The Expanding Reach of Plastic Valves

Although plastic valves are sometimes seen as a specialty product—a top choice of those who make or design plastic piping products for industrial systems or who must have ultra-clean equipment in place—assuming these valves don’t have many general uses is short-sighted. In reality, plastic valves today have a wide range of uses as the expanding types of materials and good designers who need those materials mean more and more ways to use these versatile tools.

PLASTIC’S PROPERTIES
The advantages of plastic valves are wide—corrosion, chemical and abrasion resistance; smooth inside walls; light weight; ease of installation; long-life expectancy; and lower life-cycle cost. These advantages have led to wide acceptance of plastic valves in commercial and industrial applications such as water distribution, wastewater treatment, metal and chemical processing, food and pharmaceuticals, power plants, oil refineries and more.
Plastic valves can be manufactured from a number of different materials used in a number of configurations. The most common plastic valves are made of polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), polypropylene (PP), and polyvinylidene fluoride (PVDF). PVC and CPVC valves are commonly joined to piping systems by solvent cementing socket ends, or threaded and flanged ends; whereas, PP and PVDF require joining of piping system components, either by heat-, butt- or electro-fusion technologies.

Although polypropylene has half the strength of PVC and CPVC, it has the most versatile chemical resistance because there are no known solvents. PP performs well in concentrated acetic acids and hydroxides, and it is also suitable for milder solutions of most acids, alkalis, salts and many organic chemicals.

PP is available as a pigmented or unpigmented (natural) material. Natural PP is severely degraded by ultraviolet (UV) radiation, but compounds that contain more than 2.5% carbon black pigmentation are adequately UV stabilized.

PVDF piping systems are used in a variety of industrial applications from pharmaceutical to mining because of PVDF’s strength, working temperature and chemical resistance to salts, strong acids, dilute bases and many organic solvents. Unlike PP, PVDF is not degraded by sunlight; however, the plastic is transparent to sunlight and can expose the fluid to UV radiation. While a natural, unpigmented formulation of PVDF is excellent for high-purity, indoor applications, adding a pigment such as a food-grade red would permit exposure to sunlight with no adverse effect on the fluid medium.