（1） Structural principle of medium and low pressure fire pump

中低壓消防泵也稱為串并聯離心消防泵，它主要由葉輪、泵軸、泵殼、前蓋、中蓋、進水活門、換向閥、機械密封裝置、引水裝置等組成。（以BCB40為例）

Medium and low pressure fire pump is also called series parallel centrifugal fire pump. It is mainly composed of impeller, pump shaft, pump shell, front cover, middle cover, water inlet valve, directional valve, mechanical sealing device, water diversion device, etc. (take bcb40 as an example)

中低壓消防泵的結構

Structure of medium and low pressure fire pump

1、葉輪蕌

1. Leaf whorl

BCB40泵有兩個葉輪，它們相對地安裝在泵軸上。

Bcb40 pump has two impellers, which are relatively installed on the pump shaft.

兩個葉輪各有單獨的進水腔室，而葉輪(2)的匯流出口始終與泵的出水口相通，葉輪(1)的匯流出口既可與泵出水口相通，也可與葉輪(2)的進水腔室相通。這樣葉輪(1)和葉輪(2)則可串聯供水，也可并聯供水。

The two impellers have separate water inlet chambers, and the confluence outlet of the impeller (2) is always connected with the water outlet of the pump. The confluence outlet of the impeller (1) can be connected with both the water outlet of the pump and the water inlet chamber of the impeller (2). In this way, the impeller (1) and the impeller (2) can supply water in series or in parallel.

2、泵殼與泵蓋

2. Pump casing and pump cover

泵殼與泵的前蓋、中蓋相配合，使泵內形成一定腔室，為兩個葉輪的工況變化創造條件。

The pump casing is matched with the front cover and middle cover of the pump to form a certain chamber in the pump and create conditions for the change of working conditions of the two impellers.

泵殼的水平兩側均設有吸水管，其中葉輪(1)和葉輪(2)的進水腔室在吸水管端部相隔開，并且與葉輪(2)相連的吸水管端口設有進水活門。泵殼的右側設有出水管，管上設有轉換閥，其閥芯的轉動可設定泵兩種工作狀態：使葉輪(1)的匯流出口與出水管相通，且與葉輪(2)的吸水腔室相隔造成兩個葉輪并聯供水。

The horizontal sides of the pump shell are provided with suction pipes, in which the water inlet chambers of the impeller (1) and the impeller (2) are separated at the end of the suction pipe, and the port of the suction pipe connected with the impeller (2) is provided with a water inlet valve. A water outlet pipe is arranged on the right side of the pump shell, and a change-over valve is arranged on the pipe. The rotation of the valve core can set two working states of the pump: the confluence outlet of the impeller (1) is connected with the water outlet pipe and separated from the water suction chamber of the impeller (2), resulting in the parallel water supply of the two impellers.

中低壓消防泵并聯工作狀態

Parallel working state of medium and low pressure fire pumps

使葉輪(1)的匯流出口與出水管相隔，且與葉輪(2)的吸水腔室相通，造成兩個葉輪串聯供水。

The confluence outlet of the impeller (1) is separated from the water outlet pipe and connected with the water suction chamber of the impeller (2), resulting in two impellers supplying water in series.

泵的前蓋和中蓋內均設有機械式軸封裝置。

Mechanical shaft sealing devices are set in the front cover and middle cover of the pump.

中低壓消防泵串聯工作狀態

Working state of medium and low pressure fire pump in series

3、轉換閥與進水活門

3. Change over valve and inlet valve

轉換閥與進水活門是中低壓消防泵的兩個關鍵環節，轉換閥處于串聯位置時，葉輪(1)的壓力水進入葉輪(2)的進水腔室，并在壓力下將活門關閉，使泵處于串聯供水狀態。當轉換閥處于并聯位置時，葉輪(1)與葉輪(2)同時由吸水管中吸水，活門在負壓下開啟，兩個葉輪處于并聯供水狀態。

The change-over valve and the water inlet valve are two key links of the medium and low pressure fire pump. When the change-over valve is in the series position, the pressure water of the impeller (1) enters the water inlet chamber of the impeller (2), and the valve is closed under pressure to make the pump in the series water supply state. When the change-over valve is in the parallel position, the impeller (1) and the impeller (2) absorb water from the suction pipe at the same time, the valve opens under negative pressure, and the two impellers are in the parallel water supply state.

4、引水裝置

4. Water diversion device

在泵的中蓋上，安裝有水環引水泵，以滿足中低壓泵排氣引水的要求。水環泵與中低壓消防泵使用同一泵軸。

A water ring diversion pump is installed on the middle cover of the pump to meet the requirements of exhaust and diversion of medium and low pressure pumps. The water ring pump and the medium and low pressure fire pump use the same pump shaft.

（三）、中低壓消防泵的特點

（3） Features of medium and low pressure fire pumps

既可以提供低壓大流量水流，亦可提供中壓水流。

It can provide both low-pressure and large flow water flow and medium pressure water flow.

由中低壓消防泵為核心組成的中低壓供水系統具有火場展開迅速，在復雜的高層建筑、地下建筑內部作戰機動靈活，具有撲救各種油類火災和向高層建筑上部供水的能力、具有流量較大、射程較遠的特點。

The medium and low pressure water supply system composed of medium and low pressure fire pumps has the characteristics of rapid fire spread, flexible operation in complex high-rise buildings and underground buildings, the ability to put out all kinds of oil fires and supply water to the upper part of high-rise buildings, large flow and long range.

（四）、中低壓消防泵的應用試驗

（4） Application test of medium and low pressure fire pump

1.遠距離供水情況

1. Remote water supply

2.高層供水情況

2. High rise water supply

五、中低壓消防泵的應用前景

5、 Application prospect of medium and low pressure fire pump

三、高低壓離心泵

3、 High and low pressure centrifugal pump

高低壓水泵主要由常壓外殼、高壓外殼、葉輪、泵軸、擴散器和填料箱組成。

The high and low pressure water pump is mainly composed of atmospheric pressure shell, high pressure shell, impeller, pump shaft, diffuser and stuffing box.

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