Case study

Pipeline Rehabilitation without Service Interruption

Hot Sleeves: steel collars provided by TÜV SÜD - Rehabilitation procedure applied for the first time in Southern Germany at E.ON Ruhrgas (December 2006).

Energy Supplier E.ON Ruhrgas, located in Obermichelbach near Nuremberg, has completed cost-effective rehabilitation of one of its gas pipelines using the Hot Sleeves method developed by TÜV SÜD Industrie Service.

This pipeline rehabilitation method uses special steel collars which can be applied to various defect types and geometries in both the inner and outer pipe wall. Compared to conventional pipeline rehabilitation methods, frequently involving complex preparations and welding, hot sleeve application saves time and requires only low volumes of material. When using the hot sleeves procedure, welding is only performed on the steel collar not on the product pipe itself, so that pipeline service and thus gas supply need not be interrupted for rehabilitation.

Throughout the last year alone, E.ON Ruhrgas has supplied approx. 690 billion kilowatt hours of natural gas. To ensure the integrity of a pipeline in Southern Germany, the energy supplier opted to have a reduction in wall thickness repaired. The repair measure was aimed at reinforcing the area in question with the help of hot sleeves and restoring wall thickness to that of a new pipeline.

Cost-effective application

As rehabilitation necessitated reduction of the pressure in the pipeline for a short period, gas transport had to be precisely controlled in the run-up to rehabilitation. The actual application of the hot sleeves and the associated welding activities took only one day: Using a centering device, two half shells are fitted concentrically around the area where wall thickness is reduced, evenly heated and then connected by longitudinal welds. Thus a collar is formed which after cooling fits snugly around the entire pipe surface to be repaired.

Maintaining long-term value

Hot sleeve effectiveness is inspected and verified by the experts of TÜV SÜD Industrie Service directly after application. Today, the pipeline's value is comparable to that of a new pipeline. Following this successful first application of hot sleeves, E.ON Ruhrgas is now reviewing whether this method may be a viable alternative in other future applications.

Key factors in cost-effective rehabilitation are low-cost procedures but also long-term repair of defects. According to a research report of the German Society for Petroleum and Coal Science and Technology (Deutsche Wissenschaftliche Gesellschaft für Erdöl, Erdgas und Kohle e.V., DGMK), the hot sleeve rehabilitation method developed by TÜV SÜD Industrie Service did not restrict pipeline stability and life in any way, irrespective of the substance transported in the pipeline.