Method of leak testing an assembled plate type heat exchanger

A method of positively indicating leaks in the heat transfer surface area of a heat exchanger between the normally separate fluid paths denoted by side (A) and side (B) arranged in a heat exchange relationship the method comprising:

• placing a detector gas on one side;
• placing a carrier fluid in the other side;
• applying a positive pressure differential between the detector gas and the carrier fluid;
• and
• detecting entrained bubbles within the carrier fluid in which the bubbles are stabilized by adding a surfactant or foam stabilizing agent to the carrier fluid, a stable bubble mass serving to concentrate the detector gas by flotation for sampling, visual detection and eventual chemical verification, said foam stabilizing agent further enhancing detection by producing a mass transfer barrier in the bubble mass, inhibiting the detector gas from rapidly entering solution into the carrier fluid and so maintaining a high concentration of gaseous chemical species and the foam agent reducing small bubble agglomeration into larger bubble sizes which inhibits flow bubble entrainment and detection due to an increase in buoyancy to viscous drag bubble forces.