The COS type gas holder is a large, variable capacity gas storage tank. The COS type has an inner roof in the steel outer shell and the inner roof goes up and down according to the capacity of gas. The inner roof is of sliding type. Gas leaking through the gap between the inner roof and the outer shell is sealed with pressure of viscous fluid (seal oil) stored in the upper part of the roof. The seal oil flows down little by little through the gap to the bottom of the holder. The seal oil collected in the bottom is pumped up to the ceiling of the holder for circulation and recycling so that required static pressure can be secured (maintained).
Unlike the ordinary tank such as an LNG tank, the gas holder has a special structure; the heavy inner roof (piston) goes up and down in the outer shell according to the volume of gas stored in the holder. Therefore, the behavior of the piston changes according to the height of the piston when an earthquake occurs. The gas holder itself exhibits complicated and compound behavior in accordance with the outer shell and piston. We conduct a time history response analysis to determine this behavior. The analysis entails expertise and knowhow to set appropriate conditions, as well as high analytical ability.
High-level anti-earthquake measures are required of Japan, an earthquake-prone country. The gas holder exhibits different behavior when an earthquake occurs according to its model, capacity, storage gas pressure, and other factors. The strength of the shaking of the gas holder varies with the amplitude of seismic waves, peak period, and others. We conduct an appropriate analysis and have on hand every possible anti-earthquake measures based on the results.
The gas holder is a large tank of 40 to 50 meters in diameter and 80 to 100 meters in height. Not only abilities in planning, procurement, construction, and execution management but safety and quality control abilities are needed to construct such a large structure. In addition, high overall capabilities are required to build a gas holder in a narrow area surrounded by pipes and various facilities. We have a track record of having constructed numerous gas holders in narrow places.
To fulfill its function properly, a gas holder must be periodically serviced and inspected. Symptom of possible failure include abnormal noise, an increase in piston inclination or in the number of pump station operations, etc. A gas holder serves the important function of storing large volumes of flammable gas and is integral to energy saving operations. Contact us immediately if you ever detect any abnormal condition.
NISSEKI YOKOHAMA Bldg. 1-8, Sakuragi 1-Chome Naka-Ku, Yokohama 231-0062, Japan