7 Different Types of Valves in HVAC Systems Introduction

Efficient flow control is critical to the proper operation of HVAC (heating, ventilation and air conditioning) systems. Valves play a vital role in regulating the flow of fluids such as water or refrigerant in these systems. Understanding the features and benefits of the following 7 different types of valves in HVAC systems is critical to effective system design, installation, and maintenance.

1. Electric control valve: The electric control valve is composed of an actuator and a valve body located below the actuator. The actuator and the control valve can be used after being connected and assembled and installed and debugged.

Principle of electric regulating valve: By receiving the weak signal (0–10 volts or 4–20 mA) sent by the building or industrial controller, the opening of the valve is changed, thereby adjusting the medium flow, temperature, pressure and other parameters. Realize automatic adjustment and achieve an energy-saving effect.

Note: When selecting an electric control valve, it is best to choose one with manual control if possible. This can prevent the valve from opening or closing normally due to circuit failure. As shown in the picture, the threaded disc on the top of the electric control valve is the manual adjustment disc. When using the electric control valve, pay attention to regular inspections to check whether the actuator is faulty and whether there are any abnormalities in the connection between the actuator and the valve shaft. This ensures its safe and efficient operation. Generally speaking, it should be checked every half-month.

2. Gate valve: It is a valve that uses the gate plate as the opening and closing part and moves in a vertical direction along the axis of the valve seat to achieve the opening and closing action.

Gate valve characteristics: The gate valve can only be fully open and fully closed. The opening and closing parts are gate plates. The movement direction is perpendicular to the direction of the fluid. The two sealing surfaces of the square I-shaped gate valve form a wedge shape. The wedge angle varies with the valve parameters, usually 5° , when the medium temperature is not high, it is 2°52'. Elastic gate valves are intended to improve the gate valve's processability and make up for processing-related variations in the sealing surface angle.

3. Butterfly valve: Also known as a flip valve, it is a type of regulating valve. It refers to a valve whose closing part (valve disc or butterfly plate) is a disc and rotates around the valve axis to open and close. It mainly plays a role in the pipeline. Cut-off and throttling effects.

Butterfly valve application: Butterfly valves can be used for switch control of low-pressure pipelines, and are suitable for transporting various corrosive and non-corrosive materials in engineering systems such as generators, coal gas, natural gas, liquefied petroleum gas, city gas, hot and cold air, chemical smelting, power generation and environmental protection. On the pipeline of fluid medium, it is used to regulate and cut off the flow of medium.

Butterfly valve classification: handle butterfly valve, turbine butterfly valve, pneumatic butterfly valve, electric butterfly valve, etc.

4. Ball valve: A ball valve refers to a valve that uses a ball with a circular through hole as the opening and closing component, and the ball rotates with the valve stem to achieve the opening and closing action. 

Working principle of the ball valve: It can also be used for the regulation and control of fluids. The hard-sealed V-shaped ball valve has a strong shear force between its V-shaped ball core and the metal valve seat with hard alloy surfacing. It is especially suitable for fiber-containing valves, tiny solid particles and other media. The multi-way ball valve can not only flexibly control the confluence, divergence, and flow direction switching of media on the pipeline, but can also close any channel and connect the other two channels. This type of valve should generally be installed horizontally in pipelines.

Ball valve classification: pneumatic ball valve, electric ball valve, manual ball valve.

5. Stop valve: Stop valve (globe valve), also known as a stop valve, is a forced sealing valve and is one of the most widely used valves.

Globe valve: The globe valve relies on the pressure of the valve stem to make the valve disc sealing surface and the valve seat sealing surface closely fit to prevent the flow of the medium. Since the medium is only allowed to flow in one direction, it is directional during installation. Globe valves can be divided into DC globe valves, angle globe valves, plunger globe valves, upper threaded stem globe valves, lower threaded stem globe valves, etc. They are durable, have low opening height, are easy to manufacture, and are easy to maintain. Not only suitable for medium and low pressure, but also suitable for high pressure characteristics.

Advantages of stop valve:
1. Simple structure, convenient to manufacture and maintain.
2. The stroke is small and the opening and closing times are short.
3. Good sealing performance and long service life. In addition, the stop valve also has shortcomings, such as poor adjustment performance and a large amount of force required for switching. It is not suitable for media with particles, high viscosity, and easy coking.

6. Check valve: Check valve is also called one-way valve or check valve. The main function is to prevent the medium in the pipeline from flowing back. The opening and closing parts rely on the force of medium flow to open or close by themselves. The check valve only allows the medium to flow from one direction to the other direction, and does not allow reverse flow to prevent accidents, so the check valve is also called a check valve.

Installation notes: The biggest difference in appearance between the check valve and other valves is that the check valve does not have a valve shaft and does not require manual operation or electric control. During installation, care should be taken not to allow the check valve to bear weight. Large check valves are independently supported; the direction of medium flow should be consistent with the direction on the valve arrow.

Check valve classification: Check valves can be divided into lift type, swing type, butterfly type and diaphragm type according to their structure. According to the connection method, it is divided into three types: threaded connection, flange connection and welding.

7. Solenoid valve: Solenoid valve is a basic component of automation used to control fluids and is an actuator; it is not limited to hydraulic and pneumatic. Solenoid valves are used to control the direction of hydraulic flow. Factory mechanical devices are generally controlled by hydraulic steel, so solenoid valves are used.

Working principle of the solenoid valve: There is a closed cavity in the solenoid valve with through holes at different positions. Each hole leads to a different oil pipe. There is a valve in the middle of the cavity, and two electromagnets on both sides. Which side of the magnet coil energizes the valve? The body will be attracted to which side, and by controlling the movement of the valve body to block or leak different oil drain holes, and the oil inlet hole is normally open, the hydraulic oil will enter different oil drain pipes and then pass through the oil Pressure drives the oil-steel piston, which in turn drives the piston rod, and the piston rod drives the mechanical device. In this way, the mechanical movement is controlled by controlling the current of the electromagnet.

Solenoid valve application: Solenoid valve (electromagnetic valve) is an industrial piece of equipment controlled by electromagnetism. It is a basic component of automation used to control fluids. It is an actuator and is not limited to hydraulic and pneumatic. Used in industrial control systems to adjust the direction, flow, speed and other parameters of the medium. Solenoid valves can cooperate with different circuits to achieve expected control, and control accuracy and flexibility can be guaranteed. There are many types of solenoid valves. Different solenoid valves play a role in different positions of the control system. The most commonly used ones are one-way valves, safety valves, directional control valves, speed-regulating valves, etc.