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Pressure Pulsation Dampeners for Transients and their Interception

The purpose of these 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. 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 host, then jerk it. Water spurts out. The jerk created pressure, if not, nothing would have come out. Similarly, shaking a pipe causes pressure pulsation
Generation of 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 DEFERENCE BETWEEN PUSHING LIQUID IN A PIPE, AND PULLING A PIPE ALONG A VOLUME OF LIQUID, in terms of liquid pressure.

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".Reflection of Pressure Pulsation

 

45 degree scarf jointTurn Pressure Pulsation

There are different stiffness levels for each of these direction change methods Their stiffness impacts the pipe mechanical vibration frequencies.

high frequency pressure pulse transientsWhen the 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"high frequency transients

 

pressure - timeLIQUID CHAMBERS ALONE WILL COST TOO MUCH & BE HUGE 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

importance of smaller pipes1. As high frequencies die away relative to the ratio of diameters, your dampeners will be smaller and more efficient when you keep you 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.

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° taper.

taper
orifice and taper pulse reflection

makes harder for pump to pump

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

 

 

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

 

true pulsation dampenerA true pulsation dampeners help the pump AND protect the system. There are dampeners available that follow the logic of pump dynamics and of acoustics. In essence a pulsation dampener is 1. large diameter, 2. multi ported, and 3. has elasticity. An orifice resonator is bad for a pump. Soft accumulators do not protect pipes.

 

 

Liquid Dynamics Pulsation Dampeners Information For more information about this and other pressure pulsation related topics go to the Liquid Dynamics web site.

Pulsation Dampeners - Snubbing, Surge Suppression and Shock Absorbing
Hydropneumatic Device for Acceleration Head Pulsation Prevention
No Moving Parts and Hydropneumatic Pulsation Filters
Flow Fluctuation / Suction Systems - Negative Pressure Pulsation / Supply Lines
Pressure Pulsation Pulse Signatures
Pressure Pulsation Dampeners for Transients and their Interception
Pulsation Dampeners for Amplitude of Pressure Wave Spikes
Pulsation Dampeners and Pump Vendor Responsibilities
Acceleration Head / Pressure that a System Could Create
Pulsation Dampening - Flow Smoothness Requirements
Pulsation Dampener Quick Release Manifolds / Flow Divider Manifolds



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