In this article, we are discussing what are the criteria we have to look at while choosing Solenoid Valves.
Before choosing Solenoid valves, gather the information about what type of media they will be used for. Solenoids are normally designed to operate with media without solids particles. It can use for water, oil, petroleum products, steam, compressed air, or heat transfer fluids. This guide describes the main parameters of solenoid valves. Use the Webshop filter to determine what is important in your application and identify valves that meet your needs. You can also use the Automatic Valve Selection Wizard to find the right valve for your application quickly.
Criteria for Selecting Solenoid Valve
- Principle of operation
- Temperature range
- Response time
Principle of operation
There are different types of solenoid valves, each with different operating principles:
• Direct running (running from 0 bar)
• Semi-direct operated (running from 0 bar)
• Indirect operation (pressure difference required, usually at least 0.5 bar)
It is important to choose the right working principle and the valves operate directly from the 0 bar. The valve has a small hole, which is closed by a plunger with a polymer gasket. If there is solenoid (electromagnetic) power, the plunger is lifted and the valve is opened using electromagnetic force. This principle is often used for small valves, which are ideal for small flow rates. For large flow rates, a semi-direct or indirect operating valve is recommended. Medium pressure is used to open and close both valves. Semi-direct operated valves have a stronger coil than indirect valves and work from 0 bar. Indirectly operating valves require a constant pressure difference of approximately 0.5 bar for proper operation. The main benefit of indirect valves is that they can control large flows with a small coil, resulting in lower energy consumption.
Check for a constant pressure difference of at least 0.5 bar above the valve. In this case, an indirect operating valve can be selected (in this case a semi-direct valve is definitely permissible). Select a (semi-) direct operated solenoid valve if this is not the case (low inlet pressure, closed circuit).
For a detailed description of the working principles read the article on solenoid valve types.
Solenoid valves are only used with neutral liquids and gases like oils, lubricants, fuels, water, air, or steam. While selecting a solenoid valve, it is important that the materials are compatible with the medium. The most common type of solenoid valve body is brass, which is suitable for most substances. FKM (Viton) and EPDM, for example, have different properties that make them suitable for different applications. For a complete list of media that are compatible with valve materials, see the article on the chemical resistance of materials.
The operating pressure of the system is important for selecting a solenoid valve. If the specified maximum pressure is exceeded, dangerous situations may occur, and the valve may burst or be damaged. Note that maximum pressure is usually associated with one type of medium. So, gases or liquids can have different values. The minimum pressure difference between the in-out outlet is probably more important (see ‘Operation Principle’ section). The difference between low and high pressure is usually expressed in the bar.
When selecting the appropriate solenoid valve, keep in mind the minimum and maximum temperature characteristics. Water valves should not be used below 0 C due to the possibility of freezing. The article Chemical resistance of materials discusses the temperature characteristics of valve materials.
On electrical equipment, the IP rating (English protection) or IP code indicates the level of protection against access to hazardous areas, water, dust, and body parts. The international standard IEC 60529 defines the code.
An IP rating consists of two digits. The first digit denotes the level of protection against access to potentially hazardous areas and objects.
The second digit denotes the degree of moisture resistance. The last digit, if present, indicates resistance to contact with hazardous elements. The majority of JP Fluid Control solenoid valve coils are IP-65 rated. The meaning of the first two digits of the coding is shown in the table below.
The solenoid valve response time is the time takes from the moment the solenoid becomes active until the pressure drops to 10% or rises to 90% of the maximum test pressure. If a valve’s maximum rated operating pressure is greater than six bar, the response time is measured at that pressure.
The reaction time is determined by the valve’s construction, coil characteristics, atmospheric pressure, and medium viscosity. DC valves have a slightly slower response time than AC valves. In general, direct operating valves are faster than indirect valves. Direct operating valves typically have values ranging from 5 to 50 ms.
Indirect valves have a response time of 50 milliseconds for smaller versions and up to 1500 milliseconds for larger versions. Some applications, such as avoiding water hammer, do not necessitate a quick response time. Fast closing valves can create pressure waves in the circuit, causing pipes and other components to fail. If this occurs on your system, you can read the installation instructions.
Voltage and coil
A solenoid valve is an electromechanically operated valve that converts electrical energy to mechanical energy, thereby creating a magnetic reaction. The coil is made of copper wire that has been wrapped around a tube. The plunger in the core is made of ferromagnetic material. A magnetic field is created when an electric current flows through the coil. The magnetic field exerts a force on the plunger, causing it to move. The valve will be opened or closed using this principle.
Solenoid coils are available in a variety of voltages for both direct current (DC) and alternating current (AC). The valve’s behaviour is influenced by the selection.
The importance of polarity in a DC coil is a frequently asked question. In most cases, the DC coils do not have the required polarity, and the polarity of these additional components is only important when a timer or LED connector is used.