Shell and tube heat exchanger made of stainless steel for aggressive environments 

A stainless steel shell-and-tube heat exchanger is not just a component in a circuit, but a critical point of failure in hostile environments. We have seen more than once how carbon steel begins to peel off after only 8 months of operation in chlorine-containing solutions. In sulfuric acid condensates - after 3–4 months. But stainless steel grades 316L, 2205 or even 2507 can withstand the same conditions for decades. Why? Because corrosion resistance here is not a parameter on the technical specification sheet. This is physics: the density of the passive layer, the molybdenum content, the balance of chromium and nitrogen, the uniformity of welds.

When a “conventional” heat exchanger is no longer the solution

Our engineers regularly receive requests from refineries in Iran and pharmaceutical plants in Singapore with one problem: a sharp increase in pressure drop, leaks on flanges, a decrease in heat transfer coefficient by 35-40% per year. The reason was found not in the hydraulics, but in the material. One case of chloride cracking in 304 steel tubesheet at 85°C and pH 2.8. In another, intergranular corrosion in the welding heat-affected zone due to uncontrolled heating. Such scenarios are excluded if a stainless steel shell-and-tube heat exchanger is designed and manufactured for a specific environment - taking into account temperature, concentration, flow rate, the presence of mechanical impurities and load cycling.

What makes a structure truly reliable - beyond the steel grade

Stainless steel is a base, but not a guarantee. Real durability is determined by four elements:

• Tube sheet geometry:We use clad gratings - a stainless steel layer 2.5–3 mm thick is fused onto a carbon base. This gives housing strength + corrosion resistance in the pipe fastening area, where the risk of crevice corrosion is greatest.

• Welding without defects:All connections are made by TIG welding in an argon environment with control of the weld root. For ASME models - mandatory radiography of 100% of the seams. Ultrasonic flaw detection - for casing and tube sheets.

• Heat treatment after welding:especially critical for double steels (2205, 2507). We strictly observe the annealing and cooling regimes - otherwise the phase balance is lost, and the steel loses its resistance to chlorides.

• Hydraulic stability:In aggressive environments, stagnation should not be allowed. Therefore, we calculate the flow velocity in the inter-tube space to be no lower than 1.2 m/s - even if this requires increasing the casing diameter or changing the fin pitch.

Why choosing a supplier is more important than choosing a steel grade

We don't just supply stainless steel shell and tube heat exchangers. We ensure its behavior in real conditions. Over the past 5 years, more than 120 tests have been carried out under conditions simulating operation at CNPC and CNOOC facilities: heating-cooling cycles, pulsed loads, exposure to H₂S and NH₃ vapors. The result is a database of corrosion rates for 17 types of media and 9 steel grades. This information is used in the design: if the customer specifies “NaCl + CO₂ solution at 120°C”, we immediately offer 2205 with enhanced flange protection - and not just “316L as in the catalogue”.

Another practical point: logistics. A heat exchanger weighing 4.2 tons for a plant in Italy was shipped by sea from Shanghai 11 days after the signing of the terms of reference. Access to the port within a 2-hour drive and direct rail routes to Europe allow you to avoid delays at customs and warehouse overloads - and therefore reduce equipment downtime.

How to make a decision - without overpayments and compromises

If your environment contains chlorides, hydrogen sulfide, dilute acids or ammonia, start with a corrosiveness test. Not from the choice of material, but from the chemical composition and process parameters. Not only the grade of steel depends on this, but also the type of gasket, method of fastening the pipes, and the need for anti-corrosion coating on the inner surface of the casing.

Wuxi Kaisheng Electric Power and Petrochemical Equipment Co.,Ltd offers free engineering audit of operating conditions. Based on it, a technical proposal with calculation of service life, justification for the choice of steel and a delivery schedule. No templates. No standard solutions. Only what works in your workshop, at your pressure, at your pH.

A stainless steel shell and tube heat exchanger is not an equipment purchase. This is an investment in process continuity. And it pays off not in prices, but in the absence of emergency stops, repairs and downtime.