Thermal and mechanical stress causes cracks in metallic structures. Such cracks have a tendency to grow bigger and the damage can be very disastrous in recovery boilers, which are vital pieces of equipment in the pulp and paper industry. Wall tube leaks of the furnace can lead to substantial boiler damage and unexpected shutdowns.  One way to avoid damage is to use the continuous Savcor CI-system (Cracking Indicator) to detect growing cracks.  "When compared with the conventional method, i.e. periodic visual and audible inspection, the new system can extend the life time of process equipment significantly," says Kaj Lindström of the Finnish company Savcor-Consulting Oy, a specialist in corrosion and preventive maintenance.