The pump is the central installation of the fluid industry. Its function is like the heart of the human body, providing power for the fluid in each installation in the system and ensuring the normal operation of the process flow. Commonly used pumps are divided into vane pumps, positive displacement pumps, special purpose pumps, etc. Among them, centrifugal pump in vane pump is widely used.

離心泵運轉過程中需求防止兩個問題：停泵水錘和低于小流量。處理這兩類問題，辦法較多，但根本思想都是如何盤繞離心泵配置一套適宜的系統。在這些系統里閥門起著十分重要的作用，而且隨著這兩類問題認識的加深，降生了許多專用閥門。

Two problems need to be prevented during the operation of centrifugal pump: water hammer when stopping the pump and low flow. There are many ways to deal with these two kinds of problems, but the fundamental idea is how to coil the centrifugal pump and configure a suitable system. In these systems, valves play a very important role, and with the deepening understanding of these two kinds of problems, many special valves have been born.

一、停泵水錘維護與閥門

1、 Pump stop water hammer maintenance and valve

水錘是壓力管道中介質流速的猛烈變化惹起的一系列急劇的壓力交替升降的水擊現象。水錘的危害十分大，能夠擊毀泵、管路以及其它設備。壓力管道中的水錘產生緣由有很多，比方閥門的快速關閉、非正常停泵等。

Water hammer is a series of sharp water hammer phenomena of alternating pressure rise and fall caused by the violent change of medium velocity in the penstock. Water hammer is very harmful and can destroy pumps, pipelines and other equipment. There are many reasons for the water hammer in the pressure pipeline, such as the rapid closure of the valve, abnormal pump shutdown, etc.

停泵水錘產活力理

Shut down the pump and water hammer to produce energy

當因非正常緣由，比方斷電，泵忽然中止工作：初始階段時，管道內的介質依托慣性繼續行進，但速度逐步減為零;此時，假如管道布置存在上下落差，介質在重力的作用下將向泵倒流;當倒流介質到達一定速度時，泵出口處的止回閥將疾速關閉，這樣，抵達此處的大量介質的速度忽然變成零，惹起此處介質壓力急劇升高—停泵水錘產生。大量文獻指出，停泵水錘產生的主要原是水泵出口處的止回閥忽然關閉。但有研討標明，固然某些狀況下泵出口處的止回閥能夠取消的，但大多數狀況下，為避免大量介質倒流進離心泵，泵出口處的防倒流設置是必需的。

When the pump suddenly stops working due to abnormal reasons, such as power failure: in the initial stage, the medium in the pipeline continues to travel relying on inertia, but the speed gradually decreases to zero; At this time, if there is an up-down drop in the pipeline layout, the medium will flow back to the pump under the action of gravity; When the backflow medium reaches a certain speed, the check valve at the pump outlet will close quickly. In this way, the speed of a large amount of medium arriving here suddenly becomes zero, causing a sharp rise in medium pressure here - pump stop water hammer. A large number of documents pointed out that the main reason for the water hammer caused by stopping the pump was the sudden closure of the check valve at the outlet of the pump. However, some studies have shown that although the check valve at the pump outlet can be cancelled in some cases, in most cases, the anti backflow setting at the pump outlet is necessary to avoid a large amount of medium backflow into the centrifugal pump.

停泵水錘防止措施

Measures to prevent water hammer when stopping the pump

防止停泵水錘危害的措施有許多，比方裝置水錘消弭器、泄壓閥、調壓罐等，以下只引見兩種應用較多、與通用閥門相關的措施。

There are many measures to prevent the harm of water hammer caused by pump shutdown, such as installing water hammer eliminators, pressure relief valves, pressure regulating tanks, etc. the following only introduces two measures that are widely used and related to general valves.

1、設置緩閉止回閥

1. Set slow closing check valve

緩閉止回閥是一種經過增加執行機構、阻尼器而完成遲緩關閉的止回閥。上圖為裝置有緩閉止回閥的離心泵停泵水錘維護系統簡圖，此時緩閉止回閥需求配合閘閥(開關閥)運用。當介質在重力作用下倒流時，止回閥遲緩關閉，有效地防止了因普通止回閥忽然關閉產生的水錘。其缺陷為由于關閉速度較慢，一局部介質不可防止地倒流進入離心泵，泵因而可能會產活力械毛病。

Slow closing check valve is a kind of check valve that completes slow closing by adding actuator and damper. The above figure is the schematic diagram of the water hammer maintenance system of centrifugal pump with slow closing check valve. At this time, the slow closing check valve needs to be used with the gate valve (on-off valve). When the medium flows back under the action of gravity, the check valve closes slowly, effectively preventing the water hammer caused by the sudden closure of the ordinary check valve. Its defect is that due to the slow closing speed, a part of the medium cannot be prevented from flowing back into the centrifugal pump, so the pump may have mechanical problems.

2、設置緩閉止回蝶閥

2. Set slow closing check butterfly valve

這是一種在大型水利系統中應用比擬普遍、效果比擬好的辦法。緩閉止回蝶閥由蝶閥、執行構造及液壓控制系統構成。上圖為裝置有緩閉止回蝶閥的離心泵停泵水錘維護系統簡圖。該系統只需裝置緩閉止回蝶閥即可，即能起到止回閥的作用又能起到開關閥的作用。當離心泵開啟的時分，其按先慢后快的步驟開啟，保證泵低載開啟;當泵忽然中止工作時，其按先快后慢的步驟關閉，即能夠防止水錘的產生，又能夠防止過多的介質倒流經過泵，惹起泵的機械毛病。

This is a method which is widely used and has good effect in large-scale water conservancy system. The slow closing check butterfly valve is composed of butterfly valve, executive structure and hydraulic control system. The above figure is the schematic diagram of water hammer maintenance system of centrifugal pump with slow closing check butterfly valve. The system only needs to install slow closing check butterfly valve, which can play the role of check valve and on-off valve. When the centrifugal pump is started, it shall be started slowly and then quickly to ensure that the pump is started under low load; When the pump suddenly stops working, it will be shut down according to the steps from fast to slow, which can not only prevent the generation of water hammer, but also prevent too much medium from flowing back through the pump, causing mechanical problems of the pump.

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