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How can I increase the pressure of my peristaltic pump?
When determining the pressure capabilities of your peristaltic pumping system, there are two factors to consider. One is the pump and pump head capabilities. High-quality peristaltic pumps have rollers that are mounted to springs. These springs make the pump smart, as it can adjust the pressure it puts on the tube as the tube ages. However, under high pressure applications, this spring can be compressed by the pressure in the tube, thus allowing back flow. The motor of the pump will also affect pressure capabilities. Motors can generate a certain torque force and have a specific horsepower output. If the pressure in the tube is greater than the torque force or horsepower of the pump, the motor can stall or fail. Generally, peristaltic pumps are built to function as high as 30 psi but are easily available up to 100 psi.
The second factor, and more likely reason for your pump's low pressure output, is the tubing. Pumps are generally used with platinum-cured silicone tubing or occasional thermoplastic elastomers such as bioprene, pharmed or C-Flex. Silicone tubing pressure has an inverse relationship to the ratio of bore size to wall thickness (ie, the higher this number, the lower the pressure). Generally, if you anticipate pressures of 20 psi or greater, the use of silicone tubing is not recommended. Thermoplastics are also not ideal for peristaltic pumps, as they have very low purity due to spallation (particulate matter that sheds off the tubing).
The most appropriate tubing to use to increase your pressure capabilities is STA-PURE® peristaltic pump tubing. STA-PURE® tubing has a working pressure rating of 100 psi and burst pressure that exceeds 300 psi. STA-PURE® not only allows for very high pressure applications, but also maintains superior consistency in pumping and purity because the shape and texture of the tube remain constant after thousands of hours of pumping.
How can I increase the tube life in my peristaltic pump?
During pumping, the wall of the tubing is mechanically breaking down. This mechanical breakdown is first be evidenced by a deformation in the shape of the tube. For example, the tube may start to round after only a couple of hours and become more oval in shape. Not only does this negatively impact flow rate, but should you continue to pump on a worn tube, rupture is likely. STAPURE® peristaltic pump tubing is a composite of platinum-cured silicone and EPTFE (expanded Teflon), which has remarkable tear strength. By making a composite structure of these two materials, W.L. Gore has created a tube with superior life, pressure rating and consistent flow rate in a peristaltic pump. STA-PURE has shown a consistent flow rate at pressures greater than 100 psi during pumping campaigns longer than 3 months!
How do I dampen pulsation?
Peristaltic pumps function upon the principle of peristalsis. Other famous peristaltic pumps include the human heart. Just as it is unavoidable to have a functioning heart without a pulse, it is unavoidable to have a peristaltic pump without a pulse. However, there are strategies to greatly reduce the pulsations created by a peristaltic pump.
Watson-Marlow makes the L Series pumphead for their line of peristaltic pumps. The L Series has a single channel that, prior to entering the pumphead, divides into two independent channels. As the tubing exits the pumphead, these two channels are rejoined. In the pumphead, these two channels are "out-of-phase". This means that as one channel is being squeezed shut by the roller, the other is open. As the tubes rejoin upon exiting the pumphead, the out-of-phase waves translate to a near pulseless flow.
If an L series pumphead is not available on your peristaltic pump, certain pumps can be configured with two separate pumpheads that are calibrated to be out of phase, thus accomplishing the same function as the L series. Another effective way to reduce pulsation is to increase the amount of silicone tubing on the discharge side of the pumphead. Because it is an elastomer, silicone tubing acts as a shock absorber. Even just 36" of silicone tubing will greatly decrease the severity of the pulsation.
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