Non-contact seals are designed to seal without any physical contact between the rotating and stationary elements. Therefore, there is in no parasitic drag or wear on the rotating seal element. This results in reduced heat buildup in the sealing cavity, longer seal lifespan and extended bearing lifespan.
The Centritec Seal, which generates a centrifugal pressure, is a non-contact seal that utilizes a rotating chamber within the seal to develop internal pressures and pump the lubricating fluid back into the controlled fluid cavity. This rotating chamber method significantly reduces the operational speed requirements of the traditional non-contact seal and allows fluids with extremely low-viscosities to be used.
A Centritec Seal is superior in many critical performance areas, including efficiency, performance and lifespan, in both horizontal and vertical applications. See a detailed explanation on Centritec Seals vs. Labyrinth Seals.
When the vertical shaft spins, the Centritec Seal utilizes the centrifugal pressure created within the seals integral rotating chamber to pressurize the lubrication fluid and pump the lubrication fluid back into the fluid reservoir or up to the bearings located along the shaft. Because of the vertical orientation, when the seal is used to directly lubricate the bearings, the lubricating fluid will drain down through the upper and lower bearings while they are in constant circulation. When the shaft stops spinning, the lubricating fluid will drain down through the bearings to the lower non-contact seal, which has a sufficiently large chamber to serve as a reservoir. This reservoir also creates a fluid barrier between the housing and the outside environment when the shaft is not rotating.
The seal's configuration and its centrifugal pressures allows moisture to be expelled when in motion – moisture that would otherwise stay within the controlled lubrication fluid cavity and deteriorate the voracity of the lubricating fluid. When the seal is not rotating, heat and moisture are also able to vent as a result of the non-contact feature. This ability to "breathe" significantly increases the life of the lubrication fluid and the bearing, and allows bearings to operate at much cooler temperatures – an important operating advantage.
The design of a Centritec Seal is not based upon tightly held dimensions between the rotating and non-rotating seal components. Pressure is created within the seal as a result of the operating speed of the inner seal cavity. This allows for shaft vibration, axial movement and radial movement. Centritec Seals have successfully demonstrated tolerance to shaft vibration and axial/radial movement in motors, fan shafts and jack shafts containing large eccentric loading features to generate large oscillation outputs. View our non-contact Seal Case Study for an example.
Yes, the centrifugal forces associated with the technology will pressurize the lubricating fluid and force the fluid back into the lubricating fluid sump, or the fluid can be channeled to the bearings. Sealing pressures are dependent upon the type of lubrication as well as the speed and diameter of the rotating shaft. However, ours seals have been effective up to 5 bars. Similarly, in a dual seal application the outer seal is utilized to pressurize and expel the environmental contaminants into the external environment. See pressure generation curve under Benefits of Centrifugal seals.
For a horizontal shaft, our testing shows the start of some minor leaks when the surface speed is 50 feet per second and with the lubrication media being water. Tests have shown that the threshold is a function of the type of lubricant used. For example, there will be no leaks with most greases if the operating time is limited at the slow speed.
Since the design of a Centritec Seal is not restrictive to any material, materials of construction are determined based upon application parameters and cost effectiveness. Therefore a rotating seal can be provided to operate in those conditions.
Centritec Seals are available in materials that can withstand virtually any chemical environment. Please contact us to review your specific application and for seal material recommendations.