PVC (PolyVinyl Chloride) ball valves are widely used plastic shut off valves. The valve contains a rotatable ball with a bore. By rotating the ball a quarter turn, the bore is inline or perpendicular to the piping and the flow is opened or blocked. PVC valves are durable and cost efficient. Furthermore, they can be used for a wide variety of media, including water, air, corrosive chemicals, acids and bases. Compared to brass or stainless steel ball valves, they are rated for lower temperatures and pressures and have a lower mechanical strength. They are available with different piping connections, such as solvent sockets (glue connection) or pipe threads. Double union, or true union valves, have separate pipe connection ends that are fixed to the valve body by a threaded connection. The valve can easily be removed for replacement, inspection and cleaning.
PolyVinyl Chloride production
PVC stands for PolyVinyl Chloride and is the third most used synthetic polymer after PE and PP. It is produced by the reaction of 57% chlorine gas and 43% ethylene gas. Chlorine gas is derived by electrolysis of seawater, and ethylene gas is obtained by distillation of crude oil. In comparison with other plastics, PVC production requires significantly less crude oil (PE and PP require around 97% ethylene gas). Chlorine and ethylene react and form ethanedichlorine. This is processed to yield Vinylchlorine monomer. This material is polymerized to form PVC. Finally, some additives are used to alter properties such as hardness and elasticity. Because of the relatively simple production process and large availability of the raw materials, PVC is a cost-effective and relative sustainable material in comparison with other plastics. PVC has a strong resistance against sunlight, chemicals and oxidation from water.
PVC properties
The list below gives a general overview of important characteristics of the material:
- Lightweight, strong and long service life
- Suitable for recycling and relatively low impact on the environment in comparison with other plastics
- Often used for sanitary applications, such as drinking water. PVC is an important material used to store or transfer food products.
- Resistant to many chemicals, acids and bases
- Most PVC ball valves up to DN50 have a maximum pressure rating of PN16 (16 bar at room temperature).
PVC has a relatively low softening and melting point. Therefore, it is not recommended to use PVC for temperatures above 60 degrees Celsius (140°F).
Applications
PVC valves are used intensively in water management and irrigation. PVC is also suitable for corrosive media, such as sea water. Moreover, the material is resistant to most acids and bases, salt solutions and organic solvents. In applications where corrosive chemicals and acids are used, PVC is therefore often chosen above stainless steel. PVC has also some disadvantages. The most important drawback is that regular PVC cannot be used for media temperatures above 60°C (140°F). PVC is not resistant to aromatic and chlorinated hydrocarbons. PVC has a lower mechanical strength than brass or stainless steel, and therefore PVC valves have often a lower pressure rating (PN16 is normal for valves up to DN50). A list of typical markets where PVC valves are used:
- Domestic / Professional Irrigation
- Water treatment
- Water features and fountains
- Aquariums
- Landfills
- Swimming pools
- Chemical processing
- Food processing
Post time: May-30-2020