Stainless steel heat exchanger tubes: Seamless vs Welded

Is it better to choose seamless pipe or welded pipes for stainless steel heat exchanger tubes? This is a question often asked in industrial design and manufacturing. Both have their advantages and disadvantages, and the specific choice needs to be determined according to actual needs and application scenarios.

What is a stainless steel heat exchanger tube?

Stainless Steel Heat Exchanger Tube is a stainless steel tube specially used for heat transfer. It plays an important role in industrial production and is widely used in heat exchange equipment in petrochemical, electric power, food, pharmaceutical and other industries. Its core function is to transfer heat from one medium to another medium (such as cooling water heating, steam condensation, etc.) through the tube wall. At the same time, it has the characteristics of corrosion resistance, high temperature resistance, anti-scaling, and almost no heat loss. Therefore, it is crucial to choose the right pipe to ensure efficient and reliable operation of the equipment.

Common heat exchanger tube materials on the market include carbon steel, low alloy steel, stainless steel, copper, copper-nickel alloy, aluminum alloy, titanium, etc., as well as some non-metallic materials such as graphite, ceramics, polytetrafluoroethylene, etc. Among many materials, stainless steel pipes are the first choice because of their excellent corrosion resistance and high strength.

Stainless steel pipes are mainly divided into seamless stainless steel pipes and welded stainless steel pipes. Although both are stainless steel pipes, there are significant differences in production process, performance and application.

Difference between stainless steel seamless pipes and welded pipes:

1. Production process: Stainless steel seamless pipes are formed into hollow tube billets by hot extrusion and are produced through multiple processes. Its production process is relatively complicated, usually including hot rolling, cold drawing, heat treatment and other links. Stainless steel welded pipes are made by rolling thin metal strips into tubes and then welding the edge parts together longitudinally. This process is relatively simple and has high production efficiency.

2. Wall thickness uniformity: The wall thickness of seamless pipes is generally more uniform because there are no welds in its production process. Since welded pipes are made by welding, there may be slight wall thickness changes at the welds. However, modern welding technology is very mature and can ensure that the quality of the welds is close to that of the parent material, so that welded pipes can replace seamless pipes in many applications.

3. Cost: In the case of mass production, the cost of welded pipes is about 20% lower than that of seamless pipes. This is because the production process of welded pipes is simpler, the equipment investment is small, and the production efficiency is high.

Advantages of stainless steel seamless pipes:

1. High strength: Due to its weld-free design, stainless steel seamless pipes have high overall strength and are particularly suitable for high-pressure and high-strength application environments.
2. Corrosion resistance: The surface treatment of seamless pipes is more stringent, usually undergoing processes such as pickling and annealing, which improves their corrosion resistance in harsh environments.
3. Wide range of applications: Seamless pipes are often used in industrial pipelines, fluid transportation and other fields, and their high temperature and pressure resistance make them excellent in these fields.

Advantages of stainless steel welded pipes:

1. Low cost: The production process of welded pipes is simple and the production efficiency is high, so the cost is lower in mass production.
2. Smooth surface: The surface of the welded pipe is uniformly extruded and online bright solution annealing, and the surface becomes very smooth and not easy to scale. This feature gives it an advantage in heat exchange applications because the smooth surface is conducive to heat dissipation and does not require frequent cleaning.
3. Wide application fields: Although the strength of welded pipes is slightly lower than that of seamless pipes, they are still widely used in many fields, especially in the heat exchanger industry. The advancement of modern welding technology has greatly improved the quality of welded pipes, and the performance indicators of welds can be basically consistent with those of the parent material. Click to view the seamless processing technology of stainless steel welded pipes.

Seamless pipes and welded pipes for stainless steel heat exchanger tubes: How to choose?

The selection of stainless steel heat exchanger tubes needs to comprehensively consider the medium characteristics, working conditions, cost budget and industry standards. Welded pipes and seamless pipes have their own applicable scenarios. The following is a specific analysis:

1. Situations where seamless pipes are preferred

Applicable scenarios:

1) Working pressure and temperature: If the pressure and temperature of the working environment are high, it is recommended to choose seamless pipes because of their high strength and good high temperature resistance. For example, high pressure/high temperature conditions, high pressure heat exchangers for nuclear power and petrochemicals (pressure>10MPa, temperature>300℃).
2) Strong corrosive media: If the fluid medium is highly corrosive, the corrosion resistance of seamless pipes may be more suitable. For example, in highly corrosive environments such as hydrochloric acid and chloride ions, seamless pipes have no welds and more uniform corrosion resistance.
3) High cleanliness requirements: semiconductor and pharmaceutical industries (avoid weld impurity contamination).

Recommended materials:
316L stainless steel: Chloride ion corrosion resistance (coastal or chemical environment).
2205 duplex steel: High strength and corrosion resistance (seawater cooler).

Advantages:
No weld risk: Avoid hidden dangers such as weld cracking and leakage.
Long life: The service life is 30%~50% longer than that of welded pipes under harsh working conditions.

2. Situations where welded pipes can be selected

Applicable scenarios:

1) Medium and low pressure/low temperature conditions: For general fluid media, the smooth surface and anti-fouling function of welded pipes are more advantageous. Such as ordinary industrial heat exchangers (pressure <6MPa, temperature <200℃).
2) Low cost requirements: If the budget is limited and the corrosion is weak (such as tap water heat exchange), welded pipes are undoubtedly a more economical choice, especially in the case of mass production. The high cost of seamless pipes may increase the overall budget of the project.
3) Large diameter/thin wall: diameter > 250mm or wall thickness < 1mm (difficult to achieve with seamless pipe process).
4) Maintenance requirements: The surface of welded pipes is smooth, not easy to scale, and the maintenance cost is low. Seamless pipes may require more frequent inspection and maintenance during use.

Recommended process:
Laser welding + online solution treatment: improve the corrosion resistance of welds to the level of parent materials.
Inner wall electrolytic polishing: reach Ra≤0.4μm, meet food grade requirements.

Advantages:
Low cost: 20%~40% lower than seamless pipes.
Flexible customization: special-shaped pipes (spiral pipes, corrugated pipes) can be produced.

Industry standards and certification references:
ASME BPE (biopharmaceuticals): seamless pipes are preferred.
ASTM A249: Welded pipes are allowed to be used in heat exchangers, but they must pass eddy current detection/hydraulic pressure test.
GB/T 24593 (boiler heat exchangers): high pressure must be seamless pipes.

Conclusion:

Stainless steel seamless pipes and welded pipes have their own advantages and disadvantages. Seamless pipes are suitable for high pressure, high temperature, strong corrosion environment, and long-term operation, but the cost is relatively high; welded pipes are low cost, smooth surface, easy maintenance, and suitable for general working conditions with medium and low pressure and weak corrosion. When selecting, a comprehensive evaluation should be conducted based on parameters such as medium composition, design pressure, and maintenance cycle. It is recommended to consult the pipe supplier to provide salt spray test reports and burst pressure test data. Reasonable selection of pipes can not only ensure the efficient operation of the equipment, but also control costs and improve economic benefits.

Read more: Carbon steel ERW boiler tube & air heater tube specification or Different types of boiler tubes and their role in energy