Your company’s reputation depends on how your products perform in-service, and their performance depends on choosing the right material for each component. Use PVC when the application demands stainless steel and you risk failure. Conversely, use stainless when it’s not necessary and you may price your product out of the market.
ChemTec works with design engineers to optimize performance and cost for the intended application. That’s why our flow monitors, flow meters and excess flow valves are offered in a range of materials.
Brass
This copper-zinc alloy machines easily, keeping manufacturing costs low. It offers good thermal conductivity and doesn’t become brittle at low temperatures. However, its ductile nature renders it unsuitable for high-pressure applications and it is prone to ‘dezincification.’ This is a phenomenon of low-flow environments where water with low acidity or alkalinity leaches out zinc. As this leaves a porous surface it limits the range of uses to which brass can be put. Good applications are those such as cooling systems with non-corrosive liquids and gases and low pressures.
PVC
Inexpensive, thanks to high volume production, PVC machines well and resists attack by both acids and alkalies. Considered biocompatible, it can be used in medical applications but not for higher temperature applications as it softens at temperatures over 80oC, (limiting sterilization options.) As a material for flow monitors it’s best used with unheated water. Gas analyzers are a good application as trace quantities of chemicals like ammonia can condense out and over time these would attack the flow monitor body.
Stainless Steel
Stainless resists pitting and crevice corrosion in corrosive environments and tolerates high temperatures and pressures. It is difficult to machine although it welds well, so stainless steel flow monitors and valves are more expensive than those made from brass. Applications are found in CNG and hydraulic systems where pressures are high and an excess flow valve is required to protect against the risk of pipeline ruptures.
Ultra-High Purity Stainless
In food, medical and pharmaceutical applications sterilization with steam or caustic solutions is of paramount concern. Stainless steel flow monitors and valves stand up to this treatment but unless internal surfaces are extremely smooth it is possible for bacteria to remain in micro-crevices. Electro-polishing creates the kind of finish needed, rendering stainless “Ultra-High Purity,” although it adds cost. The food industry, especially dairy producers, and manufacturers of medical and pharmaceutical products, use this material throughout their liquid handling systems.
Teflon®
This fluoropolymer provides extremely high chemical resistance, doesn’t absorb moisture, doesn’t age, withstands temperature cycling and is easy to machine. The one downside is cost: Teflon is an expensive material, costing more than stainless steel. Teflon flow monitors find application in the semiconductor industry where they handle the high purity de-ionized water used throughout the manufacturing processes.
The Application Dictates the Material
Corrosive materials, high temperatures and pressures and the importance of cleanliness all impact material selection. If in doubt, consult with ChemTec engineers to select the material best suited to your application.
