How to choose thickness?

At first glance, thickness might seem like a simple measurement—just millimeters or inches of steel, stainless, or alloy. But in reality, it's the backbone of reliability. Imagine a boiler tubing in a coal-fired power plant: it's tasked with carrying superheated steam at pressures upwards of 3000 psi and temperatures exceeding 500°C. A wall that's even 1mm too thin here could mean catastrophic failure, endangering lives and halting operations. On the flip side, a heat exchanger tube in a food processing plant needs to balance two priorities: thin enough to let heat pass through efficiently (so your product heats evenly) but thick enough to resist corrosion from acidic juices or cleaning chemicals. Thickness, in short, is the sweet spot where safety, performance, and cost intersect.

And let's not forget the long game. A tube's thickness today affects its lifespan tomorrow. In marine & ship-building, for example, a stainless steel tube submerged in saltwater faces constant corrosion. A slightly thicker wall—with a "corrosion allowance" built in—can add years to its service life, delaying costly replacements. Similarly, in pipeline works spanning hundreds of miles, the right thickness ensures the pipe can withstand soil pressure, temperature swings, and the weight of the fluid inside for decades. Thickness isn't just a specification; it's an investment in peace of mind.

Choosing thickness isn't about guesswork—it's about asking the right questions. Let's walk through the critical factors that will guide your decision.

1. What's the Tube Actually Doing? Application Matters Most

Start with the basics: what is this tube for? A tube in a power plant's boiler has (vastly different) needs than one in a ship's handrail. Let's break down a few common scenarios:

High-Pressure/High-Temperature Environments (e.g., Power Plants, Boilers): Boiler tubing here is a workhorse. It's exposed to extreme heat that weakens metal over time and pressure that pushes against every inch of the wall. Thickness here is non-negotiable. For example, ASTM A213 T91 boiler tubing—used in superheaters—typically ranges from 6mm to 12mm thick, depending on the pressure rating. The goal? To prevent bursting under stress and to resist creep (slow deformation under constant heat).

Heat Transfer Applications (e.g., Heat Exchangers, Condensers): Heat exchanger tubes and condenser tubes live in a balancing act. Thinner walls mean better heat transfer—heat moves more easily through less material. But too thin, and they can't withstand the pressure of the fluids flowing through them or resist corrosion from coolants. A typical stainless steel heat exchanger tube might be 2mm to 5mm thick, with alloys like Incoloy 800 (B407 Incoloy 800 tube) allowing for thinner walls due to their high-temperature strength.

Structural Support (e.g., Steel Tubular Piles, Building Frames): Here, thickness is about load-bearing. Steel tubular piles driven into the ground to support a bridge need to withstand the weight of the structure above and the lateral forces of wind or earthquakes. Thickness here often ranges from 8mm to 20mm, with larger diameters requiring thicker walls to prevent buckling.

2. Material Matters: Strength, Corrosion, and Weight

The material you choose directly impacts how thick the tube needs to be. A stainless steel tube, for instance, is inherently stronger and more corrosion-resistant than plain carbon steel. That means you can often use a thinner stainless steel wall to achieve the same strength as a thicker carbon steel wall.

Alloys take this further. Alloy steel tubes, reinforced with elements like nickel, chromium, or molybdenum, have higher tensile strength. For example, a 5mm thick alloy steel tube (like B167 Ni-Cr-Fe alloy tube) might withstand the same pressure as a 8mm thick carbon steel tube. This is a game-changer in weight-sensitive industries like aerospace, where every gram counts. Similarly, copper & nickel alloy tubes (like EN12451 seamless copper tube) combine corrosion resistance with good thermal conductivity, allowing for thinner walls in heat exchangers or marine applications.

Don't forget: material and thickness work hand-in-hand. Choosing a high-strength alloy might let you downsize thickness, saving cost and weight. But if your environment is highly corrosive (think: chemical plants), even a strong alloy might need a thicker wall or a corrosion-resistant coating to last.

3. Pressure and Temperature: The Dynamic Duo

Pressure and temperature are the dynamic duo that demand attention. Higher pressure pushes outward on the tube wall, requiring more material to contain it. Higher temperatures, meanwhile, weaken most metals, making them more prone to stretching or failure. Together, they're a one-two punch that dictates thickness.

Engineers often use Barlow's Equation to estimate required thickness for pressure vessels. Simply put, it states that the maximum pressure a tube can handle depends on: (thickness × material strength) ÷ (diameter × safety factor) . So, a big diameter steel pipe carrying natural gas at 1000 psi will need a much thicker wall than a small diameter tube with the same pressure. For example, a 24-inch diameter pipeline (common in oil & gas) might have a wall thickness of 12mm to 20mm, while a 2-inch diameter pressure tube in a refinery could be 5mm thick at the same pressure.

Temperature amplifies this. A tube operating at 600°C will need a thicker wall than one at 200°C, even if the pressure is the same. That's why power plant boiler tubing (which sees both high pressure and temp) has some of the strictest thickness requirements in the industry.

4. Environment: Corrosion, Wear, and the Elements

The world around the tube matters as much as what's inside it. A tube in a desert pipeline faces different challenges than one in a coastal shipyard or a chemical plant.

• Corrosion: Saltwater (marine & ship-building), acids (petrochemical facilities), or humidity can eat away at metal over time. To combat this, engineers add a "corrosion allowance"—extra thickness (often 0.5mm to 2mm) to account for material loss. Stainless steel tubes, with their chromium oxide layer, need less allowance than carbon steel in the same environment.
• Abrasion: If the tube carries sand, slurry, or other abrasive materials (like in mining pipelines), thickness adds durability. A thicker wall resists scratching and wear, (extending) service life.
• UV Exposure: Tubes above ground (e.g., in solar power plants) face UV radiation, which can degrade coatings. Thicker walls here might reduce reliance on coatings, acting as a backup.

5. Standards and Codes: The Safety Net

In industrial settings, thickness isn't just a choice—it's often regulated. Industry standards like ASME, ASTM, EN, or RCC-M (for nuclear applications) exist to ensure safety and consistency. For example:

• Boiler Tubing: ASTM A213/A213M specifies minimum thickness for tubes in boilers and superheaters, with different grades (like T22 or T91) dictating thickness ranges based on temperature resistance.
• Nuclear Tubes: RCC-M Section II nuclear tube standards are legally mandated for nuclear power plants, with thicknesses calculated to withstand radiation and extreme conditions over decades.
• Marine Pipes: EEMUA 144 234 CuNi pipe standards for copper-nickel tubes in seawater systems specify thickness to resist pitting corrosion and erosion.

Ignoring these standards to cut costs is risky. Non-compliant thickness can lead to regulatory fines, insurance issues, or worst-case, accidents. When in doubt, start with the standard—then adjust for your project's unique needs (with expert input, of course).

6. Wholesale vs. Custom: Finding the Right Fit

Finally, consider how you'll source the tube. Wholesale options offer standard thicknesses (e.g., wholesale stainless steel tube in 1mm, 2mm, 3mm increments) that are cost-effective and readily available. They're perfect for routine projects where standard specs work. But if your project is unique—like a custom heat exchanger for a space satellite or a nuclear reactor tube—custom options are the way to go. Custom big diameter steel pipe or custom alloy steel tube lets you specify exact thicknesses, often tailored to computer simulations of your specific pressure, temperature, and environment. It's pricier and takes longer, but for one-of-a-kind projects, it's worth it.

Even seasoned pros can slip up when choosing thickness. Here are three pitfalls to watch for:

1. Going Too Thin to Save Money: It's tempting to skimp on thickness to cut material costs, but this is often a false economy. A thin heat exchanger tube might fail after a year, requiring expensive shutdowns and replacements. In critical applications like power plants, the cost of a failure dwarfs the savings from thinner walls.
2. Over-Engineering (Too Thick): On the flip side, thicker isn't always better. A 20mm wall on a tube that only needs 10mm adds unnecessary weight (a problem in aerospace or marine projects) and increases material costs. It can even reduce performance—thicker walls in heat exchanger tubes slow down heat transfer, making systems less efficient.
3. Forgetting the "System Effect": A tube's thickness doesn't work alone. If you pair a thick-walled tube with undersized pipe fittings (like BW fittings or threaded fittings), the whole system is only as strong as its weakest link. Always check that fittings, flanges, and valves match the tube's thickness and pressure rating.