System Mass Acceleration Head Pulsation
Consider Suction Acceleration Head ("A.H.") Losses, + How Much Discharge"A.H." Your System Will Generate.
Estimate, how smooth will it be, with no pulsation dampeners at all.
Before specifying a smoother system, you may wish to estimate how much improvement you need from the system, as it will be. The calculation below is a rule of thumb that covers pressure pulsation generated to overcome system resistance to pump flow fluctuation only. 
EXPLANATION 
Pressure pulsation generated by a system resisting flow fluctuation from your pump mostly depends on the mass of your liquid that has to follow the variations in velocity from your pump, the "flow fluctuations". This need to create head, or pressure, is often referred to as system "mass acceleration head". Flow "friction" also plays a part (see friction page) depending on system pipe size choice. To "visualize" what has to happen, first establish the weight of your liquid that has to fluctuate. Then consider the speed at which you intend to run your pump. The mass and time available for velocity change is where your system generates the pressure pulsation excitation. How much this is dissipated or amplified by the characteristics of your piping design, controls how much pulsation your system will cause. 
Necessary Information to estimate acceleration head Pulsation.
SG Specific Gravity  Grams per Cubic Centimeter, gm/"cc", gm/cm3; Conversion from Lbs/Ft3, divide by 63
L Length of pipe in feet, Ft.
Q Volumetric flow rate, in US Gallons per hour. Consider 1 US Gallon to equal 3.8 Liters
N Number of displacements per minute, RPM x Number of displacers per rev.
ID Average Internal Diameter of the pipe that is full of the liquid.
Z A figure of relative decrease in "pulsatiousness" by number of displacers  examples are crank driven plungers.
NOTE: SG, L & ID have nothing to do with the pump.

RELATIONSHIP
Addition to system pressure, peaks from accelerated head, or on a suction supply system: the pressure loss that will prevent the pump from filling. 

Typical values for "Z" for reciprocating sine motion driven machines.
1 For simplex (Single piston, plunger, or may be reciprocating oil to move a diaphragm)
2 For duplex (Two plungers, etc. Flow still comes to a halt as one displacer takes over from the
other)
4 For triplex (Three plungers, etc. Flow still comes to a near halt unless the volumetric
efficiency is well above 75%)
6.5 For quadruplex (Four plungers, etc. phased at 90  Sounds better, but chances of resonance
are worse)
9 For Quintuplex (Five displacers, overlap even with hot compressible liquids at high pressure)
18 For Septuplex (seven displacers, smoother flow than a "Quin", but the frequency is high and
may match the natural vibration frequencies or the acoustic or the mass oscillation
frequencies of short pipe nodes)
For two displacers or more where the drive is a linear oscillation, from fluid power, the value for "Z" may
be more than doubled. How much more than doubled, depends on the dwell that occurs on direction
changeover. This is more affected by drive fluid compressibility than valve design.

TWO EXAMPLES 
In these two examples, the pumped flow rate, stays the same, the "jerkrate"  number of modulations per
minute, and everything else stays the same, EXCEPT PIPE LENGTH " L".
The formula is from general industry use by Milton Roy and Foster Wheeler, etc. The "Z" factors are modified from empirical experience since 1963.
NOTE: Increased pipe length gives more pulsation. Therefore, pulsation depends on the system. Similarly, changing the density of the liquid, or the diameter of the pipe, will change the pulsation.
PulseGuard pulsation dampeners are designed to address pressure pulsation, which is caused by the resistance of the system to flow. Therefore our dampeners focus on the system related responsibility and are less related to pump liability. Please
call 1888DAMPERS, not the pump vendor.

NOTE 
As pulsation depends on pipe system length, diameter and the specific gravity of the system liquid,
selecting a dampener without taking system details into consideration, is likely to lead to a less than
suitable dampener specification. 
