Rules for Safe Operation of gate valves and centrifugal pumps How to reasonably deal with the cavitation problem of centrifugal pumps

Rules for Safe Operation of gate valves and centrifugal pumps How to reasonably deal with the cavitation problem of centrifugal pumps

Pump is a liquid industrial production device, its role like the heart of the human body, for the system in the equipment in the liquid increase power, to ensure the normal operation of the production process. Common pumps are divided into axial piston pumps, positive displacement pumps, special function pumps, etc. Wherein, the centrifugal pump in the axial piston pump is used as. Centrifugal pump operation must prevent several problems: stop pump water hammer and less than small flow. There are many ways to deal with these two problems, but basically the idea is all the same
Pump is a liquid industrial production device, its role like the heart of the human body, for the system in the equipment in the liquid increase power, to ensure the normal operation of the production process. Common pumps are divided into axial piston pumps, positive displacement pumps, special function pumps, etc. Wherein, the centrifugal pump in the axial piston pump is used as.
Centrifugal pump operation must prevent several problems: stop pump water hammer and less than small flow. There are many ways to deal with these two problems, but basically the concept is how to tightly around the centrifugal pump equipped with a set of appropriate system software. Gate valves play a vital role in various systems, but with the increasing recognition of these two problems, there are many gate valves.
1. Stop pump water hammer protection and gate valve water hammer is a series of water hammer phenomena caused by the drastic change of medium flow velocity in the second type pressure vessel. Water hammers can be particularly harmful, destroying pumps, pipes and other machinery. There are many factors caused by the water hammer in the working pressure pipeline, such as the rapid closure of the valve, abnormal stop of the pump and so on.
Stop pumping water hammer principle
When abnormal reasons, such as power off, the pump stops working: at the beginning, the material in the pipeline continues to move forward with the help of inertial force, but the speed slowly decreases to zero; At this time, if the pipeline design has many ups and downs, the material under the action of gravity will be pump countercurrent; When the countercurrent material reaches a certain rate, the pump outlet check valve will quickly shut off, so that the rate of many media arriving here suddenly becomes zero, resulting in a substantial rise in the working pressure of the material here – caused by the stop pump water hammer. Many references emphasize that the key to stopping the water hammer is the sudden closure of the check valve at the pump outlet. But studies have shown that although the pump outlet check valve can be closed in some cases, but in the vast majority of cases, in order to avoid a lot of material countercurrent into the centrifugal pump, the pump inlet anti-countercurrent Settings are necessary.
Stop pumping water hammer prevention countermeasures
There are many countermeasures to prevent water hammer damage from stopping the pump, such as the assembly of water hammer remover, pressure reducing valve, transformer tank, etc., the following is only a detailed introduction of two more commonly used, related to the general valve countermeasures.
1. Set the slow closing check valve
Slow closing check valve is a kind of check valve that realizes slow cancellation by adding actuator and shock absorber. Xinhua News Agency reporter set a schematic diagram of centrifugal pump stop pump water hammer protection system with slow closing check valve. At this time, slow closing check valve needs to be applied with stop valve (cut off valve). When the substance under the action of countercurrent, the check valve slowly closed, effectively prevent the general check valve suddenly closed caused by the water hammer. Its disadvantage is that due to the slow shutdown, a part of the material inevitably countercurrent into the centrifugal pump, and the pump may cause equipment failure.
2. Set the slow closing disc valve
This is a common and effective method used in all kinds of water conservancy systems. The slow closing disc valve is composed of butterfly valve, operating structure and hydraulic transmission system. Xinhua News Agency reporter set the centrifugal pump stop pump water hammer protection system diagram with slow closing disc valve. This system only needs to assemble the slow closing disc valve, which can play the function of the check valve and cut off the valve. When the centrifugal pump starts, it is opened according to the process of first slow and then fast, to ensure that the pump starts with low load; When the pump stops working, it is turned off by the first fast and then slow process, which can not only prevent the formation of water hammer, but also avoid too much material countercurrent according to the pump, resulting in centrifugal pump equipment failure.
Two, prevent small flow working conditions and gate valves
Small flow is to ensure that the pump can operate normally flow. If the pump is working under the condition of less than the minimum flow, it will cause noise and vibration, the characteristics of the centrifugal pump will become unstable, and even cause abnormal cavitation of the centrifugal pump, reducing the service life of the pump. Therefore, effective measures must be taken to prevent the centrifugal pump from working under a small flow condition. At this stage, the widespread practice is to set a small flow control loop for the centrifugal pump. However, in terms of the use value of the centrifugal pump itself, it is only reasonable to set a small flow control loop for those centrifugal pumps with large flow, high head and large power. Centrifugal pumps allow this small flow value to be measured by the pump manufacturer or clear test.
Super simple flow control loop * must be assembled in the control loop a cut-off valve, such as the globe valve, when you feel that the pump will be in a small flow working condition to open the gate valve, access to the small flow control loop, to prevent the pump in a small flow condition.
Iii. Summary
The structure of the valve recommended above is the same as that of the general valve, but because of the corresponding improvement according to the working condition of the application, this gate valve becomes to deal with these two problems.
The cavitation problem of centrifugal pump how to reasonably deal with the cavitation problem of centrifugal pump, although it is not a very easy to deal with the problem, but as long as you can from each need to pay attention to the problem of effective control, or can complete the rational use of centrifugal pump. Today we will take the centrifugal pump manufactured by Shanghai Hongle Pump Factory Machinery Co., Ltd. as an example to see what aspects also need to pay attention to the problem. First of all, the liquid density, the higher the density of the liquid, the lower the relative height of the suction will be, if the centrifugal pump is used to transport the relative density is small, cavitation will occur, but the high density of the centrifugal pump is able to transport small relative density liquid
For centrifugal pump cavitation problem, although it is not a very easy to deal with the problem, but as long as you can from each need to pay attention to the problem of effective control, or can complete the rational use of centrifugal pump. Today we will take the centrifugal pump manufactured by Shanghai Hongle Pump Factory Machinery Co., Ltd. as an example to see what aspects also need to pay attention to the problem.
First of all, the density of the liquid, the higher the density of the liquid, the lower the relative height of the suction, if the centrifugal pump is used to transport the relative density is small, cavitation will occur, but the high density of the centrifugal pump is able to transport a small relative density of liquid, so it is necessary to transport the liquid density difference to select the centrifugal pump; Transport liquid environment temperature also need to pay attention to, because the temperature rise will harm the contrast of liquid vapor, when the inlet working pressure will not change the state of conveying continuous high temperature liquid, the pressure difference will be expanded, resulting in cavitation; Therefore, application companies also need to choose from different criteria.
Second, when the suction pipe water pressure is large, the inlet working pressure will be accompanied by an increase, and in the reverse case, the channel working pressure will be reduced, which is also one of the important factors causing cavitation. Is the transport of volatile liquid, under the premise of constant ambient temperature, volatile liquid saturated vapor pressure is higher than the general liquid, centrifugal pump is cavitation condition.
In summary, the suit to choose their own centrifugal pump is indispensable, but also to prevent the occurrence of cavitation is the key factor, can not be scientific and reasonable application of centrifugal pump is the main reason for the problem. The author’s summary here, I hope to be able to give you some support.