Why do diaphragm metering pumps have no leaks compared to piston metering pumps?

Based on the pump head design, metering pumps can be divided into two main categories: piston-type metering pumps and diaphragm-type metering pumps. In piston-type metering pumps, the piston moves back and forth in a linear motion; the opening and closing of valves are used to draw in and discharge liquid. In contrast, diaphragm-type metering pumps rely on the piston’s back-and-forth movement within the cylinder, which generates pulsating forces that cause the diaphragm to move back and forth. The opening and closing of valves then facilitate the drawing in and discharge of liquid. Since the diaphragm separates the piston from the liquid being transported, it prevents leakage of the liquid, thus avoiding contamination and losses. If equipped with an alarm, such pumps can stop operating immediately when the diaphragm ruptures, thereby preventing contamination of the pipelines by the liquid. Normal operation can be resumed after replacing the diaphragm. Additionally, diaphragm pumps are fitted with a three-valve system (an automatic oil replenishment valve, a safety valve, and a vent valve), which allows for timely replenishment of the hydraulic fluid in the chamber while preventing excessive oil supply. This helps extend the lifespan of the diaphragm and ensures the safety of the metering pump system. 　　Based on the type of transmission, it can be further divided into cam-type and N-axis type. The microcomputer housing (JW) features a connecting-plate cam structure; the motor drives the eccentric cam to rotate through a worm and worm gear, and this in turn causes the plunger to move back and forth in a straight line via a slider (crosshead). 　　The flow rate of the pump is adjusted by changing the plunger stroke length or the pump speed; the plunger stroke can be adjusted continuously within a range of 0–100%, and this adjustment can be made both during operation and when the pump is stopped. With devices such as electronic controls, it is possible to perform operations at the original distance or achieve automated control. By using an AC frequency converter or a variable-speed motor, dual control or a reduction in pump speed can be achieved to meet the requirements of the process flow.

Diaphragm metering pumps have a diaphragm that comes into contact with the medium, eliminating mechanical wear and making them more suitable for high-purity liquids. However, the operations must be carried out in sequence and in accordance with established procedures. Once, we accidentally closed the outlet valve first; in less than two seconds, the PTFE gasket at a flange connection not far from the outlet of the diaphragm metering pump failed, causing a leak.

Hello, may I ask which company’s diaphragm metering pump your company is using? I am also in the process of selecting one and am not sure which manufacturer is the best choice. Moreover, such pumps should be equipped with safety valves; with safety valves in place, the diaphragm shouldn’t break, right?

There are two types of leak-free positive displacement pumps: diaphragm pumps and hose pumps (peristaltic pumps)

He is referring to excessive outlet pressure, which exceeds the maximum pressure specified for that model. For diaphragm metering pumps, it is necessary to consider the parameters required by the operating conditions: such as viscosity, temperature, solid content, pressure, flow rate, pH level, and so on! We can discuss high-pressure diaphragm pumps and diaphragm metering pumps together!

A hydraulic diaphragm pump is a combination of a piston pump and a diaphragm pump: the piston pushes the hydraulic oil, which in turn pushes the diaphragm. There can also be leaks from the piston part, with fluid leaking into the hydraulic oil. In a piston pump, it is the piston that pushes the medium, while in a hydraulic diaphragm pump, the piston pushes the hydraulic oil and the diaphragm pushes the medium, ensuring absolutely no leakage. 13255513901: We offer quality assurance for the hydraulic diaphragm pumps we produce, using Riva technology