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Specifying a custom ferrofluidic seal requires more than selecting a shaft diameter and vacuum rating. This guide outlines the process, mechanical, interface and acceptance-test information required for a reliable design.
A ferrofluidic seal is designed around a magnetic circuit, shaft geometry, pressure environment, speed, temperature and process cleanliness. A seal used successfully on a similar machine may not be suitable for another application because the gas load, shaft runout, heat path or chemical exposure is may be different.
A complete specification allows the supplier to evaluate feasibility, identify interfaces and propose an acceptance test. It also separates guaranteed operating conditions from occasional transients.
Provide the following process information:
Normal and maximum differential pressure
Target base pressure and allowable leak rate, including the required test method
Process gases, vapors, plasma exposure and possible condensates
Bakeout, sterilization or cleaning temperature profile
Permitted outgassing, particle and hydrocarbon constraints
Orientation and surrounding magnetic-field restrictions
Normal operating temperature and maximum short-duration temperature
Potential exposure to corrosive or reactive process by-products
Each Moretec custom ferrofluidic seal is evaluated according to the specified process and operating conditions.
Compatibility includes the ferrofluid, elastomers, metals, coatings, bearings and lubricants—not only the nominal seal stage or differential-pressure rating.
| Input | Why it changes the design |
|---|---|
| Continuous/peak speed | Controls shear heat, bearing selection and balance |
| Shaft diameter and runout | Affects magnetic gap and seal stability |
| Radial/axial load | Determines bearing arrangement and estimated bearing life |
| Torque transmission | Sets shaft/coupling interface |
| Mounting envelope | Controls flange, bolt circle and service access |
| Duty cycle | Defines thermal equilibrium and starts/stops |
| Installation orientation | Affects bearing loading, lubrication behavior and thermal distribution |
| Rotation pattern | Distinguishes continuous rotation from indexing, reciprocating or frequent reversing operation |
Supply an interface drawing with datums and tolerances. Clarify which organization owns the mating-shaft alignment, motor coupling and installation fixture.
The drawing should identify critical dimensions such as shaft diameter, flange geometry, bolt-circle diameter, insertion depth, coupling position and allowable runout.
The specification should state continuous operating limits, short-duration transients and non-operating survival limits separately.
For example, a brief chamber vent, process temperature spike or overspeed event may be acceptable only for a defined duration and recovery procedure.
Do not combine continuous limits with emergency or occasional conditions. The following should be defined separately:
Normal continuous operating conditions
Maximum short-duration operating conditions
Emergency shutdown conditions
Transportation and storage conditions
Non-operating survival limits
Identify utilities and cooling conditions. If performance depends on water or air cooling, define inlet temperature, flow, pressure, water quality and interlock behavior.
Also define whether cooling is continuous, linked to shaft rotation or controlled by equipment temperature.
Verify dimensions and critical interface runout.
Perform the agreed leak test with the named gas, pressure and instrument setup.
Run at the specified speed, load and orientation while recording temperature and vibration.
Check breakaway and running torque when relevant.
Inspect cleanliness, packaging and traceability documents.
Define retest or disposition rules for a failed result.
Confirm cooling-channel or gas-channel cleanliness when applicable.
Record the product serial number and approved drawing revision in the final inspection report.
A helium leak-rate value is meaningful only with the test arrangement, pressure differential, calibration and background criteria. Put these details on the drawing or test specification.
The acceptance criteria should also clarify whether the leak-rate requirement applies to the complete assembly, individual channels or specific sealing interfaces.
Confirm expected service interval assumptions, replaceable components, storage orientation, shelf conditions and return-for-repair process.
Keep the serial number linked to the approved drawing, bill of materials and final test record.
Material, magnet, ferrofluid, bearing or manufacturing-process changes should follow an agreed notification and requalification route.
For critical applications, the customer and supplier should also agree on:
Recommended inspection intervals
Allowable operating-temperature trends
Vibration or torque-monitoring limits
Storage duration and storage environment
Repair evaluation and return procedures
Drawing and specification revision control
Provide pressure and leak-rate targets, gases, speed, load, temperature, duty cycle, shaft and flange drawings, cleanliness limits, quantity and acceptance requirements.
Also provide the required delivery date, prototype quantity, expected production quantity and estimated annual demand where available.
Yes, many ferrofluidic seals are designed to separate vacuum from atmospheric pressure. However, the permissible differential pressure and staging are design-specific.
State the pressures on both sides during every operating mode, including startup, shutdown, venting and abnormal conditions.
Many feedthrough assemblies integrate bearings, but the architecture depends on loads, speed, alignment and customer interfaces.
Some designs may rely partly on external support bearings. Therefore, the complete shaft-support arrangement should be evaluated rather than only the ferrofluidic sealing section.
Life depends on thermal, chemical, mechanical and duty conditions. Use application data, validation testing and condition monitoring rather than a universal hour value.
Bearing load, shaft runout, process-gas compatibility, ferrofluid temperature, cooling effectiveness and start-stop frequency may all influence service life.
Send Moretec the process envelope and interface drawings. The resulting proposal should state assumptions, excluded conditions, test method and documentation so both teams evaluate the same design basis.
To request a technical evaluation, provide the following information:
Completed operating-condition form
Process and vacuum requirements
Shaft, flange and installation drawings
Rotation speed, pattern, torque and external loads
Temperature and cooling conditions
Cleanliness and leak-test requirements
Required quantity and delivery schedule
Moretec’s engineering team will review feasibility, identify critical assumptions and recommend an appropriate product configuration, test method and documentation plan.
