[Case Study] Safety Measures with Double Isolation in Repair Work of Large-Diameter Gas Piping

Safety measures using double block in the repair work of large-diameter gas piping.

When conducting maintenance work on large-diameter gas piping, it is best from a safety standpoint to completely evacuate the gas before starting the work. However, due to the total length of the piping at A Steel Works being several kilometers, it is impossible to evacuate all the gas within that piping. According to A Steel Works' safety standards, work cannot commence unless double isolation is performed to ensure safety. While water seal valves (which fill the V-shaped sections of the piping with water to stop the gas) are installed at certain intervals along the gas piping, relying solely on these water seal valves does not constitute double isolation, leaving the work unable to commence even if there are valves to be replaced or areas to be repaired. We received inquiries about whether there might be another method to isolate the gas to allow the work to proceed. Although proposals for installing shielding plates were made, the costs associated with such work are prohibitively high, making it difficult to carry out. 1. To ensure safety during the work, double isolation (Note 1) must be performed before commencing. 2. Water seal valves are installed, but there is no other isolation method available. 3. Establishing new shielding plates or valves would incur very high costs. 4. The piping lines are located throughout the factory, making it impossible to install shielding plates or valves everywhere.

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