Size
The amount of pulsation absorbed by a dampener is a function of the dampener size to the pump stroke volume. An undersized dampener cannot absorb enough energy to adequately compensate for fluctuations in pressure and flow. An oversized dampener stores more fluid and can, in some cases, result in slow equalization and delayed response to system changes.
The first step in sizing is to quantitatively determine the amount of tolerable pressure variation. Once an acceptable pressure variation is defined, the dampener size required for the desired level of dampening performance can be calculated.
Location
To be effective, it is critical that the dampener be installed as close as possible to the source of the pulsation or water hammer pressure spike source.
Pulsation dampeners are installed at the pump discharge to fill with process fluid on the discharge stroke and then release some of that fluid on the suction stroke to keep the fluid moving smoothly downstream.
Inlet stabilizer dampeners are installed at the pump inlet to store fluid and release it back into the line on the pump inlet stroke to minimize acceleration head loss. This is important because the pump can draw fluid from the dampener instead of having to re-accelerate the mass of fluid in the pipeline.
Charge
Pulsation dampeners must have a gas pre-charge using compressed air or nitrogen that is below normal system pressure, creating a low-pressure area on the nonwetted side of the dampener. The wetted side of the dampener accepts fluid that pushes against the bladder, compressing the gas charge until the gas pressure is equal to the fluid pressure. The energy of the pulse or pressure spike is dissipated as the gas and fluid pressure equalize.
Dampener pre-charge pressure depends on the specific application, usage, and dampener model or type. Generally speaking, pulsation dampeners installed at the pump discharge are pre-charged to approximately 80% of expected mean system pressure. Once the pump is started to generate system pressure, the charge can be increased or decreased to optimize the dampening effect.
The pre-charge pressure for inlet stabilizer dampeners is much lower, typically around 50% of the pump inlet’s static system pressure. In the case of suction lift applications, the pre-charge pressure is negative. Like standard pulsation dampeners, the charge can also be adjusted higher or lower after the pump is started.
As with any pumping system component, proper setup is critical for getting the best results from a pulsation or inlet stabilizer dampener. Sizing, location and charge will lead to better dampener and pumping system performance by reducing pressure variations in all areas of the system.
This post is intended only as a general overview regarding the importance of dampener size, location and charge. Every application is different and requires expert planning, design, installation and operation for optimal performance, safety and reliability. Contact Blacoh for more information on your specific application.
Always read and observe all instructions and safety warnings in the applicable installation and operation manual before installing, operating or repairing any dampener.