Diameter change before and after the pump
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Regarding the issue of diameter changes before and after the pump, in the case of a diameter change before the pump, the pipe diameter is usually larger while the pump nozzle is smaller. Is the transition pipe welded directly to the flange of the pump nozzle? Is it better to place it in front of the pump nozzle valve assembly (filter, gate valve)?
Individuals tend to weld the reducing pipe directly to the pump nozzle flange, so that the length of the section with a smaller diameter is shorter, resulting in less resistance at the pump inlet.
Is it okay not to reduce the diameter of the inlet pipe for pumps with low flow rates (around 1 m3/h)? Can it meet the cavitation requirement? The inlet pipe is already thin, so the pump nozzle tube is under greater stress.
Refer to SH/T3012 regarding pump piping: a straight section of pipe should be added between the elbow and the pump outlet when connecting them; it is advisable to include such a section. If installation space is limited, it can be omitted without any impact
It can be calculated through hydraulic calculations to see if it meets the requirement for the minimum pressure at the pump inlet.