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New Alfa Laval solution for LPG/E cargo reliquefaction

Written by Nick Blenkey
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AUGUST 25, 2016 — Already used in the offshore oil and gas industry, the new Alfa Laval DuroShell plate-and-shell heat exchanger is now being introduced for demanding marine duties such as LPG/E cargo reliquefaction.

An innovative construction that dramatically increases resistance to thermal and pressure fatigue and a patented roller coaster plate pattern make DuroShell significantly more robust, allowing it to condense cargo with a higher ethane content.

“DuroShell is a remarkable advance in heat exchanger design,” says Matilda Mellby, Application Manager, Gas Components at Alfa Laval. “As an LPG/E cargo condenser, it provides far greater resistance to temperature and pressure extremes than most other welded solutions.”

DuroShell strengthens Alfa Laval’s position in heat exchangers for LPG/E cargo condensation, where the Alfa Laval AlfaRex plate heat exchanger is standard today. Like AlfaRex, DuroShell is a laser-welded solution combining high thermal efficiency with a very small footprint. But whereas AlfaRex handles pressures of around 30 bar and temperatures down to -50°C, DuroShell withstands pressures up to 35 bar when titanium plates are used, along with temperatures as low as ‑198°C.

“An extended pressure range is important as the ethane level in LPG/E increases,” says Mellby. “DuroShell is more than robust enough to handle ethane condensation, which demands pressures in excess of 30 bar.”

The robustness of DuroShell is the result of many factors, including the patented roller coaster pattern of its cut-wing plates. The roller coaster pattern ensures even expansion around the plate circumference, which eliminates potential weak spots and increases the heat exchanger lifetime. In addition, the entire plate pack is pre-compressed, which minimizes the effect of large differences and variations in temperature.

Further strength is added by the distribution tubes that extend through the laser-welded plate pack. These relieve stress on the plate pack itself, while at the same time ensuring the best distribution of media. Together with the roller coaster pattern, which creates high turbulence even at low velocities, the distribution tubes ensure excellent thermal performance.

“The DuroShell design merges stability with thermal efficiency, and it minimizes fouling to ensure high performance over time,” says Mellby. “For LPG/E cargo reliquefaction, no solution compares to DuroShell in simplicity, capability or reliability.”

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