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Column No.7 Safety and Nemoto - (5) "CO gas sensor for boilers" (Aug. 9, 2000)Both gas explosion and gas leakage accidents caused by fuel gases can be very disastrous. Gas explosion accidents are, by and large, prevented by the use of gas leakage detectors. Effective countermeasures to gas poisoning have remained elusive due to the absence of accurate yet inexpensive carbon monoxide (CO) sensors. Conventional CO sensors have been either too inaccurate or too expensive for residential CO gas detectors. The Japan Gas Association organized a working group in November of 1995 for the development of new CO sensors which were to be equipped in gas boilers. The working group consisted of the three major municipal gas companies and seven sensor & detector manufacturers including Nemoto. In March of 1997, it was announced that new sensors developed by Nemoto & Co. and Yazaki Keiki met the association specifications for both accuracy and cost. After this, Tokyo Gas, Osaka Gas, and Toho Gas continued their joint R&D work aimed at further lowering the cost of the CO sensors so that they might be equipped in a wide range of gas boilers. The results of this cooperative effort were presented at the Municipal Gas Symposium held on May 30, 2000. It was reported that the catalytic type CO gas sensor manufactured by Nemoto satisfied the requirements for performance, durability, and cost, and was suitable for use in both residential and industrial applications. The presentation at the symposium also indicated that the Nemoto sensor might be instrumental in the popular acceptance of CO gas detection systems. *1 Several important points were considered during the development of a CO gas sensor for gas boilers. First, both CO and hydrogen gas are generated whenever there is incomplete combustion of either natural gas or liquid petroleum (LP) gas. In addition, depending on the temperature of the heated water, flue gas can fluctuate between 60 and 200°C. At the same time, the cost of the sensors must be lowered to a level that can be accepted for popularization.
The development team at Nemoto worked to tackle these difficult questions by focusing on modification of the catalyst used for Nemoto sensors that had been in use for more than 10 years. As a result, they developed a new low-cost CO gas sensor for boilers in November of 1998. The Nemoto's CO gas sensor features;
Nemoto's CO sensor has been adopted to gas boilers manufactured by Rinnai Corporation and Takagi Sangyo Co., Ltd., and is expected to be widely used.
Graph 3 shows the number of CO gas poisoning accidents occurring in Shanghai, China, from 1990 to 1998, reported by Zhu Wei Hua et al. of Shanghai Fuel Gas Administration Office. *2 In Shanghai, more than 100,000 homes every year are fitted for gas fuel. The graph shows the recent rapid increase of gas poisoning accidents and indicates the necessity for countermeasures. It can be expected that similar statistics would be seen in other rapidly growing urban areas. In the Asian market alone, large potential demands for CO gas sensor can be expected. Nemoto's CO sensor has a bright future ahead. Remarks: *1 Summary of presentations at Municipal Gas Symposium (Japan Gas Association), P107 (2000) *2 Shanghai City Public Utility, Volume 13, First term 1999, P19 (1999.2) |
