Solenoid Valve vs. Motorized Valve

solenoid valve (left) vs. motorized valve (right)
Figure 1: Solenoid valve vs. motorized valve.

Motorized valves (also called electric valves) and solenoid valves are increasingly used in industrial fields. However, many people tend to confuse these two valves and do not know the difference between them. This article will discuss the differences between motorized valves and solenoid valves in terms of working principles, working characteristics, applications, common faults and troubleshooting methods.

1. What Is a Solenoid Valve

copper solenoid valve
Figure 2: Solenoid valve.

A solenoid valve is a valve that uses an energized coil to generate magnetic force to control the fluid. The controlled objects include but are not limited to liquids and gases. It is a device that can quickly open or close to allow the fluid to flow through the valve or stop it.

Solenoid valve features:
● The solenoid valve has a simple structure but is relatively precise. Generally speaking, it only has two states: on and off (open or closed).
● It is mainly used in applications with small diameter and small flow, and has a very fast opening/closing speed.
● The solenoid coil has poor resistance to voltage shock and is easily damaged.
● It has high requirements for the cleanliness of the medium.

2. What Is a Motorized Valve

motorized ball valve structure
Figure 3: Motorized valve structure.

The motorized valve uses an electric actuator (electric motor) to control the valve instead of manpower, and can perform linear and rotational movements. It can be divided into upper and lower parts: the upper part is the electric actuator, and the lower part is the valve.

From the structure of the motorized valve, it can be seen that the valve body part is not much different from the ordinary manual valve, except that the handwheel is replaced by an electric actuator. Therefore, in theory, all manual valves can have electric versions, and there are various motorized valves such as motorized gate valves, motorized butterfly valves, motorized ball valves, etc.

Motorized valve features:
● Motorized valves are mainly used in applications with large diameters and large flows (such as water supply pipelines with pipe diameters exceeding DN300).
● The opening/closing speed is relatively slow.
● They have strong resistance to voltage shocks and low failure rates.
● They basically have no special requirements for medium cleanliness.

3. Difference between Motorized Valve and Solenoid Valve

Athos RZMO-A-010/210 direct-acting digital proportional relief valve with integrated pressure sensor for closed-loop pressure control
Figure 4: Proportional relief valve structure diagram.

Solenoid valve

Motorized valve

Installation method

Horizontal installation

No requirement

Energized time

Unable to be energized for a long time and prone to heating up

Automatic power-off protection when finishing opening/closing

Medium flow direction

Consistent with the direction marked by the arrow

Regardless of flow direction

Media requirements

Pure liquids or gases without contain impurities

Fine particles allowed

Power consumption during operation

About 20-30 watts

About 6 watts, only consumed during the opening/closing process, no power consumption when finishing opening/closing

Opening/closing speed

Instantaneous opening/closing, easily causing water hammer and pipeline resonance

6-15 seconds, smooth opening/closing, accurate adjustment

Flow rate

Shut-off type, short stroke and poor fluid flowing

Large flow rate

Table 1: Solenoid valve vs. motorized valve.

3.1 Working Principle

Solenoid Valve
When the solenoid coil is energized, the solenoid valve generates magnetic force, which overcomes the pressure of the spring and drives the valve core to move. It has a simple structure and can only achieve the opening and closing of the valve.

Motorized Valve
Although motorized valves also use electricity as energy, they actuate the valve stem through an electric motor to drive the valve core to move.

3.2 Working Characteristics

Solenoid Valve
● Solenoid valves generally have a small flow coefficient and a small working pressure difference. For example, generally the flow coefficient of a 25DN solenoid valve is much smaller than that of a 15DN electric ball valve.
● The solenoid valve is actuated by an electromagnetic coil, which is easier to damage by voltage shock.
● It can only perform opening or closing operations, and the opening/closing time is short.

Motorized Valve
● Motorized valves are generally driven by electric motors and are relatively resistant to voltage shocks.
● The opening/closing action of the motorized valve is much slower than that of the solenoid valve. It not only has an on and off state, but also can adjust the valve opening degree according to a given signal to control the flow rate of the medium in the pipeline.

Solenoid valves can generally return the original state when the power is turned off. To achieve this function, motorized valves need to add a reset device.

different types of motorized valves
Figure 5: Motorized valves.

3.3 Application

Solenoid Valve
The solenoid valve is used for on/off control of liquid and gas pipelines, generally used for the control of small pipelines.

It has excellent anti-leakage performance, fast opening and closing speed, and low power, suitable for use as a shut-off valve in some pipelines with corrosive, toxic and other chemical substances.

Solenoid valves are widely used in some small equipment or pipelines, such as household air conditioners, water heaters, etc. In addition, they can also be used in some applications that require quick response, such as hydraulic control systems.

Motorized Valve
Motorized valves are often used to regulate pipeline flow and are used in some large industrial equipment, such as pipeline control systems in refrigeration, chemical industry, water treatment and other fields. They are installed at the air outlet of the air supply cooling pipeline, and in pipeline systems such as canning pipelines for wine and beverage production and sewage treatment pipelines.

At the same time, the motorized valve can also achieve automated control through the control system to improve production efficiency.

3.4 Common Faults and Troubleshooting Methods

Motorized Valve
Common faults of motorized valves are usually related to the motor, such as motor not rotating, motor overheating, etc. For these types of faults, it is usually necessary to check whether the motor's power supply and circuit are normal, whether the motor is stuck or damaged, etc.

In addition, the control system of the motorized valve may also malfunction, such as poor circuit contact, damaged controller, etc. It is necessary to check whether the control system circuit and controller are working properly.

Solenoid Valve
Common faults of solenoid valves are usually related to the electromagnet, such as electromagnet not attracting, electromagnet not resetting after attracting, etc. For these types of faults, it is usually necessary to check whether the power supply and circuit of the electromagnet are normal, whether the electromagnet is stuck or damaged, etc.

In addition, the spring and seals of the solenoid valve may also malfunction, such as spring failure, seal leakage, etc., so the springs and seals need to be replaced.

water solenoid valves
Figure 6: Solenoid valves.

4. Conclusion

Although motorized valves and solenoid valves are both commonly used valves in the field of industrial automation, there are certain differences in their working principles, working characteristics, scope of application, common faults and troubleshooting methods. When using these two valves, you need to choose the appropriate valve type according to the actual situation, and operate and maintain it in strict accordance with the instruction manual.

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