Principles for inlet piping of double-suction pumps
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For double-suction pumps, there is a principle stating that the straight pipe section at the inlet should be longer than 7D. Are there any other opinions on this?
There’s no requirement for straight sections, right? We have designed some double-suction pumps for use in water systems, and we’ve never heard of any problems with them. The chemical process design manual only states that when there is a elbow at the inlet of a double-suction pump, it should be installed vertically so that the fluid can flow into the pump evenly. Last edited by XYZ602 on 2007-12-20 22:07.]
Generally, there is no such requirement for straight sections, unless the pump installation instructions specify something similar.
I’ve never heard of such a requirement. OP, which manufacturer produced your pump?
Centrifugal pumps generally have high flow rates and head, yet their nominal pipe diameters at the inlet and outlet are smaller than those of ordinary pumps; therefore, diameter reduction is required at these connections.
I think what was said on the second floor makes sense. I’ve been looking for this answer; there is only one conclusion according to the standards, but I couldn’t understand it. I think it makes sense. If the elbow is oriented from top to bottom, it balances the conditions on both sides of the impeller. But if the elbow is parallel to the pump shaft, the liquid conditions on both sides of the impeller become different, which leads to vibration. There should be a straight section of pipe to achieve balance. I understand a bit more now; thanks for the guidance from the second floor. In the future, when I teach others, I’ll be able to find reasons to convince them. It’s sad to only remember the conclusion without understanding the underlying reasons.
There are principles regarding the inlet piping of double-suction pumps: 1 When the inlet pipe is introduced horizontally along the direction parallel to the pump axis and then bends to enter the inlet, a straight pipe section several times the diameter of the pipe is required. 2 When the inlet pipe is introduced horizontally along a direction perpendicular to the pump axis and then bends to enter the inlet, no requirement for a straight pipe section exists
A straight pipe section should be provided, mainly to consider the flow pattern at the pump inlet; an uneven flow pattern there can reduce the pump’s efficiency and increase the risk of cavitation. This issue applies not only to double-suction pumps but also to centrifugal pumps
For double-suction pumps, in order to avoid cavitation in two-way suction horizontal centrifugal pumps, the double-suction pipes must be arranged symmetrically to ensure even flow distribution on both sides. Vertical pipes are connected directly through elbows, but the axis of the pump must be perpendicular to the plane in which the elbow is located. At this point, the inlet piping is required to be as short as possible, with elbows connecting the reducers and then the inlet flange. Under other conditions, there should be a straight pipe section of at least 3 times the pipe diameter before the pump inlet.
Specific requirements are given on page P186 of Part 1 of the \"Manual for the Installation and Design of Process Piping in Petrochemical Plants\"; it is indeed 7DN
Since it is a continuous incompressible fluid, I believe there should be no requirement regarding the length of straight pipe sections. Does the absence of straight sections cause cavitation? I would appreciate some guidance from experts, thank you!