When starting up a chemical plant, following these steps makes it easy

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1 Pressure testing of equipment and piping systems (I) Conditions for pressure testing of piping systems: 1. The safety valves have been covered with blind plates, and the burst discs have been removed and also covered with blind plates. 2. The expansion joint has been fitted with a restraining device. 3. The spring supports and hangers have been locked. 4. When testing is conducted using water as the medium, the load-bearing capacity of the relevant structure has been confirmed or calculated. 5. The pressure gauge has been calibrated and found to be in good condition. (II) The following regulations must be complied with: 1. Pressure testing using air and process media must be approved by the production and safety departments. 2. Before the test, confirm that the test system has been effectively isolated from unrelated systems. 3. When conducting hydrostatic tests, clean fresh water shall be used as the testing medium; when austenitic stainless steel equipment or pipes are connected to the system, the chloride content in the water must not exceed 0.0025%. 4. The test temperature must be higher than the material’s brittle transition temperature. 5. When conducting tests in cold seasons, anti-freezing measures must be taken. 6. The hydraulic test pressure for steel pipes is 1.5 times the design pressure ； When the design temperature is higher than the test temperature, the test pressure shall be calculated based on the ratio of the allowable stresses at the two temperatures, but it must not exceed the yield strength of the material. When testing with gas, the test pressure is 1.15 times the design pressure. 7. When the test pressure of the equipment in the test system is lower than that of the pipeline, and the test pressure of the equipment is not less than 115% of the pipeline’s design pressure, the pipeline system can be tested at the test pressure of the equipment. 8. When the test system is connected to equipment that can only withstand a certain pressure difference, it is necessary to ensure that this pressure difference does not exceed the specified value during the process of increasing or decreasing pressure. 9. During testing, the voltage should be increased slowly. When testing with a liquid, the pressure should be maintained at the test pressure for 10 minutes, after which it should be reduced to the design pressure to check for leaks. When conducting tests with gas, a preliminary test should first be carried out at a pressure lower than 0.17 Mpa (gauge pressure); thereafter, the pressure is increased to 50% of the design pressure, then gradually raised to the test pressure and held at that level for 10 minutes. Finally, the pressure is reduced to the design level to check for leaks. 10. After the test is completed, the water and air should be drained, and the system should be returned to its original state. 2 Leakage testing of equipment and piping systems: (1) Leakage testing must be carried out when transporting toxic media, flammable media, or other media for which leakage testing is required according to design specifications. (II) The leakage test should be conducted after the pipeline has been cleaned or purged successfully. (III) When a pressure test is conducted using air, it can be carried out simultaneously with a leak test; however, after the pipeline has been cleaned or purged successfully, a final leak test must be performed, with particular attention paid to the areas where the pipeline is reconnected. (IV) The following requirements shall be complied with: 1. The test pressure shall not be higher than the design pressure. 2. The test medium is generally air. 3. The test pressure for the vacuum system’s leakiness is 0.01 MPa (absolute pressure). 4. Conduct inspections using the method specified in the design documents. 3 Water flushing: (I) Water flushing can be carried out only after the pressure test is successful, protective measures have been taken for the machinery, instruments, valves, etc. in the system, the temporary pipes have been installed, the flushing pump can operate properly, and a filter has been installed at the inlet of the flushing pump. (II) If the flushing work is carried out in cold weather, anti-freezing and anti-slip measures must be taken. (III) During filling and draining, the piping system should be in communication with the atmosphere. (IV) Before the pipelines and machinery in the previous process have been successfully flushed, the flushing water must not enter the machinery in the subsequent process. (5) The rinse water should be discharged to designated locations. (VI) After flushing, ensure that all drainage and exhaust pipes are unobstructed. 4 Steam Purging (I) Conditions for Steam Purging 1. The pipeline system has passed the pressure test. 2. According to the design requirements, locate the positions for pipe connections and splices, and install temporary pipes ； Pipeline safety standards shall meet the requirements of relevant specifications. 3. Effective protective measures have been taken for valves, instruments, and machinery. 4. Confirm that there are no flammable materials on or near the pipeline system, and that the pipelines carrying flammable materials are properly isolated to prevent fires in the event of a leak. 5. The steam supply system is now operating properly, and the amount of steam available meets the requirements for purging. 6. Fencing has been installed around the restricted area, along with prominent signs. 7. The test operators are wearing the required protective clothing and shock-absorbing earplugs. (II) The following regulations must be observed: 1. Steam purging is strictly prohibited for pipeline systems that have not taken expansion into account. 2. Before steam purging, warm the pipes by opening all drain pipes to remove condensate and prevent water hammer. 3. During purging, blow through each drain pipe one by one. 4. Conduct a thorough inspection of the reset process to ensure that the piping system has been fully restored, and that the connections between pipes and machinery are freely aligned in accordance with the specified standards. 5. Noise reduction measures must be in place for purging. 5 Chemical cleaning (I): The interior of the pipeline system is free of debris and oil stains. (II) The chemical cleaning solution has been analyzed by the quality inspection department and found to meet the standard requirements, confirming that it can be used for the system to be cleaned. (III) It shall have a chemical cleaning flowchart and a blind plate location diagram. (IV) The facilities, heat sources, chemicals, analytical instruments, tools, etc., required for chemical cleaning are all available. (5) The chemical cleaning personnel are dressed in accordance with safety regulations and wearing protective equipment. (VI) If the pipeline system after chemical cleaning cannot be put into use temporarily, it should be protected with an inert gas. (7) Sewage must be treated to meet environmental protection standards before it can be discharged. 6 Air Purging (I) Pipes with a diameter greater than 600 mm should be cleaned manually. (II) The system has passed the pressure test, and effective protective measures have been taken for the machinery, instruments, valves, etc. within the system. (III) The location of the blind flange has been confirmed, and the gas supply is ensured ； When purging oil-free pipelines, the air must be free of oil. (IV) A strict inspection should be carried out on the reset operation after purging. (5) Purging shall include measures such as shielding, warning signs, prevention of people staying in the area, and noise reduction. 7 Pre-film formation in the circulating water system (I) Conditions for pre-film formation in the circulating water system: 1. The system has been flushed with water and is qualified. 2. The circulating water system passed the joint commissioning test. 3. Tests have confirmed that the chemical solution is suitable for the water quality at the site, it provides good film formation, and its corrosivity is below the specified levels. 4. Test pieces for monitoring the pre-film condition have been installed in the system as required. 5. Effective measures have been taken to handle waste liquid. (II) The following regulations must be observed: 1. Pre-coating work should be carried out away from the cold seasons; if it must be done during such periods, anti-freezing measures are necessary. 2. The pre-coating process of the system should be completed in one go; no pipes or equipment that have not been pre-coated should remain within the system. 3. After pre-coating, drugs should be applied on time and in the correct amount to keep the system in a coated state. 8 System Purging (I) Inert Gas Purging Before introducing combustible gases into the system, the air must first be replaced with inert gas, and then the inert gas should be replaced with combustible gases. Before parking for maintenance, the flammable gases in the system must be replaced with inert gas, and then the inert gas must be replaced with air; attention must also be paid to the proper handling of toxic and hazardous solids and liquids. (II) System replacement conditions: 1. A flow diagram showing the locations of the vent points, analysis points, and blind flanges. 2. The sampling and analysis personnel are in place, and the analysis instruments and reagents are ready. 3. Inert gases can meet the requirements of displacement work. (III) The following regulations must be complied with: 1. The oxygen content in inert gases shall not exceed the safety standards. 2. Verify that the quantity, quality, and installation location of the blind plates are satisfactory. 3. When performing displacement, attention should be paid to the dead corners in the system; if necessary, the method of repeated pressure increase and decrease can be used to dilute the displacement gas. 4. When the pipeline system is connected to a gas holder, the gas holder should be raised and lowered three times to completely displace the gas in the annular water seal. 5. The replacement work should be carried out sequentially, starting with the main pipes and then moving on to the branch pipes. 6. When taking samples, analysts should pay attention to the wind direction as well as the height and direction of the vent pipes to prevent poisoning. 7. The data shall be analyzed on the basis of three consecutive successful tests, and must be signed off by the personnel in charge of production, technology, and safety. 8. After the displacement is complete, effective measures shall be taken to isolate the inert gas pipeline from the system. (IV) Qualification standards: 1. When replacing flammable gases with inert gases, the concentration of flammable gases in the gas after replacement shall not exceed 0.5%. 2. When replacing inert gases with flammable gases, the oxygen content in the gas after replacement shall not exceed 0.5%. 3. When replacing air with an inert gas, the oxygen content in the gas after replacement must not exceed 1%; if the gas is to be introduced directly into flammable or explosive media, the oxygen content in the gas after replacement must not exceed 0.5%. 4. When replacing inert gas with air, the oxygen content in the gas after replacement must not be less than 20%.