Liquid Dynamics
Pulsation Analysis, Diagnostics, Prediction by Software
Pipeline and Pump user Problem -

Pulsation Analysis, Diagnostics, Prediction by Software

LIQUID DYNAMICS Ltd. offer Pulsation / Vibraton and Shock - Analysis & Diagnostics + Software Models
Please call toll free USA 1-888-326-7377 WE HAVE PEOPLE - Not voice mail. --44-161-480-9625 UK
Fluid Flow Control animations by Liquid Dynamics.

Main Menu

plots A, B, C
Input data for
shock modeling

models relations
7 ocillographic

input data

Equations &


LDi Catalog Printable PDF27

A. Potential Danger, B. Pressure drop,
C. Lack of dissipation

Generally, it is far less expensive to determine the peak pressure level and the frequency for the system piping, by running the system in a software model compiled in LDI ShockView for you, than to drill & tap holes for transducers, add an oscillograph, & or data capture the problem.

NOTE: - Money is only saved by "modeling" when the input data is correct. Otherwise "garage in - garbage out".
Some important fact that maybe overlooked are:

The elasticity of the pipe wall and the compressibility of the liquid govern the height of the pressure spike and the time taken of the wave to travel and return. Therefore these two figures - "elastic modulus of the pipe & the bulk modulus of the liquid" - are vital figures.
For a soft garden hose the speed of the wave will be down at about Mach1 - say 700mph - OR - for a very strong heavy wall iron pipe and the most incompressible liquid at low temperature, i.e. 3250mph.
Hot highly volatile hydrocarbons may have a bulk modulus of 300e-%. Refrigerates and Ammonia can be even more compressible. Generally speaking the chemical engineer will be able to supply the right figure to you because he has it for calculating mass transfer and reactions.
The effective modulus controls the wave speed, which controls the frequency of reverberation.
Time: The time take for a valve to close, or pump to start-up is ultra important; see the "VERIFICATION" plot bottom right.
Smaller pipes-higher flow velocity, gives more dissipation so that the shock is reduced before it rebounds.
Accuracy of SHOCKVIEW depends on data accuracy - p. 28

Example output plots a, B, & C show:
In the time between i-ii & iii, which is 3.5 seconds for this long pipe, the pressure wave dissipation by rotary flow against the pipe wall, is only 2.5 psi. This warns of potential danger, that this system could easily become an amplifier. The pipe is oversized for the flow rate.

B. A 2 second pump startup, 19 bar (275psi) 150# system makes +/- 39psi shock at 2.43 Hertz. We also see first point "i" at 15.9 bar. This means that the total pressure drop for the system is 3.1 bar, or 45 psi.

C. The time chosen to run this model was a total of 21 seconds. At the end of this time, the peak has only degenerated down to 21 bar (305psi). The shockwave has traveled the length of the pipe and back 44 times (at 2.1 Hz.) and is resonating.

13 psi in 39 feet of 1/2" pipe, 1/10th second valve closure, generates 180 psi shock. 1/2 second closure produces 24psi shock.

Other tests were performed on 3 diameters of 2 pipe materials in 10 lengths & 3 closure times.
Phone USA 910.270.2737
PO Box 506 Hampstead, NC 28443 USA
UK (for EC) --44(0)161-480-9625
PO Box 47, Stockport, UK SK3-OLH


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. - Pulsation Dampener - Pulsation Dampeners - Pulsation Dampers
PulseGuard für Deutschland - Pulsationsdämpfer and to find large gas bag vessels, jumbo bladders, float separator / big bellows type pipeline shock attenuators and expansion / contraction volume compensators, surge alleviators, and shock alleviators. - Surge Alleviators - Shock Alleviators and for information about energy saving in pumping systems, standby emergency power, safety shutdown systems, hydraulic accumulators, and hydropneumatic accumulators. - Hydraulic Accumulators - Hydropneumatic Accumulators to find 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 - Flow Fuses and Breather Bags

Liquid Dynamics