How to determine whether a centrifugal pump will experience cavitation

Cavitation phenomenon: 1. It generates noise and vibration, with a popping sound similar to that of beans bursting； 2 Corrosive damage to overcurrent components ； 3 Performance declines: the flow-head curve, flow-shaft power curve, and flow-efficiency curve all show a downward trend. In severe cases, it can cause the fluid flow in the pump to be interrupted. When cavitation occurs during operation, the flow rate can be reduced or the speed can be lowered ； To determine whether cavitation will occur, it is generally necessary to reduce the installation height!

It was explained quite clearly upstairs; therefore, when purchasing a pump, NPSHa must be greater than NPSHr. Otherwise, how much can the pump height be reduced?

It is also possible to add a liquid pouring wheel, which can increase the capacity by 0.5M. Another option is to replace the pump’s impeller; these modifications can be carried out by the manufacturer, but the options are quite limited. If that doesn’t work, then the only solution is to replace the pump

1. It is related to the installation height of the pump; reducing the installation height helps. 2. The temperature of the medium – higher temperatures can lead to vaporization and thus cavitation. 3. The NPSHa value of the pump purchased must be greater than its NPSHr value

To prevent cavitation before starting the pump, the following steps should be taken: :handshake :handshake :handshake 1. First, remove any residual gas from within the pump； 2. When installing the pump, try to minimize the suction vacuum level as much as possible ； 3. In terms of operation, the temperature at which the liquid is heated should be kept as low as possible ； 4. Reduce resistance losses in the pipelines ； 5. Minimize hydraulic losses in the suction pipe, so that the pressure of the liquid at the pump’s inlet is much higher than the saturated vapor pressure of the liquid. 6. Reducing the speed at which liquid enters the impeller, that is, lowering the pump’s rotational speed and flow rate, can also prevent cavitation. 7. Using an inducer wheel can also improve the cavitation of the pump. 8. Use materials with strong cavitation resistance to manufacture the impeller.

Hello! In my opinion, there are two aspects to consider. On the owner’s side: during the design phase, for media with specific properties (such as CO2, NH3, and other substances that easily vaporize), it is necessary to take into account NPSHa thoroughly. Factors such as the owner’s equipment setup, the length of the inlet pipelines, the losses associated with those pipelines, and the level of the liquid at the inlet also need to be considered. On the supplier’s side: as the manufacturer of the pump, they need to determine the appropriate pump model based on the NPSHa value specified by the owner. Generally, design firms require that NPSHa – NPSHr be greater than 1 meter; this is the standard requirement, and similar guidelines can also be found in API standards. Common solutions adopted by pump manufacturers include a) adding an impeller, b) reducing the pump’s rotational speed, or c) enlarging the inlet diameter. These are relatively simple and feasible solutions. More complex approaches involve using materials with better resistance to cavitation, among other options. Once the pump is installed… Only then does one realize that if the net positive suction head is insufficient, it becomes quite troublesome. Options such as 1 lowering the pump’s installation height, 2 installing an inducer wheel, or 3 pressurizing the inlet tank are all rather complicated solutions

“If it is determined that cavitation will occur, then measures need to be taken to prevent it. I didn’t quite understand what the original poster meant. In fact, when cavitation is caused by design issues, there are no measures available to prevent it; the only solution is to modify the design. If the design is sound and operations are carried out in accordance with standards, then cavitation will not occur

Before starting the pump, remove any gas from its interior. After starting it, listen to the sounds it makes and monitor the pressure gauge; if anything is abnormal, stop the pump immediately

Follow the specifications carefully and there will be no problems; fill it with water completely and release air before starting

Cavitation phenomenon: 1. There is noise and vibration similar to surging； 2. The pressure at the water pump inlet is below the required NPSHr value ； 3. The outlet pressure is unstable and low ； 4. A hole was found in the impeller during maintenance. Measures: (Different situations need to be considered) 1. Lower the installation height of the pump ； 2. Install a booster pump (such as a pipeline pump) ； 3. Add an imported pressure storage tank (connected to compressed air; one of our factory’s imported oil furnaces is equipped in this way) ； 4. Increase the size of the inlet filter screen (if the filter screen is too small, it will also limit the water supply volume).

When cavitation occurs, the shaft power of the pump decreases accordingly, and the current drops

When gas cannot be completely expelled, it is called gas entrapment. Gas erosion is caused mainly by the installation height, temperature, and local air pressure; the saturated vapor pressure of this solution is higher than the pressure at that location, so vaporization occurs and gas is generated. They’re two different things!

What? LZ asked, \"How to determine whether a centrifugal pump will experience cavitation?\" Check the NPSHr of the centrifugal pump and calculate NPSHa >= NPSHr + 0.3~0.5 m (water column)

Incomplete exhaust at the 16th floor is known as gas entrapment. Pump cavitation is mainly related to the installation height, as well as the temperature of the fluid being transported; higher temperatures increase the likelihood of cavitation occurring.

When installing the pump, try to reduce its installation height, increase the inlet pressure, and enlarge the diameter of the inlet pipe to minimize inlet resistance. During operation, strive to keep the temperature of the medium low and ensure a stable liquid level in the pump’s inlet tank