Ⅰ. Introduction and principle of solenoid valves
1. Composition of solenoid valve
A solenoid valve is a valve in a refrigeration system that controls the automatic opening and closing of refrigerants. Electromagnetic valves can be divided into two types: direct acting and indirect acting. Electromagnetic valves used in commercial refrigeration equipment are generally direct acting.
The electromagnetic valve is composed of a valve body and an electromagnetic head, which are generally direct acting. The so-called direct opening and closing electromagnetic valve uses the armature in the electromagnetic head to directly control the opening and closing of the valve hole, with a diameter generally between 6-22mm.
2. The function and working principle of solenoid valves
The refrigeration system is divided into high-pressure and low-pressure, liquid and gaseous states. In order to prevent the high-pressure liquid refrigerant from forming an impact on the compressor after the compressor is shut down, an electromagnetic valve is used to protect it. When the system pressure is in a balanced state before the compressor starts, there is no impact. At this time, the electromagnetic valve powers on the compressor to start, and the refrigerant circulates and cools.
When the compressor is about to shut down, the power is cut off or the solenoid valve quickly shuts off after stopping. The refrigerant on the high-pressure side does not return to the compressor in the opposite direction, but passes through the compressor in the circulating direction, gradually restoring balance with the stop pressure of the compressor in the entire refrigeration system.
Working principle: When the refrigeration equipment is started, the electromagnetic coil generates electromagnetic force to open the valve. When the coil in the electromagnetic head is energized, the coil and armature generate an induced magnetic field. The armature drives the valve needle to move up, the valve hole is opened, and the fluid flows normally. When the set temperature is reached, when the coil in the electromagnetic head is powered off, the magnetic field disappears, and the armature falls due to self rain and spring force. The valve needle closes the valve hole and the fluid stops flowing.
The selection of solenoid valves should generally be based on the flow rate of the system, selecting the appropriate diameter of the solenoid valve, while also considering the requirements of its working voltage, applicable environmental temperature, working pressure and other parameters. When installing the solenoid valve, the valve body of the solenoid valve should be perpendicular to the pipeline to ensure that the solenoid valve core can easily move up and down.
Ⅱ. Introduction and principle of electric valves
There are two types of electric valves, one is an angle stroke electric valve, which is used by an angle stroke electric actuator in conjunction with an angle stroke valve to achieve a 90 degree internal rotation of the valve to control the flow of the pipeline; Another type is a straight stroke electric valve: it is used by a straight stroke electric actuator in conjunction with a straight stroke valve to achieve up and down movement of the valve plate to control the flow of the pipeline. Usually used in conjunction with highly automated equipment.
Electric valves are usually connected by electric actuators and valves, and become electric valves after installation and debugging. The electric valve uses electrical energy as power to connect the electric actuator to drive the valve, achieving the opening and closing and regulating actions of the valve. To achieve the purpose of switching or regulating the pipeline medium.
The driving device of the electric valve is a reversible electric motor, which drives the valve core to control the valve through a certain period of rotation of the motor. AI analog signal control is used to adjust the flow rate of the pipeline medium, and digital signal control can also be used in specific pipeline environments.
Ⅲ. Differences between electric valves and solenoid valves
1. The electromagnetic valve has excellent leak proof performance, fast opening and closing, low power, and is suitable for use as a cut-off valve in pipelines with corrosive, toxic, and other chemical substances; Electric valves are mostly used for regulating pipeline flow and are normally installed at the outlet of air supply and refrigeration pipelines. They can also be used in liquid pipelines, and are widely used in pipelines such as canned drinks and sewage treatment pipelines.
2.The solenoid valve is used for on-off control of liquid and gas pipelines and is a two position DO control. Generally used for control of small pipelines. Electric valves are used for analog quantity regulation of medium flow in pipelines of liquid, gas, and air systems, and are controlled by AI. In the control of large valves and air systems, electric valves can also be used as two position switch controls.
3.The electromagnetic valve can only be used as a switching value, for DO control, and can only be used for small pipeline control. It is common in DN50 and below pipelines, and is rarely used upwards; Electric valves can have AI feedback signals and can be controlled by DO or AO, which is more common in large pipelines and air valves.
4.The solenoid valve is driven by a coil and can only be opened or closed, with a short action time when opening and closing; The drive of an electric valve is usually achieved by a motor, which takes a certain amount of time to simulate the opening or closing action and can be adjusted.
5.Electromagnetic valves generally have a small flow coefficient and a small working pressure difference. For example, the flow coefficient of a 25 caliber solenoid valve is much smaller than that of a 15 caliber electric ball valve. The drive of the solenoid valve is through an electromagnetic coil, which is relatively easy to be damaged by voltage shocks. Equivalent to the function of a switch, it has two functions: on and off.
6.The driving of electric valves is usually done by a motor, which is relatively resistant to voltage shocks. Electromagnetic valves are quick opening and quick closing, generally used in places with low flow and pressure, and require high switching frequency. Electric valves are the opposite. The opening of the electric valve can be controlled, with states of open, closed, half open, and half closed. It can control the flow of medium in the pipeline, but the electromagnetic valve cannot meet this requirement.
7.Electromagnetic valves are suitable for a special process requirement, such as leakage, special fluid medium, etc. More expensive electric valves are generally used for regulation, and there are also switch quantities, such as the end of the fan coil.