Overview of Selection and Protection of Check Valve

Check valve, also known as check valve, check valve or check valve, its role is to prevent the flow direction of the medium in the pipeline without the function of back flow. Pump suction valve at the end of the valve also belong to the category. Check valve by structure, can be divided into lift check valve, swing check valve and butterfly check valve three. Lift check valve can be divided into vertical and horizontal two. Swing check valve is divided into single-valve type, double-and multi valve type three. Butterfly check valve for the straight-through, the above several types of check valves in the connection can be divided into threaded connection, flange connection and welding of three.

Check valve installation selection and protection points Overview:

First, the pump outlet check valve selection, the pump outlet check valve selection, should follow the following principles; on the pump outlet pipe diameter smaller pipe, that DN <50mm, should use the lift check valve .

On the pump outlet pipe diameter greater than DN50mm pipeline should be used Swing check valve. Swing check valve can be installed horizontally or vertically. Swing check valve disc rotating around the axis of rotation, the fluid resistance is generally less than the lift check valve, which applies to larger caliber occasions, the installation location is not restricted, usually installed in the horizontal pipeline, which applies and Large diameter of the occasion. According to the number of valve flap can be divided into single-leaf swing type, double-swing type and multi flap swing type three. Single-swing swing check valve is generally used with medium-caliber occasions. Large-diameter pipe selection single-valve swing check valve, in order to reduce the water hammer pressure, the best use of water hammer to reduce the slow closing of the check valve. Double flap swing check valve for large and medium diameter pipe. Clamp double-flap swing check valve structure is small, light weight, is a faster check valve; multi flap swing check valve for large diameter pipe.

Second, the pump outlet check valve installation.

1.Swing check valve is generally installed in the horizontal pipeline: For the diameter DN ~ 80mm of the check valve, can also be installed in the vertical or upward slope of the pipeline.

2.straight through the lift check valve should be installed in the horizontal pipe; vertical lift check valve must be installed in the vertical pipe, the media is bottom-up flow.

3. As the check valve is easy to damage, therefore, should be installed near the pump outlet check valve, check valve in the upper part of the cut-off valve (usually with ball valve or gate valve) to facilitate maintenance.

4. In order to facilitate the pressure relief valve before the demolition, for the check valve itself without a net valve, check valve should be installed between the valve and the release valve with a relief valve.

Third, to prevent the hydraulic impact on the check valve sealing surface damage protection measures Check valve settings, played to prevent the material back, to avoid the pump impeller subjected to the role of liquid strike. However, the check valve itself, set inappropriate, will result in a water valve produced by the valve seat of the sudden impact, damage and check valve sealing surface. Therefore, several protective measures should be taken.

1, for the pump outlet settings> 80mm Swing check valve should be installed using the horizontal approach to weaken the valve seat back and the resulting impact.

2, for the pump outlet check valve diameter> = 150mm of the pipeline should be set before and after the bypass check valve to prevent the valve before the pressure rise is too high on the check valve sealing surface damage.

3, on the pump discharge pipeline starting point and the end of the higher pressure pipelines, does not allow the bypass, you can take the following measures.

Set the safety valve to replace the bypass valve. Its role and similar to the bypass valve. It is located near the outlet of the check valve, when the water pressure to raise the pressure, can be part of the water release to prevent the pressure continues to increase damage caused by the installation of air or inert gas buffer tank. Set in the vicinity of the check valve outlet, when the water hammer generated by the buffer tank with compressed gas is compressed to ease the water hammer produced by the pressure rise.