Monday, September 14, 2015

What are Lined Valves and its Uses?

The lined valves are made using fluorocarbons which include PTFE, PFA, UHMWPE, ETC. The use of these elements depends upon the request of the customers. For locking the liner to the lock or locking holes, grooves and dovetails melting process is carried out. As compared to PFA lined valves and FESP lined valves, PTFE lined valve are more porous.

The lined valves can be categorized into two broad types as: plug, ball, and butterfly valves which works well as lined valves and are relatively simple in shape and gate, globe, and other rising stem valves which are not so lining process friendly.

A lined valve consists of metallic parts which are made from inexpensive materials such as ductile iron. For a fully lined valve, there is no media contact with the metal parts. The lining materials used for theses valves are PFA (perfluoroalkoxy) and FEP (fluorinated ethylene propylene). The reason for the use of such materials is their quality of being chemically inert. Although FEP is not expensive, PFA can withstand high temperatures. While coming on to PTF, it is not much used due to inherent qualities and hence as a lining material.

Lined valves are used extremely and preferred over more expensive alloy valves. These valves are more versatile than expensive alloy valves. Unlike conventional alloy valves their corrosion resistance is almost unaltered by changing the fluid, concentration levels of the chemical used in the process, etc. thus these qualities eases their use with almost any corrosive fluid. But if we look at alloy valves, they can be affected as well can be dangerous with many corrosive fluids. Lined valves can also be used appropriately with multiple product processing lines where different types or different concentration of fluids flow at the same time. These valves also offer an advantage during effluent and recycle processing.

Alloy valves cannot withstand the change in chemical compositions and temperature changes, but the lined valve flexibly works in these scenarios also. Lined valves have limitations too. The major limitation factor which hinders these valves to give a complete optimum performance is the temperature. FEP lined valves comes with a temperature rating of 300 degree Fahrenheit while PFA lined valves comes with a limitation of 400 degree Fahrenheit. The PTFE valves cannot withstand high temperatures due to their characteristic of being blow molded and hence there is the possibility of leakage causing the body material corrosion.