Liquid Dynamics International Ltd. - Piping System Analysis / Piping System Simulation

LDi – P3

C. Continued – When it is more than transient
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 Damper?

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

C. Continued – When it is more than transient

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 damper 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.
Liquid chambers alone will cost too much and be huge

D. Importance of smaller pipes.

1. As high frequencies die away relative to the ratio of diameters, your dampers 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”.
Reducer is fine for flow but not for acoustics – “pulse reflection”
7 degree is good for acoustics and for flow
Nearly all of a pressure spike can be caused to go into a damper 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 Damper.

An orifice makes it harder for the pump. It reflects the pulsation, but helps to protect the pipe system. And makes it harder for the pump to pump.
A gas bag makes the system soft, which is good for the pump. The residual pressure pulses go past, no good for the pipe. The pulse will by-pass a volume accumulator.
A true damper helps the pump and protects the system.
True pulsation damper with nitrogen compressibility for acoustic and volumetric protects pump and pipes.
There are dampers available that follow the logic of pump dynamics and of acoustics. In essence a damper is large diameter, multi ported, and has elasticity. An orifice resonator is bad for a pump. Soft accumulators do not protect pipes.