If you are looking for a valve to complete a project but you aren’t a professional plumber or plant engineer, you may not be able to tell which valve is specifically best for what you’re working on.
There are many different types of valves available today, and they are majorly classified into two categories: regulation (control) valves and shutoff valves. This classification is in accordance to the function that each type of the valve performs.
Here are the differences:
Shutoff valves come in a wide variety of configurations and sizes, but they all do what their name suggests: completely stopping or closing down the flow of liquids and gases in piping systems. Shutoff valves are very important in many applications. For example, they can be used to shut off part of the plumbing system in a home to allow for plumbing work to be carried out in a specific room or individual appliance such as a dishwasher without having to shut off water for the whole house.
The two most common types of shutoff valves are ball and gate valves.
Ball valves are the most common type of shutoff valves, which rely on a lever handle and are designed for quick turn-on and turn-off. They are designed with a solid brass ball that has a pipe-sized opening drilled through its center. When the valve is open, the opening aligns with the direction of the water pipe and water flow is made possible. When the handle is closed and the ball rotates, the opening is closed and water flow instantly stops.
The valve is common in main water pipes as it helps cut off water flow immediately in case of a disaster.
Gate valves, like the one at left, are also common shutoff valves that rely on a hand wheel to turn the valve on and off. Gate valves are made of a gate inside the valve body that raises or lowers to close a pipe’s opening when the hand wheel is rotated. When the gate is raised, water or gas flows through; when the gate is lowered, flow stops.
The valve is also an all-or-nothing valve like the ball valve, designed to either permit full flow or shut off flow completely. Gate valves are more common in industrial applications than in residential plumbing.
Control valves, on the other hand, allow you to control, regulate, or select the amount of liquid or gas you want to flow through a piping system. They also allow you to determine the direction of flow when need be. Control valves are typically applied in industrial applications and areas such as the laboratory to regulate and ensure the accurate flow of liquids such as sulfuric acid during chemical experiments.
Control valves come in a variety of designs.
Globe valves and needle valves
The design of globe valves and needle valves differs, but they both share a zigzag-shaped channel. They both have a stem that comes down the valve and introduces a stopper or needle into the channel to completely shut off the valve. When the stopper or needle is raised, fluid or gas flows freely through the opening and around the stopper or needle itself.
Needle valves are commonly used in areas where there is high pressure but a low flow rate, whereas globe valves, like the one at right, are used to regulate almost any type of material.
Check valves are a different type of regulation valve, as they seek to control the direction gases and liquids flow instead of the flow rate. The two most common types of check valves are the swing check valve and the spring-assisted check valve, which both work through pressure exertion.
The swing check valve uses a swinging flap hanging vertically inside the pipe and held in place by gravity. When adequate pressure is applied from one side, the flap swings open and allows flow. When the pressure is reduced, the flap swings back into position and stops flow. And in case pressure is applied from the other side, the flap stays firmly in place and prevents backflow.
The spring check valve uses a spring-loaded stopper that presses against a valve seat. When adequate pressure is applied, the spring contracts and allows flow through the pipe. It only opens as wide as the pressure applied to ensure only the required amount of flow is achieved. Spring check valves are more versatile than swing check valves because they can be used both vertically and horizontally.