Ti U-Tubes for Shell-and-Tube Heat Exchangers on Offshore Platform

The shell-and-tube heat exchanger is a key piece of equipment for natural gas cooling on offshore platforms. The tube side is usually made of ASTM B338 grade 2 titanium U tubes. Its unique U-tube design and efficient heat transfer capabilities make it ideal for the limited space and harsh environmental conditions encountered on offshore platforms.

1. Design and Structure

• U-tube Bundle: The core component of this heat exchanger is the titanium U-tube bundle. These tubes are fixed at one end while the other end can freely expand or contract, accommodating the thermal expansion caused by temperature changes. This makes the design particularly suitable for cooling natural gas, which undergoes significant temperature fluctuations.

Titanium grade 2 U tube bundles for a shell-and-tube heat exchanger.

• Shell and Tube Side: The shell side is filled with the cooling medium (usually seawater or air), while natural gas flows through the U-tubes. Heat is transferred through the tube walls, cooling the gas without direct contact with the cooling medium.

2. Application Scenarios

• Natural Gas Cooling: On offshore platforms, after extraction, natural gas is usually at a high temperature and needs to be cooled in multiple stages. The U-tube shell-and-tube heat exchanger plays a critical role in this process. After compression, the gas flows through the heat exchanger, where heat is transferred to the cooling medium inside the shell, lowering the gas temperature.

An offshore platform in Brunei.

• Dehydration and Purification: After cooling, the gas reaches a suitable temperature for further dehydration and purification. The high-efficiency heat transfer capability of the U-tube exchanger ensures rapid cooling, which enhances the efficiency of subsequent processing equipment.

Corrosion Resistance & Maintenance

ASTM B338 titanium grade 2 is used for seawater heat exchangers primarily due to its exceptional corrosion resistance in harsh environments, like seawater, which helps prevent rust and degradation. Its high strength-to-weight ratio allows for lighter and more efficient designs, while its durability ensures reliable performance over a wide range of temperatures. Additionally, Titanium grade 2 reduces maintenance needs and provides adequate heat transfer efficiency, making it an ideal choice for applications where longevity and resistance to corrosion are critical.

The U-tube design allows one end of the tube to move freely, reducing the risk of tube damage due to thermal stress. This simplifies maintenance in high-temperature environments, making the U-tube shell-and-tube heat exchanger suitable for long-term operation on offshore platforms. The U-tube structure allows for a more compact design, making it suitable for space-limited offshore platforms. Compared to straight-tube exchangers, U-tube exchangers provide greater heat exchange surface area within the same volume.