Air-only testing: reliable decisions depend on stated operating conditions, material evidence and equipment limits. An air-only test operates a pneumatic conveying line without feeding solids. It establishes the aerodynamic resistance of the empty route and provides a baseline for commissioning, blower verification and future troubleshooting. The test cannot prove material capacity, but it can reveal whether the installed air system matches the design before bulk solids are introduced.
What the Test Measures
At controlled blower speeds, the commissioning team records airflow, blower inlet conditions, discharge pressure, pipeline pressure, air temperature, motor current and receiver-filter differential pressure. The results show how empty-line resistance changes with airflow.
The measured baseline includes:
- Clean supply piping and silencers.
- Straight conveying pipe.
- Bends, valves and transitions.
- The open conveying route to the selected receiver.
- Receiver and clean-filter resistance.
- Air leakage present during the test configuration.
It does not include material acceleration, particle-wall friction, vertical solids lift or solids-related bend loss.
Prepare a Controlled Test Boundary
Before testing, the line should be mechanically complete, clean and safe to pressurize. Material feeding must be positively isolated according to the plant procedure. The selected route and every diverter position should be confirmed, and receiver venting must be available.
Protective devices, instrumentation ranges and shutdowns should be verified before increasing speed. An air-only run is not permission to bypass relief protection or operate against closed valves.
A Practical Test Sequence
- Record ambient pressure, inlet temperature and the condition of filters and valves.
- Start at the approved minimum package speed with no material feeding.
- Allow readings to stabilize and record airflow, pressure, temperature and motor current.
- Increase speed through planned test points within the model’s permitted range.
- Repeat the test for each normal destination or diverter route.
- Compare measured results with the predicted empty-line pressure budget.
- Save the baseline for later maintenance comparison.
Actual operating and site safety procedures take precedence over this general sequence.
Interpreting Higher-Than-Expected Resistance
An excessive pressure drop can indicate:
- A partly closed or incorrectly oriented valve.
- A blocked or contaminated receiver filter.
- A pipe bore smaller than specified.
- Internal deposits, protruding gaskets or misaligned liners.
- An incorrect diverter route.
- More bends or hose than shown on the calculation.
- An airflow instrument or pressure instrument error.
The investigation should locate the pressure increase by comparing readings at available taps rather than raising blower speed immediately.
Interpreting Lower-Than-Expected Resistance
A low measured pressure can result from insufficient blower speed, belt slip, an open branch, air leakage, a relief valve passing air, incorrect flow compensation or a route shorter than the design case. Low pressure is not automatically evidence of good efficiency; the actual airflow must also be verified.
Adding Material Changes the Operating Point
Once the feeder starts, pressure rises because energy is transferred to the solids. The difference between loaded and empty operation contains the effects of particle acceleration, elevation, bends, wall interaction and solids concentration.
If loaded pressure is excessive while the air-only baseline remains normal, attention should shift toward material properties, feed rate, feeder surging, deposits or an unsuitable conveying mode. If both baselines are high, the aerodynamic route or filter may be responsible.
Value for Roots Blower Selection and Maintenance
The air-only curve confirms whether the installed Pasifik roots blower package delivers the expected airflow against the empty-line resistance. It also creates a maintenance reference. A gradual rise in pressure at the same speed and corrected airflow can indicate filter loading, internal deposits or route deterioration.
Final model acceptance still requires a controlled loaded test with representative material. The blower must remain within approved pressure, speed, motor-power and discharge-temperature limits under the maximum credible solids duty.
Glossary
Air-only baseline: Recorded empty-line relationship among blower speed, airflow and system pressure.
Empty-line resistance: Pressure loss of the conveying route without transported solids.
Loaded test: Commissioning run conducted with representative material at controlled solids flow.
Pressure tap: Connection used to measure static or differential pressure at a pipeline location.
Route verification: Confirmation that valves and diverters connect the tested feed and receiving points.
Stabilized reading: Measurement taken after transient start-up effects have sufficiently settled.
Test boundary: Defined equipment and pipeline included between the measurement reference points.
Test point: Planned combination of speed, flow and recorded operating conditions.