It is quite common to re-use components from one system in a new one, to save money. However, this may cause premature failure unless attention is paid to the conditions of use, compared with the previous service.

The photograph below shows an aluminium alloy shell, naval brass tube plates and aluminium brass tubes from a cooler that originally had seawater as the coolant in the tubes and lubricating oil on the shell side. Then the unit was used as a water heater with brackish water on both sides of the unit. The aluminium alloy shell suffered rapid galvanic corrosion coupled to the large area of copper alloy and leaked very quickly. The use of an aluminium alloy shell with copper alloy tubes is only acceptable with a non-conducting process-side fluid, such as lubricating oil.
 

Corrosion of aluminium alloy shell in a copper alloy heat exchanger.