When choosing a mechanical pump for the core of the production process and measuring corrosive chemicals, engineers need to find a pump that meets the following three requirements at the same time:

　　◆A pump that can withstand chemical corrosion and runs stably.

　　◆Pump capable of metering, using less chemicals to obtain large output.

　　◆A pump that can be quickly and easily maintained and operated.

　　 Process engineers are increasingly using peristaltic pumps to solve these three problems, while reducing life cycle costs and improving process efficiency.

　　 Working principle of peristaltic pump:

　　 It is said that the peristaltic pump is a fast-developing technology in the world, and it is replacing other complex and frequently maintained positive displacement pumps in chemical metering. Acids, alkalis, and solvents corrode the valves, seals, rotors and moving parts of diaphragm pumps and single screw pumps (two commonly used positive displacement pumps), resulting in damage to the pump, downtime, and increased life cycle costs.

　　On the contrary, the working principle of the peristaltic pump can reduce these costs. Peristaltic pumps have no valves, no leakage, and no mechanical parts in the product line. The fluid is only in contact with the inner wall of the hose or the pipe, and the cost of the pipe is very low, and maintenance is low, and it is very durable.

　　 In physiology, "peristalsis" refers to the alternating contraction and relaxation of muscles around tubular organs (such as the larynx and esophagus), thereby promoting the flow of internal fluid. The operating principle of the peristaltic pump is very simple. A section of hose or tube is placed along the fixed pump housing and compressed from the outside by rollers or bumps (hose pump) (see Figure 4). When the roller or bump moves along the outside of the tube, the fluid is pushed toward the outlet; when the hose or tube behind the bump returns to its original shape, more fluid is sucked into the pump.

The core of the 　　 pump is a hose or tube, which can be made of different elastomer materials, can have a long service life, and is resistant to corrosion by concentrated acids, alkalis and solvents. The simplicity of the "wet end" of the peristaltic pump is the opposite of the complexity of the diaphragm pump. The casing, diaphragm, ball valve and sealing materials of the diaphragm pump must be carefully selected to prevent the pump from malfunctioning under the erosion of corrosive liquids.

　　Measurement:

　　 Positive displacement pumps are usually used for metering or adding quantities of chemicals. For a peristaltic pump, the flow rate is proportional to the speed. The hose or tube that has been completely sealed makes the pump continue to perform positive displacement movement to prevent the flow rate reduction caused by the reverse flow. The peristaltic pump does not have a check valve, which eliminates the root cause of inaccurate metering, so there is no vapor lock phenomenon.

　　 There are valves in the diaphragm pump, which may jam or block (because of the corrosion of the valve ball or valve seat), causing flow changes, thereby destroying the consistency of the final product or causing differences in product quality. In addition, chemicals that can generate gas (such as sodium hypochlorite) may cause vapor lock of the diaphragm pump, completely preventing the passage of fluid.

　　 The adjustment ratio (large flow/small flow) or flow range of the peristaltic pump is unmatched by other pumps. By simply controlling the rotor speed, the turndown ratio of a high-quality peristaltic pump can reach 2000:1. By equipping tubes of different sizes, the adjustment ratio can be expanded to 1 million. Diaphragm pumps can only achieve a speed ratio of 20:1 under the control of conventional controllers. Although the stroke length of the diaphragm can be adjusted to increase the adjustment ratio, the measurement accuracy will be greatly reduced in the case of short strokes. When a large flow range is required, two or more diaphragm pumps are usually used to control the flow, and this can be solved by a peristaltic pump.

　　 Life cycle cost:

　　 The initial investment cost of a peristaltic pump may be slightly higher than other positive displacement pumps, but the costs of related auxiliary equipment, installation, maintenance and spare parts for other pumps may be very large. In terms of life cycle costs, peristaltic pumps are even better.

　　 In a peristaltic pump, pipes or hoses are the main wet parts, almost no maintenance, no expensive seals to replace, no check valves that can block, and no rotors or stators that can wear out. Of course, hoses or tubes need to be replaced regularly. Even so, the industrial-grade peristaltic pump can achieve thousands of hours of reliable operation before the hose fails due to fatigue. The process of replacing the hose takes less than an hour, and in some cases only a few minutes. In addition, the hose can be quickly and safely replaced without any special tools.

　　 This is much less than the 4-6 hours of repair time required for diaphragm pumps or single screw pumps. This does not include the extra time they take when they are moved, transferred and reinstalled. Compared with the repair of a diaphragm pump or a single screw pump, the cost of the hose is very low. The latter's wet end replacement parts (such as ball valves, rotors and stators) can account for 75% of the initial purchase cost of the pump.

　　 Peristaltic pump does not need to install auxiliary equipment. Diaphragm pumps need back pressure valve and exhaust valve to ensure the correct operation of the internal check valve. Single screw pumps usually require dual mechanical seals, flushing systems, dry running protection, and built-in check valves. With a peristaltic pump, the cost of these auxiliary components can be avoided.

　　The need for process control and chemical compatibility usually make the cost of peristaltic pumps lower than other positive displacement pumps. For example, when a single screw pump can only use expensive metals to meet the corrosion resistance requirements, its price may increase exponentially.

　　 Many positive displacement pumps need to purchase an additional independent control board or frequency converter to achieve variable flow measurement. If the flow range needs to be increased, the cost and complexity will also increase. However, the peristaltic pump itself has a high flow range, closed-loop speed control capability and an expandable I/O interface that can be connected to DCS, SCADA and PROFIBUS systems.

　　 The peristaltic pump has a self-priming function (about 10 meters), which improves the safety of the operator because it reduces the handling of hazardous chemicals. This pump also has a certain dry running function, which is very suitable for emptying storage tanks.