What are the hazards of reversing a Roots blower?

The Roots blower used in our factory is equipped with an oil pump attached to the shaft; if it runs in reverse, oil from the main oil tank cannot be pumped into the other set of bearings, which will result in the bearings being damaged. We have experienced such a tragedy, and the memory remains vivid.

Under normal operation, a check valve is installed at the outlet of the Roots blower; therefore, if the motor is connected in reverse, the inlet will become blocked, negative pressure will increase, and the motor will overload. Structurally, the impeller can be reversed; it’s just that the installation method varies when it is used in conjunction with other components

When the Roots blower runs in reverse, in mild cases this can damage the impeller (the impeller has stressed and unstressed areas due to its clearance settings, and running in reverse causes the unstressed area to come into contact)； Bearing damage (no need to say more about this). In severe cases, the gear teeth break (commonly known as root cutting). Therefore, when operating a Roots blower, it is still necessary to follow the principle of \"starting under no-load conditions and stopping with reduced load.\"

Under normal operation, centrifugal fans are not allowed to reverse suddenly; reversing a two-blade fan can cause the rotor to break immediately. Gear damage can also occur in three-blade fans. The best way to address this issue is to install a check valve, and it is important to ensure that the check valve can close properly. 　　Under normal circumstances, a Roots blower can be reversed, but this must be done with the blower stopped. If it is to operate in reverse for a long period, the fan must have its front and rear end face clearances adjusted before leaving the factory. A sudden power outage of the fan, or a drop in pressure at the outlet, can cause the fan to rotate in the opposite direction due to forward inertial force and backpressure at the outlet. This can result in the destruction of the fan’s gears and couplings; in severe cases, it may even damage the rotor or the entire fan. 　　Rotary vane blowers can be reversed, but it is generally required to disconnect them from the existing piping before doing so, and reversal must take place only after the blower has come to a complete stop. When the fan stops due to a power outage, the rotor and coupling are often damaged; it is advisable to install check valves ahead of the fan outlet or at the fan outlet itself to prevent back pressure in the pipeline from affecting the fan.

We have seen the situation mentioned upstairs where the coupling breaks down in the field. Upstairs: handshake

Reversing a Roots blower can easily damage the gears and impeller

If a fan operating normally suddenly stops and then reverses direction, it is easy for the impeller to get damaged; such accidents occur very frequently

Under normal operating conditions, some rotary vane blowers are designed with equal clearances on both sides, which allows them to operate in reverse