Dampening of pressure pulses downstream of Centrifugal pump 1

[nipra03]

I have read about some issues on the subject but would like to gain more information.

By how much would the pressure pulses generated by vane pass of centrifugal pumps be dampened out as the fluid flows down the line ?
Is there any method to estimate or an empirical corelation ?

We normally caution our designers to consider the impact due to fluid pressure pulsations on piping and small bore connections immediately downstream of a main line centrifugal pump for crude oil pipelines (~ 30" dia., discharge pressure 9000 Kpa) but are not sure of the dissipation in energy say 50 km downstream.
Appreciate any help here.

 

[1gibson]

Hard to believe that pressure pulses from vane pass frequency would limit the design, after considering more severe transients like valve changes and startup / shutdown events.

 

[BigInch]

You should only be cautioning designers for pressure pulses coming from reciprocating pumps.

I hate Windowz 8!!!!

 

[DubMac]

Dampening: to make damp ; moisten: to dampen a sponge

Damping: a decreasing of the amplitude of an electrical or mechanical wave.

 

[Artisi]

Blade pass frequency can impact on down-stream systems. How / when / why etc I can't comment but from experience one particular small 2 bladed impeller paper stock pump I used to supply / sell could destroy stainless steel pipe work in some incidences in very short order. Also in paper stock pumps application pumping up to the head box on a paper machine, the blade pass frequency is extremely critical.

So to say that blade pass frequency is a non-event is not true.

Is this a theoretical or actual problem, is a problem more info will assist, if suffering from blade pass frequency - there are a few trick that can help to alleviate the problem.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[DubMac]

If you've got vane pass vibration, it should be diagnosed and remedied; not covered up with bandaids. Your pump is slowly destroying itself.

 

[nipra03]

The issue is realistic.
The concern here is that pressure pulses can cause vibration and worse - resonance in the piping system especially in attached small bore cantilever type connections e.g. instrument/ drains/vents as a result of the pulse resonating with the mechanical or acoustic natural frequencies.

As i see it the damping (corrected by dub) of thise pulse as it travels downstream can limit the severity of the impact.

 

[BigInch]

He did say 30" dia., discharge pressure 9000 Kpa right?

I hate Windowz 8!!!!

 

[nipra03]

Correction. I mean't 9000 kpag.

any thoughts guys ?

 

[hessczoo]

The vane pass pulses should be quite irrelevant, care should however be taking to protect piping/equipment from sudden changes in valve positions, and gas pockets in fluid causing hammering. If all piping is properly bolted and supported it will withstand a lot more abuse than vane pass pulses. Normally systems are designed with centrifugal pumps due to no pulsation.