How to prevent centrifugal pump from running dry

From the design point of view, the placement of dry running depends on what is in front and behind the pump, what kind of pump, and what kind of process is suitable for design. I think that frequent emptying can definitely indicate that the operator is not dedicated, because once an emptying accident occurs, then this will be a key place for future inspections. If the same accident occurs frequently, what is not being disloyal? Is the design unreasonable? Once an unreasonable design is found, it must be monitored carefully to prevent accidents until it is rectified to a reasonable level.

The simplest method is to add a liquid level switch. When the liquid level of the container connected to the inlet is lower than a certain value, the liquid level switch will act and the pump will automatically stop. This is easy to achieve. If there is no container, other aspects can also be considered, and other signals can be used to automatically control the operation and stop of the pump, such as pressure, flow, etc.

Install a tuning fork switch on the pump inlet pipe. When the pump is empty, the tuning fork frequency signal is reversed and the pump automatically stops.

Mechanical seals are often damaged due to the entry of mechanical impurities or dry running of the pump. Pay attention when designing the process! The situation mentioned by the poster should be due to the following reasons:: 1) There is air leakage at the pump inlet and no water supply. 2) The power of the pump is too large and the system does not match. 3) The temperature of the material is too high, causing cavitation. Please check carefully, if this is the case, an automatic control device can be installed. :handshake

You can add low liquid level lock in dcs.

The float level gauge can be used to control the start and stop of the pump by itself. It starts when a certain liquid level is reached and stops when the liquid reaches a certain level. In addition, it prevents emptying. It can also transmit the pressure of the pump to the control room remotely. When the pressure drops, the DCS will directly stop the pump.

Dry running conditions can also have other adverse effects on the pump, which are best avoided. If you just want to protect the mechanical seal, but think the instrument control is too expensive, the simplest way is to protect the mechanical seal through cooling water. There is a part in our company where the lower layer is water and needs to be drained, and the upper layer is medium-high viscosity material. The centrifugal pump transports very slowly and will burn the mechanical seal. At the beginning, we also asked the operators to pay attention, but the mechanical seal still often burns. Now we add cooling water to the mechanical seal, and there has been no problem again.

The simplest way: Just install a U-shaped elbow in front of the pump. :lol Experience, this is all experience.

Choosing different seal flushing solutions according to usage conditions can help prevent mechanical seal burnout, which requires close cooperation between the design department's process and machinery. In addition, on-site inspections by operators are also very important.

Very simple! Just look at the liquid level gauge! If there is no magnetic drive, there will be no mechanical seal! :lol

Our company's pumps often dry-run and burn out the mechanical seals. The operators are very concerned about when the pump will empty out, but the possibility of negligence is still common. I don't think the operators should be blamed for not being dedicated enough. The key is how to prevent dry-runs through design. Do you have any good methods? To ask if you have any good methods, you must first analyze the reason why the pump often evacuates, whether it is due to the quality of the pump or process operation problems, whether the operating medium and operating parameters match the pump model, and whether the process pipeline has excessive resistance or is blocked. Only by finding the cause can we solve it. Of course, for insurance, you can add a low pump outlet flow interlock shutdown circuit. The key is to find the reason why your pump is idling.

If the DCS and FCS control systems are easy to implement, just program a low-level pump stop or frequency modulation program based on the liquid level. If cavitation is caused by excessive material temperature, the temperature can be controlled or the pump can be stopped at high temperature. If it is a smaller or simple device, a float can be installed on the container in front of the pump and used to interlock with the pump switch using a lever. The low position contacts the stop button of the pump switch and the high position opens the pump. Our workshop originally had an automatic alkali pump that was controlled in this way. It was simple but practical and was made by the master workers 20 to 30 years ago.

1. Add a float control valve for automatic water replenishment 2. Set up a low-level interlock in the pool

It is related to the pump starting method, material properties and pipeline design. 1. Start the pump and start it. 2. For material impurities, a filter is added in front of multiple pumps to be switched and cleaned regularly. 3. The flow rate of the pump, the liquid level of the tank in front of the pump and the pump switch are interlocked. 4. The mechanical seal cooling system ensures normal operation. If it still doesn't work and idling still occurs, I think the poster should replace the magnetic pump, which has no mechanical seal.

It is better to strengthen personnel management. It is meaningless to add any anti-idling device. Today, an anti-idling device for pumps has been released. If personnel management is not strengthened, other problems will arise!

Set up a resistance meter at the inlet or a flow meter at the outlet, and set flow and resistance value alarms. In addition, regular inspections must be strengthened to avoid accidents! ! ! :handshake

1. A dry running protection can be installed. 2. The root cause is to check whether the designed inlet resistance meets the requirements (NPSH). 3. From the mechanical seal point of view, when the liquid medium is self-cooled or circulated, check the condition of the process medium to see if there is crystallization or impurities entering the mechanical seal (whether the inlet filter has been removed by bad actors). 4. Is there any quality issue with the mechanical seal itself, and did the installer install it correctly? Aspects that need to be considered for pump evacuation include: 1. The pressure of the liquid level in the tank or tower 2. The density of the liquid 3. The saturated vapor pressure of the liquid at the operating temperature 4. The resistance of the suction pipe 5. The cavitation allowance

Our company's pumps often dry-run and burn out the mechanical seals. The operators are very concerned about when the pump will empty out, but the possibility of negligence is still common. I don't think the operators should be blamed for not being dedicated enough. The key is how to prevent dry-runs through design. Do you have any good methods? In this situation like what the poster said, it is necessary to clean out the materials in the storage tank. I give you the following suggestions: 1. Pay attention to the liquid level in the storage tank, and judge whether the pump is empty by listening to the sound of the pump or looking at the pump outlet pressure. If it is empty, just stop the pump according to the regulations. 2. If no one is monitoring the site, an anti-idling switch can be installed to automatically stop the pump by detecting the pump current when idling. 3. You can consider replacing the pump with a clutch-type mechanical seal. This type of pump is not afraid of idling and we use it a lot. 4. If the pump has been idling for a period of time without any discovery. At this time, the pump must be allowed to cool down for a period of time before conveying. Otherwise, the machine seal will be damaged due to sudden cooling.