The pulsation phenomenon is an inherent phenomenon of the peristaltic pump, and it is impossible to eliminate it for all the current peristaltic pump structures. However, in some applications, the pulsation phenomenon is not allowed, or needs to be appropriately reduced to meet the requirements. If the application requires no pulsation, then the peristaltic pump is not suitable, so you need to choose a more stable pump type, such as an impeller pump or a fine gear pump.

The so-called pulsation phenomenon refers to the transmission of liquid by the peristaltic pump. Two parameters are generally used to describe the pulsation phenomenon, the frequency and the amplitude of the pulsation.

The frequency of pulsation refers to the number of pulsations per unit time, and the unit time can be 1 second or 1 minute or other time. The peristaltic pump has the same amount of transmission in a long period of time, such as one minute, that is, the amount transmitted in the previous minute and the next minute is the same, but if the time is shortened to a few seconds or less, the peristalsis The transfer volume of the pump will be different, this is because the instantaneous speed of the peristaltic pump transfer liquid is changed periodically. In some occasions, for example, when dispensing glue from a gas palm machine, it needs to be evenly spread on the packaging bag. In order to achieve a more uniform application process, usually a peristaltic pump is used to transfer the glue to the cotton or sponge first, and the packaging bag will evenly take away the glue by contacting the cotton or sponge. If you want to apply more evenly, then the glue saturation of the cotton or sponge must be relatively stable. If the pulsation frequency of the peristaltic pump is low, then the interval between the two strands will be a little longer, because the gas palm machine is always running at high speed, this interval will take away a lot of glue, making cotton or sponge glue. The saturation has dropped drastically, resulting in uneven application. Therefore, in order to apply evenly, it is necessary to quickly add glue to the cotton or sponge to maintain the saturation at a relatively stable value. At this time, this problem can be solved by increasing the pulsation frequency of the peristaltic pump. There are two ways to increase the pulsation frequency, which is to increase the speed of the peristaltic pump. In the case of a certain pump head structure, increasing the speed is a direct way to increase the pulsation frequency. However, if there are strict requirements on the flow rate, simply increasing the speed is not possible, because an increase in the speed will increase the flow rate accordingly. Therefore, a thinner hose should be replaced, and then the speed should be increased. This will ensure the flow rate requirement and increase it. frequency. The second is to increase the number of pump head rollers. At the same speed, the frequency of pulsation will increase significantly, but when the number of rollers increases, the flow rate of the pump head will decrease under the same arc and roller structure, so increase the pump speed. Achieve the same flow rate, so the frequency of peristaltic pump pulsation will further increase.

The amplitude of the pulsation is another important parameter of the pulsation phenomenon. Different pump heads and hoses have different pulsation amplitudes. The pulsation amplitude is determined by two parameters: the size of the hose and the diameter of the roller. Place the tube in a straight line and horizontally, and then press the roller down in a direction perpendicular to the direction in which the tube is placed. After the tube is fully compressed, the volume of the tube reduced by the compression and deformation is the amplitude of the pulsation. In fact, when the peristaltic pump transfers fluid, not only is there a pause between the two pulsations, but the fluid is not transferred, but it also flows back a short distance. Then in the entire transmission process, the fluid is transmission-reverse flow-transmission, and so on. In a long period, the transmission speed of the peristaltic pump is stable, and the instantaneous speed is changing at any time. In some occasions, such a transmission method is not allowed. In order to reduce or even eliminate this pulsation phenomenon, there is a product called pulsation damper. The general principle is to enter the liquid in a large mouth and discharge the liquid in a small mouth. As each stream of liquid arrives quickly, the liquid cannot flow out of the small mouth completely and quickly. The pressure generated by the excess liquid will be absorbed by the air in the damper. The pressure of the air in the cavity gradually increases, and the flow velocity at the narrow opening will increase accordingly, eventually reaching a relatively stable state. Why this can reduce the pulsation is because in principle, under the condition of all the pipelines unchanged, as long as the air pressure in the cavity is stable, the flow rate at the outlet will be stable. If the volume of the cavity is far larger Due to the amplitude of the pulsation, when a single pulsation arrives, the impact on the air pressure of the damper cavity will be small, so that the relative pressure of the cavity will be relatively stable under a small fluctuation. There will be only a small fluctuation in the flow rate at the location. Because the pulsation damper cannot be unlimited, so the fluctuation of the fluid will definitely exist, but the phenomenon of backflow has been eliminated. The use of a pulsation damper is restricted. The fluid must be able to contact the air. The volume of the second damper must be compatible with the flow rate. That is, the size of the cavity must be in a proper ratio to the pulsation amplitude, which must be stable according to the flow rate. Sexual requirements are determined. The same pulsation damper cannot adapt to all flow rates, but only has a better buffering effect on a very narrow flow rate range. Therefore, if the liquid transmission involves a wide range of flow rates and must significantly reduce the pulsation of the flow rate, then the pulsation damper alone cannot be achieved. It can be imagined that if the flow rate is too low, the pulsation damper cavity cannot If a stable pressure is generated, the pulsation cannot be reduced well; if the flow rate is too fast, the pulsation can be significantly reduced, but because the narrow mouth wants to increase the flow rate, the pressure in the cavity needs to be doubled, and the peristaltic pump itself is a For low-pressure pumps, the general working pressure does not exceed 0.15Mpa, and the service life of the hose will be significantly reduced under the critical pressure for a long time, so comprehensive consideration should be given to the use. In addition, after using the pulsation damper, when the pump stops, because of the pressure in the cavity, the outlet will continue to emit liquid until the pressure in the cavity is reduced to the same degree as the external pressure.

Using a similar principle, you can also consider using the elasticity of the hose to absorb pulsation. The requirement of the hose point used by the peristaltic pump is that the elasticity should be high enough to ensure the stability of the flow rate. Then the hose can be properly extended at the outlet of the pump head, generally more than one meter will have a very obvious effect. According to the requirements of different flow rates, adapt a thin connector or needle with a suitable inner diameter at the outlet of the hose. Also when the peristaltic pump is working, every time the pulsation comes, because the thin connector or needle is too late to discharge all the liquid quickly, the hose at the outlet Pressure will be generated inside. When the flow rate of the fine joint or the needle is the same as the rate of the peristaltic pump, the internal pressure of the hose at the outlet will be stable, and every time a pulsation arrives, the excess pressure will be absorbed by the entire hose. Expansion to absorb, to achieve the effect of reducing pulsation. This can achieve the same effect as using a pulsation damper, and can transmit air-sensitive liquids, so the pulsation damper is rarely used. Similarly, thin joints or needles of different calibers can only adapt to a very narrow flow rate range. After the pump is stopped, the outlet will continue to flow out until the pressure inside and outside the tube is balanced.

The third method of reducing pulsation has a slightly different principle. It uses the working principle that the flow rate of the fluid at the outlet does not change when the liquid level difference and the pipeline state remain unchanged. In fact, the fundamental principles are the same, all trying to construct a stable pressure to achieve the purpose of reducing pulsation. Using a peristaltic pump to control the liquid level of a tank to change within a small height difference, then the flow rate at the outlet will definitely maintain a very stable state, but this method of use is only suitable for very few cases and is not used much. The current commonly used method is the second solution, which uses the elasticity of the hose to work.