In chemical, oil and gas, pharmaceutical, new material and other industries, purging serves as a fundamental process to guarantee stable operations and site safety during equipment startup and shutdown, pipeline maintenance and material changeover. Traditional methods mostly rely on liquid nitrogen or cylinder nitrogen purchased from suppliers. Restricted by transportation scheduling, tank refilling and inventory management, the continuity of gas supply may be disrupted, and long-term operating costs tend to fluctuate. Built on air separation technologies, the on-site nitrogen generation purging system produces inert nitrogen directly from compressed air, and matches purging requirements under diverse working conditions. It has become an alternative gas supply option for many production sites.

　　The core objective of purging is to displace air, combustible vapour, moisture and trace impurities inside vessels, pipelines and reaction chambers with inert gas. It keeps oxygen concentration within a safe range, lowers risks of oxidative corrosion and accumulation of flammable mixtures, and protects raw materials and semi-finished products sensitive to oxygen and humidity. Two common purging methods are displacement purging and dilution purging. Displacement purging applies to long pipelines and large storage tanks, pushing out original media by gas flow. Dilution purging suits closed chambers, where continuous nitrogen feed gradually reduces internal oxygen level. Both methods require stable nitrogen supply with adjustable flow.

　　Two mainstream technologies are adopted in such systems: pressure swing adsorption and membrane separation. Pressure swing adsorption utilises the difference in adsorption speed between oxygen and nitrogen on carbon molecular sieve. Oxygen is captured under pressurised conditions while concentrated nitrogen is delivered. Adsorption towers alternate between adsorption and depressurisation regeneration to maintain continuous production, which fits scenarios demanding high nitrogen purity. Membrane separation relies on hollow fibre membrane modules. Gas molecules pass through the membrane at different permeation rates to achieve separation. It features simple structure and fast start-stop response, and is suitable for purging tasks requiring moderate purity and instant activation. A complete system generally includes air pretreatment unit, core separation unit, buffer and pressure stabilisation unit, online monitoring and automatic control modules. Some projects are equipped with flow regulators and oxygen feedback devices to adjust production parameters automatically according to purging conditions.

　　Compared with cylinder and liquid nitrogen tanker supply, the on-site nitrogen generation purging system has distinctive characteristics. First, it improves supply independence. The system generates nitrogen continuously once connected to compressed air and power supply, reduces reliance on external gas sources and avoids supply interruptions caused by transportation and delivery cycles. Second, for long-term operation, it eliminates extra expenses such as liquid nitrogen vaporisation loss, round-trip transportation and cylinder inspection. It fits plants with frequent purging and stable year-round gas consumption. Besides, the modular layout is flexible. The skid-mounted package can be installed near process units to shorten delivery pipelines and reduce gas transmission loss.

　　Nevertheless, gas supply mode is not the only factor for selection. Working parameters should be evaluated comprehensively. Users need to confirm required nitrogen purity, instantaneous flow, continuous supply duration, ambient temperature, space constraints and quality of supporting compressed air. Purging for chemical and oil storage tanks usually has strict oxygen control requirements, so pressure swing adsorption with reliable purity and high monitoring precision is preferred. Membrane separation can meet basic demands for regular pipeline replacement and simple equipment purging. For maintenance, air filters, molecular sieves and membrane elements are consumables that need periodic replacement. Oil and water removal of compressed air must be properly handled to prevent contaminants from damaging core separation components and sustain stable gas output.

　　Safety control is also essential for purging work. Even though nitrogen is inert, massive injection in enclosed spaces may lead to oxygen deficiency. On-site oxygen alarms, ventilation arrangements and work permit procedures should be implemented. Automatic control logic of the system shall include interlock triggers. Alerts will be activated once oxygen or pressure readings go beyond thresholds, to avoid hazards caused by improper operation.

　　Overall, the on-site nitrogen generation purging system is not suitable for every situation. Purchased gas remains flexible for occasional short-term purging and small consumption. For factories with continuous production and regular pipeline and vessel purging, however, this system can build a stable inert gas source, balancing process protection, operational safety and long-term economic efficiency. It is a technically viable solution worthy of rational assessment within industrial inert gas supply frameworks.