I would like to ask whether nitrogen blanketing is now required for naphtha storage tanks

According to the regulations of the **work safety supervision authorities, nitrogen blanketing is now required for naphtha storage tanks. Nitrogen blanketing is a commonly used safety measure that reduces the oxygen content inside storage tanks, thereby minimizing the risk of fire and explosion involving naphtha. Small naphtha storage tanks with fixed roofs also need to be nitrogen-sealed. In addition to the flame arrestor breathing valve, a nitrogen supply system and related control equipment also need to be installed. It is recommended that you consult relevant professionals or the local safety regulatory authorities to understand the specific requirements and procedures. .

1. \"Installation of gas seals\" HG/T 20570.16-1995 1.0.1.1 To prevent the materials in storage tanks from being contaminated or deteriorated due to contact with external gases (air) that enter the tanks, as well as to avoid chemical and/or biological reactions with such external gases, it is often necessary to install a gas seal system. An air seal is used to maintain a certain pressure (positive pressure) inside the storage tank, preventing the contents of the tank from coming into contact with external air. 2. \"Code for Fire Protection Design of Petrochemical Enterprises\" (GB50160-2008) (2018 edition) 6.2.2 When internal floating roof storage tanks with a single tank volume of 5000 m3 or less use floating roofs made of fusible materials, safety measures such as nitrogen protection shall be implemented ； 6.2.2 Interpretation of the provision: For liquid materials of types A and B with special requirements, such as styrene, hydrogenation feedstocks, acrylonitrile, and other liquids that are prone to polymerization, oxidation, or are toxic, it is also feasible to use fixed-roof storage tanks or horizontal storage tanks with nitrogen sealing for storage ； Clause 6.2.4A: For fixed-roof tanks storing heavy oil at temperatures exceeding 120°C, nitrogen padding shall be provided. 6.2.4 Interpretation of the provision: When storing Class A liquids in fixed-roof tanks or low-pressure storage tanks, measures should be taken to reduce temperature rise due to sunlight exposure, in order to prevent excessive vaporization of oil and gas and improve the safety of the storage tanks. The measures mainly include a fixed cooling water spray (mist) system, gas venting or gas condensation, nitrogen blanketing, or applying qualified thermal insulation coatings. 3. Explanation of Clause 5.1.5 in the “Fire Protection Standards for Engineering Design of Fine Chemical Enterprises” (GB 51283-2020): 1) For equipment such as reaction tanks, storage tanks, and filters that generate high-concentration organic waste gases, a nitrogen blanketing system should be employed to prevent the formation of explosive mixtures with oxygen. The waste gases should then be conveyed to the main exhaust pipe under positive pressure. 6.2.2 Interpretation of the provision: For the storage of Class AB and Class BA liquid materials with a single tank volume of less than 100 m3, or those with special requirements such as being prone to oxidation or polymerization, fixed-roof tanks sealed with nitrogen or inert gases can be used. 4. According to Article 6.1.2 of the \"Code for Design of Oil Storage Tanks\" (GB 50074-2014) and its explanatory provisions, when internal floating-roof tanks or fixed-roof tanks are used to store Class A/B liquids with a boiling point below 45°C or a saturated vapor pressure greater than 88 kPa at 37.8°C, a nitrogen sealing system must be installed. When storing Class A and B liquid chemical products as well as light naphtha with a boiling point of not less than 45°C or a saturated vapor pressure of not more than 88 kPa at 37.8°C, in fixed-roof storage tanks with a capacity of 10,000 m3 or less, low-pressure storage tanks, or horizontal storage tanks with a capacity of 100 m3 or less, a nitrogen sealing protection system shall be installed. Storage tanks for Class A B and Class B A liquids with toxicity levels I and II should be equipped with a nitrogen purge protection system. Some Type B and Type A liquid chemical products have special storage requirements, such as prevention of polymerization; therefore, internal floating roof tanks are not suitable for them. Fixed-roof tanks, low-pressure tanks, and horizontal tanks with a capacity of 50 m³ or less can be used instead. However, safety measures such as nitrogen blanketing must be implemented. For typical unstable chemicals prone to self-polymerization, such as butadiene and styrene, a nitrogen blanketing system should be installed to prevent air from entering the tank. 5. \"Code for Design of Tank Areas in Petrochemical Storage and Transportation Systems\" (SH/T 3007-2014) 3.5 The operating pressure of flammable liquid storage tanks shall be determined in accordance with the following principles: a) The operating pressure of low-pressure tanks and pressure tanks shall be the saturated vapor pressure of the liquid at its highest storage temperature, or the highest pressure required for the process operation ； b) For storage tanks protected by nitrogen sealing, the operating pressure should be in the range of 0.2 kPa to 0.5 kPa. For other storage tanks equipped with breather valves, the operating pressure should be 1 kPa to 1.5 kPa ； c) The operating pressure of other storage tanks should be at atmospheric pressure. 4.2.4 For storing Class A/B liquids with a boiling point below 45°C or a saturated vapor pressure greater than 88 kPa at 37.8°C, pressure tanks, low-pressure tanks, or atmospheric-pressure tanks with cooling systems shall be used, and the following requirements shall be met: a) When using pressure tanks or low-pressure tanks, measures shall be taken to prevent air from entering the tanks, and the gases discharged from the tanks shall be collected and treated in a sealed manner ； b) When using atmospheric-pressure storage tanks with cooling for storage, one of the following measures should be taken: — Use internal floating-roof tanks, install a nitrogen or other inert gas sealing system, and control the storage temperature so that the vapor pressure of the liquid does not exceed 88 kPa. — Use fixed-roof tanks, install a nitrogen or other inert gas sealing system, and keep the storage temperature 5°C or lower than the liquid’s flash point. — Use fixed-roof tanks, install a nitrogen or other inert gas sealing system, control the storage temperature so that the vapor pressure of the liquid does not exceed 88 kPa, and capture and treat the gases emitted from the tank in a sealed manner. 4.2.5 For storing Class A and Class B liquids with a boiling point greater than or equal to 45°C, or those having a saturated vapor pressure not exceeding 88 kPa at 37.8°C, floating roof tanks or internal floating roof tanks shall be used. When special storage requirements apply to other Class B and Class C liquid chemical products for human use, fixed-roof tanks, low-pressure tanks, and horizontal tanks with a capacity of 100 m³ or less may be used. However, one of the following measures must be taken: — Install a sealing protection system using nitrogen or other inert gases, and collect and treat the gases discharged from the tank in a closed manner ； ———Install a nitrogen or other inert gas sealing protection system to keep the storage temperature 5°C or lower than the liquid’s flash point. 6 Corrosion protection of storage tanks and other aspects 7.4 When storing materials that are prone to oxidation or polymerization and are unstable, measures such as using nitrogen coverage to isolate them from air should be taken.