| 摘要 |
PROBLEM TO BE SOLVED: To recover a furnace in a short time by detecting pressure in the furnace when the inside thereof is exposed definitely to the atmosphere and informing if abnormality of a pressure gauge if the detected value deviates from a specified range. SOLUTION: When a steel material is subjected to vacuum annealing repeatedly, pressure variation between vacuum and atmospheric pressure is applied repeatedly to a pressure gauge 61 while pressure variation between atmospheric pressure and an increased pressure is applied repeatedly to a pressure gauge 62. The steel material fatigues gradually and when an allowable level is exceeded, actual indoor pressure can not be detected. The pressure gauges 61, 62 detect the indoor pressure when the inside of gas cooling chamber or heating chamber is exposed to atmospheric pressure and when the detected value exceeds an allowable range, an arithmetic unit 71 transmits a signal informing of abnormality of the pressure gauge 61, 62 and actuates an alarm 81. According to the arrangement, the furnace can be recovered in a short time.
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