Shandong Hengtong Expansion Joint Manufacturing Co.,Ltd is located at the foot of the Tai mountain as the head of the five mountains “World Double Inheritance”,a large-scale factory which is specialized in expansion joint of the corrugated pipe design,research and development,manufacture;has “People’s Republic of China Special Equipment (pressure piping component)Manufacturing Permit”,has passed the ISO9001 quality control system authentication,thereinto,”multi-corrugation(containing single-orrugation) thick wall integral forming metal corrugated expansion joint”has obtained the national patent (patent number:ZL200520124753X)and the national patent ....