Fail-safe heat exchangers
The fail-safe heat exchanger is a variation of the tube assembly heat exchanger, Figure 4. One tube is fitted inside another such that a space exists between them, which is filled with a harmless heat transfer medium and kept at a pressure of at least 0.5 bar by the expansion tank. In the case of leakage through corrosion or breakage, either the water or the oil mixes with the heat transfer medium but they cannot mix with each other; contamination is impossible. This type of heat exchanger can be used in the food or pharmaceutical industry, or for providing hot drinking water.