Technical Requirements for Power Tower Assembly
I. Technical Preparations Before Power Tower Assembly
1. Foundation Acceptance: Before tower assembly, ensure that the concrete foundation meets the specified strength. C25 and above strengths require 28 days of curing, and the rebound hammer test value must be ≥ 95% of the design value (according to GB 50204-2015). The foundation top surface elevation error must be controlled within ±5mm, and the exposed anchor bolt length deviation must be ≤ ±10mm.
2. Tower Material Inspection: All tower materials must be individually inspected. The zinc coating thickness must be ≥ 86μm (GB/T 13912-2020), and the curvature must be ≤ 1‰ of the length. The bolt hole spacing deviation must be ≤ ±1.5mm; otherwise, the holes must be enlarged or replaced.
II. Core Technical Requirements for Assembly Construction
1. Selection of Assembly Method
- Integrated Assembly: Applicable to straight towers ≤ 50m in height. A two-point balanced lifting method is required, with a rope angle ≤ 60° to prevent excessive lateral forces.
- Segmented Hoisting: Towers with a height greater than 50m or corner towers must be installed in sections, with the weight of each section not exceeding 80% of the crane's load (e.g., a 50t crane has a 40t load limit).
2. Bolt Tightening Standards
- The torque for grade 4.8 bolts is 70-120 N·m, and for grade 8.8 bolts it is 150-200 N·m (DL/T 5285-2018). A torque wrench should be used for secondary tightening.
- Bolt insertion direction is consistent: from inside to outside for three-dimensional structures, and along the line direction for horizontal structures.
3. Verticality and Deflection Control
- After assembly, the verticality deviation of the tower must be ≤0.3% of the tower height (e.g., a 100m tower allows a 30cm deviation). Bidirectional calibration is performed using a theodolite.
- Deflection Compensation: For overhanging towers, a pre-deflection value of 0.5‰ of the design span is reserved (refer to GB 50545-2010).
III. Safety and Environmental Protection Requirements
1. Operating Environment Restrictions: Hoisting must be stopped when wind speeds are ≥8m/s (approximately force 5). High-altitude work is strictly prohibited during thunderstorms.
2. Personal Protection: Personnel working at height must wear a double-hook safety harness, and the anchor point must be independent of the tower material.
3. Environmental Protection Measures: Waste galvanizing slag must be disposed of as hazardous waste (HJ 2024-2012). Noise levels must be controlled to ≤70dB during the day.
IV. Acceptance and Recording Standards
1. Process Records: Bolt tightening spot inspection records (10% inspection rate) and weld flaw detection reports (100% inspection of first-level welds) must be retained for each tower.
2. Final Acceptance: This must be carried out in accordance with GB 50233-2014, with a focus on checking the ground resistance value (≤10Ω) and anti-theft measures (such as bolt spot welding).
