Staying Dry by ‘Going Wet’
Oil shear clutches support remote monitoring and actuation of stormwater drainage pumps
When heavy rains, or the occasional hurricane or tropical storm occur, flooding can follow. At the Michoud Assembly Facility in New Orleans, Louisiana, a world class manufacturing facility providing vital support to NASA exploration and discovery missions, personnel would sometimes have to brave the elements to manually actuate stormwater pumps.
When the centrifugal-style twin disc clutches previously used at Michoud would engage at low speed, they would slip until fully engaged. Slip-induced vibration required frequent repairs and rebuilds, and worse, while the clutches were slipping, they were neither fully engaged nor pumping the 60,000 U.S. gallons per minute they were rated for.
Today, oil shear clutches manufactured by Force Control Industries are helping to keep Michoud dry when Mother Nature unleashes her wet fury on the Big Easy. The oil shear clutches can be monitored and actuated remotely even at low speed, and they operate with virtually no maintenance or adjustment, which lowers their overall cost of ownership.
How Oil Shear Technology Works
Normal dry clutches employ a sacrificial surface — a disc or pad — to engage the load. With no good way to remove the heat caused from engagement between the disk and plate, this material must absorb the heat. These extremely high temperatures will eventually degrade the friction material. As the friction surface wears away and begins to glaze, the spring force is reduced, causing ensuing torque fade. This causes positioning errors, which requires adjustment or replacement of the friction surface.
Oil shear technology plays a major role in ensuring that the axial pumps at Michoud can operate at full capacity. Since a fluid film flows between the friction surfaces, the fluid is compressed as the clutch is engaged. The automatic transmission fluid (ATF) in shear transmits torque. This torque transmission causes the stationary surface to turn, bringing it up to the same relative speed as the moving surface. By the time the surfaces actually meet or “lock up,” wear is virtually eliminated because most of the work is done by the fluid particles in shear.
In addition to transmitting torque, the ATF also helps to dissipate heat, due to a patented fluid recirculation system. Along with torque transmission and heat removal, the fluid also serves to continually lubricate all components, thus extending service life. Oil shear technology also provides a “cushioned” engagement that reduces shock to the drive system, further extending service life. Unlike dry clutches, the totally enclosed oil shear system is impervious to external elements such as wet, dusty or dirty environments. Since the layer of oil eliminates wear, the Force Control clutch provides a long service life. With the elimination of wear comes the elimination of adjustment — and increased “uptime” for the stormwater pumping system.
It may seem ironic that keeping the Michoud assembly facility dry meant that they had to “go wet” with their pump clutches. But if it takes a paradox to keep this vital NASA facility from flooding, then facility engineer Bill Winsor and the thousands of employees who work for him don’t mind, especially when it is accompanied by virtually no downtime for maintenance and repair — and means they can engage the clutches to keep the facility dry while staying dry themselves.
Force Control Industries Inc. manufactures industrial clutch and brake products based on oil shear technology. Learn more at www.forcecontrol.com.