General Process Guidelines for Nitrogen Protection of Pressure Vessels
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； 3. The connection pipes for the nitrogen filling port of the equipment should be welded firmly to prevent loosening due to vibrations during transportation, ensuring that the nitrogen pressure gauge still shows a proper reading once the equipment arrives at the installation site, so that it can fulfill its protective function properly. 4. Nitrogen displacement: 4.1 Nitrogen enters from above and exits from below. To save nitrogen, intermittent displacement is used ； 4.2 Specific procedures: First, close all valves at the bottom (including the vent valve), then purge the container with nitrogen. Once a certain pressure is reached inside the container (0.1 MPa), stop the nitrogen supply and open the vent valve to release gas at maximum flow; close the vent valve when the pressure drops to 0.01 MPa ； 4.3 Recharge with nitrogen, repeat this process 3 times; use a portable oxygen content detector to check the level at the vent – the process is complete when the oxygen content is below 5%. Then stop the gas exchange, close all valves, and seal the container ； 4.4 If it fails, replace it again until it passes ； 4.5 The positions of the intake valve and the vent valve should be arranged as far apart as possible, not on the same plane; this helps to save nitrogen and makes it easier to clean out any dead zones. 5. After nitrogen filling is complete, close the valve on the nitrogen filling device, remove the nitrogen filling tube, and tighten the valve on that device. Use soapy water to check whether the connections, plugs, manholes, and pipes are properly sealed; if there are any leaks, tighten them again before checking once more. Install the pressure gauge guard. VI. Safety considerations: Nitrogen is not toxic in itself, but an environment with a nitrogen concentration of over 78% can affect the oxygen level in the air. When the oxygen level drops below 18%, people may experience symptoms such as dizziness, nausea, and chest tightness; in severe cases, there is a risk of suffocation.
This post was last edited by bluishice on 2021-8-24 07:45. Nitrogen has a density slightly greater than that of air; therefore, it should flow in from below and out from above. Air is drawn in slowly through the lower inlet, while the upper outlet remains open. The approximate time required for air to fill the space can be estimated based on its volume. When that time has passed, light a match and try it at the outlet; if the match goes out, the space is filled. Of course, this is the practice for new equipment; if an existing device is being used, it is necessary to check whether the medium is flammable and whether the environment permits open flames.
Before nitrogen flushing, our factory usually evacuates the space first.