What You Need to Know: Double-Walled Heat Exchangers

August 12, 2019

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.