The export of centrifugal pump check valve and selection problem

by:J&T     2020-05-24

the role of the centrifugal pump discharge check valve is to prevent the export pipeline in the liquid flow back to form water hammer within the pump impeller damage.

check valve installation has nothing to do with how much pump, pump the check valve is mainly in order to stop after the operation, prevent the reverse flow of liquid, invert the pump, causing damage to the pump of accident, and in order to prevent the liquid flow back to other tank damage (such as From the high fill reversals will cause pot smoking bad) 。 So it's best to add the check valve.

if you can guarantee before the pump is going to turn off the outlet valve, and export valves do not leak or damage, and can check.

centrifugal pump outlet check valve 'check valve selection

pump station engineering general situation, the pump discharge check valve choice, should follow the following principles;

1, the pump discharge pipe diameter smaller pipe, or DN 50 mm or less, should choose lift check valve.

2, the pump discharge pipe diameter DN> 50 mm line, should choose swing check valve swing check valve can be installed in a horizontal or vertical. Swing check valve disc around the axis of rotation, the fluid resistance is generally less than lift check valve, it is suitable for large caliber, installation position is not restricted, are normally installed in horizontal pipe, which applies with the occasion of the large diameter. According to the number of the disc can be divided into single swing, more than double disc swing and swing three segments. Single swing check valves are generally used with medium caliber. Large diameter single swing check valve is used in the pipeline, to reduce the water hammer pressure, had better use can reduce the water hammer pressure slowly-closing check valve. Double disc swing check valve applicable to large and medium diameter pipeline. Double disc swing check valve to the clamp structure is small, light weight, is a kind of fast check valve; Many disc swing check valves apply to large diameter pipeline.

the installation of centrifugal pump outlet check valve

1. Swing check valve installed in horizontal pipe runs commonly: for check valve diameter DN - 80 mm, also can be installed in vertical or upward sloping line.

(2) the straight-through lift check valve should be installed in horizontal pipe runs. Vertical lift check valve must be installed in vertical pipe runs, medium to flow from bottom to top.

(3) due to the check valve is easy to damage, therefore, should be installed near the pump discharge check valve, the check valve upside sets cut-off valve ( Ball valve or gate valve) is commonly used in And convenient maintenance.

(4) for ease of check valve pressure relief before disassembly, put a net for check valve itself without valve, between the check valve and shut-off valve should be equipped with pressure relief with net valve.

prevent damage of hydraulic impact of check valve sealing surface protection

check Settings, the prevent the backflow of material, to avoid the pump impeller liquid impact effect. But in terms of check valve itself, Settings, and will cause water hammer produced by the sudden impact of disc to seat, and the check valve sealing surface. Therefore, to some protection measures should be taken.

1, for the centrifugal pump export Settings> 80 mm swing check valve, horizontal installation, should be adopted to undermine the impact valve seat and back.

2, for water pump discharge check valve diameter> = 150 mm pipe, should be set up before, during, and after check the bypass, prevent the valve pressure rise too high, before the check valve sealing surface damage.

3, the pump discharge line starting point and end point, high pressure pipeline is not allowed to bypass, can take the following measures.

set the relief valve to replace the bypass valve. Its role is similar to the bypass valve. It set up near the check valve export, when water hammer pressure, part of the water can be released in order to prevent the damage caused by the pressure continues to increase.

setting air or inert gas buffer tank. Set it near the check valve export, when water hammer produced by buffer tank with pressurized gas is compressed, to mitigate water hammer pressure.

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