Common Types
Gear Metering Pump: This is one of the commonly used types of metering pumps in coating machines. It adopts high-precision external meshing straight tooth profiles and has a precise fit with the pump cavity. The volume of fluid discharged per revolution is accurate, ensuring precise, pulsation-free and repeatable fluid output under various conditions of temperature, viscosity and pressure. The QCB series slit coating metering and delivery pumps are made of universal stainless steel 304 material with high hardness. The gear accuracy grade is 5, and the displacement ranges from 0.6 ml/rev to 150 ml/rev. Parameters such as the speed range, inlet and outlet pressures, and temperature all have clear ranges, which can well meet the requirements of the coating machine for the quantitative delivery of bentonite.
Diaphragm Metering Pump: It changes the volume of the pump cavity through the reciprocating movement of the diaphragm to achieve the suction and discharge of fluid. It has the advantages of high metering accuracy, corrosion resistance and good sealing performance, and is suitable for transporting bentonite slurries containing solid particles or with high viscosity.
Peristaltic Pump: It consists of three parts, namely the driver, the pump head and the hose. By squeezing the hose with rollers to create a negative pressure inside the hose, fluid is sucked in and transported forward. Its advantages include being able to transport fluids containing particles without causing damage to the particles, having a relatively wide flow range, relatively high accuracy and low maintenance cost. It is applied in some small coating machines or in situations where the requirement for flow accuracy is not extremely high.
Working Principles
Gear Metering Pump: A pair of meshing gears forms a closed gear space with the pump body. Material is transported from the inlet of the pump to its outlet. Relying on the driving gear to drive the driven gear, the meshing of the two gears forms a suction cavity and a discharge cavity. When the gears rotate, the liquid in the suction cavity will be brought into the discharge cavity by the rotating gears.
Diaphragm Metering Pump: The motor drives the diaphragm to make a reciprocating movement inside the pump head. When the diaphragm is pulled backward, the volume of the pump cavity increases, creating a negative pressure, and the bentonite slurry is sucked into the pump cavity. When the diaphragm is pushed forward, the volume of the pump cavity decreases and the pressure increases, and the slurry is discharged from the pump cavity.
Peristaltic Pump: The driver drives the rollers to rotate. The rollers squeeze the hose to make the bentonite slurry inside the hose move forward. Meanwhile, a negative pressure is formed behind the rollers, constantly sucking in new slurry, thus achieving continuous transportation.
Selection Points
Flow Accuracy: Select a metering pump with appropriate flow accuracy according to the requirements of the coating process. Generally speaking, the gear metering pump has relatively high flow accuracy, which can reach ±0.3% to ±0.5%. The flow accuracy of the diaphragm metering pump can also reach about ±1%. Although the flow accuracy of the peristaltic pump is relatively low, it can also meet certain coating accuracy requirements through calibration and appropriate control methods.
Viscosity Adaptability: The viscosity of bentonite slurry is usually high, so it is necessary to choose a metering pump that can adapt to high-viscosity fluids. Gear metering pumps and diaphragm metering pumps perform better in transporting high-viscosity fluids, while peristaltic pumps are more suitable for fluids with lower to medium viscosities. However, some specially designed peristaltic pumps can also handle materials with higher viscosities.
Pressure Requirements: Consider the pressure conditions in the coating machine system to ensure that the metering pump can work normally within the required pressure range. Different types and specifications of metering pumps have different pressure-bearing capacities. For example, the inlet and outlet pressures of the QCB series slit coating metering and delivery pumps are ≤ 100 Bar. Matching should be done according to the actual situation when selecting.
Material Compatibility: Since bentonite slurry has certain corrosiveness, the material of the metering pump should have good compatibility with the slurry to prevent the pump body and components from being corroded and damaged. Common materials include stainless steel, engineering plastics, etc. Appropriate materials can be selected according to the chemical properties of the slurry and the working environment.
Cleaning and Maintenance: Choose a metering pump that is easy to clean and maintain to ensure the normal operation and service life of the equipment. For example, the structure of the peristaltic pump is relatively simple, and its cleaning and maintenance are relatively convenient. While gear metering pumps and diaphragm metering pumps need to have seals and lubricating oil regularly checked and replaced, but their overall reliability and stability are relatively high.
