1, pickling passivation planning
1.1 The purpose of pickling passivation is to clean the inner wall of the pipe and welds of the stainless steel sanitary pipeline and the stainless steel sanitary material container connected to it that has completed the welding construction, to remove the weld oxidized layer and to form a metal protective film on the surface of the inner wall to ensure the internal cleanliness of the pipe and the container and at the same time to extend its service life.
1.2 before the start of the work, with temporary piping (hose or stainless steel piping) all the pipes need to be cleaned to connect into an independent circulatory system, and then use a temporary pump to the pipeline through the acid circulation flushing, flushing is completed after the pipeline acid and continue to use hot deionized water flushing, and at the appropriate time to take a sample of the water for laboratory testing, such as unqualified continue to use hot ionized water flushing, until the water sample is qualified, so as to Completion of the acid washing task.
2、Connection of pipeline and mobile storage cylinder
2.1 will need to pickling passivation of all the pipeline valves, pressure gauges, temperature gauges, pressure sensors, etc., all removed, and wrapped in plastic film, should be removed parts and valves and instrumentation for numbering and marking, in order to complete the construction of the installation after restoration. After the removal of valves and vacancies should be connected with temporary piping, pressure gauges, temperature gauges and other removed locations should be properly sealed with plugs or plug caps, and other short pipes should be connected to the circulation system in various ways. Connect the inlet of the temporary pickling pump with the outlet of the mobile storage cylinder, connect the inlet of the pump to the return port of the circulating pipeline at the same time, and connect the outlet of the pump with a tee, one to return to the mobile storage cylinder, and one to connect the inlet of the circulating pipeline. Install valves at each outlet to control the direction of liquid flow. Pump outlet should be installed pressure gauge and temperature gauge to monitor the pressure and temperature of the pickling process.
2.2 After completing the connection, the temporary pump should be turned on with tap water leakage test, pipeline pressure 1.0MPa; at the same time, check each weld, valves, live joints, to ensure that the connection is solid, no leakage. Leakage points found in the water test process in a timely manner to ensure the safety of the pickling and passivation process.
3、Pipe cleaning (newly installed pipes)
After the successful leakage test of the pipeline, flush the pipeline with hot ionized water, and at the same time, drain the tap water from the pipeline, configure 0.5% lye with hot deionized water in the mobile storage tank, mix it well and then pump it into the circulating system with a temporary pump to keep the pressure of 0.4-0.5MPa for 15 minutes, and then remove the oil and grease and other stains in the inner wall of the pipeline. Recycle the lye and flush the system with hot deionized water for 20 minutes.
4、Pipeline pickling passivation process
4.1 Configure the corresponding acid solution with hot deionized water according to the required amount in the mobile storage tank, and the acid solution is prepared by nitric acid + hydrofluoric acid, and the concentration is controlled within 3%.
4.2 Starting from the acid liquid filling pipeline timing, with a temperature of about 50 ° C acid circulation pipeline, pipeline pressure of 3-4 MPa, it takes about 2-4 hours.
4.3 When the acid circulation is finished, connect the hot deionized water to drain the acid in the pipeline back to the mobile storage tank and transport the mobile storage tank to a safe location for disposal.
4.4 After the acid discharge is completed, the outlet of the circulating pipeline is connected to the sewage pipe and continue to pass the hot deionized water for rinsing, after 60 minutes, notify the owner of the QA to take water samples to test the PH value, free iron, conductivity and other technical indicators, and continue to rinse the pipeline until the test is qualified.
5、Pipeline pickling passivation construction safety measures
5.1 Prepare 100KG soda ash at the site before construction, ready to neutralize the acid that may leak to protect the environment and surrounding equipment.
5.2 Install guardrail or cloth to the entire pickling area (including pipeline through the place) closed up and posted at the entrances and exits conspicuous marking: pickling, non-staff are not allowed to enter. If the pickling area involves the entire workshop, it must be properly timed to ensure that no one enters during construction.
5.3 Every person entering the pickling area must wear the correct PPE chemical protective clothing, acid boots, face mask, industrial acid and alkali gloves, gas masks, etc. Contact with leaking chemicals must be rinsed with tap water immediately afterward, and no touching of other personnel or surrounding equipment is allowed.
5.4 Acid washing area and each channel to send a person to monitor to ensure personal safety.
5.5 After the completion of pickling, firstly, use tap water to rinse the outer wall of the mobile cylinder and connecting pipeline, rinse the gloves and the surrounding ground, sprinkle the soda ash surface and then use tap water to ensure that there is no residual acid. Clean up all temporary pipes, mobile cylinders, temporary pumps, etc., rinse the whole acid washing area with tap water and clear away the garbage.
5.6 Remove all guardrails, collect away the fence and equipment cover cloth, and unseal the whole acid washing area.
6、Addition
6.1 There will be a large amount of wastewater to be discharged to the sewage pond when rinsing the pipeline, then the sewage station needs to be prepared in advance z good.
6.2 Pickling passivation requires a large amount of hot deionized water, in the pickling passivation within 24 hours must ensure its supply.