Abstract: A vessel such as a dairy pasteuriser having a path B for product and a separate path A for coolant in intimate relationship is tested for leaks by circulating a donor fluid under pressure in path A whilst a recipient fluid such as clean tap water is circulated in path B. The donor fluid is a gas, and leakage is detected using an ultrasound probe.

Abstract: A vessel such as a dairy pasteuriser having a path B for product and a separate path A for coolant in intimate relationship is tested for leaks by circulating a donor fluid under pressure in path A whilst a recipient fluid such as clean tap water is circulated in path B. If the donor fluid is an electrolyte, a probe (12) is placed in path B to measure the conductivity of the recipient fluid. A rise in conductivity over a period indicates leakage between the two paths, the rate of change indicating the size of the leak. Alternatively, the donor fluid can be a gas, and leakage detected using an untrasound probe.