Straight Length Requirement in Pump Piping

Turbulence knows no orientation. This is especially true on the suction side of the pump where cavitation may occur if the incoming fluid stream is unsettled. The outlet side isn't as critical, since the fluid is under pressure at discharge.

Yes, straight pipe into suction side.

Again we have a "General Question" asked and a "General Answer" given. Both lead to gross misinterpretations of the facts.

Not ALL pumps require "X" straight length on the suction and not ALL commodities benefit from no turbulence.

I do not have personal experience with ALL types of Pumps but some Centrifugal and most Positive Displacement Pumps do not require any fixed straight length in the suction.

Some commodities such as any Slurry would not be adversely effected by turbulence in fact it is better to have turbulence in a slurry.

My point is, you really need to consider every pump type/commodity individually on a case by case basis.

Can't argue with that. More information will get a better answer.

Thanks for the caution.

"Some commodities such as any Slurry would not be adversely effected by turbulence in fact it is better to have turbulence in a slurry."

The term "Slurry" is general. Some commodities that exhibit the properties of non-Newtonian fluids are affected by turbulence at the inlet of certain types of pumps.

Though I agree with what you say about generalisations, I believe that most, if not all centrifugal pumps benefit from steady non-turbulent flow at the impeller eye.

This can be most easily achieved by having a section of straight pipe - the length of which will vary depending on type of pump and fluid. The same can be achieved where there is limited space by installation of flow straighteners etc. Turbulence may be good for the pumped fluid, but is seldom if ever good for the hydraulics of the pump.

I do try to follow manufacturer recommendations. But at times space will not allow it and I will impede on those recommendations, but I try to flag it if issues arise. Fortunately for there must be some safety factor in these recommendations. I am sure viscosity of medium will effect these also.

One design practice used in several refineries I worked at was to use a one or two size reducing 90 on the pump inlet. So the 6 inch inlet on the pump was fed directly by a 6 x 10 inch reducing ell. Probably not a general solution, but often used.

Not for a peristaltic pump.

...or a gear pump, or a diaphragm pump, or a lobe pump, or a progressive cavity pump.

It all depends on what you are pumping. Never overlook the obvious. Read the instructions/manual.