Fluid characteristics of dispensing needle valve and its sizing application（3）

Fluid characteristics of dispensing needle valve and its sizing application

3. Aggressive fluid

The hardness of the fluid is also a factor to be considered. For example, corrosive fluids may contain acids, bases, methanol and solvents. These substances react with the wet chamber, piston and O-ring. Therefore, the diaphragm valve or needle valve must be able to withstand corrosive substances, and the piston and O-ring should be made of acid resistant ultra-high molecular weight materials. Ultra high molecular weight materials can also withstand alcohol and methanol. Depending on the specific corrosive strength, peek materials are also applicable.

Pinch valves are usually used for acids and all solvent based materials because their polyethylene pipes are disposable. The pinch valve has no wet chamber that can be corroded. Adhesive fluid, such as cyanoacrylate, is a solvent adhesive with strong corrosiveness. Therefore, if diaphragm valve is used, the materials of its wet chamber, piston and O-ring must be ultra-high molecular weight. Abrasive fillers are usually paste like, which can improve the conductivity and dielectric properties of the material. Not all fillers are abrasive, so the specific product properties have to be confirmed with the manufacturer or supplier to avoid buying unnecessary and expensive rubber valves at high cost. However, once it is determined that the fluid is abrasive, such a dispensing valve should be selected: the wet chamber must be made of high hardness stainless steel; Seals must be strong, able to withstand continuous wear and maintenance rates as low as possible.