Hydraulic Tube Expansion in Heat Exchangers and Condensers

Hydraulic tube expansion in heat exchangers is a method where tubes are expanded and sealed into a tubesheet by applying hydraulic pressure. This process can be divided into two main techniques:

1. Bladder/Mandrel System: A clean and controlled method where a mandrel expands the tube without getting it wet. It is precise and efficient for thick tubesheets, as it completes the expansion in a single cycle.
2. Sealed Water Pressure: In this method, water is pressurized between seals inside the tube to cause expansion. It works well for uniform, high-pressure expansion but is more involved than the mandrel method.

Hydraulic tube expansion for a heat exchanger. The tubes are seamless cold-drawn low carbon steel tubes made to ASTM A179.

Hydraulic expansion has several advantages:

• Consistency: Provides uniform expansion in one cycle, eliminating the need for multiple rolling passes.
• Time Efficiency: Especially useful for thick tubesheets, as it completes expansion faster than traditional roller methods.
• Material Flexibility: Works well with a wide variety of tube materials, though some alloys (less ductile materials) may not be suited for this technique.

Hydraulic expansion of ASTM A213 TP316L seamless tubes to the tube sheet of a condenser.

This method is commonly compared with other expansion methods like explosive expansion, which is quicker for large exchangers, and roller expansion, which is slower and more suited for smaller operations. However, hydraulic expansion is valued for its precision, cleanliness, and the fact that it does not require as many cycles as other methods when dealing with thicker sheets or complex tube bundles.