What are the different sealing methods for carbon steel storage tanks?

Carbon steel storage tanks are classified into two main categories based on the characteristics of the stored medium and the operating pressure: atmospheric pressure sealing and pressure sealing. Atmospheric pressure tanks primarily employ flexible sealing structures, including a combination of liquid-embedded seals, mechanical primary seals, and secondary seals. Liquid-embedded seals utilize an annular sealing fluid groove at the edge of the floating roof, forming a liquid film barrier with oil or water seals to effectively prevent oil and gas evaporation. Mechanical seals employ a scraping structure made of metal or elastic materials, tightly adhering to the tank wall to achieve primary sealing. Secondary seals are often skirt seals made of elastic membranes or fabric materials, serving as supplementary protection to the liquid seal. These sealing systems require regular inspection of seal wear and timely replenishment of sealing fluid to maintain sealing performance.

Pressure storage tanks, on the other hand, fall under the category of rigid seals. Common forms include flange bolt connection seals, welded seals, and quick-opening blind flange seals. Flange seals use spiral wound gaskets or rubber gaskets secured with high-strength bolts, suitable for medium and low pressure applications. Welded seals provide permanent connections, ensuring airtightness through full penetration welds, and are often used for sealing fixed top covers or inlet/outlet pipelines. Quick-opening blind flange seals use hydraulic or mechanical locking devices for rapid opening and closing, but have limited pressure resistance. All pressure sealing structures must comply with ASME standards and undergo airtightness testing for verification. For special media storage, the compatibility of sealing materials must be considered; PTFE gaskets are used for acidic media, while graphite composite gaskets are used for high-temperature applications.