UV CIPP: Rehabilitation of DN800 Gravity Sewer Pipeline

Project Overview

Anyue recently completed a challenging UV Cured-In-Place Pipe (CIPP) lining project involving two segments of DN800mm underground gravity sewer pipelines, measuring 161 meters and 158 meters respectively. The pipelines were located under a high-pressure irrigation area, with a maximum depth of 9 meters and a required 500-meter-long pumping bypass system. Despite these significant challenges, the project was successfully completed in a single attempt using trenchless UV CIPP technology.

Technical Challenges and Solutions

The project was part of the Phase 1 Expansion and Upgrade of the Pinghu City Sewer Network, specifically the rehabilitation of the main sewer pipeline connecting Xincang Pump Station #2 to Pump Station #3. Constructed in 2008, this pipeline is a critical component of the sewage collection and transmission system in the Xincang region. Over time, corrosion, cracking, and joint misalignment had developed due to prolonged use and surrounding construction activities. These defects jeopardized the safe and efficient operation of the sewer system, necessitating immediate rehabilitation.

The pipeline consists of DN800mm gravity sewer pipes running from Pump Station #2, crossing Guangquan Road to the north, and then following the greenbelt along Guangquan Road southward to Pump Station #3. Due to limited construction space and tight deadlines, trenchless rehabilitation using UV CIPP technology was proposed as the optimal solution. After careful evaluation of site conditions and long-term benefits, the client approved this innovative approach.

Construction Process

1. Preparatory Work

Before the UV curing process, the pipeline underwent pre-treatment to meet the technical requirements of the in-situ curing method. Key preparatory steps included:

• Inspecting and cleaning the UV curing lamps to remove dust and fingerprints.

• Measuring the lamp's radiation flux density after 400 hours of operation and re-checking every 150 hours. Lamps exceeding a 30% reduction in radiation density were promptly replaced.

• Maintaining detailed inspection records for each UV lamp, including batch number, coding, first-use date, operational hours, inspection dates, measurements, and results.

  
  

2. Liner Insertion

Prior to inserting the wet liner, the following procedures were followed:

• A base film was laid at the bottom of the existing pipeline, covering more than one-third of the pipe circumference, and securely fixed at both ends.

• The base film was inspected to ensure no damage that could compromise the wet liner. Universal swivel rings were prepared to distribute pulling forces evenly.

• The wet liner was carefully pulled into the pipe along the base film at a controlled speed of 6–8 meters per minute, ensuring stability and alignment with manufacturer specifications.

  
  

3. UV Curing Process

The UV curing process was conducted with strict adherence to manufacturer guidelines:

• Compressed air pressure inside the wet liner was maintained at a consistent level as specified in the pressure table for the given pipe diameter and wall thickness.

• After reaching the required pressure, it was sustained for at least 10 minutes before commencing the curing process.

• UV curing lamps were selected based on product specifications, including model, wattage, and number of lamps.

• During the curing process, the liner's internal surface temperature was continuously monitored, while the UV equipment automatically recorded temperature, pressure, curing speed, and distance every minute.

• Upon completion of curing, internal pressure was gradually reduced to atmospheric pressure at a rate not exceeding 0.01 MPa/min.

  
  

4. Post-Curing InspectionAfter curing, the rehabilitated pipeline underwent CCTV inspection to ensure quality and integrity. The following criteria were met:

• No visible damp spots, leaks, or seepage.

• A smooth inner liner surface, free of cracks, holes, or weak points.

• Minimal occurrence of wear, bubbles, or dry spots, with no more than one defect every 10 meters.

• Maximum liner wrinkles of 6mm where no specific design requirement existed.

• Tight adhesion between the liner and the original pipe.

Project Outcome

The rehabilitation of the DN800mm gravity sewer pipeline was completed successfully, meeting all technical standards and ensuring long-term durability. The UV CIPP method proved to be an efficient, non-invasive solution, overcoming significant challenges such as deep excavation, limited space, and bypass pumping. This project highlights the effectiveness of UV CIPP technology in rehabilitating aging sewer infrastructure, ensuring reliable operation for years to come.

About Us

Anyue specializes in cutting-edge trenchless pipeline rehabilitation solutions, offering unmatched expertise in UV CIPP technology. Contact us today to learn how we can help maintain and upgrade your sewer infrastructure with minimal disruption: info@anyuetrenchless.com