Not all solenoid valves were created equal

The humble solenoid valve has been providing efficient and reliable process control to countless industries for decades. Michael Hannig, Global Product Manager for Solenoid Valves at Bürkert Fluid Control Systems, looks at the design improvements that have taken this essential device to the next level of performance.

Solenoid design now and into the future

Over 90 per cent of all solenoid valves are equipped with single coils, the simplest of all coil types, which uses an enamelled copper wire wound on a coil bobbin. Bürkert coils are designed for continuous operation and are always coated with an insulating mass to ensure high electrical and mechanical protection. For applications involving ambient temperatures up to 250°C, anodised enamelled aluminium wires are used to ensure reliable operation.

Development of the basic design principles has led to reduced energy consumption with the introduction of the double coil design. This uses two independent windings with high and low power. The high power coil opens the valve and then integrated electronics switch over to the low power coil to provide the holding force.

As many industries look to reduce the footprint of a variety of control processes, so there is a need to develop smaller control devices that still provide the necessary power and energy savings. Bürkert has addressed this requirement with the introduction of the TwinPower solenoid which uses two parallel windings on the coil yoke. The integrated electronics switch the coils from parallel to series connection, which reduces the holding power to 25 per cent of that required for opening the valve.

The design of the coil and its operation has a direct effect on the performance of the valve. The latest energy saving designs allow the coil to be overexcited to open the valve and, within half a second, the current is reduced by 95 per cent. This is still sufficient to hold the valve in the open position. The cumulative effect of this type of feature can have a significant impact on the energy required for process control. Increased reaction speed, energy saving and reduced size are all themes that are expected to continue to influence valve design into the future, as are more specialised applications.

Specialised applications

Bürkert assisted Spanish company BioSystems S.A. in the development of a new biochemical analysis instrument used for clinical analysis of blood samples. The new development is based on Type 0127 (2/2- or 3/2-way solenoid valve) and the direct-acting media separated 3/2-way Twin Power rocker solenoid valve Type 6628 from Bürkert.

Both valves feature rocker technology, which ensures not only a complete back pressure tightness, good flushability and a low internal volume, but also precise switching of micro volumes with minimal temperature rise through the coil. Due to complete fluid separation, these valves can be used for aggressive media.

The new one-for-all dosing unit can now be used in more than one analysis device. Large quantities mean lower manufacturing costs, so that in the end both partners benefit from the solution that was found. BioSystems due to a low-priced, universal component. Bürkert due to the larger order size from the Spanish blood analysis specialist.

Complete control over production delivers quality and peace of mind

Manufacturers such as Bürkert not only design a comprehensive range of solenoid valves, to cover both standard and specialist applications, but also manufacture every component. This includes the machining of the valve body, the winding of the coil and the injection moulding of the coil encapsulation. In this way, Bürkert has control over every aspect of the valve and can therefore guarantee performance.

The testing of individual components and complete valves is a continuous process. Partly to ensure continued compliance with a wide range of certification, but also to ensure that the high quality standards are being maintained. This approach assures reliable operation, even in harsh operating conditions.

On the face of it, selecting a solenoid valve appears to be a simple enough decision. However, making the right choice requires an in-depth knowledge of the process under control, as well as expertise in the materials and designs available. By combining the knowledge of the process engineer with the fluid control experience of a manufacturer, customers can be sure of a high quality product that will deliver long-term reliability while also complying with the appropriate industry standards.

With over 60 years' experience in the design of solenoid valves, Bürkert continues to improve the technology and the materials used in their construction. The expertise in designing and specifying components for fluid control systems is available to every customer, ensuring that both the component and the application will perform as designed.

For more information visit www.burkert.co.uk.