Valves Types and Classifications
Valves are essential components in any piping system. There are a variety of valve types, each with their own purpose and functionality. Understanding valves and their function is critical to proper system operation. This article will explain the different types of valves and their uses, as well as provide brief overviews of the different types and classifications.
The different types of valves serve a variety of functions in a piping system. Valves are typically classified by either their function or material composition. Valve functions are generally divided into three categories:
Control valves: Control valves are used to regulate the flow of a fluid in a system. These valves may also be referred to as regulating valves, throttling valves, or check valves.
Shutoff valves: Shutoff valves are used to close a piping system completely. Examples of shutoff valves include gate valves, globe valves, and ball valves.
Isolation valves: Isolation valves are used to separate two parts of a piping system. These valves can be used to isolate a part of a system that needs servicing, or to separate two parts of the system that are not compatible.
Each type of valve can be classified further according to its material composition or construction. United States classification systems classify valves according to the American Society of Mechanical Engineers (ASME) and the American Petroleum Institute (API).
Material Classifications
Materials used in the construction of valves are typically divided into two categories: cast iron and steel. Cast iron valves are typically the least expensive type of valves and are commonly used in residential and industrial applications. Steel valves are generally more expensive, but are used where higher pressure and temperatures are needed.
Cast iron valves are further divided into two classes: black iron and malleable iron. Black iron is the most common type of cast iron valve, and is typically used in residential applications. Malleable iron valves are more expensive, but are stronger and suitable for higher pressure applications.
Steel valves are typically divided into three categories: alloy, stainless steel, and chrome-moly. Alloy steel valves aremade from a combination of steel, nickel, and chromium, and are typically used in oil or gas pipelines. Stainless steel valves are made from an alloy of iron, chromium and nickel, and are commonly used in chemical and pharmaceutical applications. Chrome-moly steel valves are the strongest type of steel valve and are used in extreme temperature and pressure conditions.
Classification by Construction
Valves are further divided by their construction and design. Commonly used valve designs include globe, butterfly, and gate valves. Globe valves are the most commonly used type of control valve, and feature a sliding disc on a seat that can be used to regulate and control flow. Butterfly valves are typically used for larger flow applications, and feature a disc that rotates to control flow. Gate valves are used for on/off applications, and feature a gate that rises or falls to open or close the valve.
In addition to these valve types, there are also several specialty valves that are used in certain applications. Bursting discs and safety relief valves are often used in high pressure systems to provide an additional layer of protection from pressure overloads. Solenoid valves are also popular in automated systems, and are used to control fluid flow through an electric signal.
Conclusion
Valves are an essential part of any piping system, and understanding the types and classifications of valves is critical to proper system operation. Valves are typically classified by either their material composition or design, and are further divided into various types according to the system they are used in. Control valves, shutoff valves, and isolation valves are the most commonly used types of valves, while specialty valves are often used in specific applications. Knowing the different types of valves and their function is key to selecting the right valve for the job.
