The role of the check valve at the outlet of the centrifugal pump is to prevent the liquid in the outlet pipe from flowing backward to form the water hammer and cause damage to the impeller in the pump. The installation of the check valve has nothing to do with the number of pumps. The main purpose of the check valve is to prevent the liquid from flowing back after the pump has stopped running, which will cause the pump to reverse and cause damage to the pump.
1. The swing check valve is generally installed on horizontal pipelines: for check valves with a diameter of DN <80mm, it can also be installed on vertical or upwardly inclined pipelines.
2. The straight-through lifting check valve should be installed on the horizontal pipeline; the vertical lifting check valve must be installed on the vertical pipeline, and the medium flows from bottom to top.
3. Since the check valve is easily damaged, a check valve should be installed near the pump outlet, and a shut-off valve (usually a ball valve or a gate valve) is provided on the upper part of the check valve to facilitate maintenance.
4. In order to facilitate pressure relief before the check valve is disassembled, if the check valve itself does not have a relief valve, a relief valve for pressure relief should be installed between the check valve and the shut-off valve.
Protective measures to prevent damage to the sealing surface of the check valve due to hydraulic shock:
The setting of the check valve prevents the material from flowing backward and prevents the pump impeller from being hit by liquid. However, as far as the check valve is concerned, improper installation will cause a sudden impact of the valve disc generated by water hammer on the valve seat, and damage the sealing surface of the check valve. Therefore, several protection measures should be taken.
1. For the swing check valve with an outlet of> 80mm, it should be installed horizontally to reduce the valve seat return and the impact.
2. For pipelines with a check valve diameter of 150mm or more at the outlet of the pump, a bypass should be set before and after the check, valve to prevent the pressure in the valve from rising too high and causing damage to the sealing surface of the check valve.
3. For pipelines with higher pressure at the starting and ending points of the pump discharge pipeline, bypassing is not allowed. The following measures can be taken: a safety valve is used instead of the bypass valve. Its effect is similar to that of a bypass valve. It is set near the outlet of the check valve. When the water pressure increases the pressure, a part of the water can be discharged to prevent the damage caused by the continued increase in pressure.
The above information is provided by china Marine valve manufacturer.
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