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
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A brief A to Z of pulsation and what to do about it -
"Don't excite the system so much"

Causes of pulsation, more details.
An approach to excitation reduction, & damping the residual.

Modulating devices cause pressure pulsation:
Relief valves bouncing on their seats.
Flow controllers in spill back loops, opening a tad, closing a bit, constantly changing the resistance to flow, and so changing the pressure.
Check valves clacking, "Back Pressure" valves hunting position.

Pipes that are shaken cause liquid pressure pulsation:
This is highest pressure and lowest frequency when shaken along the pipe axis.
Lower pressure pulsation, but at higher frequencies, come from shaking side-to-side and shaking up and down. The characteristics are greatly affected by the distance between pipe hangers, Clamps, Saddles and other forms of support.

Pumps on the other hand, make flow.


the flow fluctuates because:
The pump shaft deflects, impeller blades pass an opening, vanes cut off a flow slot, lobes nest between each other, worms take new gulps from their supply, diaphragms hesitate between strokes, peristaltic tubes and hose are squashed or rolls lift off them, gear teeth mesh, and the check valves from plunger and piston chambers flutter.
the resistance of the system turns the flow fluctuation into acceleration head pressure change. This is the instigator, or excitor of pulsation. It is like the plectrum that plucks the string.
This excitation is very easy to reduce (Note we did not say prevent):
Simply provide a soft compressible place, close to the pump, so that the pump can suck and blow -WITHOUT HAVING TO ACCELERATE THE WHOLE OF THE MASS IN THE PIPES.
Unless the soft cushion near the pump is infinitely large, there will be some residual acceleration head excitation. How much pressure pulsation this becomes depends on the system response, whether it resonates, whether the system amplifies it.
To address the resulting residual pressure pulsation, however small it may be, because it is now pressure traveling up and down the pipe at 1400 meters per second, and not flow at a 300th of that velocity, it has to be INTERCEPTED. Fortunately, a cushion chamber that is also an in line through flow, in and out device, is smaller and costs less than purely a cushion, or "Accumulator".
the pressure waves can enter through the flow damper, and are not reflected away by elbows, or by orifices, neither resonance nor amplification will occur.

Decoupling, isolation, excitors from system response, with TRUE DAMPERS is simple logic. PULSATION IS USUALLY A VALVE PROBLEM, OCCASIONALLY PUMP RELATED, AND LEAST OFTEN CAUSED BY A RECIPROCATING PUMP, (because that is so simple to resolve).
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