Add a nitrogen seal design to the oil tank

Before implementing any additional nitrogen sealing designs, the storage tank must undergo the following inspections and preparations: 1. **Structural integrity check**: Verify that the structure of the storage tank is in good condition, including checking for any damage or corrosion on the floating roof, tank walls, and bottom. 2. **Airtightness test**: An airtightness test is conducted to ensure that the storage tank can effectively isolate external air after the installation of the nitrogen sealing system, thereby preventing nitrogen leakage. 3. **Safety assessment**: Evaluate the safety of the storage tank after being filled with nitrogen, including the material’s pressure resistance and explosion-proof measures. 4. **Pipeline and Valve Inspection**: Check that all pipelines and valves connecting the storage tanks are suitable for nitrogen, and ensure they are in good condition with no leaks. Precautions: - **Ensure compatibility**: Verify that all materials and system components are compatible with nitrogen to prevent damage to the materials due to chemical reactions. - **Preventing overpressure**: When designing, the pressure changes resulting from nitrogen injection must be taken into account to ensure that the storage tank can withstand the maximum pressures expected; a pressure release system should be installed. - **Monitoring system**: Install gas concentration and pressure monitoring systems to continuously monitor the nitrogen filling status and the internal conditions of the storage tanks. - **Operational training**: Train operators on the use and maintenance of the nitrogen sealing system, ensuring they understand the operating procedures and safety measures. These preparatory steps will help ensure the proper installation and safe operation of the nitrogen sealing system. .

Thank you for your detailed answer! I have two more questions: (1) Does the storage tank need to undergo another hydrostatic test? (2) “Assess the safety of the storage tank after nitrogen filling, including the compressive strength of the materials and explosion prevention measures,” can the compressive strength of the materials be replaced by a hydrostatic test?

Regarding the question you raised, my answer is as follows: (1) Whether a hydrostatic test needs to be conducted again depends on the current condition of the tank and whether any major structural modifications have been made. If the tank has not been used for a long time prior to renovation, or if there are noticeable repairs and modifications (such as replacement of plates or major welds), it is recommended to conduct a hydrostatic test to ensure the structural integrity and tightness. If the storage tank is well-maintained and no major structural modifications have been made, it may not be necessary to conduct another hydrostatic test. However, this decision should be based on specific **standards and industry norms. (2) As for whether the compressive strength of materials can be replaced by a hydrostatic test, generally hydrostatic tests are used primarily to verify the sealing performance and structural integrity of storage tanks, rather than directly testing the compressive strength of the materials. The compressive strength of a material is usually determined during the material design and selection phase based on engineering calculations and material property standards, taking into account the physical and chemical properties of the material itself. Therefore, hydrostatic testing cannot completely replace the evaluation of a material’s compressive strength. For safety reasons, it is advisable to conduct a series of evaluations and tests prior to filling with nitrogen, including but not limited to structural analysis, material testing, and suitability assessments, to ensure that the tank system can operate safely after the installation of the nitrogen sealing device. At the same time, considering that nitrogen may cause certain materials to become brittle under specific conditions, material selection and testing are particularly important in such cases. .

Thank you very much for sharing and answering.

Apart from ensuring safety during construction, it seems there are no other inspection items required, not even for a small pipe.

Our plant’s straight-run diesel tank on Line 3 of the diesel hydrotreating unit is also set to be equipped with a nitrogen seal, as currently straight-run diesel and catalyzed diesel mix together in the feed tank for hydrotreatment.