Issue with the installation sequence of pump inlet and outlet accessories
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I recently noticed some issues while checking the pump piping, so I’d like to discuss them with everyone in hopes of gaining some insights. The situation is that a flexible joint, a reducer, and a butterfly valve need to be installed at the pump inlet, while a reducer, a flexible joint, a check valve, and a butterfly valve should be installed at the pump outlet. What should be the installation sequence? If elbows are installed at the inlet and outlet, it is necessary to determine the appropriate distance from the pump. I believe that flexible joints and reducers should be placed as close to the pump as possible, while the outlet butterfly valve should be located downstream of the check valve. Since the operating conditions at the inlet and outlet are different, there should be specific considerations in place. I hope everyone will participate actively, learn together, and make progress through discussion.
I agree with your view; the flexible joint should be placed near the pump. The positions of the butterfly valve and the variable diameter section are determined based on the nominal diameter of the butterfly valve, while the check valve is installed between the outlet and the butterfly valve
At the suction inlet of a single-suction pump, it is advisable to install a section of straight pipe with a length of about 3 times the diameter of the suction inlet； At the suction inlet of a double-suction pump, it is advisable to install a section of straight pipe with a length of about 7–10 times the diameter of the suction inlet
One of a check valve or a butterfly valve is sufficient; a check valve is used only in special situations, such as when backflow must be prevented.
Wouldn’t it be better to take a look at the process flow diagram?
When the inlet and outlet pipes of the pump are connected to the ground pipes and the civil engineering water tanks, flexible joints should be installed if the pipes are short. Check valves are required only on the outlet pipe, while gate valves or butterfly valves are needed for both the inlet and outlet.
Flexible joints and reducers should be placed as close as possible to the pump； The installation order at the pump outlet is: reducer fitting, flexible joint, check valve, butterfly valve ； Elbows should be installed at the pump’s inlet and outlet; if the pump manufacturer does not specify otherwise, the shorter the distance, the better ； If the pump manufacturer specifies distance requirements, install it in accordance with those requirements.
As for whether the reducer should be connected directly to the pump inlet or a straight section should be connected first, I believe connecting the reducer first also has its disadvantages, as changing the inlet diameter can disrupt fluid flow and affect the pump’s operation； Furthermore, if the inlet and outlet pipes are arranged vertically through elbows, and the elbows are located close to the pump, is it appropriate to install the inlet valve at the exit of the vertical pipe, while installing the check valve also on the vertical pipe?
The installation sequence at the pump outlet is: reducer, flexible coupling (or metal hose – which can be omitted if the pump vibration is low), check valve (installed upstream of the shut-off valve), and flat gate valve (or other shut-off valve).
There should be a filter and a backwash device in front of the pump inlet valve, as well as a backwash device in front of the outlet valve; the check valve is located between the diameter change section and the valve.