Why are the inlet and outlet of a centrifugal pump designed with different diameters?

This post was last edited by 3983596_FPPZ on 2018-11-2 at 14:28. The diameter of the pipes is set to meet standard values in order to reduce the flow velocity of the liquid within the pipes (the economic flow velocity), thereby minimizing the losses caused by high flow velocities. Therefore, the diameter of the pipes in the pipelines is generally larger than that of the pump’s inlet and outlet ports; hence, reducer pipes are needed at each of these points to adjust the dimensions. The flow velocity of the liquid as it passes through the pump changes in the following manner: slow (inlet pipeline) – acceleration (inlet reducer) – maximum velocity (outside diameter of the impeller) – deceleration (volute channel of the pump casing) – further deceleration (diffuser of the pump casing) – further deceleration (exit reducer) – slow (exit pipeline). A centrifugal pump works by using the rotation of the impeller to increase the velocity of the liquid, and then gradually reducing this velocity to convert it into pressure. To achieve this, it is necessary to reduce and then increase the area through which the liquid flows. If a diffuser tube is not used and different pipe diameters are connected directly to each other, the sudden change in area results in significant local hydraulic losses, **reducing the efficiency of the pump. Therefore, a tapered tube is used to achieve a gradual transition, thereby minimizing losses. It is reasonable for the diffusion cone angle of the diffusion tube (not the one-sided slope) to be between 6–10°. Moreover, the diffusion losses are much greater than the contraction losses; hence, it is essential to carefully control the cone angle of the outlet diffusion tube.

The thickening of the inlet pipe is mainly intended to reduce the flow velocity and thereby increase the net positive suction head of the device. Thickening the outlet is also intended to reduce the flow velocity and minimize pipeline losses. There are standards for the pressure drop per 100 meters. It’s about considering the economic flow rate; a high flow rate results in greater losses, while a low flow rate requires larger pipe diameters, increasing costs.

Isn’t this kind of installation complete nonsense? What’s the point of having supervisors at all?:@ The outer diameter of the elbow is the part that wears out the most; welding the support points right there is simply absurd.:@ Is no one in charge? ? ?

Agreed. Elbows are the worst in terms of both stress and erosion wear; even when supporting horizontal pipes, gusset plates should be welded in place. Thanks for the insight

The selection of pipeline flow velocity is mentioned in many process design specifications, but the issue of pump inlet and outlet diameters is not determined by process design; it is a matter related to the pump’s structural design.

It seems that this is how welding is done here too – by welding it to the elbow

The installation specifications permit welding the supports in this manner

The last time I saw a pipeline, it had stress corrosion cracking at the weld seam