Fluid characteristics of dispensing needle valve and its sizing application（2）

Fluid characteristics of dispensing needle valve and its sizing application

When gelatin or silica gel is used for dispensing needle high viscous fluids, the glue container is usually 0.1 gallons of cartridge or 1 to 5 gallons of barrels. The barrel of viscous fluid pushes the pressure plate through the pneumatic pump, extruding glue through the high-pressure pipe to feed the valve chamber.

It should be noted that the pneumatic pressurized cartridge will produce a phenomenon called tunneling effect, that is, the fluid in the middle can be extracted. Especially if the cartridge packaging is not specially designed for automatic dispensing needle, this phenomenon is more prominent.

2. Thixotropy

In addition to viscosity, the thixotropic properties of some fluids have to be considered. Thixotropic fluids are difficult to pour, but after stirring, these fluids will become creamy, which makes dumping much easier. Ketchup is a good example of this. The requirements for fluids and gels with the consistency of syrup are the same. The difference is that these fluids are normally stored in small cans that are not yet degassed. Therefore, we have to consider how to extract the fluid from the can into the dispensing valve to degass it. The paste fluid has higher viscosity and can be directly extracted from the packaged container into the glue valve. Usually, such fluids have been degassed, but this needs to be confirmed with the manufacturer. Pneumatic dispensing valves suitable for paste fluid include short pipe valve, lift valve and high-pressure needle valve. If it is a micro dot sizing application for high viscosity fluids, it is recommended to use an electric screw valve.