... 8mm up to 114mm. HG20-114 High Frequency Welded Pipe Machine High frequency welded pipe machine uses roll forming theory to coil long ... under the force of squeeze roller.And it uses induction welding to heat the longitudinal seam.That is ,feed ... saw,straightener,end milling equipment,hydrostatic testing machine,charge table,sack&bale machine,high frequency DC drag,product line electric applicance. ...