In high-precision manufacturing sectors such as chemicals, electronics, and pharmaceuticals, high-purity nitrogen is an essential production input. When a PSA pressure swing adsorption nitrogen generator experiences a sudden drop in nitrogen purity or consistently fails to meet specifications, it can easily lead to significant losses, including production line shutdowns, scrapped finished products, and failed quality‑control inspections. Faults causing abnormal nitrogen purity in PSA units can arise from numerous sources; by following a practical troubleshooting sequence—initial diagnosis, layered fault isolation, and targeted corrective action—it is possible to quickly pinpoint the issue and restore the equipment to its standard nitrogen‑production performance.

I. Preliminary Diagnosis: Three Steps to Quickly Identify the Major Fault Category
Complete the preliminary diagnostic screening before the formal disassembly and maintenance to accurately identify the fault type, thereby minimizing unnecessary repair work.

Operational Data Comparison and Determination
Retrieve historical operating data from the equipment and compare values for nitrogen purity, inlet pressure, and product gas flow rate: sudden, sharp drops in purity are typically caused by internal leakage in pneumatic valves, misconfigured operating parameters, or transient pipeline leaks; sustained, gradual declines in purity (with periods exceeding one month) should first be investigated for molecular sieve aging and failure, as well as contamination of the adsorbent due to malfunctions in the feed‑gas pretreatment system.

Finished gas dew point detection
A portable dew‑point meter is used to measure the dew point of the finished nitrogen gas. If the measured dew‑point value exceeds **–40°C**, it indicates that the moisture content of the feed compressed air significantly exceeds the permissible limit, allowing water to enter the adsorption tower and directly contaminate the carbon molecular sieve, thereby degrading its adsorption‑based nitrogen‑production performance.

Whole-machine airtightness leak testing
Apply soapy water to equipment flange connections, pipeline joints, valve packing glands, adsorption tower interfaces, and other such locations. If bubbles appear after application, these indicate leak points; the ingress of ambient air into the finished nitrogen product is a direct and obvious factor that lowers nitrogen purity.

II. Hierarchical Troubleshooting: Conduct fault diagnosis step by step, progressing from simple to complex.
(1) Investigation of Process Operating Parameters (for the fastest resolution of minor purity issues)

Intake Pressure Calibration

The equipment is designed to operate at a constant inlet air pressure of 0.6–0.8 MPa. When the inlet pressure falls below 0.5 MPa, the molecular sieve lacks sufficient adsorption capacity, failing to effectively remove oxygen from the air. Conversely, when the inlet pressure exceeds 0.9 MPa, the selectivity of nitrogen–oxygen separation deteriorates significantly, adversely affecting nitrogen purity.
Optimization plan: Adjust the air compressor’s output pressure, inspect the upstream gas‑supply piping for pressure‑relief leaks, and install a pressure‑stabilizing gas storage tank to mitigate significant pressure fluctuations under high‑load conditions.

Adsorption–Desorption Cycle Commissioning

If the adsorption–desorption switching cycle is too short, the molecular sieve does not complete oxygen adsorption before the tower is switched; if the cycle is too long, the molecular sieve undergoes premature self‑desorption and loses its effectiveness. In either case, the product purity will be insufficient.
Commissioning procedure: Strictly follow the equipment manufacturer’s technical manual, switch to manual operation mode, and conduct segmented testing over specified durations. Fine-tune the switching time until the nitrogen purity stabilizes and meets the required specifications. Simultaneously monitor the exhaust backpressure; blockages in the silencer can impede the discharge of waste gases—regularly clean out any accumulated debris, and replace aged silencers promptly.

PSA nitrogen generator

(II) Inspection and troubleshooting of the compressed air pretreatment system (to prevent molecular sieve damage at the source)

Oil, moisture, and particulates in compressed air are the primary sources of degradation for carbon molecular sieves, and ineffective pretreatment is the root cause of chronic malfunctions in nitrogen generators.

Pre-filter maintenance and replacement
The air precision filter element must be replaced immediately if its service life exceeds 6 months or if the pressure differential across the element exceeds 0.1 MPa. Once the filter element fails, dust and solid contaminants can enter the adsorption tower, clogging the molecular sieve’s micropores and permanently reducing its adsorption capacity.

Drying Equipment Operating Condition Inspection
Verify the operating status of the refrigerated dryer; if the dew point of the dried air exceeds –20°C, this indicates an abnormal condition, and the refrigeration components should be promptly inspected and repaired. In humid or high-humidity operating conditions, consider upgrading to an adsorption dryer and regularly replace the desiccant inside to prevent moisture from entering the nitrogen generation unit.

Special Inspection of the Oil Removal System
In pharmaceutical and electronic applications requiring oil-free, high-purity nitrogen, prioritize inspection of the oil–water separator and the high-efficiency oil‑removal filter element. If oil contamination is visible on the filter surface, replace the premium oil‑removal filter immediately. When oil contamination has severely penetrated the adsorption tower, disassemble the unit to thoroughly clean the internal oil deposits, thereby preventing permanent deactivation of the molecular sieve due to oil poisoning.

(3) In-depth inspection of core equipment components (to eliminate severe purity‑related failures)

Pneumatic Control Valve Troubleshooting
In PSA nitrogen generators, high-frequency switching pneumatic valves are prone to internal gas leakage due to aging of the sealing rings and wear of the valve spools—this is the most common type of internal leakage failure.
Simple troubleshooting: During operation, if the adsorption tower emits whistling noises or unusual internal airflow sounds, it can be reasonably concluded that a valve is leaking. During maintenance, disassemble the valve body and replace aged seals, and periodically lubricate the valve’s pneumatic actuator to extend its service life.

Carbon Molecular Sieve Status Monitoring and Replacement
Open the maintenance access port of the adsorption tower to inspect the molecular sieve condition: under normal conditions, the molecular sieve particles are plump and uniform. If blackening and caking, pulverization and fragmentation, or agglomeration into solid lumps are observed, it indicates that the molecular sieve has completely lost its effectiveness.

Service life reference: Under clean gas‑supply conditions, the molecular sieve has a service life of 5–8 years; when the gas supply is severely contaminated with oil and water, the service life is reduced to 3–5 years.
Key replacement considerations: Ensure the molecular sieve is packed densely and evenly to prevent gas flow maldistribution and bypass; simultaneously inspect the internal protective wire mesh and the upper and lower fiber mats, replacing any damaged components promptly to prevent loss of molecular sieve particles.

Calibration of Nitrogen Purity Analyzers
The device’s display shows a significant deviation between the indicated purity and the actual measured purity. This is not due to a malfunction of the nitrogen-generation equipment, but rather to drift in the sensor readings.
Solution: Use 99.99%–grade high-purity nitrogen to calibrate the built-in oxygen‑sensor battery of the instrument. In industrial settings, it is recommended to perform a precision calibration once per quarter to prevent sensor misinterpretation of purity, which could lead to unnecessary maintenance.

III. Daily Operations and Maintenance Preventive Measures (Ensuring Long-Term, Stable Nitrogen Purity)
Strictly replace air filter elements and desiccant consumables on schedule to ensure that the raw compressed air remains clean and dry.
Conduct daily inspections of intake pressure, switching cycles, and exhaust flow integrity, and make timely fine adjustments to operating parameters.
Conduct monthly leak tests on the complete system’s piping to verify air tightness, and perform quarterly calibration of purity‑monitoring instruments.
It is strictly prohibited to operate equipment at excessive load for extended periods; use it within its rated gas production flow rate to slow down the aging of the molecular sieve.