Abstract: This article details the characteristics and application ranges of commonly used mechanical seal materials, helping customers make correct material selection decisions based on medium characteristics.
The performance and service life of mechanical seals largely depend on the rationality of material selection. Below are the characteristics and application guidelines for various sealing materials.
End Face Materials
1. Carbon-Graphite Materials
Carbon graphite offers good thermal conductivity, chemical stability, self-lubricating properties, and machinability, making it the most widely used soft ring material. Suitable for various equipment including water pumps, hot oil pumps, boiler feed pumps, and nuclear secondary pumps.
2. Silicon Carbide Ceramics
Silicon carbide is currently one of the most ideal friction pair materials. When paired with carbon graphite, its dry sliding friction coefficient is smaller than that of alumina and cemented carbide, with higher PV value.
- Performance characteristics: Excellent chemical corrosion resistance, high mechanical strength, wear resistance, high temperature resistance, good self-lubricating properties
- Application range: Resists corrosion from almost all chemicals except for a few media such as hydrofluoric acid, including concentrated nitric acid, sulfuric acid, and hydrochloric acid
3. Alumina Ceramics
Features extremely high hardness, good wear resistance, chemical stability, high insulation, and high melting point. Resists almost all corrosive media except hydrofluoric acid, fluorine-containing substances, hot or concentrated alkali solutions.
Auxiliary Sealing Materials
1. Fluororubber
After vulcanization, exhibits excellent heat resistance, ozone resistance, oil resistance, and resistance to various chemical reagents. Maximum service temperature up to 170°C (in ordinary media).
2. Nitrile Rubber
Most widely used oil-resistant rubber, with wear resistance 30-45% higher than natural rubber, maximum service temperature 95°C. Resists various animal, vegetable, and mineral oils, as well as glycol.
3. Butyl Rubber
Suitable for acidic mud conditions, maximum service temperature 100°C, resistant to strong acids and alkalis (such as hydrochloric acid, sodium hydroxide).
4. Polytetrafluoroethylene
Applicable temperature range -100 to +250°C, suitable for corrosive media such as weak acids and strong alkalis.
Braided Packing Materials
1. Carbon Fiber Braided Sealing Packing
A high-strength, high-modulus new material with advantages including high strength, large elastic modulus, high temperature resistance, chemical corrosion resistance, good thermal conductivity, low thermal expansion coefficient, and self-lubricating properties.
2. Expanded Graphite (Flexible Graphite)
In addition to graphite’s inherent excellent self-lubricating properties, corrosion resistance, high/low temperature resistance, radiation resistance, wear resistance, and low friction coefficient, it also offers flexibility, low density, good compression resilience, and wide service temperature range. Applicable medium pH value 0-14, usable with all media except a few strong oxidizers.
Material Selection Recommendations
When selecting sealing materials, comprehensively consider medium characteristics, temperature range, pressure rating, particle content, and other factors. For strong corrosion conditions, ceramics, silicon carbide, and filled PTFE are ideal choices; for high-temperature conditions, metal bellows combined with cemented carbide or silicon carbide work better; for media containing particles, choose hard-to-hard friction pairs with enhanced flushing and filtration.