Feedthrough parameters that can be modified or customized include the mounting configuration, the ferrofluid used, bearing type and position, the shaft size, strength and termination features, the residual magnetic field, the pressure capacity and the location of sealing stages.

Mounting Configurations

Virtually any mounting requirement can be accommodated for securing the housing to a chamber wall or securing components to the rotating shaft. Industry standard mounting flanges and custom configurations for the housing are available and custom lengths and designs can be provided for the shaft. Standard mounting configurations include threaded nose, nut mount, flange mount, cartridge mount, compliant mount, ConFlat^®, ISO-K, ISO-F and ISO-KF flange mounts.

Fluid

The standard ferrofluid used is synthetic hydrocarbon based with very low volatility and therefore low outgassing and long product life. It offers medium drag torque and excellent all round reactive gas and temperature resistance. However, for certain applications other types of ferrofluid may be more appropriate. Where low torque is required, synthetic ester based ferrofluids are used, but due to their higher volatility a degree of lifetime and temperature capability will be sacrificed. Fluorocarbon based ferrofluids are used in applications involving the most reactive gases and highest temperatures. They have the lowest outgassing rates and offer the longest life. However they have a higher viscosity which increases starting and running torque and can limit the maximum attainable speed due to heat generation caused by viscous shearing.

Bearings

Nearly all feedthroughs use either radial contact or angular contact ball bearings. Bearing configurations are divided into 2 types depending on how they support the seal - simply supported or cantilevered. Simply supported seals generally allow higher shaft loading due to bearing spacing, but necessitate having one bearing exposed to the process (PFPE grease lubricated). Cantilevering removes the need for a process side bearing, but may limit the radial and moment loads that can be applied. Typical uses for cantilevered seals are UHV and reactive gas applications.

Water Cooling

Most seals can be water-cooled which allows operation at higher temperatures. This is usually achieved by passing a cooling liquid into the pole-pieces through channels in the feedthrough housing. For higher temperature applications, shaft cooling, where coolant is supplied to the rotating shaft through a rotary water union, is also available and can be used along with the housing cooling option.

Additional Features

Ferrofluidics' engineering department has over 100 years combined experience in designing feedthroughs for all types of applications and is always available to assist you in selecting or designing a feedthrough or sealing sub-system. Additional features that can be incorporated include:

• custom magnets for resistance to demagnetization or for processes sensitive to magnetic fields
• heat treated shafts for higher torque capacity
• electrically or thermally insulating sleeves and flanges
• advanced bearing lubricants to meet stringent outgassing, speed, temperature or life requirements
• alternative materials to reduce cost or withstand special environments
• co-axial, tri-axial, linearly translating and other shaft options
• integration with other system components such as motors, drives, gears, slip rings, sensors and electrical/gas passthroughs