Daily Question: Working Principle and Characteristics of Reciprocating Pumps – Methanol and Purification Technology Forum, 20191021

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Working principle and characteristics of reciprocating pumps: Reciprocating pumps are a type of positive displacement pump; they rely on the back-and-forth movement of a piston inside the cylinder to change the working volume, thereby achieving the purpose of transporting liquids. Taking a piston pump as an example, it draws in and discharges liquid through the reciprocating motion of a piston inside a cylinder. As the piston moves from the left end to the right, the volume of the working chamber gradually increases, causing the pressure inside to drop; the fluid then pushes open the suction valve and enters the working chamber, until the piston reaches its far right position. This process is the suction process. When the piston begins to move from the rightmost end to the left, the fluid filling the pump is compressed, which closes the suction valve and opens the discharge valve to allow the fluid to be discharged. As the piston moves back and forth continuously, the pump continuously draws in water and discharges it. This type of pump is characterized by the ability to achieve arbitrarily high pressures; its flow rate is independent of pressure, it has self-priming capability, and its flow rate is not uniform. It is suitable for delivery systems that require low flow rates but high pressures. For example, the boiler water chemical dosing system. Key items to check before starting a reciprocating pump: 1. Whether all safety accessories are present and in good working condition. For example, check whether pressure gauges, thermometers, level gauges, safety valves, as well as the various valve assemblies in the inlet, outlet, and return pipelines are properly installed, have been put into operation successfully, and function smoothly. 2. Are the amount and quality of oil in the lubricating oil tank meeting the requirements? 3. Are the fastening bolts and nuts of the connecting rod and crosshead loose? 4. Are the opening and closing positions of the inlet and outlet valves correct? 5. Is the vent valve open, and is the lubrication oil path unobstructed? 6. Rotate the shaft before startup; there is no sticking. 8. While the pump is in operation, regularly check for any abnormal noises. Do not close the outlet to regulate pressure. 9. Regularly check the bearing temperature, pump vibration, and current levels, and address any issues that arise promptly.