hi guys: i have trouble in heat exchanger (sheel and tube) tube thickness:0.65 mm flow : clorine condensate tube and tube sheet made of titanum (grade 7) sheel and heads made of carbon steal descripstion: Visual inspection after cleaning on subject exchanger revealed tube to tubes sheet welds wash away on few tubes in inlet pass. Tubes inside have featherlike thin metallic layers lift up from side wall. The existing tubes are appeared to be in poor state and will not be fit for further use. As mentioned earlier, there are four plugged tubes. One plug to tube sheet weld cracked and others have pinholes. Tube sheets are appeared to be in good condition. Exchanger shell side was filling-up with water to test and identify the leaking tubes. Three tubes were found leaking by just filling the water. The leaking tubes have been marked. Total number of tubes: 76 tubes Already plugged: 4 tubes Leaking tubes by filling water: 3 tubes please tell me if you can,what is the exactly reasons that caused this failur