This document summarizes a parametric study evaluating design parameters for pulsation dampeners on plunger pumps. The study uses a pulsation model to examine the effects of: 1) Pump system configuration, finding that complex piping can significantly impact pulsations compared to just the pump package. 2) Dampener location, finding pulsations generally increase as the dampener moves farther from the pump, and are still high when located next to the pump due to quarter-wave resonances. 3) Dampener neck geometry, finding pulsations decrease with a larger neck diameter and shorter neck length to maximize the dampener's effect. The study also examines the impacts of fluid compressibility and

1. Study of pulsation dampener designs
for plunger pumps
Kelly Eberle, PEng
Michelle Witkowski, PE
Mathieu Barabe, PEng
David Zhou, PhD, PEng

2. Kelly Eberle, PEng
Principal Consultant
Wood
Kelly is a principal consultant for vibration, dynamics and noise
and has been with Wood since 1988. Kelly graduated from the
University of Saskatchewan with a Bachelor of Science in
Mechanical Engineering in 1986. He has accumulated a wide
range of design and field experience, particularly in the area of
pressure pulsation analysis and mechanical analysis of
reciprocating compressor and pump installations. His
experience also includes field vibration analysis, flexibility
studies, structural analysis and foundation analysis.
Presenter
2

3. Diwen (Dave) Zhou,
PhD, PEng
Computational
Dynamics Scientist
Wood
Dave is a Computational Dynamics Scientist and has been with
Wood since 2013. He graduated from the University of British
Columbia with a Ph.D. degree, Chemical and Biomedical
Engineering 2010. His experience includes pulsation and
mechanical analysis of reciprocating compressors and pumps.
His current role also includes the development of Wood’s
pulsation analysis software.
Presenter
3

4. Overview
• Presentation of a parametric study evaluating the design
parameters for pulsation dampeners on plunger pumps
• Today’s presentation will focus on appendage type gas
charged dampeners
• Paper discusses pulsation filters and surge volumes
4

5. Why is this topic important?
5
High-impact consequences
• Safety and environmental risks
• Corporate liability
• Extended downtime
• Significant financial costs
Piping vibration → integrity risk
21% of hydrocarbon releases are due to fatigue and vibration
21%
Degradation of material properties
Fatigue or vibration
Incorrect installation
Corrosion or erosion
Procedural
Other
28%
21%
13%
7%
10%
21%

6. What is a dampener?
Device added to a reciprocating pump system to
“smooth out” or “dampen” flow and pressure
fluctuations
6
Dampener

7. Why is a dampener needed?
7
• Reciprocating pumps generate
pressure and flow pulsations
due to their normal operation
• Pulsations can be amplified due
to resonances in the piping
system
• Pulsations can be a root cause
for fatigue failures
Pulsation Forces Vibration Stress Failure

8. Agenda
• Pulsation control devices
• Selecting a dampener
• Parametric study: system effect, location,
neck geometry, fluid type, number of
plungers
• When is a dampener needed
• Conclusions
8

9. Types of pulsation control devices
9
• Many different commercial products for
controlling pump pulsations
• Different names: dampeners, stabilizers, acoustic
filters, desurgers, surge suppressors,
accumulators, snubbers
• Three main types
1.Dissipative or resistance
devices
2. Absorptive devices
3. Acoustic filters

10. Absorptive devices
10
• Large volume that reduces pressure
and flow pulsations
• Volume acts like a spring to absorb
pulsations generated by the pump
• Most common devices are gas filled.
Gas has a much greater absorptive
effect as compared to a liquid.

11. Absorptive device
11
A small gas volume is equal to a large liquid volume; device
can be smaller
𝑉𝑔 = ൘
𝑉𝑙 × 𝜌 𝑔 × 𝑐 𝑔
2
𝜌𝑙 × 𝑐𝑙
2
Where V is volume, ρ is density, c is acoustic velocity, and
g and l are subscripts for gas and liquid

12. Absorptive device
12
Example: Assume a water system at 60oF (15.6 oC) and 350
psia (2414 kPa). What is the equivalent water volume for 300
in3 (~5 L) of nitrogen?
The density and acoustic velocity of nitrogen is 1.775 lbm/ft3 (28.433
kg/m3) and 1147 ft/s (349.6 m/s). The density and acoustic velocity of
water is 62.4 lbm/ft3 (999.6 kg/m3) and 4830 ft/s (1472 m/s).
𝑉𝑙 = ൙
300𝑖𝑛3 × 62.4
𝑙𝑏 𝑚
𝑓𝑡3 ×
4830𝑓𝑡
𝑠
2
1.775
𝑙𝑏 𝑚
𝑓𝑡3 ×
1147𝑓𝑡
𝑠
2
𝑉𝑙 = 187,014 𝑖𝑛3
The equivalent volume of nitrogen to water is about 1:625

13. Absorptive device
13
• “Appendage” type gas charged dampener are
most common
• Elastomeric bladder used to separate gas from
liquid
• Pros:
– Easy to install, readily available
– Large equivalent liquid volume
• Cons:
– Limited bladder life
– Adjust charge pressure if line pressure
changes
– “Neck” makes device less effective
• “Dampener” will be used in the remainder of
this presentation for this device
Neck
Bladder
Flow

14. Selecting a dampener
14
• API 674 and 675 define two analysis approaches:
– Approach 1: Empirical or other proprietary analysis technique
– Approach 2: Design based on acoustical simulation
• In our experience, the most common approach for
selecting a dampener volume, 𝐷𝑉, is from formula similar
to:
𝐷𝑉 =
𝑃𝐷 × 𝐶 𝑝 × ൗ𝑃𝑚𝑒𝑎𝑛
𝑃 𝑚𝑖𝑛
𝑛
1 − ൗ𝑃𝑚𝑒𝑎𝑛
𝑃𝑚𝑎𝑥
𝑛
𝑃𝐷 is the pump displacement per stroke
𝐶 𝑝 is a pump constant
𝑃𝑚𝑒𝑎𝑛 is mean line pressure
𝑃 𝑚𝑖𝑛 and 𝑃𝑚𝑎𝑥 are the minimum and maximum pressure due to pulsation
𝑛 is the polytropic expansion coefficient of charge gas

15. API 674 Approach 1: empirical sizing
15
• Case study: Suction Dampener Sizing
– Quintiplex pump with 2.75” (70mm) bore, 4” (102 mm) stroke
– Dampener charged to 80% of line pressure with nitrogen
– Sized for 10% pressure pulsation (peak-peak) for a line
pressure of 350 psig (2,413 kPa)
𝐷𝑉 =
𝑝𝑖
4
2.752 × 4 × 5 × .06 × ൗ350
332.5
.714
1 − ൗ350
367.5
.714
𝐷𝑉 = 216 𝑖𝑛3 (3.54 l)
• Standard dampener size is 300 in3 (4.9 l)

16. API 674 Approach 1: empirical sizing
16
Conclusion: Larger dampener volume=lower pulsation

17. API 674 Approach 2: pulsation model
17
• FEED stage only the pump package design is
known. Pipe system not defined
• Pulsation model only include pump and package
piping
Pump
package
flange
Pump and dampener pulsation suction model
Pump
fluid end
Passage to
each valve
and plunger
Suction pipe Pump
package
flange
Dampener
Pump package CAD Model

18. API 674 Approach 2: pulsation model
18

19. API 674 Approach 2: pulsation model
19
• Pulsation model shows the pulsation reduction is
insensitive to the dampener size
• Small amount of gas has a significant impact
• Neck geometry and location controls the
dampener effectiveness
• Dampener sizing by empirical formula is too
simplistic

20. Why does pulsation stay the same?
20
• Pulsation is the result of a ¼ wave resonance
between the pump manifold and dampener
• ¼ wave resonance forms between a closed and
open boundary
n=1
n=3
n=5
Open Closed
Length

21. Why does pulsation stay the same?
21
• Pulsation model show there is a ¼ wave resonance
• A larger volume does not change the resonance
• Neck geometry limits the absorptive effect

22. Parametric study
22
• Approach is to evaluate different aspects of the
gas charged appendage type dampener by using a
pulsation model
• Study effects such as
– Pump system
– Dampener location relative to the pump
– Dampener neck geometry
– Fluid type
– Number of plungers

23. Parametric study: system effects
23
Consider the same pump used in
the previous example
- Quintiplex pump operating 90 to 385
rpm (VFD motor)
- 2.75” (70 mm) bore, 4” (102 mm) stroke
- Produced water application, SG=1.2
- Suction pressure 350 psig (2,314 kPa)

24. Parametric study: system effects
24
Recall the pulsation model for the pump package
only
Pump and dampener
pulsation suction model
Previous result
at 350 rpm

25. Parametric study: system effects
25
• Suction system is quite complex
– Tank as source of produced water
– Many branches for relief, bypass and other flow paths
Pump
Suction piping arrangement Suction pulsation model
Skid
edge
Pump

26. Parametric study: system effects
26
• Many pulsation resonances
due to complex pipe
arrangement.
• Pressure pulsations are
much different for the pipe
system model vs the pump
package model
• High risk in selecting a
gas-charged dampener
before evaluating the
effect of the piping

27. Parametric study
27
• Approach is to evaluate different aspects of the
gas charged appendage type dampener by using a
pulsation model
• Study effects such as
– Pump system
– Dampener location relative to the pump
– Dampener neck geometry
– Fluid type
– Number of plungers

28. Parametric study: location effects
28
• Little industry guidance as to the recommended
dampener location
– Common to see “locate as close to pump as practical”
– One reference states “within 10 pipe diameters”
• Evaluate range of dampener locations relative to
the pump inlet flange
• Use the same pump and operating parameters
from the previous examples.
• Simplify the model to a straight suction line of
fixed length
• Compare pulsation results at the model
termination

29. Parametric study: location effects
Pump
6”XS pipe
3” XS neck,
x 10” long
300 in3
dampener
Dampener located
24” from pump
flange
Pulsation results
compared at
model termination
29

30. Parametric study: location effects
30
• Dampener are sometimes installed on the non-
flow end of the pump

31. Parametric study: location effects
31
• Pulsation is generally
higher as dampener moves
farther from pump
• Pulsation is still high when
next to pump
• ¼ wave resonance between
dampener and pump
– Lower frequency at longer
distance so pulsations are
higher
– Trend drops at some
distances. ¼ wave tuned to
lower speed
• No ¼ wave resonance
when dampener on non-
flow end. May increase
when system piping added

32. Parametric study
32
• Approach is to evaluate different aspects of the
gas charged appendage type dampener by using a
pulsation model
• Study effects such as
– Pump system
– Dampener location relative to the pump
– Dampener neck geometry
– Fluid type
– Number of plungers

33. Parametric study: neck effects
33
• Use the same pump operating parameters
• Use the same model of dampener as that for
location effects study. Set the dampener
location at 24” (about 4X mainline diameter)
• Vary the diameter and length of the “neck“. All
other geometry is fixed.
• Compare maximum overall pulsation at the
model termination
Neck
length, L
Mainline
Diameter, Dm
Neck
Diameter, Dn

34. Parametric study: neck effects
34
• General result: make the
neck diameter as large as
possible and neck length as
short as possible
• Neck diameter at least 50%
of mainline diameter will
reduce pulsation 15% to
20%
• Neck length of less than 2x
to 3x neck diameter will
maximize dampener effect
• Even an ideal dampener
with no length and a
diameter equal to the
mainline still results in 8%
line pressure pulsation
• Illustrates limitation of appendage
type gas charged dampeners

35. Parametric study
35
• Approach is to evaluate different aspects of the
gas charged appendage type dampener by using a
pulsation model
• Study effects such as
– Pump system
– Dampener location relative to the pump
– Dampener neck geometry
– Fluid type
– Number of plungers

36. Parametric study: fluid effects
36
• Fluid compressibility is important to the pulsation response
• Water is relatively incompressible
• Propane at low pressure or high temperature is very compressible
• Dampener sizing formula does not consider fluid compressibility
• Bulk modulus is the fluid property describing the compressibility. In
our study, the bulk modulus was varied from 16250 to 339000 psi.

37. Parametric study: fluid effects
37
• Evaluated same pulsation model from the previous example
• Two factors that were changed: fluid bulk modulus and density

38. Parametric study: fluid effects
38
• The higher the bulk
modulus, the higher the
pressure pulsations
• Compressible fluids have
lower pulsations
• Low bulk modulus means
the fluid easily
compresses. More relative
motion between fluid
particles gives more
resistance to pressure
pulsations propagating

39. Parametric study
39
• Approach is to evaluate different aspects of the
gas charged appendage type dampener by using a
pulsation model
• Study effects such as
– Pump system
– Dampener location relative to the pump
– Dampener neck geometry
– Fluid type
– Number of plungers

40. Parametric study: # of plungers
40
• Dampener sizing formula includes a pump constant.
More plungers = lower pump constant so smaller dampener volume
is required
• Rationale based on superimposing plunger motion (red trace below)
• More plungers results in lower amplitude fluctuation. Quintiplex better
than Triplex for pulsation assuming same power, flow, and pipe system
Quintuplex Pump Triplex Pump

41. Parametric study: # of plungers
41
• Superimposing plunger motion is not a true representation of the flow
fluctuations
• “Shark-fin” shape of flow versus crank angle is a precise model
• Decomposing the time wave to frequency components demonstrates
the differences
• Conclusion: Triplex pump creates more flow fluctuations (pulsations)
than a quintuplex

42. Parametric study: # of plungers
42
Quintuplex
Pump Triplex
Pump
• Evaluate the pulsation and dampener effectiveness for a quintuplex
and triplex pump
• Piping, dampener and fluid are identical
• Flow, power, speed and pressures are identical
• Triplex plungers are larger than quintuplex

43. Parametric study: # of plungers
43
• Pulsation results show much high amplitudes for the quintuplex pump
• This result is opposite to previous knowledge about the pulsation
source from the pump. Why?
• Quintuplex ¼ wave resonance occurs at 4x PPF
• Triplex ¼ wave resonance occurs at 10x PPF
• Shorter pump fluid end results in higher resonant frequency
Quintuplex Pump Triplex Pump
¼ Wave
Resonant
Frequency
¼ Wave
Resonant
Frequency

44. Parametric study: # of plungers
44
• Pump pulsation input
– 4xPPF for the Quintuplex is greater than 10xPPF for the Triplex
– Lower pump pulsation input means pulsation at resonance is lower
• Conclusions
– Not always true that more plungers means lower pulsations
– Need to consider pulsation resonances

45. When is a dampener needed?
45
• Parametric study demonstrated shortcomings of convention dampener
sizing approaches and complexities of pulsation analysis
• What does a pump package design do?
– Do I need a dampener?
– Will a dampener always work?
– When might an orifice plate work and a dampener is not necessary?
– Is a pulsation filter required?
– I don’t have time for a pulsation study.
• The concept of a Source Strength Coefficient is proposed
𝑆𝑆𝐶 = 𝜌𝑐𝑄
– 𝜌 is the fluid density
– 𝑐 is the acoustic velocity
– 𝑄 is the Acoustic volume flow rate
• Units of SSC are force (lb or N); analogous to the pulsation driving
force created by the pump

46. When is a dampener needed?
46
• 𝜌 and 𝑐 can be determined from the pump performance
• 𝑄 (acoustic volume flow rate) is based on the FFT of the
“shark fin” of flow versus time (as discussed previously)
• Calculations of the Source Strength Coefficient can be
done after sizing of the pump is done with a simple
spreadsheet
• Authors have conducted a large number of pulsation
studies. Correlated SSC to the recommended pulsation
control design
• A less direct measure of the potential pulsation generated
by the pump is the required power. Guidance given related
to power.

47. When is a dampener needed?
47
Pulsation control approach* Source strength
coefficient
Pump required power
lbf N HP kW
Traditional dampener sizing is
appropriate
<120 <535 <25 to 50 <18 to 37
API 674 pulsation study
recommended
>120 >535 25 to 50 18 to 37
Surge volume or volume-choke filter
is likely required
>220 >980 >50 to 100 >37 to 75
Volume-choke-volume is likely
required
>400 >1780 >100 to 200 >75 to 150
* Suggested approach when pump operates over a wide speed range or pump
operates over a range of pressures, temperatures or fluid properties. SSC and Power
criteria could be higher for fixed speed pumps with constant operating conditions.

48. Surge Volume
48
26” OD x 74” s/s
Discharge Surge Volume

49. Pulsation Filter
49
Volume-choke-volume filter Volume-choke filter

50. Conclusions
50
• API 674 Approach 1 gas-charged dampener sizing formula may
NOT be suitable (variable speed, varying fluid properties)
• Selecting a gas charged dampener with only a pump package
pulsation model WILL NOT give reliable results
• Selecting a pulsation filter or surge volume with only a pump
package pulsation model WILL give reliable results
• Install dampener as close to the pump flange as possible, less
than five pipe diameters
• Keep the gas-charged dampener neck as large (50% mainline
diameter) and short (2 to 3 neck diameters)
• Variable-speed pump is more likely to have excessive pressure
pulsations
• Consider range of liquid properties when selecting a dampener
• Source strength coefficient can indicate the type of pulsation
control device required for a pump application

51. Thank you
Questions?
Kelly Eberle
kelly.eberle@woodplc.com
Dave Zhou
dave.zhou@woodplc.com
Visit us at table #10