Investigation of dry environment construction Equipment's medium displacement system for submarine pipelines

Innovative underwater pipeline repair and inspection technologies utilising a dry chamber represent a novel approach. This technique involves injecting high-pressure air into a chamber to displace the surrounding medium. However, sealing becomes very challenging owing to the irregularity of the sealing surface, and diver operations pose significant risks at high gas pressures. This study presents a novel design that integrates inflation and drainage methods. It employs an air compressor for chamber inflation and submersible pumps, along with an air-operated diaphragm pump for water drainage. This system could effectively manage various degrees of leakage and maintain continuous drainage, thus establishing a normal pressure environment. Consequently, the sealing requirement is significantly reduced, and divers are allowed to perform multiple tasks within the chamber at atmospheric pressure. Furthermore, the inflation parameters were optimized during the inflation and drainage processes through a numerical method, and the designed system was validated via offshore experiments. The results indicated that the system could handle a leakage rate of 50 m3/h and maintain a dry chamber for at least 5 h.