IMG_1133_croppedKeystone installed the world’s first tapered spiral welded tower on May 7th, 2015 in Middleton, Massachusetts, USA




Keystone’s automated tower manufacturing is able to simultaneously perform all of the rolling and welding operations needed to produce tubular steel towers. Unlike conventional spiral mills, Keystone can achieve the variable diameter and wall thickness required for towers.





keystonetechnologyTrapezoidal sheets are fed into the Keystone mill, joined on the fly, and rolled and welded into the tower shell.


Continuous welding dramatically increases throughput, reduces defects, and facilitates 100% automated inspection.




Keystone has performed extensive structural testing of tapered spiral welded structures under both extreme and fatigue loads. The specimens have performed extremely well, with measured strengths meeting or exceeding Eurocode structural standards.