Microscopic flaws on the surface of a seal lip, over time, create directional performance characteristics. Vanseal examines the causes and solutions when a negative load affects a seal that must run in reverse.
Torque to Rotate Measurements and Resistance to Directional Forces
The automotive market is resistant to using seals with directional sealing features or limitations. Seal designs that require different part numbers for CW versus CCW shaft rotation are typically not desirable. Directional seals can also have negative load effects when running in reverse.
This graph conveys the results of a test using a rubber lip seal with a directional lip pattern. Torque is affected when a change in direction is applied. The increase in torque between clockwise and counterclockwise seal direction is an increase in energy consumption.
While this may be minimal, as the condition may only occur when a vehicle is in reverse, it still a higher use of energy. With geometry changes, such as the addition of bi-directional hydrodynamic aids, or the use of other material options like PTFE, this effect can be neutralized.
Unlocking the Mysteries of Torque
Loads, coefficient-of-friction of the material, and geometry all interact and affect torque. Torque Testing, along with other types of tests, have helped develop efficient seals that save energy and improve the overall performance of equipment.
Torque, to rotate a radial lip seal, changes with shaft speed and is further affected by temperature. The diagram demonstrates from the initial start, frictional heat builds in the shaft and has an adverse effect on the rotational force. As the temperature rises, torque equalizes in the shaft and the lip seal rotational force decreases and stabilizes.
Torque testing helps us understand how different materials affect energy consumption under pressurized conditions. Torque Testing provides quantifiable data as to how a variety of factors impact energy consumption in the assembly.
Many manufacturers think it is purely a function of the coefficient of friction of the seal material, but torque testing tells us there is more to it.
Testing Material Properties and Energy Consumption
Radial loads driven by a material’s tensile properties, hoop stresses, and secondary loading elements like garter springs and lip geometry can contribute as much or more to torque levels than just friction coefficients alone. Armed with this insight, Vanseal matches the coefficient of friction, geometry, and material properties, to the operating conditions, to deliver optimum torque to rotate that results in reduced energy consumption through a cooler running, more efficient machine.
Torque Testing is an Invaluable Step in Development Process
Torque testing is especially useful for seals in applications such as electric motors, gear boxes, electric pumps, generators, and automotive drive trains, engines and pumps. It’s a valuable process whether you want to understand the energy consumption of every element in a system, or you’re seeking fuel savings for your product line.
By incorporating Torque Testing early in the engineering process, it can reduce development timing by demonstrating how materials and geometries affect seal energy and efficiency, and thereby lessen the likelihood of seal failure further along the road during system testing.