| Seal Material | Chemical exposure, temperature, pressure, and required service life | PTFE offers very broad chemical resistance and a low coefficient of friction; the exact performance depends on grade, filler, temperature, and mating surface | Select virgin or filled PTFE according to wear, extrusion, friction, and media requirements | Request the compound formulation, temperature limits, pressure limits, and compatibility data for the actual medium |
| Spring Energizer | Corrosive gas, salt water, cleaning chemicals, sterilization, and cyclic loading | Cobalt-chromium alloy spring materials are commonly selected where high corrosion resistance, spring force retention, and elevated-temperature stability are required | Use a corrosion-resistant energizer with sufficient preload for the pressure and temperature range | Confirm alloy designation, heat treatment, surface condition, and resistance to the specific process fluid |
| Operating Temperature | Minimum and maximum continuous temperature, short-term excursions, and thermal cycling | Many PTFE lip-seal compounds are used across approximately −60 °C to +260 °C, but the usable range varies by compound, pressure, speed, and energizer | Rate the seal for continuous temperature and separately check intermittent peak temperature | Obtain temperature derating data rather than relying only on the polymer’s nominal temperature limit |
| System Pressure | Pressure level, pressure direction, pressure spikes, and static or dynamic operation | Pressure capability depends strongly on seal geometry, radial clearance, extrusion gap, temperature, and speed; unsupported PTFE lips are more sensitive to extrusion | Use anti-extrusion support or a pressure-optimized profile when pressure or clearance is high | Provide maximum differential pressure, pressure cycling frequency, and worst-case extrusion gap |
| Shaft or Rod Speed | Rotational speed, reciprocating speed, stroke length, acceleration, and duty cycle | PTFE seals generally support higher sliding speeds than many elastomeric seals, but heat generation is governed by speed, load, lubrication, and surface finish | Choose a low-friction compound and verify the pressure-velocity limit for dynamic service | State rotational speed in rpm or sliding speed in m/s, together with pressure and operating temperature |
| Pressure-Velocity Load | Combined pressure and sliding motion during normal and peak operation | PV performance is compound-specific; increasing pressure, speed, or temperature can increase frictional heat and accelerate wear | Compare the actual duty point with tested PV limits and include a safety margin | Ask for test conditions, counterface material, lubrication state, and allowable leakage criteria |
| Chemical Compatibility | Fluid composition, concentration, contaminants, additives, and cleaning agents | PTFE is resistant to most acids, bases, hydrocarbons, solvents, and gases; molten alkali metals, elemental fluorine, and some high-temperature reactive agents require special review | Evaluate both the PTFE compound and the metallic energizer because the spring may be less resistant than the polymer | Submit the complete fluid list, concentration, pressure, temperature, and exposure duration for compatibility review |
| Shaft or Counterface Material | Material hardness, coating, corrosion resistance, and surface integrity | Common counterfaces include hardened steel, stainless steel, ceramics, and coated surfaces; the correct pairing depends on speed, load, and lubrication | Use a hard, smooth, defect-free counterface compatible with the selected PTFE compound | Confirm hardness, coating thickness, porosity, runout, scratches, and lead or spiral marks |
| Surface Finish | Dynamic sealing surface roughness and direction of machining marks | A typical dynamic sealing surface may require approximately Ra 0.1–0.4 µm, subject to seal design, speed, lubrication, and manufacturer validation | Avoid rough, porous, or directional surfaces that can increase wear or pump fluid past the lip | Specify the measurement method, roughness parameters, lay direction, and allowable surface defects |
| Radial Clearance and Extrusion Gap | Housing-to-shaft clearance, pressure direction, temperature expansion, and tolerance stack-up | Larger extrusion gaps increase the risk of PTFE lip deformation, especially at high pressure and temperature | Reduce clearance or add a support feature when pressure, temperature, or dimensional tolerance increases the extrusion risk | Provide minimum and maximum clearances at assembly and at operating temperature |
| Installation Geometry | Groove dimensions, lead-in chamfers, assembly direction, and available installation tools | PTFE seals can be damaged by sharp edges, splines, keyways, or forced stretching beyond the seal design | Specify controlled lead-in geometry, edge radii, and installation protection for the lip and energizer | Request dimensional drawings, groove tolerances, installation instructions, and inspection gauges |
| Leakage and Friction Target | Allowable leakage, breakaway torque, running torque, noise, and energy consumption | A tighter lip can reduce leakage but may increase friction and heat; a lighter lip can reduce friction but may require better surface control | Balance sealing force, friction, wear, and acceptable leakage for the actual duty cycle | Define measurable leakage and friction limits, test duration, temperature, speed, and pressure |
| Lubrication and Dry Running | Process fluid lubricity, external lubrication, start-stop cycles, and accidental dry running | PTFE has low friction, but dry running can still generate heat and wear; filled grades may improve wear resistance | Select a compound validated for lubricated, marginally lubricated, or dry-running conditions | Confirm lubricant type, compatibility, replenishment method, start-up condition, and maximum dry-running duration |
| Thermal Expansion and Compression Effects | Temperature variation, trapped volume, seal interference, and dimensional changes | PTFE has relatively high thermal expansion and can exhibit creep or cold flow under sustained load | Use a groove and interference design that maintains sealing force without excessive friction or deformation | Review dimensional tolerances at minimum and maximum operating temperatures |
| Cyclic and Pulsating Service | Pressure frequency, direction reversal, reciprocating motion, vibration, and shock loading | Repeated cycling can cause lip fatigue, spring movement, wear, and transient leakage if the profile is not designed for reversal | Select a profile and energizer configuration designed for the actual motion and pressure cycle | Provide cycle count, frequency, pressure waveform, stroke or rotation direction, and target service life |
| Cleanliness and Regulatory Needs | Particle sensitivity, contamination limits, sterilization, vacuum service, and export requirements | Clean applications may require controlled manufacturing, cleaning, packaging, and traceability; not every PTFE compound is suitable for every regulated process | Specify cleanliness level, extractables limits, documentation, and required material declarations | Confirm batch traceability, inspection records, packaging method, certificates, and applicable compliance documents |
| Quality and Validation | Critical dimensions, incoming inspection, sample approval, and production consistency | Seal performance is sensitive to lip geometry, spring force, material condition, and surface defects | Use defined drawings, inspection criteria, functional testing, and change-control requirements | Request dimensional reports, material certificates, spring-load data, sample test results, and notification of design or material changes |
