What You Need to Know: Double-Walled Heat Exchangers


To safeguard from cross contamination of potable water in the event of heat exchanger failure, many states and municipalities have special system requirements. The solution is a double-walled heat exchanger constructed in order to make cross contamination impossible. For decades, Bell & Gossett (B&G) has offered such heat exchangers which perform well in a variety of facilities. Over the years, they’ve added to the sizes, types, and materials available in double-wall heat exchangers.

Since the beginning, B&G has made their double-walled heat exchangers a true double wall noting that in the event of ANY failure of a connection, wall, or joining point, cross contamination would NOT occur. Many other vendors claim to have a double-walled unit only to have one or more vulnerable points where a failure would result in contamination of potable water.

Originally, double-walled heat exchangers were constructed from a single tube fitted inside another. The inner tube was knurled with multiple grooves to provide a leak path in the event of either tube failing. The cross-hatched grooves gave this series of heat exchangers its name “Diamondback”. The U-Tube configuration units can utilize water/glycol as a heat source (Model WU) or steam (SU) and are available in sizes up to 12” diameter shells and 10-foot long tube bundles.

Responding to designers’ desire for better performance from smaller units, plate and frame heat exchangers (GPX Series) were modified to double-walled configurations. While looking different and being capable of operating at lower spreads between mediums, Bell & Gossett plate and frame heat exchangers are a true double-wall unit. These units are available in applications ranging from 1” NPT to 8” flanges.

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