For over 90 years, Standard Xchange has been a leader in designing and manufacturing shell and tube heat exchangers. Originally founded as Ross Heater Manufacturing Company Inc. by Scott Ross in 1917, the company supplied heat exchangers to major oil refineries like Texaco, ESSO, and Standard Oil. In 1933, Ross Heater was purchased by American Radiator and Sanitary Standard, merged with Kewanee Boiler, and later became American Standard Heat Transfer Division. ITT Corporation acquired the company in 1986, renaming it ITT Standard. Today, known as Standard Xchange, it is part of Xylem Inc., a global water technology company with operations in over 150 countries.
The shell is typically constructed from steel pipe or rolled plate metal. Steel is favored for its cost-effectiveness, while other metals or alloys are used for extreme temperatures or corrosion resistance. Using off-the-shelf pipe reduces manufacturing costs and lead time. Ensuring a consistent inner shell diameter, or 'roundness,' is critical to minimize excessive baffle spacing, which can degrade performance. Roundness is achieved by expanding the shell around a mandrel or double rolling it after welding. In some cases, the shell is cast and then bored to the correct diameter. High fluid velocity at the nozzle necessitates an impingement plate to distribute fluid evenly, preventing erosion, vibration, and cavitation.
Heat exchangers use tubes typically 0.625 to 1.5 inches in diameter, made from materials such as low carbon steel, copper, stainless steel, Hastelloy, and titanium. Tubes can be seamless or welded, with high-quality electro resistance welded tubes offering good grain structure. Surface enhancements like fins improve heat transfer rates. Finned tubes are useful when the shell-side fluid has a lower heat transfer coefficient than the tube-side fluid. U-tube designs handle significant thermal differences to manage expansion, but are harder to clean and maintain.
Bonnets and end channels regulate fluid flow in the tube-side circuit. They are typically cast or fabricated and mounted against the tube sheet with bolts and gaskets. Multi-pass designs may include pass ribs to direct flow through the tube bundle, ensuring consistent fluid velocity and pressure drop. Cast bonnets for smaller diameters are made from materials like iron, steel, bronze, Hastelloy, nickel-plated, or stainless steel, with various pipe connection types available.
Baffles guide tubes during assembly, prevent flow-induced vibration, and direct shell-side fluids to increase heat transfer. They must fit tightly within the shell to prevent fluid bypass. Baffles are stamped, punched, or machined, with material choices compatible with the shell-side fluid to avoid corrosion. Precise manufacturing of tube holes ensures easy assembly and maintenance. In liquid applications, baffles typically occupy 20-30% of the shell diameter, while in gas applications, they occupy 40-45%. Baffles are evenly spaced to reduce pressure drop and ensure even fluid velocity.
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