An Introduction to the Anatomy of a Valve

In order to keep a fluid filled system at a desired set point, you can use a valve. Valves regulate the pressure and flow of the fluid in the system’s passageways. Depending on the type of system, fluids can be gases, liquids or fluidized solids like the ones found in the manufacturing process of polypropylene or polyethylene plastics.

The type of valve products you’ll need depends on the exact nature of the fluidic system you apply them to. So different systems need completely different flow mechanisms, and as a result, you might need to install completely distinct valves on them. In this guide we’ll discuss the anatomy of the valve and the various types of valve products available.

Valves come in different sizes and shapes, as some systems need small valves (water softeners or engine components), while others need large valves (oil refinery and wastewater treatment facilities) in order to control the movement of large volumes of fluid. The best valve type for you also depends on its exact purpose in the system.

All valves have pretty much the same basic principle – they need to redirect, reduce or completely stop the flow of fluid in the system. For this reason, most of the components in both large and small valves are similar. As a group, the inner parts of a valve are known as the trim. The outer casing is known as the body, as it contains all the parts needed to make the valve work. Bodies are made of metals like brass, cast iron, steel alloys, bronze or plastic, depending on the purpose of the system and the regulator in which it is placed.

Bonnets are common features in a valve, though they aren’t considered essential. The bonnet covers the body and is usually bolted or screwed to it in order to keep the working elements of the valve secure in place while allowing access for servicing. Handles are also present and they’re used to manually control the valve. Actuators do a similar job, except they can be remotely controlled. If the valve has automatic control, it may not have a valve or a handle, but instead can have a stop-check valve.

Valves also have ports which allow fluid into the valve. Valves can have as few as 2 ports up to 20. The disc is also known as a member, which is the movable part of the valve which is used to determine how much fluid can flow through. Discs can be both metal or plastic, and are shaped differently – depending on how the valve is made to work.