What Is Tube Sheet Cladding in Heat Exchangers?

In a shell-and-tube heat exchanger, the tube sheet is the plate that supports and seals the ends of hundreds of tubes. It separates the shell-side and tube-side fluids, ensuring heat transfer takes place safely without cross-contamination. During operation, this plate is exposed to high temperatures, pressure fluctuations and aggressive fluids that can cause corrosion or pitting. When the base material alone cannot withstand these conditions, tube sheet cladding is applied to extend service life and maintain reliability.

What Is Tube Sheet Cladding?

A tube sheet is a thick, perforated plate that anchors tubes and prevents cross-contamination between process fluids. When exposed to aggressive media such as seawater, condensate, or acidic vapours, even high-grade carbon or alloy steels begin to corrode.

Tube sheet cladding solves this challenge by metallurgically joining a corrosion-resistant alloy layer onto the base metal.

• The base metal provides mechanical strength and structural stability.
• The cladded layer shields against chemical attack, erosion and high-temperature oxidation.

This dual-metal construction offers the durability of exotic alloys at a fraction of their cost delivering optimal strength-to-corrosion resistance for long-term exchanger performance.

Different of Tube Sheet Cladding Methods.

Different cladding processes are used depending on size, material and service conditions.

• Explosion Bonding: A controlled detonation propels the cladding plate onto the base metal at supersonic velocity.
  The impact forms a solid-state metallurgical bond without melting either layer. This technique is ideal for large plates and for joining dissimilar metals like carbon steel with stainless steel, titanium, or nickel alloys.
• Weld Overlay Cladding: A corrosion-resistant alloy is welded over the surface of the base plate using TIG, MIG, or submerged-arc welding. It creates a fusion bond and is often used for specific sections like tube joints or sealing faces that require added protection.
• Roll Bonding (Hot Rolling): Both metals are heated and passed through heavy rollers under high pressure, creating a uniform, solid-state bond across the surface. This process ensures even thickness and excellent adhesion between layers.
• Laser or Thermal Spray Coating: A fine metal powder is melted onto the surface using a laser or plasma torch.
  Although thinner than traditional cladding, this process is used for repair work or smaller components requiring precise control.

Materials Used for Tube Sheet Cladding

Selecting the right combination of base and cladding materials is critical to achieving the perfect balance of mechanical strength, corrosion resistance and thermal compatibility in a heat exchanger. Each layer serves a distinct function: the base metal carries the structural load, while the cladding alloy provides long-term protection against chemical, thermal and mechanical degradation. The choice depends on factors such as process fluid composition, temperature, pressure and maintenance accessibility.

1. Base Metals: Base plates are selected primarily for their mechanical strength, weldability and cost-efficiency. They form the structural backbone of the heat exchanger tube sheet, designed to sustain internal pressure, flange loads and thermal expansion without distortion.

• • Common Base Metals Include:
    • Carbon Steel (SA 516 Gr. 70): The most widely used boiler-quality steel due to its excellent weldability, toughness and strength under high pressure. It provides the rigidity needed to hold hundreds of tubes in alignment during service.
    • Boiler-Quality Steel (BQ Steel): Offers superior resistance to deformation at elevated temperatures, making it suitable for steam condensers and feedwater heaters.
    • Mild and Low-Alloy Steels: Used when moderate strength and machinability are required. Low-alloy steels like SA 387 provide improved creep and fatigue resistance in thermal cycling environments.

Base materials are typically chosen for strength and structural integrity, while corrosion protection is achieved through a bonded alloy layer reducing overall cost without sacrificing performance.

2. Cladding Alloys: The cladded surface directly faces the process fluid, making corrosion and temperature resistance the top priorities. The cladding alloy must remain chemically stable under operating conditions and compatible with both the base metal and process media.

• • Stainless Steels (304L, 316L): 304L provides reliable corrosion resistance in mildly corrosive environments such as freshwater and cooling-water systems. 316L, enriched with molybdenum, offers enhanced pitting and crevice corrosion resistance, making it the industry standard for chemical and refinery tube sheets.
  • Duplex and Super Duplex Stainless Steels: Combine the strength of ferritic steels with the corrosion resistance of austenitic grades. Ideal for chloride-rich seawater and offshore applications, resisting stress corrosion cracking and localized attack.
  • Nickel-Based Alloys (Inconel 625, Inconel 825, Monel 400): Maintain exceptional corrosion resistance in acidic and high-temperature environments, such as urea reactors, sour-gas coolers and hydrocarbon reformers. Inconel 625 and 825 resist oxidation and carburization up to 1000°C, while Monel 400 performs exceptionally in brine and caustic media.
  • Copper-Nickel Alloys (Cu-Ni 70/30, Cu-Ni 90/10): Favoured for marine condensers, desalination plants and heat exchangers using seawater. These alloys offer natural biofouling resistance and excellent thermal conductivity, maintaining efficient heat transfer under continuous operation.
  • Titanium and Titanium Alloys: Provide near-total resistance to chloride-induced corrosion, making them indispensable for seawater cooling, desalination and high-purity chemical systems. Titanium cladding ensures longevity even under extreme pH and oxidizing conditions. 

Material Pairing in Tube Sheet Cladding:

Choosing the right base cladding combination ensures both economic efficiency and long-term durability:

After material bonding via weld overlay cladding, explosion bonding, or roll bonding the tube sheet undergoes precision machining, ensuring ±100 µm tolerance and 0.8 Ra surface finish. Each plate is tested for metallurgical integrity, bond strength and corrosion resistance under simulated service conditions.

Why Choose Schilthorn Precision for Your Heat Exchanger Tube Sheets?

With over 18 years of specialized experience in precision engineering, Schilthorn Precision Engineering Pvt. Ltd. is a trusted manufacturer of ASME and TEMA compliant heat-exchanger tube sheets that deliver measurable performance under demanding operating conditions. Our facility integrates weld-overlay and explosion-bond cladding, multi-axis CNC machining & CMM-verified inspection under one controlled workflow to achieve ±100 µm tolerances and 0.8 Ra surface finishes. Backed byISO 9001 and AS9100 certifications, every component we produce undergoes rigorous Quality Standards.