The properties of stored liquids are critical factors in selecting tank configurations and designing tank process systems.

Key chemical and physical properties include: flash point, boiling point (at atmospheric pressure), saturated vapor pressure (abbreviated as vapor pressure), toxicity, corrosiveness, chemical reactivity, and density.

1) Flash Point, Boiling Point, and Vapor Pressure

The flash point, boiling point, and vapor pressure of stored liquids are closely related to their flammability and volatility. These properties serve as the primary basis for selecting tank configurations and safety accessories.

2) Toxicity

Tanks storing toxic media require consideration of specific issues, such as preventing environmental contamination and ensuring operator safety. Therefore, vented gases must not be directly discharged within the tank farm but undergo special treatment to remove harmful components. All detection instruments and accessories should minimize operator poisoning risks. All internal butt welds must be continuous welds, employing sealed weld techniques to prevent toxic media from entering and accumulating in gaps. To facilitate complete tank cleaning, liquid inlet/outlet structures should allow full drainage.

3) Chemical Reactivity

The chemical reactivity of stored liquids encompasses polymerization reactions, decomposition reactions at specific temperatures, and contamination or chemical reactions with air. The former is typically addressed through agitation, addition of polymerization inhibitors to prevent polymerization and sedimentation, water spraying, or cooling measures. The latter is managed by inert gas blanketing. Nitrogen is commonly used for this purpose, with nitrogen sealing pressures ranging from 0.5 to 2.0 kPa. Nitrogen purity is determined by the requirements of the protected liquid.

For high-temperature storage tanks, never add low-boiling-point liquids to tanks containing high-boiling-point liquids (e.g., adding water to a tank holding oil) to prevent explosive vaporization and tank rupture.

4) Corrosivity

The corrosivity of stored liquids dictates tank material selection. Beyond accounting for corrosion allowances in material design, attention must be paid to potential contamination of stored liquids by tank materials. For example, carbon steel materials may introduce Fe ion contamination and potentially reduce product purity (especially for liquid chemicals). For stainless steel materials, consideration must be given to the intergranular corrosion and stress corrosion resistance properties of different grades relative to the stored liquid.