PulseGuard UK Ltd.

Pump Pulsation Dampers / Dampening by PulseGuard UK


Pump Pulsation Dampers

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Where does Pulsation come from ?
Pulsation is caused by the mass of a liquid system being accelerated and decelerated by a pumping action, or the repeated opening and closing of a valve.

The most exaggerated form of pulsation comes from simplex diaphragm type "metering" pump systems.  Lesser pulsation is seen when duplex pumping .  Triplex pump piping experiences even less pulsation.

 

What is a Pulsation Damper ?
A Pulsation Damper is a liquid pressure container that reduces pressure variations and flow fluctuations .  The container is often divided in to two sides by a flexible membrane, diaphragm, bladder, flextube, one containing compressibe nitrogen gas, and the other side through which the liquid goes;  in the process the liqid pressure and flow variations are reduced or "dampened".

 

Why is a Pulsation Damper necessary ?
In a metering system constant flow is normally required. A damper is essential to reduce the flow fluctuations to ensure process control and mixing.  In pipes pressure pulsation will shake the piping and dampening the pulses prevents fatigue and connection failures. In general removing pulsation reduced the energy usage to transmit liquid over distances.

 

What info to collect for selecting a pulse Damper ?
1.)  FIRST and foremost - HOW MUCH DAMPENING DO YOU NEED ?
EX / EG ; DOWN TO Plus & Minus %age of theorectical steady state  :- 
For increased pump life -   6%
To stop pressure safety valve from lifting  - 5%
To stop overload "burst disks" fracture  - 4.5%
Protection of gauges and instruments    -  3%
For constant supply to static mixers    -   2%
To improver atomization from spray nozles  1.5%
Use with "paddle wheel" type merter     -  1%
For turbine meters          -  0.75%
Use with vortex shedding meters     -  0.3%

2.) Pump data
A.  Simplex, Duplex, Triplex,  Quintuplex, Gear (number of teeth) vane number of vanes, hose /peristaltic number of rolls or "shoes",
B. Flow rate
C. Relief valve set pressure.
D. Design temperature.
E. Pipe length
F. Compatible metal or plastic.
G. Compatible elastomer or PTFE

3.)  System information
A. Pipe diameter
B. Connection type, weld, thread, flange, union. etc.
C. Pressure rating -  #150, #300, #600, #900  etc.
D. Pipe and connection material
E.  Other ?

 

Where is a Pulse Dampener installed ?
For best performance a Pulsation Dampener should be installed at the start of the pipe down which the flow has to be forced
OR
When the dampener is to perform as a suction side acceleration head loss reducer, then the installation is after the suction supply line at the entry to the pump inlet check valve.
Generally
A pulsation dampner is installed as close to the source of the pulsation as possible.

 

Why are there different types of Pulsation Dampner ?
A. To accomodate large diameter, substantially "FLAT" PTFE diaphragms, dampers that are "flying saucer" shaped are needed.
B.  To handle corrosive liquids, dampeners where the liquid goes INSIDE an elastomer bladder are needed.
C.  For high pressure economically, small diameter dampeners in which the volume is more from its cylindrical lenght, are needed.
D. To handle sludges and slurries, that can block a dampner,"straight through" flow path damper design is necessary.

 

What are the normal quality controls on a Pulsation Dampener ?
A. Traceability of materials.
B. Pressure vessel code compliance
C. Weld procedures
D. Non destructive testing
E. Pressure test certification
F. Surface preparation and coatings.
G. Documentary package submittals.

 

What are the "pre-charge" or nitrogen cushion pre-fill needs for a Bladder , Diaphragm, and flex-tube membrane type pulsation dampener ?

1st. You do not want the membrane to block the damper inlet outlet flow holes. Therefore it is normal to use a pre-fill nitrogen"theoretical steady state presure". This will cause the damper membrane to be lifted away from the liquid flow holes when you get up to normal system pressure. This may be called an 80% pre-fill pressure.

2nd. If your consern is primary PRESURE PULSATION, as opposed to flow fluctuation smoothing, and if the pulsation frequency is above 10Hz. (10 pulses per second) OR there is acoustic resonance then a pre-fill pressure of 50% is better than an 80% pre-fill pressure.

3rd. Remember that if the system runs hotter than your Nitrogen pre-fill temperature, your prefill pressure will increase when the system starts to run. This is allowed for by reducing your pre-fill nitrogen pressure to start with.

4th. If you wish to work over a wide range of pressures without having to reset the pre-fill pressure, then the volume of the damper to be otherwisebe selected, will need to be icreased by the RATIO of the lowest pressure at which you wish damping to begin to the highest pressure at which you need the dampening.

 

How do pulsation dampers work ?- animations



When liquid is being moved, whether by: a gear tooth, a vane, a piston, or a diaphragm etc. , the flow can only happen if the liquid infront of it is pushed out of the way. Moving a column of liquid - causing flow - therefore requires energy (force / pressure)

The pressure or force will be stored by compressing some nitrogen that is above a diaphragm, outside a flex-tube, around a bladder; between the strokes / movements of one vane or piston or diaphragm and the next movement the pressure falls away. The compressed nitrogen expands forcing out the stored volume - this evening-out process is often called "dampening".

 

 

Why Nitrogen ?

At the temperatures that are compatible with flexible membranes Nitrogen gas is not reactive. 80% of the air around us is Nitrogen, therefore nitrogen is inexpensive. Nitrogen is compressed and expands in accordance with the gas laws.

 

 

Are there "bladderless no moving part" maintenance free Pulsation Dampers ?

There are solid state dampners. the principles of operation are pressure wave dissipation over distance AND pulse volume smoothing by the compressibility of the particular pumped liquid. As liquids are only slightly compressibe, the size of these dampers is enormous unless for use with at least septruplex reciprocating plunger pumps, or pumps

Size of these dampeners can be moderated by allowing much higher levels of residual pulsation that would be tollerated form "elastic" nitrogen loaded dampers.

 

 

The major application requirements for applying the above "zero servicing" acoustic pulse Dampers ?

1. Liquids without any entrained solids or particulate.
2. Hot liquids because they are more compressible.
3. Residual pulsation allowable of 7% of the steady state perssure.
4. Very large spaces after the pump discharge.
5. A hugh budget.
Absolute need for ZERO servicing

 




Pulsation Dampers for 50 Years

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