**The impact and countermeasures of Roots blower reversal**
Roots blowers are designed as unidirectional rotating equipment. If they undergo reverse rotation (i.e. running in the opposite direction to the design direction), it can cause a series of problems and even damage the equipment. The following is a detailed analysis:
---
**1、 The consequences of reversing the Roots blower**
**1. Rotor collision damage**
-The two rotors of the Roots blower maintain non-contact meshing through synchronous gears, and there is a small gap (0.1~0.4mm) during normal rotation.
-When reversing, the gear meshing relationship is disrupted, and the rotor may collide directly, resulting in:
-Wear and deformation of impeller
-Gear tooth breakage or misalignment
-Bearing damage
**2. Reverse airflow leads to decreased performance**
-During normal operation, gas is drawn in from the intake port and forced out from the exhaust port.
-When reversing, the airflow direction is opposite, resulting in:
-The exhaust port has turned into an intake port, and the system cannot establish pressure.
-The intake port becomes the exhaust port, which may suck in external impurities such as dust and water vapor.
**3. Lubrication system failure**
-The gearbox lubricating oil pump of some Roots blowers relies on correct steering to supply oil properly.
-Reversal may lead to:
-Poor lubrication of gears accelerates wear
-Bearing overheating due to lack of oil
**4. Motor overload**
-When reversing, the load characteristics of the fan may change, which may lead to:
-Abnormal increase in current
-Motor overheating or even burning out
---
**2、 Common reasons for reversal**
1. * * Power wiring error**
-The phase sequence of the three-phase motor is reversed (such as L1, L2, L3 sequence error).
2. Belt installation error**
-Cross installation of belts leads to reverse transmission (only affecting belt transmission models).
3. * * Human error operation**
-After repair, the steering was not checked and started directly.
4. * * Inverter parameter setting error**
-The output phase sequence of the frequency converter is reversed.
---
**3、 How to determine if the Roots blower is reversing**
**1. Observe the turn mark**
-The fan casing or motor is usually marked with a * * rotation direction arrow * * (such as "CW" clockwise or "CCW" counterclockwise).
-Observe whether the actual steering is consistent with the markings when starting.
**2. Airflow testing**
-Short time jog start, feel with your hand whether there is airflow discharged from the exhaust port (normally strong airflow).
-If there is no air or suction at the exhaust port, it may reverse.
**3. Listen to the sound**
-During normal operation: a uniform "buzzing" airflow sound.
-When reversing: may be accompanied by metal friction noise (rotor collision).
---
**4、 Measures for handling after reversal**
**1. Immediately stop the machine**
-Immediately cut off the power after discovering the reversal to avoid continuous operation and damage to the equipment.
**2. Check and correct the steering**
-* * Three phase motor * *: Swap the two-phase power lines arbitrarily (such as swapping L1 and L2).
-Belt drive: Adjust the belt layout (parallel instead of intersecting).
-Variable frequency control: Check the phase sequence parameters of the frequency converter or install a phase protector.
**3. Check for damage**
-Manually rotate and confirm if the rotor is stuck or making abnormal noises.
-Check if the gear meshing is normal (such as broken teeth, misalignment).
-If serious damage is found, the rotor, gear, or bearing needs to be replaced.
**4. Try running again**
-After correcting the steering, conduct a no-load jog test to confirm:
-Turn correctly
-No abnormal noise
-Normal current
---
**5、 How to prevent reversal**
1. * * First start-up must check the steering direction**
-After installation or maintenance, first test the steering by tapping, and then proceed with formal operation.
2. * * Install phase protector**
-Automatically detect power phase sequence and prohibit startup in case of errors.
3. * * Clearly marked**
-Mark the correct rotation direction on the motor and fan.
4. * * Regular maintenance**
-Check the condition of gears and bearings to avoid accidental reversal due to component wear.
---
**6、 Special case: reversible Roots blower**
-A few customized models are designed for bidirectional rotation, but they must meet the following requirements:
-The rotor profile is symmetrical (such as a two blade profile).
-The gearbox lubrication system is compatible with both forward and reverse rotation.
-Ordinary Roots blowers are strictly prohibited from reversing**
---
**Summary**
-Reverse rotation poses a great danger: it may cause rotor collision, gear damage, and performance failure.
-Correction method: Swap the power phase sequence or adjust the belt.
-* * Preventive measures * *: It is necessary to check the steering and install phase protection when starting for the first time.
If you notice a reversal accompanied by abnormal noise, it is recommended to stop the machine for inspection and contact professional maintenance personnel if necessary!
