Compressed Air: Measure the System, Not Only the Compressor
Compressed air passes through several stages before reaching a tool or process: compression, storage, treatment, distribution, and final use. Poor performance can originate anywhere along that path.
Low pressure at one machine does not establish that the compressor lacks capacity. Compare supply pressure and point-of-use pressure during the same demand period. Restrictions, demand peaks, leaks, and controls can produce different patterns.
Build a Useful Operating Record
Record electrical input, delivered airflow on a stated reference basis, load/unload status, header pressure, treatment pressure drop, and dryer condition. Include production demand and measurement time. Free-air delivery and actual compressed-air volume are different quantities; comparisons require a common basis.
Investigate Before Increasing Pressure
If header pressure remains stable while a remote user loses pressure, investigate the distribution path and local demand. If the header also falls, review available delivery, sequencing, and simultaneous users. These observations narrow the investigation; they do not prove a single fault.
Reference for system assessment: U.S. Department of Energy — Improving Compressed Air System Performance.
Worked Example: A Measured Reduction in Electrical Demand
Illustrative example: these assumed values demonstrate arithmetic, not actual plant results or recommended operating targets.
Suppose comparable measurements before and after a repair show average electrical demand falling from 90 kW to 82 kW. At 4,000 equivalent operating hours per year:
Estimated annual energy difference = (90 − 82) × 4,000 = 32,000 kWh.
At an illustrative energy tariff of PKR 40/kWh, the energy-charge difference is PKR 1,280,000 per year. This excludes changes in demand charges and other billing items. The estimate is meaningful only if production, pressure, and operating conditions are comparable. A repaired leak does not automatically produce this saving: the compressor controls must actually reduce energy use.
What Should the Maintenance Record Explain?
Record the symptom, measurements, confirmed cause, approved action, and follow-up result. Avoid a record that says only “separator replaced” or “pressure increased.” The next investigation needs to know why the action was taken.
Next step: Compare your operating record with the compressor manual, then use the running-cost calculator with measured demand.
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
- Header pressure and point-of-use pressure
- Delivered airflow at stated reference conditions
- Compressor input kW and operating hours
- Air-treatment pressure drop and pressure dew point
Maintenance Checklist
- Log pressure, temperature, load hours and alarms.
- Inspect accessible leaks and drain performance.
- Trend filter differential pressure and dryer dew point.
- Schedule lubrication and cooler servicing using OEM intervals.
Evidence-Based Diagnosis
Low delivery pressure
- Possible Causes
- Demand exceeds capacity; distribution leaks; restricted filters; inappropriate sequencing.
- Evidence To Collect
- Compare simultaneous pressure readings at the receiver and remote users. Review demand and compressor load history.
- Qualified Follow-Up
- Investigate leaks and restrictions, then have an authorised engineer review sequencing. Avoid raising pressure before diagnosing the loss.
High discharge temperature
- Possible Causes
- Reduced cooling; dirty cooler; lubricant issues; high inlet temperature.
- Evidence To Collect
- Compare inlet and discharge temperatures with the model manual; examine cooling airflow and recorded service history.
- Qualified Follow-Up
- Arrange cooler and lubricant inspection under isolation. Follow OEM trip limits; do not repeatedly reset temperature trips.
Water at point of use
- Possible Causes
- Dryer overload or malfunction; failed drains; distribution condensation.
- Evidence To Collect
- Review pressure dew point, dryer alarms and drain operation against actual flow and ambient conditions.
- Qualified Follow-Up
- Service drains and dryer according to the manual and verify air quality before supplying sensitive equipment.
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.