Today let’s discuss the installation location of check valves

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This post was last edited by Thank goodness you're here on 2019-10-14 at 14:31. Today, let’s discuss the installation location of check valves. So, how is the installation location of a check valve determined? What are the differences between installing a check valve before and after the pump, and in which situations is it appropriate to install it before the pump? Check valves are usually used in conjunction with other valves; then, where should a check valve be installed when used together with those other valves? Let’s discuss this together. A check valve, also known as a non-return valve, is an automatic valve that uses the pressure of the fluid flowing within the pipeline to push the valve disc, thereby enabling the valve to open and close. When the flow of fluid stops, the valve disc closes, effectively preventing backflow of the fluid in the pipeline – which plays a crucial role in ensuring the safety of the pipeline. Classified by structure, check valves can be divided into lift-type check valves, swing-type check valves, and butterfly check valves. Lift-type check valves can be divided into vertical and straight-through types. Swing check valves are divided into three types: single-disc, double-disc, and multi-disc. Butterfly check valves are divided into double-disc butterfly types and single-disc butterfly types. These various types of check valves can be connected in four ways: threaded connection, flange connection, welding, and clamp connection. Check valves are installed to ensure the flow direction of water inside the pump, thereby ensuring its proper operation. So, regarding the installation location of the check valve – whether it should be installed in front of or behind the water pump – there are two possible scenarios: one is to install it at the end of the vertical suction pipe in front of the water pump, which is also known as a foot valve. The purpose is to avoid having to fill the water pump with water each time it needs to be used. Since the pump cannot draw water when there is no water inside it or in the suction tube ahead of it, the pump must be filled with water in order to be able to draw water out. The installation of this type of water pump involves placing it above the liquid level, and this method is also known as the negative pressure method. Another option is to install it behind the water pump. This installation method allows the water level to be above the water pump, which facilitates starting and stopping the pump without the need to close the pump’s outlet valve; it is especially useful in master pipe water pump systems to prevent backflow. The check valve must be installed at the pump’s outlet, in front of the outlet control valve, to facilitate its maintenance. In a typical pump, the first component at the outlet is a flexible connection (shock absorber); followed by a check valve, and then by a isolation valve (such as a butterfly valve, gate valve, or globe valve). It is advisable to install the check valve first, and then the gate valve or butterfly valve. The advantage of this approach is that it protects the check valve – especially in systems with pumps connected in parallel. When one pump stops operating and its outlet valve closes, the impact force is absorbed by the gate valve or butterfly valve when the other pump starts operating. If a check valve fails, the inlet and outlet valves can be closed to isolate the system for repair. Disadvantage: Who will protect the gate valve or butterfly valve? There was a case where the disc of a butterfly valve was damaged. 2. Install the gate valve or butterfly valve first, and then the check valve – advantage: this protects the butterfly valve or gate valve, as the impact forces are absorbed by the check valve. Disadvantage: Who will protect the check valve? The check valve operates based on pressure differences – it closes when the pressure in the main pipe is high and opens when the pressure from the pump is high. If the flow rate used is unstable, the check valve will open and close repeatedly, which can affect its lifespan. Moreover, the check valves are broken, especially in the main piping system; repairs can only be carried out after shutting down the system. Generally speaking, since check valves open and close frequently, their internal connections and sealing components are prone to damage. To facilitate repairs and prevent the entire system from coming to a stop due to failures in the check valves, they are installed in front of outlet gate valves or butterfly valves. Is that basically the case everywhere you see them?