2014 Volume 10 Issue 2 Pages 59-67
The air-tightness test for the propane storage cavern was conducted in June 2012 at Kurashiki national LPG stockpiling base, using the hydraulic containment type underground rock storage cavern tank system, which was the first attempt for preserving high pressure liquefied petroleum gas in Japan. The aim of this paper is to report the advanced air-tightness evaluation system we developed in order to evaluate the air-tightness of the cavern rigorously, and the result of evaluating the cavern air-tightness at Kurashiki base at the test pressure 950kPaG by the system.Air-tightness of an underground rock cavern is evaluated by measured cavern pressure variation throughout the test period under the condition the cavern is pressurized by compressed air up to the test pressure and all the lines between the cavern and the ground are closed. The measurement value of cavern pressure should be corrected from various factors affect to the cavern pressure, or variation of temperature and gas-phase volume in the cavern caused by seepage into the cavern and its pumping-up, and the air dissolution into seepage, etc. For evaluating the air-tightness of the 800,000 m3 world’s largest storage cavern at Kurashiki base rigorously, the advanced air-tightness evaluation system was designed, which included the field suitable temperature measurement instrument with uncertainty of ±0.01°C, the appropriate layout of temperature sensors in the cavern, and the management procedure for the field installation. As the test result evaluated by the advanced air-tightness evaluation system, the corrected cavern pressure variation at the test pressure 950kPaG during the 72-hour test period was 0.002kPa and it was substantially within the criterion0.5kPa derived from the instrument uncertainties. It indicates the air-tightness of the cavern was validated very rigorously and verified the applicability of our advanced air-tightness evaluation system.
