Selecting the right Pulsation Dampers - "A Road Map"
1. Pulsation Dampers selection by material.
I Pulsation Dampers selection, preliminary - by external materials,
a). Pulsation Dampers that are for an externally corrosive environment, whether or not the pulsation damper is for use with a corrosive liquid. PipeGuard pulsation dampers 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 Damper, is also standard in stainless steel - these Pulsation Dampers are for high frequency pressure wave resonance prevention, by interception.
b). Where the associated pumping equipment with the Pulsation Dampers are not made of stainless steel, EG the drive end of pump; then the Nitrogen cushion housing drive end of Pulsation Dampers may be of Epoxy painted carbon alloy steel. An example of one such Pulsation Damper is the PIPEHUGGER, another example is the PUMPGUARD Pulsation Damper.
II Pulsation Dampers 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 these Pulsation Dampers membranes, inside the pressure shell. "PIPEHUGGER" Pulsation Damper means to "HUG" - or look after – your pipe system!
b). The PUMPGUARD Pulsation Dampner where the liquid goes through a straight "Flex Tube" of an elastomer - this configuration being an ideal Pulsation Damper for sludges and slurries.
c). The FLEXORBER Pulsation Dampener for system liquids that require PTFE, FLEXFLON or Dupont "Teflon", where the Pulsation Dampers can not have an elastomer gas bag nor bladder nor Flex Tube.
2) Pulsation Dampers application definition, decide whether you need:
a). Pulsation Dampers for accumulating FLOW FLUCTUATION alone, for example: pulsation dampers 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 Dampers will fill this need perfectly.
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b). Pulsation Dampers that "dampen 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 category, because they are all of the FLOW THROUGH interceptors AND flow fluctuation accumulating Pulsation Damper category.
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c). Pulsation Dampers only for system response PRESSURE pulsation, Generally known as an "Acoustic Pulsation Dampers". Examples the WAVERGUARD/cer dispersal type Pulsation Dampner, and the WAVEGUARD/rj explosive dissipation Pulsation Dampner - neither have any moving parts.
3) Pulsation Dampers type selection, from the above the choice will be from:
a). A corrosion resistant outer shell Pulsation Dampers, 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 Dampers, example the PUMPGUARD by PulseGuard.
d). A Pulsation Dampers with PTFE diaphragm, example the FLEXORBER by PulseGuard.
e). A no moving parts acoustic Pulsation Dampers, 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.
5. Pulsation dampers pressure selection. Pulsation Dampers 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 additional + 15% may be added to the safety valve set pressure to produce a Pulsation Dampers "Pressure for design" of MAWP x 1.27.
Also Pulsation Dampers 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 Pulsation Dampers with a design pressure rating not less than 50% above any published Euro "P Max" figure.
Pulsation Dampers are 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 Pulsation Damper 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 pulsation dampers.
The responsibility for stating to the Pulsation Damper 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 Pulsation Damper builder.
Pulsation dampers installation mode selection.
a). Pulsation Dampers installed for suction acceleration head reduction should be placed with the liquid side uppermost. Doing this with Pulsation Dampers ensures that gravity enables all the little bubbles that would otherwise collect in the Pulsation Damper to continue on to the pump. This Pulsation Dampner installation method prevents the bubbles becoming one large bubble, which will suddenly come out of the Pulsation Dampener and cause the pump to "loose its prime".
b). Pulsation Dampers piping method for discharge acceleration head generation prevention - by flow fluctuation accumulation - also requires the use of in-line flow-through Pulsation Damper 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 Pulsation Damper 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 Pulsation Dampers.
c). Pulsation Dampers that are 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 Dampeners performance monitoring.
a). Determining Pulsation Dampers performance is almost impossible to do with a "Pressure Gauge".
b). Pulsation Dampers 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). Pulsation Dampeners 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 Pulsation Damper, because the response characteristics of the Pulsation Damper 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 Pulsation Dampener is required to work, and that is to be detected.