Pulsation Damper Selection
Making the right Pulsation Damper choice - "A Road Map"
1. Pulsation Damper selection by material.
I Pulsation Damper selection, preliminary - by external materials,
a). Pulsation Damper that is for an externally corrosive environment, whether or not the pulsation damper is for use with a corrosive liquid. The PipeGuard pulsation damper in standard with a stainless housing. For Example the PipeGuard Pulsation Damper is therefore a norm for saline environment use; EG on oil and gas production platforms. The WAVEGUARD no moving parts Pulsation Dampener, is also standard in stainless steel - this Pulsation Damper is for high frequency pressure wave resonance prevention, by interception.
b). Where the associated pumping equipment with the Pulsation Damper is not made of stainless steel, EG the drive end of pump; then the Nitrogen cushion housing drive end of the Pulsation Damper may be of Epoxy painted carbon alloy steel. An example of one such pulse dampener is the PIPEHUGGER, another example is the PUMPGUARD Pulsation Dampener.
II pulse dampener selection, secondarily - by liquid contact parts compatibility.
a). The PIPEHUGGER Pulsation Damper where liquid goes inside a rolling diaphragm bladder made of a suitable elastomer, and the gas cushion is outside this pulse dampener membrane, inside the pressure shell. "PIPEHUGGER" pulsation dampener means to "HUG" - or look after – your pipe system!
b). The PUMPGUARD Pulsation Damper where the liquid goes through a straight "FlexTube" of an elastomer - this configuration being an ideal pulse damper for sludges and slurries.
c). The FLEXORBER Pulsation Damper for system liquids that require PTFE, FLEXFLON or Dupont "Teflon", where the Pulsation Damper can not have an elastomer gas bag nor bladder nor FlexTube.
2) Pulsation Damper application definition, decide whether you need:
a). A Pulsation Damper for accumulating FLOW FLUCTUATION alone, for example a pulsation damper where you only use one connection and add it to a "T" piece. A single connection PIPEGUARD Pulsation Damper, or a single integral flange face PIPEHUGGER Pulsation Damper will fill this need perfectly.
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b). A Pulsation Damper that "dampens pulsation", - meaning "dissipates pressure waves" - AND ALSO is a "Pulsation Damper", or more correctly a Pulsation Damper PREVENTOR, - which works by accumulating the flow fluctuations, which would otherwise cause acceleration head change without a Pulsation Damper . The Pulsation Damper called PIPEHUGGER TW, and the PUMPGUARD, also the FLEXORBER Pulsation Damper are all in this DUAL PURPOSE catagory, because they are all of the FLOW THROUGH interceptors AND flow fluctuation accumulating Pulsation Damper category.
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c). A Pulsation Damper only for system response PRESSURE pulsation, Generally known as an "Acoustic Pulsation Damper". Examples the WAVERGUARD/cer dispersal type Pulsation Dampner, and the WAVEGUARD/rj explosive dissipation Pulsation Damper - neither have any moving parts.
3) Pulsation Damper type selection, from the above the choice will be from:
a). A corrosion resistant outer shell Pulsation Damper, example the PIPEGUARD by PulseGuard.
b). A dual-purpose Accumulator and pressure Pulsation Damper, Example the PIPEHUGGER by PulseGuard.
c). A sludge and slurry Pulsation Damper, example the PUMPGUARD by PulseGuard.
d). A Pulsation Damper with PTFE diaphragm, example the FLEXORBER by PulseGuard.
e). A no moving parts acoustic Pulsation Damper, example one of the WAVEGUARD units by PulseGuard.
4) Pulsation damper volume selection. Pulsation Damper volume required for flow fluctuation reduction by accumulation, is a volume of Pulsation Damper dependent on the level of tolerable residual pulsation, and dependent on the level of flow fluctuation that would otherwise occur.
a). A Pulsation Damper for addressing a given volume of an individual flow fluctuation, will depend on the characteristics of the source of the fluctuation to be smoothed by the pulsation damper.
b). Relative to the volume necessary for a simplex single acting reciprocating pump, the Pulsation Damper volume will be :-
c). Pulsation Damper for duplex pump as little as 25%
Pulsation Damper for a 2 lobe pump, down to 20%
Pulsation Damper for a hose pump as low as 15%
Pulsation Damper for a triplex machine as little as 10%
Pulsation Damper for quintuplex plunger type as small as 6%
Pulsation Damper for the displacement per vane of a vane type 2%
Pulsation Damper centrifugal as small as 0.5%
For the math please GOTO ?????????????
5. Pulsation damper pressure selection. Pulsation Damper pressure selection depends on whether the design pressure "Pd" is to be the same as the MAWP, or whether 10% is to be added for a higher than MAWP safety valve setting. For the safety of a Pulsation Damper an aditional + 15% may be added to the safety valve set pressure to produce a Pulsation Damper "Pressure for deesign" of MAWP x 1.27.
Also a Pulsation Damper may be rated with a Euronorm "P Max", that is some 40% less safe, than for example an ASME VIII 1995 rating Pulsation Damper where the allowable working stresses were more conservative.
As a general rule it is wise to choose a pulse dampner with a design pressure rating not less than 50% above any published Euro "P Max" figure.
A Pulsation Damper is not for a "static pressure application", Pulsation Damping is a cyclic duty, therefore to avoid fatigue failure low working stress levels should be used for any pulse dampner application. Current European practice based on the Pressure Equipment Directive "the PED" and new high stress issues of ASME VIII part 2D, are both unproven and potentially dangerous for a pulsation damper.
The responsibility for stating to the pulse dampner fabricator, what pressure for design, should be used, and whether to use an unsafe static pressure / non-cyclic pressure vessel code or not, is the responsibility of the Pulsation Damper user, not the liability of the pulse damper builder.
Pulsation damper installation mode selection.
a). A pulse damper installed for suction acceleration head reduction should be placed with the liquid side uppermost. Doing this with a pulsation dampener ensures that gravity enables all the little bubbles that would otherwise collect in the pulsation dampener to continue on to the pump. This Pulsation Damper installation method prevents the bubbles becoming one large bubble, which will suddenly come out of the Pulsation Damper and cause the pump to "loose its prime".
b). A Pulsation Damper piping method for discharge acceleration head generation prevention - by flow fluctuation accumulation - also requires the use of in-line flow-through pulse dampener connection. Flow through configuration ensures that the Pulsation Damper does not cause pressure pulsation by the need for pressure change, i.e. pulsation, simply to cause the mass flow to go up, stop, then come back down, a single pulsation damper connection in a split fraction of a second. Single connection pulse dampener flow reversal causes them to be, in many cases only one third as efficient a damper, as a genuine flow through multi-port, zero direction change, pulse dampener.
c). A Pulsation Damper that is being installed to intercept the high frequency pressure pulsation, typically traveling at 3500 mph, emanating from short pipe length reflection times, must be an in-line flow-through connected Pulsation Damper.
Pulsation Damper performance monitoring.
a). Determining Pulsation Damper performance is almost impossible to do with a "Pressure Gauge".
b). A pulse dampener becomes partially irrelevant because a pressure gauge has its own response characteristics, it is after all a weight of mechanism on a spring.
c). It will "wag" at a rate, and over a width of "swing", dependent on its characteristics. A pulse is purely the exciter.
d). A Pulsation Damper will modify the form of the excitation, but there is a difficult correlation between a Pulsation Damper characteristics and those of a gauge.
e). It is also misleading to monitor by a gauge connected to the cushion gas side of a pulse dampener, because the response characteristics of the pulse dampener gas/liquid/separator membrane may be phase lagging.
f). It is advisable to deploy a pressure transducer with very high response characteristics after the Pulsation Damper outlet, and to have data capture at least 4 times faster than any frequency, at which the pulse dampener is required to work, and that is to be detected.