1. chemical compatibility

The pipe must be chemically compatible with the fluid to be pumped in order to have good pumping and safety performance.

Many pump pipe suppliers provide chemical compatibility tables. However, engineers should pay attention to the chemical compatibility table specially developed for pump pipe instead of common pipe. Because the common pipeline and chemical substances only have general contact, and the peristaltic pump pipe is in contact with chemical fluid under pressure, the chemical compatibility level of common pipeline and peristaltic pump pipe cannot be equal. Therefore, only reference should be made to the chemical compatibility level of pump pipe, rather than the chemical compatibility level between general pipe and related substances, otherwise, the pump pipe will be invalid or damaged, cracked and leakage, resulting in damage or dangerous accident of pump.

The end user shall check the compatibility of each component of the solution when referring to the chemical compatibility table, not only the main components, with the pipe to be used. Some acid or solvent will cause enough damage to the pump pipe even if it is only a small amount after contacting with the pump pipe for hours or days. The end user should check each chemical in the solution to ensure that it is compatible with the selected pump tube. Also remember that the chemical resistance of the pump pipe decreases with the increase of temperature. Some chemicals do not affect the pump pipe at room temperature, but when the temperature rises to a certain extent, it will cause damage to the pump pipe. In the chemical compatibility table, it is necessary to indicate the specific environmental conditions, especially the temperature limit, to determine the chemical compatibility.

If a chemical is not listed in the chemical compatibility table, or if the operating environment conditions of a factory are too different from those specified in the table, soak test can be used to obtain more reliable information. This method can be used if there is no other information to refer to when determining chemical compatibility.

The immersion test steps are as follows: take a small section of pump pipe, weigh it, measure diameter and length. Then the pump tube is immersed in a closed container containing the relevant chemicals for 48 hours. Take out the pipe and wash it to dry, weigh the weight and measure the size, and record the change of the two measurements before and after. Also check the pump tube for signs of softening or embrittlement, which indicates that chemicals have been harmful to the pump pipe. After one or more pipes are selected, pumping test can be carried out. Each candidate pump tube sample shall be put into the actual environment of the factory for trial operation and the test results shall be closely observed. If the pump pipe does not show signs of discoloration, swelling, crack, loss of fluidity, or other deterioration after commissioning, it shall be proved to be compatible with the fluid.

Remember that the ultimate responsibility for selecting the appropriate pipe, whether it is to refer to the compatibility table, to do physical test, or to use both methods, shall be borne by the end user. Careful analysis and test can ensure the correct test results, so as to avoid the damage of the pump and ensure the safety of the person and property.

The chemical compatibility of different pipes and solutions is very different. But there are also some materials that have strong resistance to most chemicals. For example, Viton fluororubber pump tubes can resist a variety of inorganic chemicals, even some organic chemicals. For example, PTFE pump tubes can be compatible with almost all chemicals. But Teflon pump pipe is a rigid pipe, and a special pump head is needed. In the case of pumping many corrosive chemicals, the best choice is to be the pipe which can resist many chemicals.

2. pressure

The pressure source of a fluid conveying system can be different. Back pressure is generated when the fluid is pushed through a filter, or when it is pushed through a flow meter or valve, or pumped into a pressurized reaction vessel. Before selecting pipe, the user should first make sure that all the pressure sources in the system have been clarified and the measured value of the total pressure of the system has been obtained. When selecting pump pipe for peristaltic pump, the user shall ensure that the pressure in the system does not exceed the recommended working pressure of pump pipe. If the pressure is too high, the pump pipe will swell and the pump head will not fit well, which will cause excessive wear and failure. When the system pressure is much higher than the capacity of the pump pipe, it will even burst the pump pipe, eject fluid and endanger the safety. After selecting a pipe, ensure that the pressure is maintained within the pressure range recommended by the manufacturer. If the system exceeds the maximum working pressure, a simple pressure release valve or pressure switch can be installed to prevent the accumulation of excess pressure. The function of pressure release valve is: when the system pressure exceeds the set value, it will exhaust air to the atmosphere, so that the system pressure will be reduced to a safe level. A more complex pressure switch can also be used, which will turn off the device or sound the alarm device through a relay when the pressure value exceeds the set value. When the system pressure exceeds the safety line, the above two methods are beneficial to safety.

3. temperature

The operating temperature range of the pump pipe is another important factor to be considered. Some pipes, such as silicone rubber, have a wide temperature bearing range, which is suitable for high temperature and low temperature process; And some pipes like Tygon? And C-Flex? It is only suitable for a small temperature range. Before the end user selects the pipe, he should first make clear the maximum temperature and the lowest temperature in the system, and then ensure that the selected pump pipe works safely in this temperature range. In the application of increasing temperature gradually, the end user should consider the influence of temperature on the chemical resistance and pressure bearing capacity of pump pipe. When the temperature increases, the pressure bearing capacity of the pump pipe will be reduced.

4. dimensions

As each roller in the pump head is pressed over the pump pipe, the peristaltic pump will pump a certain amount of fluid. Therefore, the size of the pump pipe is directly related to the pump flow, that is, it has a great influence on the operation of the fluid conveying system. Pump pipe is a key part of design of high quality peristaltic pump. The best size or range of the pump pipe should be calculated. The size here mainly refers to the inner diameter and wall thickness of the pump pipe. The inner diameter determines the amount of fluid pumped by the rotor every revolution, while the thickness of the wall determines the ability of the pump pipe to recover its original shape after each rolling, which greatly affects the service life of the pump pipe. The size of pump pipe is too small relative to the pump head size, so the pump head cannot be clamped firmly, and the pump pipe will be pulled out of the pump head; Moreover, the pump pipe size is too small, the roller in the pump head can not hold the pump pipe, which will cause insufficient or complete failure of the pump flow. If the pump pipe size is too large, the excess pipe will wrinkle between the roller and the pump shell or between the roller and the bite bed, which will lead to excessive wear and premature failure. When choosing the pump pipe size, the end user shall follow the manufacturer's recommendations to ensure the system function is in good condition. In some applications requiring high accuracy (such as chemical dose pump), the role of pump pipe size is more prominent. A slight deviation in size will result in too much deviation of flow or distribution quantity to be unqualified. Although some manufacturers provide pump pipe sizes that are "close to" and "look the same" as recommended, there are still gaps. Therefore, in order to achieve the best performance and working accuracy of the pump system, the user should adopt the pump pipe size which is exactly the same as the recommended size of the manufacturer.

4. tolerance

Tolerance is the allowable error of the pump pipe size. The smaller the tolerance, the smaller the performance deviation of the pump pipe, the better the consistency and repeatability. The larger the tolerance, the more unstable the performance of the pump pipe. Some pump tubes have very small manufacturing tolerance, and their size deviation is strictly controlled during extrusion forming. Although the manufacturing tolerance of pump pipe is slightly expensive, it is worth the cost compared with the increase of pumping performance.

5. average life of pump pipe

The conditions of peristaltic pump are relatively bad, so the inner quality of the pipe, especially the pipe with good rebound performance, will have a long service life. In the long run, the longer the service life of the pipe, the lower the operating cost. The less the number of pump pipe replacement, the less maintenance cost and downtime. The less likely the pump pipe leaks and bursts. In short, the longer the service life of the pump pipe, the lower the total cost of pumping. The pump pipe manufacturer shall provide test data to prove its declared pump pipe life. Some manufacturers have published information in their manuals (such as the "master flex pump information of Cole Parmer instruments". In any case, the engineer should have an understanding of the average life of the pipe when designing a system, so that the end user can develop preventive maintenance plans so that they can be replaced before the pump tube fails. Pump pipe suppliers with rich technical knowledge can provide useful information for users in specific application situations so as to select the appropriate pump pipe materials.

6. transparency

Whether transparent pipes should be used, first of all, it depends on whether the operator needs to observe the condition of the fluid in the pipe at any time, and whether the fluid is sensitive to light. If the operator needs to observe the fluid, bubble, particle, pollution and other conditions in the pipe at any time, transparent pipes such as Tygon polyethylene or silicone rubber shall be selected; If the solution is not suitable for exposure, opaque pipe should be selected

7. air permeability

For some gas sensitive fluids, such as those susceptible to oxidation, or anaerobic cell culture, the user should consider the permeability of the pipeline. In general, the silicone hose has the highest permeability. Therefore, for the fluid which is not suitable for contacting with gas, the pipe with low permeability should be selected.

8. regulatory permission

For the pharmaceutical industry, regulatory certification is essential. In this industry, every item in contact with the final product must meet the specific standards and standards. Therefore, many pump pipe materials are developed in strict accordance with the requirements of the regulations. These include the USP, EP, FDA, USDA, and NSF. Of course, it is not enough to claim that a certain material conforms to a certain regulation. The pump pipe manufacturer shall provide the user with certificate proving that the pipe conforms to the regulations according to the requirements of the user. This allows the user to provide the necessary certificates to prove that the pump system complies with the necessary regulatory license.

9. cost

Cost is almost a factor to be considered in the development of each project plan. As with other components selected, the user should evaluate the overall cost of the alternative pump pipe. For example, a pump tube costs $2 per foot and needs to be replaced every 500 hours; The other pump pipe costs $1 per foot, which needs to be replaced every 100 hours; The former is more cost-effective than the latter. The sudden rupture of the low-quality pump pipe will cause the loss of valuable fluid or damage of the pump, which will cause high cost downtime, large amount of maintenance, and even replace the whole pump. Therefore, the cheapest pump tube is not necessarily the most economical choice. It seems unlikely to choose an ideal pump pipe in a wide range of pump and pipe markets. However, as long as the system requirements, the technical indicators related to the reference are carefully studied, and the pump pipe manufacturers or suppliers with application knowledge and experience are closely communicated, the pump pipe that is most suitable for the relevant pump system can be selected.