Liquid Dynamics - Pulsation Analysis, Diagnostics, and Software Models

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Explanations A through F

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"Controllers" of Pulsation

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The purpose of the analogies is not absolute definition; it is to assist in visualizing the different phenomena.

A. Shake a pipe, generate a pressure pulse.
B. Turn a pulse instead of reflecting it.
C. Dissipate a transient, why increase the frequency.
D. Importance of smaller pipes.
E. Changes in diameter - Orifices, Eccentric and "Conc" reducers, the 7 Degree taper.
F. Is it an Accumulator, Orifice Reactive Resonator, or a true Pulsation Dampener?

A. Shake a pipe, generate a pressure pulse.

Leave the end of the garden hose attached to a closed "tap" or faucet. Extend the hose uphill, and leave open but full of water. Hold the middle of the hose, then jerk it. Water spurts out. The jerk created pressure, if not, nothing would have come out. Similarly, shaking a pipe causes pressure pulsation in the liquid.

When the engine or motor attached to a pump, is not perfectly installed, the pipe attached to the pump will vibrate. This can be measured as liquid pressure pulsation. It will be significant when the shaking is along the axis of the pipe. There is no difference between pushing liquid in a pipe, and pulling a pipe along a column of liquid, in terms of liquid pressure.

B. Turn a pulse instead of reflecting it.

Reflection makes yet another frequency	Whereas a long radius 90 will be better in terms of volume / mass flow, a pressure wave traveling over 5,000 kilometers per hour, will see it as a "brick wall", - just as it does with a "hard 90".
	A 22.5 Degree + 22.5 Degree

There are different stiffnesses for each of these direction change methods.
These stiffnesses impact the pipe mechanical vibration frequencies.

Ldi Page 3

C. Dissipate a transient, why increase the frequency.

Where Diameter of a vessel is 8 times the Diameter of a pipe, high frequency pressure pulse transients will have died away before they can bounce off the nearest point of reflection and find their way out into the rest of the system.
This is "good" to the extent that it is not increasing the load on the pump by imposing an orifice against pump delivery.

"High frequency transients"

Liquid chambers alone will cost too much and be huge Pulse Volume

The problem is that the pulse may have a substantial volume as well as pressure amplitude. When the duration of a pulse is sustained for a measurable length of time, the pulse will have volume; it will not simply be a transient. The volume of the dampener vessel required to provide sufficient liquid compressibility will be between 10,000 & 100,000 times the volume of the pulse, depending on the pulse characteristics.

D. Importance of smaller pipes.
No Orifice

1. As high frequencies die away relative to the ratio of diameters, your dampeners will be smaller and more efficient when you keep your pipe sizes down.
2. Even more important is that the smaller the pipe, the more dissipative it is, so the pipe will scrub out some pulsation.
3. Additionally, a dissipative pipe system will not become a pulse amplifier.
Unfortunately you can not just step the pipe diameter down, the step will return the pulse.

E. Changes in diameter - Orifices, Eccentric and "Conc" reducers, the 7 Degree taper.
A pressure occurrence travels at Mach 5 and sees any reduction in cross sectional area that is steeper than an included angle of 7 degrees as a “brick wall”.

Nearly all of a pressure spike can be caused to go into a dampener from a large diameter pipe by compressing it down a 7 degree taper.

F. Is it an Accumulator, Orifice Reactive Resonator, or a true Pulsation Dampener.

An orifice makes it harder for the pump. It reflects the pulsation, but helps to protect the pipe system.

A gas bag makes the system soft, which is good for the pump. The residual pressure pulses go past, no good for the pipe.

A true dampener helps the pump and protects the system.

In essence a dampener is large diameter, multi ported, and has elasticity. An orifice resonator is bad for a pump. Soft accumulators do not protect pipes.

Pulsation Dampeners - PulseGuard Inc.

Liquid Dynamics International provides pipeline and pump user problem analysis, diagnostics, prediction by software, pulsation analysis, piping system analysis, and piping system simulation. For water hammer and shock solutions pulsation dampening and shock alleviating devices can be obtained from our associate websites:

PulseGuard Inc., and Ltd. for further information about pulsation dampeners / pulsation dampers.
PulseGuard.com: Pulsation Dampeners | Pulsation-Dampeners.com: Pulsation Dampener
PulseGuard.co.uk: Pulsation Dampers | PulseGuard für Deutschland: Pulsationsdämpfer

Large gas bag vessels, jumbo bladders, float separator / big bellows type pipeline shock attenuators and
expansion / contraction volume compensators, surge alleviators, and shock alleviators.
Shock-Guard.com: Surge Alleviators | Water-Hammer.com: Water Hammer
ShockGuard.co.uk: Shock Alleviators | Suction-Stabilizers.com: Suction Stabilizers

Information about energy saving in pumping systems, standby emergency power, safety shutdown systems,
hydraulic accumulators, and hydropneumatic accumulators.
Accumulators-Hyd.com: Hydraulic Accumulators
Accumulators.co.uk: Hydropneumatic Accumulators | HydroTrole.co.uk: Hydraulic and Control Engineering

Protection against excess flow. Guard against toxic spills when pipes burst, guard against gushers and fluid
loss when hoses split, Flow-Guard guards against excess flow floods with flow fuses and breather bags
Flow-Guard.com: Flow-Guard - Flow Fuses and Breather Bags