What is a Flow Control Valve

A flow control valve is a type of valve used in hydraulic systems such as hydraulic lifts, presses and even dampers. The purpose of a flow control valve is to regulate the amount of fluid flowing through it. A flow control valve is used when the speed of the flow is important to the functionality of a system. For example, when the flow speed must be controlled to enter a motor or a cylinder. 

Due to its ability to control flow rate, flow control valves influence the rate of energy transferred at a given pressure as a result of the relation between work, energy and power.  

There are two main types of flow control valves: check valves and ball valves

The core concept of flow control valves is to allow a specific volume of fluid to pass at a given position. The most simple flow control valves have an aperture that will open and close to either let the flow through or stop it. 

Ball Valve

A ball valve is among the simplest design of control valves. The design of a ball valve consists of a spherical body with a hole connected to a handle. As the handle is rotated, the hole in the body will either open up to the flow or close off. The valve tends to be designed such that when the hand is parallel with the flow, it is open, and when it is perpendicular to the flow, it is closed. 

Check Valve

A check valve, as known as a non-return valve, is a valve that only allows the fluid to travel in one direction. Check valves are two-port valves which means they have two openings, one to let fluid in and one for the fluid to escape. Like ball valves, check valves are common flow control valves and are present in many household items. A check valve does not require any control by a person, as it does not contain a handle or stem, making it desirable for many applications. 

The main component of a check valve is a spring and valve disk. When no flow is present or the flow is in the same direction as the spring extension, the valve disk is held against the body opening, preventing any flow. As flow travels towards the valve, the spring compresses, meaning the fluid can flow through the body opening. As the spring is a central component that allows fluid through the valve, the stiffness of the spring is a key mechanical property that determines the characteristics of the valve. 

Disadvantages of a Flow Control Valve

Although a flow control valve is a cost-efficient solution for controlling valves, they also have disadvantages. If one becomes partially obstructed, it will result in a pressure drop, negatively affecting the performance of the system. With basic flow control valves such as a ball valve, changes in flow rate may occur when the valve is in a stationary position. Similarly to a pressure drop, a varying flow rate will impact the hydraulic system’s performance.