Heat exchangers are core heat-transfer equipment widely used in petrochemical, power generation, pharmaceutical, food processing, seawater desalination, and shipbuilding industries. Among all components, heat exchanger tubes directly handle medium flow and heat exchange, and their condition critically affects system efficiency and safety. Prolonged exposure to high temperature, pressure, corrosive fluids, and high-velocity flow makes tube failure frequent, causing severe economic losses and hazards. Statistics show that corrosion, erosion, fatigue, and leakage are leading causes of unscheduled shutdowns, problems largely preventable through scientific material selection and maintenance. This article systematically analyzes five major failure modes, pitting, stress corrosion cracking, erosion corrosion, thermal fatigue, and fouling, along with special types like dezincification and galvanic corrosion. Practical material selection recommendations and prevention strategies are provided to help engineers, maintenance teams, and procurement professionals understand failure mechanisms, extend heat exchanger life, reduce costs, and ensure safe production.
Before examining specific failure modes, it is essential to clarify the basic concept of tube failure. As critical heat-transfer components in various industries, tubes operate under combined effects of pressure, temperature, fluid chemistry, and flow velocity. Failure is rarely caused by a single factor; rather, it results from incompatibility between material properties and operating conditions, leading to gradual degradation and eventual damage. Even high-quality stainless or alloy tubes cannot completely avoid failure during long-term service. Tube failure reduces efficiency and may cause leakage, environmental risks, production interruption, and high repair costs. Therefore, understanding failure causes and mitigating risks through material selection, inspection, and design optimization is crucial for reliability and service life extension.
Tube failure is seldom accidental; it accumulates from design, material selection, and operational decisions. Common factors include corrosive or poorly controlled fluids, high velocity and turbulence, high temperatures with thermal cycling, dissimilar metal combinations between tubes and tube sheets or supports, and inadequate inspection and maintenance. When materials cannot meet operating conditions, corrosion, erosion, fatigue, and localized damage develop—often causing severe degradation before leakage appears. Understanding these causes is vital for engineering and procurement personnel. Through reasoned selection and scientific management, downtime can be reduced and service life extended.
After understanding basic concepts, it is necessary to master the five major failure modes—each with unique mechanisms, manifestations, and preventive measures.
Pitting is one of the most common and hazardous failure modes. It is localized corrosion forming deep, narrow pits, typically caused by chlorides, insufficient passivation, or protective film breakdown. Unlike uniform corrosion, pitting is highly concealed—the tube may appear intact while localized areas suffer severe metal loss, eventually leading to perforation and leakage. Common causes include inadequate post-weld cleaning, improper use of 304 or 316 stainless steel in high-chloride environments, and stagnant zones from low velocity. To mitigate pitting, select materials with higher corrosion resistance—254 SMO, duplex 2205, or titanium alloys in seawater. Bright annealing reduces surface defects. Maintaining velocity above 1.5 m/s minimizes deposits and localized corrosion.
SCC is another severe failure mode, resulting from combined tensile stress, high temperature, and corrosive media, commonly in systems with chlorides, ammonia, or other aggressive substances. Austenitic stainless steels like TP304 and TP316 are susceptible under specific conditions, frequently in refineries, power plants, and fertilizer facilities. To prevent SCC, select more resistant materials—duplex stainless steel, Incoloy 825, or Alloy 20. For sour service with hydrogen sulfide, choose materials meeting NACE MR0175. Additionally, minimize operating temperature, mechanical loads, and residual stress to reduce crack initiation and propagation.
Erosion corrosion is material loss from synergistic high-velocity fluid, particle impact, and chemical corrosion. When flow is excessive or the medium contains suspended solids, sand, or bubbles, the fluid impacts the tube wall, disrupting the protective oxide film. Once exposed, corrosion accelerates. Manifestations include inlet wall thinning, directional groove wear, pitting, and bundle damage from vibration. This commonly occurs in cooling water systems, condensers, and high-flow exchangers. To reduce risk, add impact baffles or tube liners. In seawater systems, CuNi 90/10 or Monel 400 offers good resistance. Optimizing inlet design for smooth entry also reduces turbulence and erosion.
Thermal fatigue is another important failure cause. As heat exchangers undergo startup, shutdown, and load changes, tubes experience cyclic temperature variations causing repeated expansion and contraction. Over time, fatigue damage accumulates, forming cracks and potentially leading to rupture. Causes include frequent cycling, uneven temperature distribution, and inadequate expansion compensation. To reduce risk, use seamless tubes with low residual stress, incorporate flexible supports and expansion compensation, and perform post-weld heat treatment for welded connections to improve stability.
Fouling and blockage are common operational problems affecting efficiency and causing failure. Fouling refers to accumulation of calcium carbonate, iron oxide, microbial films, and organic deposits on tube surfaces. These deposits reduce heat transfer, increase energy consumption, and create under-deposit corrosion environments causing localized damage. Common causes include untreated cooling water, inadequate cleaning intervals, and high suspended solids. To mitigate fouling, select bright-annealed tubes with lower surface roughness, use low-finned tubes to enhance turbulence and self-cleaning, and establish regular online cleaning programs.
Beyond five major modes, tubes also face dezincification and galvanic corrosion, requiring attention in material selection and system design.
Dezincification is selective corrosion in brass tubes, common in corrosive water or low-velocity, stagnant conditions. Zinc is preferentially dissolved, leaving a porous, low-strength copper-rich layer. The surface may appear undamaged, but internal structure is compromised, with reduced mechanical properties that can lead to rupture or leakage. This typically occurs with ordinary brass under poor water quality or in warm, mildly acidic conditions. Therefore, select inhibited brass alloys or more suitable corrosion-resistant materials. For cooling water systems and condensers, naval brass is widely used for its good strength, thermal conductivity, and corrosion resistance. Under good water quality control, inhibited naval brass resists general corrosion and dezincification.
Galvanic corrosion occurs when two dissimilar metals contact and form an electrical connection in the presence of an electrolyte, causing the more active metal to corrode preferentially. This commonly occurs at tube-to-tubesheet joints, tube-to-support contacts, or areas with incompatible materials during maintenance. Even materials with good individual resistance may fail rapidly when combined with incompatible metals. Therefore, carefully consider compatibility, avoid unreasonable dissimilar metal combinations, and take insulation isolation measures when necessary.
Corrosion is among the most significant failure causes in power, marine, refining, chemical, and desalination industries. Through chemical or electrochemical reactions with fluids, dissolved substances, or deposits, tube wall thins, strength declines, and perforation and leakage occur. Different alloys have different corrosion resistance; materials cannot be selected solely by price or general performance. Comprehensive evaluation must consider specific medium, temperature, pressure, and service life. Mismatch leads to severe problems over time. Leakage is typically the final manifestation of long-term corrosion, not the initial cause. Since early wall thinning is not visually detectable, use non-destructive testing like eddy current for periodic assessment. Early identification prevents sudden leakage and unscheduled shutdowns.
After understanding failure modes, master key selection principles considering fluid properties, temperature, velocity, service life, and compatibility with other components.
Reasonable selection is critical for reducing failure risk. Consider fluid composition, operating temperature, velocity, turbulence, expected life, and compatibility with tube sheets and supports. For cooling water systems and condensers, naval brass is widely used. For more corrosive or higher-velocity environments, aluminum brass offers better adaptability, forming a stable oxide film that improves erosion and biofouling resistance—hence its broad use in power plants, large condensers, and industrial cooling. In seawater and marine applications, copper-nickel alloys have advantages including chloride corrosion resistance, biofouling resistance, and good erosion resistance, making them common in desalination, marine systems, and offshore engineering. In these environments, material selection often directly determines service life.
Based on medium composition, temperature, pressure, velocity, and expected life, select appropriate materials. TP316L, TP321, Incoloy 825, duplex 2205, and copper-nickel alloys provide reliable corrosion and high-temperature performance depending on conditions. In seawater or brine, prioritize 254 SMO, duplex 2205, or titanium alloys. For sour service with hydrogen sulfide, choose materials meeting NACE MR0175. In systems with chlorides, ammonia, or other aggressive substances, duplex stainless steel, Incoloy 825, or Alloy 20 are more suitable. High-quality tubes should undergo rigorous inspection including corrosion, hardness, grain size, and pressure testing to meet industrial requirements.
Many premature failures originate from excessive focus on initial cost while neglecting long-term conditions. Using low-cost materials in highly corrosive or high-load environments reduces initial investment but leads to shortened life, increased maintenance, frequent shutdowns, and higher lifecycle costs. Therefore, material selection should be viewed as risk control rather than merely procurement. To reduce failure risk, develop reasonable plans—matching alloys to fluid properties and temperature, controlling velocity to reduce erosion, avoiding incompatible dissimilar metal combinations with insulation when necessary, and requiring material traceability, quality certification, and strict inspection for critical equipment.
Beyond selection, systematic management of heat exchangers is essential, including traceability, inspection, maintenance, and design optimization.
Insufficient traceability is an important cause of premature failure. Incorrect grades or lack of documentation can result in performance failing to meet requirements—for example, using ordinary stainless steel in highly corrosive environments drastically shortens life. For critical applications, suppliers should provide 3.1 or 3.2 certificates per EN 10204, and verify composition before installation. Select manufacturers with comprehensive quality systems and proven capabilities. For major projects, full certification, traceability, and custom processing are important selection criteria.
Through scientific selection, proper installation, and effective maintenance, reliability can be significantly improved. Failure is generally not unavoidable but results from combined effects of material, environment, and maintenance. By understanding corrosion, erosion, dezincification, galvanic corrosion, and wall thinning, and selecting appropriate materials, engineers can reduce leakage risk, minimize losses, and improve efficiency. Establish regular online cleaning, employ eddy current testing for periodic assessment, select bright-annealed tubes to reduce contaminant adhesion, and use low-finned tubes to enhance turbulence and self-cleaning.
During design, optimize inlet structure for smooth entry, reducing turbulence and erosion. Add impact baffles or liners to minimize direct high-velocity impact. Incorporate flexible supports and expansion compensation, and perform post-weld heat treatment for welded connections to reduce residual stress. Control velocity above 1.5 m/s to reduce deposits and localized corrosion. Minimize operating temperature, mechanical loads, and residual stress to reduce crack initiation and propagation.
Heat exchanger tube failure is complex but preventable. This article reviewed five major failure modes—pitting, SCC, erosion corrosion, thermal fatigue, and fouling—along with dezincification and galvanic corrosion, analyzing mechanisms, manifestations, and influencing factors. From a material perspective, tubes are not necessarily better when more expensive; scientific matching to actual conditions is required, considering fluid properties, temperature, pressure, velocity, service life, and compatibility. Naval brass suits general cooling water, aluminum brass performs well in high-velocity environments, copper-nickel alloys excel in seawater, and duplex stainless steel, Incoloy 825, and titanium alloys offer irreplaceable advantages in highly corrosive environments. Quality assurance and traceability are equally important—complete certificates and composition verification are fundamental. At the operational level, velocity control, inlet optimization, impact prevention, and regular cleaning and inspection are all effective. Ultimately, elevating material selection from procurement to systematic risk control—considering total lifecycle cost rather than initial price—is essential for stable operation, reduced losses, and industrial safety. For engineering, maintenance, and procurement professionals, mastering and applying this knowledge is key to improving management and extending service life.
