Solenoid Valves

Solenoid Valve

Solenoid valves are valves which are activated by an electromagnet. The advantage lies in a fast reaction time. In addition, solenoid valves with position determination can also be operated as servo valves and can therefore control the fluid flow. They are therefore used in all areas of fluid technology, for example, for operations with water and neutral liquids, and also as specialised models, for instance, to fill beverages, control pneumatic and hydraulic drives, as oil burner valves, or for use with highly corrosive liquids. 

There are three structural variants:

Direct-operated

In this model, the drive is directly connected to the valve piston. When the electromagnet is switched off, a pressure spring holds the valve in its home position. In order to move the solenoid valve from its home position, the piston must be lifted from the valve seat by the electromagnetic drive. The force required for this depends on the spring, the size of the valve seat and the maximum differential pressure of the closed pressure valve. Direct-operated valves are therefore used principally for small nominal diameters and low operating pressure.

Pilot-operated

This type of solenoid valve uses the differential pressure of the operating pressure to open and close. The minimum pressure required for this is specified in the technical data sheet. In this model, higher pressures can also be controlled with smaller magnets. Pilot-operated pressure valves can therefore achieve higher flow rates at higher pressures. They are used, for example, in heating boilers.

Positively-operated

This model is a combination of direct-operated and pilot-operated valves. Like the direct-operated valve variants, they can operate at a differential pressure of 0 bar, but can also be used at higher operating pressures. 

Modes of function

Solenoid valves are used in fluid technology in different ways depending on the field of application and requirements:

‘Normally open’ refers to a type of valve which is open in the de-energised state.

‘Normally closed’ means that the component closes in the de-energised state. For the latter, an emergency manual override is optionally available, which allows the valve to be opened even in the event of a complete power failure. 

The solenoid coils are operated with direct current voltage or alternating current voltage, depending on the model. Alternating current coils usually have better switching times and better performance during the switching operation but may tend to "hum". This humming can be intensified further by contamination of the pole surfaces and cannot be completely suppressed for physical reasons. 

Depending on the area of application, materials such as anodised aluminium, stainless steel, brass, a zinc alloy or plastic are used. Pipe connection, base plate, banjo, CETOP, NAMUR and ISO are offered as mounting solutions. In addition, a wide selection of different seals is available, as well as other accessories and spare parts.

In order to ensure optimum operation, the valve should be carefully selected according to the basic technical conditions. We will be happy to advise you on the selection of a suitable solenoid valve and are also available to assist you with assembly and maintenance.