φ70mm (inner diameter) galvanized metal bellows for pre-tensioning of precast beams - nationwide direct sales by manufacturer

Prestressed galvanized bellows are widely used in post-tensioned prestressed concrete engineering as protective sleeves for prestressing tendons (strands, wires, etc.). Their construction quality directly affects the safety and durability of the prestressed structure. Below is a detailed construction process and precautions.

1. Pre-construction Preparation

1.1 Material Inspection

• Bellow quality: Check for uniform zinc coating without damage, φ70mm (inner diameter) galvanized metal bellows for pre-tensioning of precast beams - nationwide direct sales by manufacturer ensure no crushing or deformation of the pipe body.
• Sealing performance: Ensure all joint accessories (such as connecting sleeves, waterproof tape) are complete to prevent grout leakage.
• Specification matching: The bellows diameter should meet design requirements, typically 5~10mm larger than the prestressing tendon diameter.

1.2 Tool Preparation

• Cutting machine (special bellow cutting tools to avoid burrs)
• Waterproof tape/heat-shrink tubing (for joint sealing)
• Tie straps/rebar supports (to fix bellow position)
• Positioning measuring instruments (ensure accurate bellow coordinates)

2. Bellows Installation

2.1 Positioning and Fixing

• Position according to design coordinates: Use rebar supports or special positioning bars to fix bellows, φ70mm (inner diameter) galvanized metal bellows for pre-tensioning of precast beams - nationwide direct sales by manufacturer spacing ≤1m (reduced to 0.5m in curved sections).
• Curved section treatment: Adopt smooth transitions, avoid sharp bends (minimum bending radius ≥30 times pipe diameter).
• Height control: The centerline of bellows should align with the designed position of prestressing tendons, deviation ≤5mm.

2.2 Connection and Sealing

• Straight pipe connection: Use one-size larger bellows for sleeve connection, overlap length ≥30cm, wrap waterproof tape or heat-shrink seal at joints.
• Branch pipe connection: Use special tees or cross fittings to ensure sealing.
• Vent hole setup: Reserve vent holes (Φ20mm plastic pipe) at the highest points of curves to prevent air accumulation during pouring.

2.3 Anti-blocking Measures

• Insert temporary lining pipes (such as PE pipes or rubber rods), remove φ70mm (inner diameter) galvanized metal bellows for pre-tensioning of precast beams - nationwide direct sales by manufacturer after initial concrete setting to prevent grout leakage blockage.
• Check pipeline patency before pouring, use high-pressure air guns or hole cleaners for clearing.

3. Concrete Pouring Protection

• Vibration avoidance: Vibrators should not directly contact bellows to avoid damage or displacement.
• Leakage inspection: Focus on monitoring joints, immediately flush pipes with water if leakage is detected.
• Protection during curing: Avoid external impact or welding operations that could damage the zinc coating.

4. Prestressing Tendon Installation

• Installation timing: Proceed after concrete strength reaches 75% of design value.
• Lubrication to reduce friction: Apply special lubricant (such as wax-based materials) inside bellows before installation.
• Anti-rust measures: Temporarily seal exposed ends with waterproof tape after strand installation.

5. Common Issues and Solutions