Nitrogen Generation: Define the Product Before Comparing Performance
On-site nitrogen generation separates nitrogen from compressed air. Pressure swing adsorption and membrane systems have different operating characteristics. Select and assess a generator against the required flow, pressure, purity, and other product-quality limits.
Manufacturer performance tables must be read at the specified conditions. A maximum flow headline and a maximum purity headline may not describe the same operating point.
References: Atlas Copco — Nitrogen Generation and NGP PSA Generators.
What to Record When Product Quality Changes
Document the analyzer reading and units, product flow, delivery pressure, feed-air condition, alarms, and demand pattern. Record whether the reading represents oxygen concentration or a reported nitrogen-purity value. Do not treat an oxygen-only measurement as proof that every possible impurity meets the process specification.
Have analyzer condition and sampling arrangements checked under the applicable procedure before assuming the separation media has failed. Review the complete feed and product system with qualified personnel.
Worked Example: Electricity per Unit of Nitrogen
Illustrative example: these assumed values demonstrate arithmetic, not actual plant results or recommended operating targets.
Assume the compressor, dryer, and generator auxiliaries together consume an average 45 kW while delivering 150 Nm³/h of nitrogen at the required specification.
Specific electricity consumption = 45 ÷ 150 = 0.30 kWh/Nm³.
At an illustrative tariff of PKR 40/kWh, electricity contributes PKR 12/Nm³. This excludes maintenance, financing, depreciation, backup supply, and other costs. State the normal reference conditions used for Nm³. Use compliant product volume over the same measurement period as the electricity total.
Nitrogen can create an oxygen-deficient atmosphere. Follow the site's ventilation, gas-monitoring, and access procedures; this guide is not a procedure for entering or testing an atmosphere.
Next step: Compare product demand with the generator's performance table at the required specification.
Record observations only where it is safe. Inspection inside equipment, electrical testing, chemical work and changes to protective controls require qualified personnel, approved isolation and the installed equipment manual. Never bypass a trip or repeatedly restart unsafe equipment. Engineering disclaimer
Measurements To Record
- Product oxygen concentration or verified purity
- Feed-air pressure and pressure dew point
- Product pressure and flow at stated reference conditions
- Cycle and valve alarm history
Maintenance Checklist
- Log purity, feed pressure and product flow.
- Maintain filters and dryers to the specified air-quality requirement.
- Schedule analyser calibration using certified gases and procedures.
- Inspect ventilation and maintain oxygen-deficiency controls.
Evidence-Based Diagnosis
Product purity below requirement
- Possible Causes
- Excess product flow; inadequate feed air; faulty analyser; separation-system problem.
- Evidence To Collect
- Check analyser calibration and sample conditions. Compare flow and feed-air quality with the specified operating envelope.
- Qualified Follow-Up
- Protect the downstream process using approved off-spec procedures; have the supplier diagnose the separation system.
Low product pressure
- Possible Causes
- Insufficient feed; leaks; high demand; restricted distribution.
- Evidence To Collect
- Compare feed, generator outlet and user pressures while recording demand.
- Qualified Follow-Up
- Investigate supply limitations and leaks, then review buffering and demand with the system designer.
PSA switching alarms
- Possible Causes
- Valve or actuator problem; control fault; unsuitable feed conditions.
- Evidence To Collect
- Record the exact alarm and cycle timing; consult the model manual.
- Qualified Follow-Up
- Use OEM service support for valve and control checks. Do not alter switching logic without approval.
Record The Confirmed Result
Keep the asset model, time, load, ambient conditions, alarm code and relevant readings together. Compare with the last healthy baseline. Record the confirmed cause, approved corrective action and readings after restoration; check that the improvement persists before closing the investigation.