Solenoid valve , an electrically operated device that varies the current flowing through a solenoid (conductor located around a piston, in the form of a coil ) and is used to control the flow of liquids or gases in the fully open or fully closed position. When the current flows through the solenoid, it generates a magnetic field that attracts the moving piston. At the end of the effect of the magnetic field, the piston returns to its position due to the effect of gravity , a spring or pressure of the fluid to be controlled.
Summary
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- 1 General
- 2 Classification
- 1 According to your application
- 2 According to its construction
- 3 According to its shape
- 3 Materials used for its manufacture
- 1 Valve body
- 2 Coil
- 3 Sealing materials
- 4 Choice of a solenoid valve
- 5 Valve installation
- 6 Source
General
In many industrial processes it is necessary to control the passage of some type of flow, from electric current to gases or liquids . This task is performed by valves . In particular, those operated by solenoids allow their implementation in places of difficult access and facilitate the automation of the process by being electrically actuated. Unlike motorized valves , which are designed to operate in a modulating position, the solenoid valve does not regulate flow although it can always be fully open or fully closed.
The solenoid, under the effect of circulating current, behaves like an electromagnet . It attracts ferromagnetic materials , product of the alignment of atomic magnetic moments. The magnetic field , created by current flowing through the solenoid, acts on the moving piston of magnetic material. A force is produced that causes the piston to move allowing the valve to close or open .
Classification
Many types of solenoid valves are found. All of them work with the physical principle described above, however they can be grouped according to their application, construction or shape.
According to your application
- Direct Action or Pilot Operated.
According to its construction
- Normally open or Normally closed
According to its shape
- According to the number of routes.
Materials used for its manufacture
In order to choose a suitable valve for each application, it is necessary to take into account the materials used in its construction. The type of work to be performed will depend on this. The materials used are chosen in order to be compatible with the type of fluid, achieve maximum reliability and life time, and minimize costs. Here are some materials used in each component of a solenoid valve:
Valve body
For neutral fluids bronze or tin is used . In fluids subjected to high temperatures (or steam for example), steel or stainless steel (more resistant to corrosion) is used. In other cases, in order to reduce costs, plastic or PVC materials are used .
Coil
It is generally constructed from insulated copper conductors . The area of the mobile piston that comes into contact with the fluid is made of stainless steel , thus achieving resistance to corrosion.
Sealing materials
The temperature , chemical and mechanical conditions of each particular application are taken into account for the choice of this material . For neutral fluids at low temperatures, Viton is generally used . For work with high temperatures, EPDM and PTFE are used , materials that offer great resistance to adverse temperature and acidity conditions .
Choosing a Solenoid Valve
When choosing a valve , we must take into account the following aspects:
- Fluid to be controlled ( viscosityand pH characteristics )
- Pressureranges with which you want to work (MOPD and MinOPD)
- Fluid (and external medium) temperature.
- Pipe or connection type (size and style).
- Valveelectrical characteristics (working voltage ranges; DC or AC)
- Specific options for the application:
- Normally open or closed.
- Safe working pressure(SWP)
- With or without manual stem, etc.
Valve installation
About the installation it should be remembered that most are designed to work in horizontal lines, with the coil on top. There are valves , equipped with springs, that allow installation in any position. Another relevant consideration is that the direction of the fluid in the installation must be respected. This should match the arrow that is usually found on the valve body. Also, it is convenient to install a filter before the valve, in order to filter out foreign particles.
