Silicon Carbide vs Rubber Mechanical Seal: Which is Better?

Mechanical seals are a set of parts in industrial pumps. They are used to prevent leakage and protect machine internals from damage. Silicon carbide and rubber are 2 popular seal materials. Both of them are widely used in industries needing mechanical seals, fitting different industrial working conditions.

This article mainly focuses on the differences, like characteristics and use cases, between silicon carbide mechanical seals and rubber ones. After reading, you can make a selection by yourself quickly for your own industrial systems.

Material Properties Overview of Silicon Carbide and Rubber

Material composition decides the basic performance of mechanical seals. Hardness, chemical stability and heat resistance are 3 biggest differences between silicon carbide and rubber seal solutions.

Silicon Carbide Ceramic Seal Material

Silicon carbide, also called SiC, is a high-performance ceramic material. It is tailored for harsh industrial sealing environments with ultra-high hardness and stability. Moreover, this ceramic seal material can maintain stable properties even under extremely high pressure and temperature.

Silicon carbide mechanical seals exhibit low friction coefficients and superior wear resistance to resist abrasion from particle-laden fluids, such as slurry and wastewater. Besides, their dense structure also delivers excellent chemical inertness, rarely reacting with acidic, alkaline, or organic industrial fluids.

Seals made of sintered silicon carbide have an enhanced uniform structure. They are more suitable for longer continuous operation.^[3]

Rubber Seal Material

Industrial mechanical rubber seals mainly adopt EPDM, nitrile rubber, and FKM (Viton). These elastic polymer materials place more attention on flexible sealing performance. Their elastic deformation helps to fill any tiny gaps between rotating and stationary parts.

Rubber seal materials offer great flexibility and easy installation, fitting most standard low-load pump equipment. Their soft texture provides tight sealing for clean, low-pressure fluid systems.^[1]

However, rubber materials have obvious limitations in hardness and structural stability. Under harsh working conditions, they are more likely to age, swell and deform.^[2]

SiC vs Rubber Mechanical Seal: Performance Comparison in Industrial Working Conditions

Operating environments are greatly different. Thus, these 2 seal types have different performance in actual field operation.

Temperature Resistance

Silicon carbide mechanical seals work well in high-temperature environments without failure up to 250℃. Their low thermal expansion rate prevents deformation at high heat and thermal shock from sudden temperature rises and drops.

Rubber mechanical seals, on the other hand, have strict temperature limits. Common nitrile rubber seals can only be used under temperatures below 100℃. Even high-end FKM rubber ones fail to remain stable above 180℃. High heat will accelerate their aging, causing gradual leakage and frequent replacement needs.^[4]

Wear and Abrasion Resistance

Abrasion resistance is important for equipment handling impurity-containing fluids.

Silicon carbide mechanical seals work better than rubber ones in this aspect. As a high-hardness material, silicon carbide is capable of resisting the effects of friction caused by solids.

Rubber seals have poor abrasion resistance.^[2] Their soft surfaces are easily scratched and worn by solid impurities. Long-term operation with particle-laden fluids will cause irreversible damage to the seals,^[1] finally leading to leakage and even shutdown for maintenance.

Chemical Corrosion Resistance

The sintered silicon carbide mechanical seals show great resistance to corrosive chemicals.^[3] They have a high level of resistance to corrosion caused by acids, alkalis, and solvents. The tight structure prevents the intrusion of any liquid and the erosion of its composition.

The corrosion resistance of the rubber seal varies according to the type of rubber. Rubber tends to swell or even dissolve in various chemical solutions and, thus, become non-sealing. EPDM can be used in the presence of weak acids and water but not in oil and strong solvents. While nitrile ones adapt to oil-based fluids, corroding quickly in strong alkaline liquids.

Pressure Bearing & Sealing Stability

Silicon carbide ceramic seals are rigid enough to avoid deformation under high fluid pressure. The flat, smooth seal face ensures uniform contact without leakage under stable pressure, helping them work well in fluctuating pressure environments.

Rubber mechanical seals fit low- to medium-pressure working conditions. They cannot support high-pressure continuous operation for industrial process equipment. Their elastic structure deforms under excessive pressure, and over time, permanent deformation will occur, leading to gap enlargement and then leakage.^[4]

Cost

Silicon carbide ceramic mechanical seals have higher upfront costs than ordinary rubber ones due to the precision sintering process and high-purity ceramic materials. However, SiC seals have a very long service life in harsh environments. This greatly reduces your replacement frequency and manual maintenance costs, resulting in a lower long-term comprehensive cost.

Rubber mechanical seals feature simple production processes and low material costs, well-suited for small-budget, low-demand equipment projects. But they age and wear quickly in complex environments. You need to always replace them to avoid leakage. This will increase your downtime, adding to hidden operational costs.

Applicable Industries for Silicon Carbide & Rubber Seal

Matching seals with your equipment and working conditions can maximize your operational efficiency and cost performance.

Ideal Applications for Silicon Carbide Mechanical Seals

Silicon carbide mechanical seals are designed for harsh industrial working conditions. They are the preferred mechanical seal solution for high-demand systems.

You should choose SiC seals for high-temperature and high-pressure process pumps in chemical plants. They also fit slurry pumps, desulfurization circulating pumps, and mining sewage pumps with solid impurities.

For food and pharmaceutical industrial equipment requiring high cleanliness and zero contamination, silicon carbide seals work perfectly too.

Silicon carbide seals are also perfect for long-term uninterrupted operation equipment. They reduce frequent shutdown maintenance and improve your overall production efficiency.

Ideal Applications for Rubber Mechanical Seals

Rubber mechanical seals are cost-effective for common, mild working environments. They serve basic industrial sealing needs well.

You can use rubber seals for ordinary water pumps, domestic sewage equipment, and low-pressure circulating water systems. They fit such low-temperature and clean fluid environments without solid particles or strong corrosivity.^[1]

General HVAC equipment and light industrial transmission pumps also match rubber seals.

Rubber seals are your best choice if your equipment runs under mild conditions and pursues low procurement costs.

FAQs

Why do rubber seals leak frequently in slurry pumps?

Slurry contains hard solid particles. They will scratch rubber seal surfaces. And rubber possesses a weak abrasion resistance, causing leakage after surface wear.

Is it necessary to replace rubber seals with silicon carbide seals for old industrial pumps?

Depends on your working conditions. You can upgrade to SiC seals if your pump handles high-temperature, corrosive, or particle-containing fluids.

What is the main failure mode of rubber mechanical seals?

Aging deformation, medium swelling, particle wear, and high-temperature cracking.

How long is the service life difference between the two seals in desulfurization systems?

Rubber seals last 3-6 months in desulfurization slurry environments.

Silicon carbide seals can work stably for 2-3 years with minimal wear.

Can SiC mechanical seals be used for vacuum pump equipment?

Yes. Silicon carbide features low outgassing performance and a stable structure, very suitable for high-purity vacuum pump sealing scenarios.

Conclusion

Silicon carbide mechanical seals and rubber mechanical seals target completely different industrial applications. You need to match seals with working conditions. Choose rubber seals for conventional mild working conditions. Upgrade to high-performance sintered silicon carbide mechanical seals if you pursue long-term stability and low failure rate for industrial equipment.

Newthink New Materials is a professional advanced ceramic manufacturer and supplier. We provide high-quality silicon carbide mechanical seals to assist your important industry. Contact us for more information on customization.

Thanks for your reading. Hope this article will be helpful.

Reference

[1] Chandrasekaran, C. (2009). Rubber seals for fluid and hydraulic systems. William Andrew.

[2] Feyzullahoğlu, E. (2015). Abrasive wear, thermal and viscoelastic behaviors of rubber seal materials used in different working conditions. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 229(1), 64-73.

[3] Guo, X., Wang, R., Zheng, P., Lu, Z., & Yang, H. (2019). Pressureless sintering of multilayer graphene reinforced silicon carbide ceramics for mechanical seals. Advances in Applied Ceramics, 118(7), 409-417.

[4] Tiwari, A., Dorogin, L., Tahir, M., Stöckelhuber, K. W., Heinrich, G., Espallargas, N., & Persson, B. N. (2017). Rubber contact mechanics: adhesion, friction and leakage of seals. Soft Matter, 13(48), 9103-9121.