The Insuffient of Spiral Steel Pipe for Boiler in the Quality

(1) spiral boiler tube manufacturing process to determine their residual stress is large, according to foreign information records, and some even close to the yield limit, LSAW pipe boiler tube expansion process due to the use of residual stress close to zero.

(2) spiral seam welding boiler pipe-line tracking and detection of ultrasound to track than those in difficulties, therefore, the probability of excessive boiler tube weld defects than straight seam submerged arc boiler tubes.

(3) spiral weld boiler tube in the wrong side of the majority of the amount of 1.1 - 1.2 mm, in accordance with international practice, the amount is less than the thickness of the wrong side of 10%, such as pipe wall thickness is small, the wrong side of the volume is difficult to meet the requirements, and straight seam buried boiler tubes arc no such problem.

(4) and straight seam submerged boiler tubes, spiral weld flow line is poor, serious stress concentration

(5) spiral submerged arc welding boiler tubes heat-affected zone than LSAW steel heat affected zone, and the quality of welded heat affected zone is the weak link.

(6) spiral seam welding boiler tube geometry accuracy, to the construction site (such as counterpart, welding) to bring some difficulties.

(7) the same diameter, spiral seam welding boiler tubes can achieve far less than the thickness of LSAW steel pipe.