New gas-shutdown system planned for quakes

Tokyo Gas Co. has developed the nation's first automatic, remote-controlled system to cut gas supply and prevent gas leaks in the event of an earthquake, company sources said Wednesday.

The system, which will go into partial use in July, is designed to shut off the valves of home gas-pressure regulators when the new Tokyo Gas earthquake sensor detects a quake with an intensity of five or more on the Japanese seismic scale.

Telephone lines can also be used to shut off a valve installed for a residential block if the automatic system does not work during a large-scale earthquake.

The new system requires one hour to halt gas supply, a drastic improvement on the time required under the conventional disaster prevention system.

Gas leaks in the 1995 Great Hanshin Earthquake occurred at about 26,000 locations. It took 15 hours to halt gas supply leaking from low-pressure gas pipes installed in homes.

Tokyo Gas invested 2.5 billion yen to design the new system as well as an advanced earthquake sensor to automatically halt gas-pressure regulators installed for each group of homes ranging from several dozen to 2,000.

The system has been installed in about 1,300 locations in Tokyo and eight neighboring prefectures. The system will be installed in 3,700 gas-pressure regulators by 2007.

Tokyo Gas employees will be on alert in six locations, including Tokyo and Kanagawa Prefecture, to shut the valves in all areas by sending signals via telephone lines should the automatic system fail to operate.

Before this system was developed, Tokyo Gas had earthquake sensors installed in 332 gas-pressure regulators in its entire service area. Since it did not have a remote-control shutdown system, the company had to send workers to manually close off valves in case of emergencies. This process required at least dozens of hours.

Out of a total of about 47,000 kilometers of gas pipeline owned by Tokyo Gas, about 40,000 kilometers, or 85 percent, are low-pressure pipelines supplying gas to homes, or to about 8.8 million people. Others are high- and medium-pressure pipelines supplying gas to power plants, factories and hospitals.

Tokyo Gas supplies gas to high-, medium-, and low-pressure pipelines in that order. In emergencies, the entire supply can be cut off by closing the high-pressure pipeline, which also halts the supply to power plants and medical facilities.

The company says the new system can shut off gas supply to homes without cutting the supply to such institutions.

"The system is a dramatic improvement to our disaster simulation and secondary disaster prevention system. This is the best emergency system for earthquakes in the world. We hope to further improve the system by cooperating with the government and the private sector," Yoshihisa Shimizu, deputy general manager in charge of the Tokyo Gas disaster prevention team, said.

yomiuri.co.jp