanation for the cause of certain types of damage seen in bearings, seals, and gears. In 1971, John established Sohre Turbomachinery® Inc. to provide guidance on dealing with electrostatic and electromagnetic problems in power-generating turbines, problems that only increased as power ratings increased and machines aged, through the 1950s and beyond. In 1978 at the urging of customers, John designed, developed, and began production of what has evolved into a patented line of shaft-riding brushes for turbomachinery that is now in use in many industries throughout the world. These brushes help to dissipate and monitor shaft currents with a level of effectiveness and resilience unmatched by other shaft-riding devices.
Electrostatic and mild electromagnetic problems have been present since turbines first generated electricity. As power ratings have increased, however, so too have electrostatic and electromagnetic problems become more severe. Arc welding, magnetic particle testing, and other techniques that leave strong residual magnetic fields began an epidemic of severe shaft-current problems. These, in turn, led to significant operating losses in the process and power industries. Reliable and suitable shaft brushes or demagnetization procedures were not available at that time; therefore, Sohre Turbomachinery® Inc. was established to deal with these problems, both in theory (through several published papers) and in practice (through development of a more useful type of shaft-riding grounding brush).
The first Sohre brush was developed in the late 1960s to control massive and epidemic failures of turbine-driven turbocompressor trains caused by self-induced electromagnetic stray currents. Later, the LW-M1 grounding brush was developed for the U.S. Navy for its highly critical propeller-shaft applications. Similarly, the Type-LW-STD (Standard), was developed by request for an electric utility, and has been available since 1992.
Sohre products have been exhibited since 1993 at the Texas A&M University Turbomachinery Symposium. A major paper, “Shaft Riding Brushes to Control Electric Stray Currents,” by John S. Sohre, P.E., was presented at the 20th Turbomachinery Symposium at Texas A&M University in Dallas that same year. We have sold more than 8,000 shaft-grounding brushes worldwide since 1978, both for installation by original equipment manufacturers and for field retrofits. Several turbomachinery manufacturers now include Sohre brushes as standard equipment.