| 摘要 |
PURPOSE:To prevent fuel gas from leaking out to atmosphere directly, by connecting a seal box, which is provided in the fitting part of an inlet duct and an outlet duct of fuel gas and a tube header so as to surround the side of fuel gas ducts of a tube header, to the side of an outlet duct of exhaust gas by an exhaust gas communicating pipe. CONSTITUTION:If a crack occurs in the neighborhood of a tube header 10, leaked fuel gas gets into a seal box 21 since the pressure of a fuel gas 7 is positive pressure. But the seal box 21 is connected with the side of an outlet duct 5b of exhaust gas which is under negative pressure by an exhaust gas communicating pipe, so that the leaked fuel gas can flow to the side of an exhaust gas duct 5 through the exhaust gas communicating pipe 23. While if a crack occurs in the welded part of an expansion plate 22 which consists of the seal box 21, the fuel gas does not leak out to atmosphere because the inside of a seal box 21 is under negative pressure. Besides a gas detector 24 is provided in order to detect the occurrence of leakage of fuel gas and the degree of leakage of it, and the leakage of gas can be discovered in early time by monitoring the output from the gas detector 24 continuously or intermittently.
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