DAMPENERS
Working principle of pulsation dampeners
According to Boyle’ s Law:
PV
= PV( 1)
1 1 2 2
the volume of a gas is inversely proportional to its pressure. Thanks to this principle, it is possible to compensate for vibrations in the pipeline by changing the volume of gas. A pulsation dampener is essentially a hydraulic accumulator connected in parallel with the fluid system. Its internal structure consists of a flexible diaphragm, bellows, or bladder separating the fluid side from a gas side( usually nitrogen). During pressure increase: When the pump forces fluid into the system, the increased pressure pushes the fluid into the dampener, compressing the gas. This compression absorbs the energy of the pressure wave. During a pressure drop: When the pressure drops at the end of the pump stroke, the compressed gas expands and releases its stored energy back into the system. This process allows the fluid to maintain its motion even during low pressure. This cycle ensures that the fluid has a more stable and laminar flow profile.
Determining the dampener volume
The volume of a pulsation dampener is a key indicator of how effectively a system can dampen pressure fluctuations. A dampener with insufficient volume will fail to perform its function effectively, while an oversized dampener will result in unnecessary costs and wasted space. Therefore, accurate dampener volume calculation is critical to system reliability and economic efficiency. The dampener volume must be determined through a precise engineering analysis to meet the system’ s requirements. The volume calculation is based on parameters
Figure 2. Diaphragm-type dampeners( PVC body and stainless steel body)
such as the pumped fluid flow rate, pump type, and the desired maximum pressure tolerance(% ΔP). Pulsation dampener volume calculations are based on the principle of balancing the irregularity in the fluid volume delivered to the system by the pump on each stroke. The basic parameters required for these calculations are: Pump type: The number of pistons( cylinders) in a pump naturally determines the amount of pulsation it creates. For example, a threepiston pump produces much less pulsation than a single-piston pump. Average flow rate( Qavg): The average amount of liquid the pump pumps per minute or hour. Number of revolutions( n): The number of revolutions per minute of the pump. This determines the number of strokes. Desired damping percentage(% ΔP): This is the maximum percentage of pressure fluctuation allowed to remain in the system. This value should be kept low( 3 %) for
sensitive systems, while it can be higher( 10 %) for more tolerant systems. The commonly used scientific approach for this calculation is as follows:
V d
K
Qs n f
Pc P min
( 2)
The variables in this formula are:
V d
: Dampener volume( liters or m 3). K: Flow irregularity coefficient depending on pump type and number of cylinders.
Q s
: Maximum volume of liquid pumped by the pump during a single stroke. n: Number of revolutions per minute of the pump. f: Correction coefficient depending on the desired damping percentage.
P c
: Gas pre-pressure, usually set below the minimum working pressure( 80-90 %).
P min
: Minimum working pressure of the system. This formula specifically highlights the impact of gas pre-pressure and operating pressure on dampener performance. The ratio P c
/ P min at the end of the formula indicates how much the gas inside the dampener can be compressed at the system’ s minimum pressure, which in turn affects the amount of energy the dampener can store. However, in most practical engineering applications, the ratio P c
/ P min
is generally considered to be close to 1( because Pcis often set very close to P min
). Therefore, the simpler formula is
V d
K V stroke( 3) f
|
more widely used. |
|
|
Figure 3. Illustration of Boyle’ s law |
V
strokes
Q
= ̇ n
ort
|
( 4) |
π |
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