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Friday, April 26, 2019 

Alfa Laval says that new research into glycol freezing has enabled its DuroShell plate-and-shell heat exchanger from Alfa Laval to be optimised for use as an LNG vaporiser.

The company says that the DuroShell is robust, fatique-resistant and provides higher thermal efficiency than conventional plate-and-shell heat exchangers, meaning it can provide more compact and cost-effective installations.

“The continued rise in the number of vessels sailing with LNG is one of the most significant trends in today’s marine industry,” said Jonny Hult, Head of Marine Heat Transfer Equipment at Alfa Laval. “With more and more ships relying on LNG as fuel, we are seeing greater demand for vaporiser technology that can dependably resist freezing and the fatigue caused by pressure and temperature. DuroShell is exceptional in this regard.”

With DuroShell's 100% stainless steel construction, it can reliably handle LNG entry temperatures that approach -170°C or lower. Extensive laboratory freeze testing has offered knowledge that will lead to lower capital and operational costs.

“Extreme low temperatures are not an issue for DuroShell, but a glycol mix with a freezing point of around -50°C has the potential to freeze when it meets plate surfaces as cold as -90°C,” Hult explains. “Solving this problem with a higher glycol flow is a very expensive solution for our customers, so Alfa Laval has worked with SINTEF Energy Research to find the correlation of flows on both sides and thereby avoid freezing of fluid on the hot side.” Hult concludes that this will let shipbuilders use a more compact plate-and-shell design with smaller pumps and pipes, which, in turn, will mean CAPEX and OPEX savings for the ship owner.

DuroShell features special CutWing plates, to the patented Alfa Laval RollerCoaster plate pattern, providing high turbulence that improves heat transfer efficiency and reduces the risk of freezing and fouling, and PowerPack distribution tubes, to secure optimum flow distribution onto the heat transfer surface. The design enhances the strength of the plate pack for fatigue resistance in demanding LNG duties.

“From the laser-welded plate pack to RollerCoaster™ and PowerPack™, DuroShell is loaded with features that help us secure far higher resistance to temperature and pressure fatigue than possible with conventional plate-and-shell designs,” added Hult. “Based on this and our knowledge about freezing behaviour, we can confidently state that DuroShell is the market’s best solution for LNG applications today.”

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