If you are engaged in corrosive, high-temperature industrial process environments, you may know how important exchanger tube material is.
A proper tube can greatly reduce your downtime and operating costs. PSSiC heat exchanger tubes are rapidly replacing graphite. Let’s see why and how through this guide.
What is a PSSiC Heat Exchanger Tube?
Pressureless sintering creates a dense, single-phase ceramic without free silicon and binder residues. PSSiC usually contains ≥98% silicon carbide by volume and reaches a density of 3.10-3.12 g/cm3. It delivers thermal conductivity of 116-140 W/m·K at room temperature[1].
PSSiC possesses a thermal expansion coefficient of 4.0-4.7×10-6/K. It can withstand sudden change in temperature, whereas other ceramics fail under these conditions.[2] These properties make PSSiC heat exchanger tubes ideal for demanding process conditions.
Further Reading: What is PSSiC? Definition, Properties, and Applications
Silicon Carbide Heat Exchanger TubesLimitations of Graphite Heat Exchanger Tubes
Graphite tubes have served the chemical process industry well for many years. Their good thermal conductivity, corrosion resistance and lower cost are attractive. However, using graphite also brings some challenges.
Porosity
Graphite is porous. It requires resin or carbon impregnation to become impermeable. Those impregnants can break down, leach out, or react with process fluids over time, leading to gradual permeability loss and finally failure.
Limited Mechanical Strength
Graphite cannot withstand high pressure differentials, high flow velocities or physical impact. This limits its maximum operating pressure and flow rates.[3] Besides, graphite tubes crack easily during installation, cleaning, or pressure spikes.
Oxidation & Thermal Degradation
In oxidizing environments, graphite begins to degrade at temperatures above 400℃. This restricts its use in high-temperature air or oxygen-containing processes.
Graphite also performs poorly under rapid thermal cycling. Its uneven expansion causes micro-cracking.
Maintenance Frequency
Fouling builds up faster on graphite than on smoother ceramic surfaces. More frequent cleaning means more downtime and higher risk of tube damage during maintenance.
Why Pressureless SiC Tubes Outperform Graphite Tubes?
PSSiC can solve these graphite limitations and delivers additional benefits, including longer service life, lower costs, and higher efficiency for your heat exchange system.
Thermal Properties & Energy Efficiency
The heat transfer performance of PSSiC matches or exceeds graphite. PSSiC also offers far greater complete structure.
Comparable Heat Transfer, Smaller Scale
Silicon carbide delivers thermal conductivity nearly equal to impervious graphite, roughly 120-140 W/m·K at room temperature. That is 5 times higher than stainless steel and twice that of tantalum.
Because PSSiC transfers heat so efficiently, you can achieve the same thermal duty with fewer tubes or a smaller exchanger shell to save floor space.
Better Performance at Operating Temperature
Unlike many materials, PSSiC retains most of its thermal conductivity at high temperatures. Even at 1,200℃, it still delivers approximately 35 W/m·K.
Graphite also retains conductivity at high temperatures. However, its structural limits prevent its use at those temperatures in practice.
Withstands Rapid Temperature Changes
Because of its low thermal expansion coefficient and high thermal conductivity, PSSiC can withstand rapid temperature swings that would shatter other materials. Standard testing shows that it withstands 50+ cycles from 1,000℃ directly to room temperature without cracking.
Corrosion Resistance & Chemical Compatibility
Corrosion resistance is where pressureless sintered SiC truly separates itself from graphite and other tube materials.
Chemical Inertness
PSSiC is almost universally corrosion-resistant. It withstands virtually all common acids, even hydrofluoric acid. PSSiC is one of the few materials that can handle HF.
It also resists strong bases, solvents, oxidizing media, and chlorinated organics.
No Leach or Degrade
Unlike impregnated graphite, PSSiC does not contain any resins, pitches, or binders that can dissolve into your process stream.[1] There is nothing to leach out, nothing to degrade, and no gradual loss of impermeability over time.
Moreover, corrosion rates for PSSiC in common media are extremely low, typically under 2 mg/cm2 per year in 98% sulfuric acid at 100℃. It shows near 0 in many other chemicals.
Zero Metal Ion Leaching
PSSiC tubes do not contain metallic binders or additives. Nothing will leach into your product, even under extreme temperatures and pressures.
Graphite impregnants, by contrast, can break down and introduce carbon or resin contaminants into sensitive processes.
Mechanical Strength and Durability
If you have ever broken a graphite tube during handling or cleaning, you will immediately know the mechanical advantage of silicon carbide.
Exceptional Hardness & Wear Resistance
PSSiC reaches 9.5 Mohs hardness. It is harder than tungsten carbide, second only to diamond among industrial materials. Such extreme hardness gives PSSiC tubes excellent wear resistance against abrasive slurries and high-velocity fluids.
High Pressure Capability
With flexural strength of 320-400 MPa and compressive strength near 3900 MPa, PSSiC tubes safely handle much higher pressure differentials than graphite. This allows them to operate at higher process pressures and flow rates without breaking.[2]
Smooth & Non-Stick Surface
The dense, smooth silicon carbide surface does not readily adsorb process residues. Scale, precipitates, and organic films form more slowly and adhere less strongly than they do on graphite.
When cleaning does become necessary, deposits remove more easily with less aggressive methods. This reduces the chance of tube damage during maintenance.
Lower Lifetime Maintenance Cost
PSSiC tube service life typically extends to 10+ years, compared to 3-5 years for many graphite ones. Industry case studies show that facilities switching from graphite to SiC heat exchanger tubes reduce maintenance costs by 30-40% over three years.
Industries That Benefit Most From SiC Tube Replacement
Pressureless sintered SiC heat exchanger tubes deliver value across nearly every sector of process manufacturing. Here are the industries that get the fastest return by changing to PSSiC tubes.
Chemical Processing
Specialty chemical, acid production, and fluorochemical operations gain the most from PSSiC’s corrosion resistance. Whether you handle sulfuric acid, nitric acid, HF, mixed acids, or caustic solutions, SiC tubes outlast graphite by a wide margin.
Petrochemical & Refining
Refineries and petrochemical plants use PSSiC tubes for corrosive process streams, high-temperature heat recovery, and sour gas applications. The material’s resistance to sulfidic corrosion and high temperatures improves reliability in distillation, hydrotreating, and alkylation units.
Metallurgy
Metal pickling, plating, and surface treatment processes use highly corrosive acid baths at elevated temperatures. PSSiC tubes resist attack from pickling acids and plating chemistries that rapidly degrade graphite and metallic exchangers.
Silicon Carbide Heat Exchanger Tubes in Practical Industrial UseFAQs
Can I replace graphite tubes with SiC tubes in a shell-and-tube exchanger?
In most cases, yes. PSSiC tubes are available in standard diameters and lengths that match common graphite tube dimensions. You need to verify tube sheet compatibility and operating pressure limits.
How does the cost of PSSiC tubes compare to graphite tubes?
PSSiC tubes have a higher purchase cost than graphite. However, they typically last 2-3 times longer and require far less maintenance. Most operations achieve full payback within 2-4 years.
Are PSSiC tubes compatible with hydrofluoric acid?
Yes. PSSiC resists both aqueous HF and HF gas across a wide temperature range, making it the standard for fluorochemical production and HF processing.
What is the maximum operating temperature for PSSiC heat exchanger tubes?
Pressureless sintered SiC can operate continuously at temperatures up to 1,300℃ in inert atmospheres, and up to approximately 1,600℃ for short-term exposure. Always verify temperature limits with your specific application parameters.
How to clean silicon carbide heat exchanger tubes?
They can be cleaned with most standard chemical cleaning agents, high-pressure water washing, and mechanical pigging methods.
Can PSSiC tubes handle abrasive slurries and particulate-laden fluids?
Yes. It withstands abrasive slurries and particulate-laden process streams far better than graphite or metallic tubes.
What is the service life of PSSiC tubes?
Under normal operating conditions within design parameters, SSiC heat exchanger tubes typically last 10-15 years or more. Actual service life depends on temperature, chemical environment, flow conditions, and maintenance practices.
Conclusion
If you are dealing with tube failures, high maintenance costs, contamination, or process limitations with graphite tubes, trying PSSiC is a proven upgrade path.
Still not clear about how to choose? Contact Newthink for more information. We have been manufacturing and supplying advanced ceramic products since 2011. Newthink can help you solve your industrial challenges.
Thanks for your reading. Hope this article will be helpful.
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