Packing are critical components for equipment sealing in the food and chemical industries. Due to differences in material composition, PTFE gaskets and graphite gaskets are suitable for distinct applications. Selecting the wrong type may lead to risks such as leakage and contamination. This article focuses on two primary scenarios to assist you in making an accurate gasket selection.
1、Core Feature Comparison
The PTFE packing uses PTFE as its core, while the graphite packing employs flexible graphite as its base material. The key performance differences are as follows:
|
Dimension for Comparison |
Tetrafluoro Packing |
Graphite Packing |
|
Temperature Tolerance Range |
Long-term exposure: 180°C to 260°C; for special models, up to 280°C. |
Long-term: 200°C to 450°C; short-term: up to 600°C |
|
Corrosion Resistance |
Exhibits extremely high chemical inertness, resistant to all strong acids, strong bases, and organic solvents (except molten alkali metals). |
Resistant to most acids and alkalis, but not to strong oxidizing agents (e.g., concentrated nitric acid). |
|
Friction Factor |
Extremely low (0.08–0.12), suitable for high-speed devices |
Slightly elevated; lubrication is required under high-speed operating conditions. |
|
Health Safety |
The pure white variant complies with food-grade certification, is free from impurities, and can be sterilized. |
Only food-grade pure graphite meets hygiene requirements, while the standard version contains impurities. |
|
Pressure Resistance |
Generally the long-term pressure should be ≤16 MPa, as high pressure may cause deformation. |
Excellent performance: long-term pressure resistance ≤30 MPa; composite variants can withstand up to 50 MPa. |
|
Core Advantage |
Clean and non-toxic, highly corrosion-resistant with minimal friction, suitable for sanitary-grade and highly corrosive operating conditions. |
Resistant to high temperatures and high pressures, suitable for harsh operating conditions |
2、Precision Selection for Food/Chemical Applications
Core logic: In food applications, hygiene and safety take precedence; in chemical applications, compatibility with the medium, temperature, and pressure is prioritized.
(1) Food Industry Scenario
Prioritize tetrafluoroethylene packing; for special high-temperature static seals, food-grade pure graphite packing may be used.
1. Applicable scenarios for PTFE packing
General food equipment (for beverages, dairy products, etc.): Pure white PTFE packing, compliant with hygiene standards and resistant to cleaning and sterilization.
High-speed equipment (stirrers, centrifuges): Equipped with oil-filled PTFE packing to reduce wear, suitable for linear speeds ≤20 m/s.
For weak-corrosion cleaning applications: Use pure PTFE or black PTFE packing, which is resistant to weak acids and alkalis, preventing leakage and contamination.
2. Graphite packing suitable for various applications
This product is exclusively designed for high-temperature static seals (e.g., cooking pot valves). Use food-grade pure graphite material and conduct regular inspections to prevent powder shedding.
Selection Contraindications
❌ Ordinary graphite packing does not come into contact with food;
❌ Oil-containing PTFE packing does not contact high-temperature food;
❌ PTFE packing is not used in equipment operating above 260°C.
(II) Chemical Industry Scenario
For strong corrosion resistance, choose tetrafluoroethylene; for high-temperature and high-pressure applications, opt for graphite, with fine adjustments based on equipment type.
1. Applicable scenarios for PTFE packing
Strong corrosive media (strong acids, strong alkalis, organic solvents): Pure PTFE or segmented wire PTFE packing for leak prevention.
Low to medium temperature and pressure (≤260°C, ≤16 MPa): Standard PTFE packing, offering moderate cost and easy maintenance.
Clean Chemical Industry (Pharmaceutical, Fine Chemical): High-purity PTFE packing ensures medium purity.
2. Graphite packing suitable for various applications
High temperature and high pressure (>260°C,>16 MPa): Composite reinforced graphite packing, suitable for reactors, boilers, etc.
Solid particle-containing medium: Graphite packing, wear-resistant and clog-proof, suitable for pumps and mixers.
Static sealing (flanges, manholes): Pure graphite or composite graphite packing, offering excellent cost-performance ratio.
Selection Contraindications
❌ Graphite is not suitable for strongly oxidizing media;
❌ PTFE is not suitable for highly corrosive environments exceeding 260°C;
❌ Pure PTFE is not suitable for high-pressure and high-speed operating conditions.
3、Selection Techniques and Correction of Common Misconceptions
Three-step selection process:
A-Clarify the requirements (Hygiene> Corrosion> Temperature and Pressure> Equipment)
B-Matching parameters (temperature and pressure, medium, hygiene)
C-Perform fine adjustments to the equipment (dynamic/static seals, rotational speed)
Common Misconceptions
Misconception 1: Graphite is universally corrosion-resistant – incorrect! It is not resistant to strong oxidizing agents; for severe corrosion, PTFE should be selected.
Misconception 2: Only PTFE can be used in food applications – Incorrect! Food-grade pure graphite may be selected for high-temperature static sealing applications.
Misconception 3: PTFE is resistant to all temperatures – Incorrect! Long-term use should not exceed 260°C.
Misconception 4: All graphite can be used in food applications—this is incorrect! Only food-grade pure graphite is suitable for high-temperature static sealing applications.