Pump operating problems

Is it because pump B is on the bypass path and the outlet resistance is too high under the influence of the elbow?

Installation problems, check the pipeline

It’s probably not because this has only appeared recently. In the past, these two pumps were running normally. I think we should start with the pumps themselves.

The poster posted such important information only for the second time, haha. If you want to start with the pump, then check the bearings of pump B, or there may be a problem with the bearing wear monitoring device. Are you using a canned pump from Dalian Empire? Ask the after-sales department and the measures may be more targeted.

Do you have pressure gauges before and after your pump? Are the two pumps connected in parallel to one pipeline or are they connected to the container separately?

study* , be sure to pay close attention to

This situation is so incredible that it probably has nothing to do with the pump itself. It may be related to the resonance between the foundation and the pipeline. It happens that the vibration frequency of pump B at a specific flow rate is consistent with the surrounding vibration frequency, forming a resonance. Try to make certain changes to the foundation and surrounding pipes to eliminate resonance. It's possible. . . Especially for equipment that is not fixed to the ground.

Can we consider the following two aspects?: 1. There is a problem with the pump itself. This aspect should be checked. The structure of the canned pump is very simple. If there is a problem with the pump itself, the problem can be found during the switching process. According to your description, the problem with the pump itself is not big. ； 2. Operational problems. This aspect is more likely to be caused by a replacement operator, incorrect operation method, air in the pump, or when the outlet valve of station A is about to close, the valve setting of the entire outlet pipeline is inappropriate, causing a sudden increase in flow of station B, causing vibration.

Thank you for your enthusiastic help. Just like what CY3M said, it is incredible. I have never seen such a situation. 1. It is indeed a canned pump from Dalian Empire. 2. There is a pressure gauge behind the pump and two pressure gauges use the same pipeline. 3. There is no problem with the operation. I wrote the operation card. I was there when I did the operation. If there is a problem, it should be a problem before. It is impossible to say that there is a sudden increase in flow, because when switching, the emphasis is on slowness and not causing process fluctuations, which means turning off pump A. The inlet valve does not close quickly, so it is not true that the inlet flow of B pump suddenly increases. After the B pump is started, the pressure gauge is very stable, including when it finally starts to vibrate. It may be because of the problem of the oil gauge. I can't figure it out. I prefer the resonance explanation of CY3M. I will do experiments and equipment some other day. This is how I get along with some equipment. Maybe it will be better next time. Welcome everyone to continue to pay attention and think about the possible reasons. After all, this kind of situation is rarely encountered.

Will there be any problems if A is stopped first and then B is started without using the normal pump reversing operation? Have you tried it before?

1. How long has pump B been actually used? Has it been inspected during this period? 2. When pump B was running some time ago, did any abnormal phenomena occur, such as dry grinding due to shortage of bearing lubricant? 3. When you need to switch to pump B, extend the co-running time with pump A, and then press the operation card to switch. ； 4. Check whether pump B is within its installation accuracy requirements. After long-term use, some pumps will loosen themselves and loosen from the foundation. You can use thin copper sheets to adjust the level. 5. Perform maintenance on pump B, focusing on checking the graphite bearings. Watch this pump. . .

While gradually closing the outlet valve of pump A, the flow rate of pump B will gradually increase, and the load of the pump will also gradually increase. This is the cause of the vibration. The real reason should be to dismantle and inspect pump B and the pipeline. If the pump is small, there is no need to consider the foundation.

62343404 said, instead of using the normal reverse pump operation, stop A first and then start B. I think so too, but I haven't dared to implement it yet. I'm afraid that the process director will do it to me. I'll ask the equipment director for instructions and let them do it. After I implement it, I will tell everyone the results!

I think it's pump B that's faulty. When outlet A is closed, the amount of pump B increases.； As soon as B is measured, it is loaded, because the vibration is high due to mechanical failure.

Hehe announced the answer. When the outlet valve of pump B was running alone and had an opening of about 4 clicks, it started to vibrate strongly. Today I opened the pump and the gap between the bearing and the sleeve reached more than 80 steps. The normal gap is 15 steps. Analyze the reason. : When the two pumps are running, pump A is about to shut down and pump B is really pumping up. As a result, eddy currents are generated when the liquid phase flows through, causing violent vibrations in the gap between the motor and the rotor. When the opening of the outlet valve is very small, the liquid in the pump chamber is self-circulating. I am not very clear here. I guess it has something to do with fluid mechanics. The vibration is not very big. I hope you can help me analyze it carefully. The initial suspicion is correct, and there is indeed a problem with the pump body, but there are two problems.: 1. When the outlet valve of pump B (problem pump) is fully open and the outlet of pump A is almost closed, does pump B experience strong vibration? 2. Why does pump B not vibrate after starting, but only vibrates after excessive use? What are the characteristics of the fluid and pump?

I feel that when pump A is about to shut down, the liquid creates a vortex in the pipe. The increase in temperature of the liquid will cause some of the gas in the liquid to escape, causing slight cavitation at the suction port of pump B. After a while the vibration of the pump will decrease!

Answer 1 Maybe pump A is easier to suck in the liquid than pump B: When the outlet valve of pump A is not closed or closed to a small extent, pump B may inhale less material liquid, resulting in a near-idling operation. When the outlet valve of pump A is about to close, most of the material is sucked in by pump B. Due to the gap problem, the vibration is strong. Possible reasons for different inhaled feed liquids include:: Piping configuration factors of pumps A and B ； Is the flow rate of the canned pump not large? When pump A is running, the material liquid still takes a shortcut when pump B is turned on. Could you please post a simple piping diagram of the AB pump? You can analyze it based on the pipe diameter and distance. ； The possible reasons for the enlarged gap of pump B are:: A is the main pump and B is the backup pump. The time of each switching may be too long, causing the B pump to frequently run almost idling, and the graphite bearings will suffer from increased wear due to the lack of cooling and lubrication of their own material liquid. Answer 2 If there is a lot of vibration when pump B is started, then the bearing wear has reached an extremely serious condition, and the monitoring device has not fulfilled its mission well - to control the damage in the early stages. Before the pump reaches full load, the internal circulation of the liquid and the smooth flow of the outlet may not affect the strong vibration of the pump. ； When excessive, a large pressure is formed at the outlet, and the internal material liquid looks for a way out, directly causing the worn bearing to vibrate. These are all taken-for-granted ideas, so please take a look.

Thank you to friends Dingdang and all the friends above for their help. The pipelines are arranged in a "herringbone" shape, so there is no problem of rushing for quantity. I have carefully observed the conditions of the disassembled bearings and the pump body because there is such a situation. It has been about half a year since the start of the construction. The filter may have been cleaned because the finished product was very clean. After disassembly, there were indeed some impurities with relatively large particles and ground graphite bearings on the ground. As for the two questions I asked, Ding Dang answered them in agreement, because the outlet pressure of this pump is 0.8MPA. Therefore, it is difficult to switch the valve on and off during switching, which results in a long switching time. During normal operation, it is not possible to hold the pump running for more than 5 minutes. In fact, it is not exceeded, but this happens every time when switching. The above problems can also occur after such a long time. This also makes me understand a problem. When switching pumps, it is best to do it with two operators. If there is not enough manpower, you should first open the outlet valve of the backup pump half way. Shut down the main pump to prevent trace amounts of cavitation from causing damage to the pump. This damage can only be seen after a long time. Another thing is that there is another pump that is being repaired at the same time as this pump. It usually hovers between the green line and the yellow line. After opening it this time, the wear is quite serious and needs to be returned to the factory for repair. It seems that once the canned pump vibrates to the end of the green line, it is best to replace the bearings and sleeves immediately. Otherwise, when the yellow line is reached, it will not be said that the rotor is already worn.

There is a problem with pump B. There may also be a problem with the outlet check valve of pump B.

Thank you very much for asking this question and I learned a lot! In fact, this kind of post is very meaningful. In a word, strict maintenance of operating equipment must be ensured.