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

Safety measures using double isolation 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. In this gas piping, water seal valves (which fill the V-shaped sections of the piping with water to stop the gas) are installed at regular intervals, but during construction, these water seal valves alone do not constitute double isolation, leaving the situation where work cannot begin even if there are valves to be replaced or areas to be repaired. We received inquiries about whether there is another method to isolate the gas to proceed with the work. Although there were proposals for the installation of shielding plates, the costs associated with such work are prohibitively high, making it difficult to carry out. 1. To ensure safety during construction, double isolation (Note 1) must be performed before starting work. 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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