Fabrication Quality Requirements for Angle Steel Tower or Lattice Tower for Power Transmission

Fabrication quality requirements to to be followed by China transmission steel lattice tower or pylon manufacturer must be strictly in accordance with national standard GB/T269-201 “Technical Conditions for Manufacturing process of Electric Power Transmission Line Tower ”, if components is processed by anti-corrosion hot-dip galvanizing treatment, if thickness of angle steel is equal or more than 5mm, zinc coating thickness shall not be less than 70μm, average thickness is 86um and 610g/m²,however, if thickness of angle steel is less than 5mm, zinc coating thickness shall not be less than 55μm, average thickness is 65um and 460g/m²and the adhesion test shall yield a single-side coating weight >600 g/m². and the quality certificate for raw steel materials must indicate the original furnace number and chemical composition from the steel mill.

Workshop processing workflow:

Lofting for power transmission line pylon or tower shall be verified against both electronic CAD drawings and construction drawing, and error range of the value converted by three-dimensional coordinate is permitted at ±0.15 mm. 

Assembling stage:

Axis positioning of main body shall use a laser level meter to calibrate joint positions.Secondary fastening torque values shall be set at 210 N·m ±6% by intelligent wrenches.

Hot-dip Galvanizing Process Parameters:

Pickling concentration before galvanizing shall be controlled at 17.5%–21% (room temperature, HCL ), then after cleaning, twice neutralization and rinsing shall be carried out. 

Fluxing is carried out at a temperature 60°~ 80°.

Galvanizing temperature is  455°~ 465°for Q235 and  440°~ 455°for Q355 

Passivation is carried out at room temperature,and cooling should be accomplished in flowing water.