Service & Support

I. Correct Selection and Application of Fans

1. Before selection, define the fan's intended use, draw the duct routing diagram, calculate the required flow rate and system resistance, and then choose a fan that matches.
2. If insufficient or excessive flow occurs the moment a new fan is put into use, the cause is usually deviation in the system-resistance calculation, or the selected fan operating in its surge / unstable region. If the flow gradually decreases over long-term use or drops sharply in a short time, the cause is usually duct-network blockage.
3. If a newly installed fan delivers insufficient or excessive flow as soon as it enters formal operation, the main reasons are:

   ① The actual duct-network resistance differs significantly from the calculated value.

   ② The fan was selected without accounting for its total-pressure deviation. A positive total-pressure deviation increases the actual flow; a negative deviation reduces it.

4. When excessive or insufficient flow occurs, either at first start-up or during normal use, any one of the following methods can be used to correct it:

   ① Adjust the flow with a throttling device.

   ② Change the fan speed to adjust the flow.

   ③ Replace the fan with one of higher or lower pressure rating to adjust the flow.

   ④ Change the duct-network resistance coefficient to adjust the flow.

II. Installation, Adjustment and Operation

(A) Installation and Adjustment

1. The foundation must be flat with sufficient strength and rigidity. The fan and motor must be protected by a rain shelter; never leave the equipment in the open or allow it to sink into mud or water.
2. Before installation, check all components: confirm that all parts and accessories are complete, that all connections are tight, and that rotating parts move freely.
3. Verify that no tools or foreign objects have been left inside the casing or other housings.
4. The weight of the inlet and outlet ducts (especially for boiler induced-draft fans) must not be transferred to the fan, and the shaft must remain horizontal — axial tilt can cause lubrication loss and bearing burnout.
5. After installation, rotate the impeller by hand or with a lever to check for binding or contact. The fan may only be test-run when the rotation is free and smooth.
6. For non-direct-drive (non-A type) fans during installation and subsequent maintenance, measure the alignment between the fan shaft and motor shaft and the face squareness of the pulley or coupling. Allowable misalignment between motor and fan: radial offset ≤ 0.05 mm; shaft inclination ≤ 0.2 / 1000.
7. Pre-assembled units shipped as a complete package can be placed directly on the foundation; whether to add vibration isolators depends on the specific situation.
8. Verify which lubrication type the bearing housing uses. For grease-lubricated new fans, the grease may be replaced after the first 2 months of operation. For oil-lubricated fans, regardless of whether the housing already contains oil, carefully check that the oil level is slightly above the centre line of the sight glass.
9. Induced-draft fan transmission groups use either air or water cooling. With air cooling, ensure no obstacles around the cooling fan; with water cooling, an external water circuit is required and must be unobstructed and leak-free.

(B) Operation

After installation and commissioning, the fan must be test-run before formal operation. Starting current must not exceed 6.5 times the rated current.

Test-run requirements for axial-flow fans:

① The motor rotation direction must be correct; the number of blades, blade angle and motor power must match the documentation supplied with the fan.

② All control valves and dampers must be fully open.

③ Rotate the impeller by hand — the fan must turn freely.

④ Personnel must stay clear of the inlet and outlet ducts.

⑤ After start-up, monitor every part of the fan for abnormal conditions.

⑥ If no abnormalities are detected, run the fan for about one hour before placing it into formal service.

Test-run requirements for centrifugal fans:

① Close the inlet damper; leave the outlet damper slightly open.

② Check the clearances between fan parts; rotating components must not contact stationary ones.

③ Check that the bearings are properly lubricated and in good condition.

④ Check that the pulley, belt or coupling is reliably installed.

⑤ Rotate the moving parts by hand — they must move freely without obstruction.

⑥ Briefly jog the fan and confirm the impeller rotation direction is correct.

⑦ Gradually open the inlet and outlet dampers, watching that motor current does not exceed the rated value.

⑧ If no abnormalities occur, run the fan for about one hour before placing it into formal service.

(C) Shutdown Precautions

① The fan should normally be stopped under light load. After shutdown, the inlet and outlet dampers should be fully closed.

② When water cooling is in use, close the cooling-water valve only after the fan has stopped.

③ When handling hazardous gases, ensure no leakage from any part of the system.

④ For induced-draft fans handling high-temperature gas, the fan may only be stopped when the gas temperature inside the casing has dropped below 100°C.

⑤ For prolonged shutdown, apply rust-preventive coating to corrosion-prone parts.

⑥ For prolonged shutdown, rotate the rotor by 180° at regular intervals to prevent static deflection of the shaft.

III. Fan Maintenance

Maintenance Discipline

① The fan may only operate when all equipment is in fully normal condition.

② Periodically clean dust, dirt and water from inside the fan and ducting, and prevent corrosion.

③ Repairs to fan equipment must never be performed while the fan is running.

Things to Watch During Normal Operation

① If the flow becomes too high for the application, or a temporarily lower flow is required, use a throttling device to adjust it.

② Periodically check the sensitivity of thermometers and oil-level gauges.

③ During start-up, shutdown or operation, immediately investigate any abnormality.

④ Replace lubricating oil after every disassembly / repair, and inspect rolling bearings on a regular schedule (every 3 months).

IV. Common Faults, Causes and Remedies

Possible Fault	Cause and Remedy
Fan fails to start	System resistance too low (centrifugal fan) or too high (axial fan), causing excessive starting current; or fault in start-up circuit / equipment. Inspect carefully against the operating-requirement checklist.
Bearing housing leaks oil	Bearing housing tilted or over-filled with oil. Re-level the housing and observe the oil level.
Severe fan vibration	1. Impeller contacting the inlet during rotation — adjust the clearance. 2. Impeller dynamic balance disturbed — check for accumulated dust or foreign objects. 3. Anchor bolts loose — tighten the connections.
Excessive temperature rise of motor or bearing	1. Severe fan vibration — find the root cause. 2. Bearing damaged — replace the bearing. 3. Insufficient lubrication or cooling — top up the lubricant; check the cooling-water circuit.
Excessive motor current	1. Insufficient system resistance, motor overloaded — install a throttling valve. 2. Bearing damaged — replace the bearing. 3. Voltage too low or motor missing a phase — inspect the electrical equipment.