Amini Tajdani - Dezful Islamic azad university- Ahvaz Ramin Power Plant
Mohammad Ali Sadeghi - Dezful Islamic azad university- Ahvaz Ramin Power Plant
Abdolkarim Mashak - Dezful Islamic azad university- Ahvaz Ramin Power Plant

The boilers by various capacities are used assteam generators for turbines or industrialprocesses in many industries. Among them thepower plant boilers which many of them havecapacity over than 1000 ton per hour, have aconsiderable position in industry. According tothe fact which boilers are working in highpressures and temperatures and they arevulnerable mechanic part in power plant, sothe cracking in their steam lines is evident.One of these lines is the reheating by-pass linewhich connects the cold reheating line to thehot reheating line and is used in specific cases.The sudden stresses in the operation andvariable load cycle which are reasons of cracksand failure in the line are caused byinappropriate operation, malfunction of theequipments or material fatigue. And this caseleads power plants to have occasionallystopped units which caused huge economicaldamages. In this research the problem isconsidered the various aspects which includes,thermal stresses, thermal fatigue, welding,maintenance, pipe material and operation. Asconclusions the reheating by-pass pipe shouldtotally change and should not be repaired afterthe cracks appear. And all hangers of livesteam and reheating line should be regulatedas the factory instructions. And also in the caseof operation and maintenance a sufficientsupervision should be used.

boiler-fraction-steam line-reheat bypass-thermal power plant