What advantages do pressure switches with metal bellows offer and what is the foundation for these? Advantages derive from the seamless design of these measuring system. This solution enables permanently stable repeatability and, simultaneously, eliminates the risk of leakage.
Bellows measuring systems derive from a mature manufacturing technology. The production of metal bellows, for instance from stainless steel or perhaps a copper alloy, occurs in several steps. Circular discs are first cut from the flat little bit of metal, and these are then shaped into cup-shaped objects. They’re softened through an annealing process in a furnace at more than 600 �C and then drawn into long, thin-walled and seamless tubes.
Constant elasticity
The tubes are corrugated by using forming tools at high pressure, and then are trimmed to the designed size. In the next stage, the spring-like metal cylinders are pressed together in accordance with the specified dimensions (length, outer and inner diameter). This creates the constant elasticity needed for the stable repeatability of the movement. In the final step, the bellows are degreased and passivated, i.e. given a protective coating against corrosion.
Bellows manufactured from stainless steel for pressure switches
Seal-free functionality
In a pressure switch, the metal bellows is brazed or welded to the process connection. Its other end is in contact with the transmission mechanism. Therefore the instrument includes a fully seamless measuring system with no need for just about any rubber sealing materials and the risk of leakage is eliminated. This feature makes pressure switches with metal bellows suitable for an array of applications. Process reliability can be guaranteed with liquid media.
Permanent accuracy
A metal bellows changes its length in line with the pressure. When a defined switch point is reached, it triggers the switching function via a transmission mechanism. If the pressure drops or rises again, the bellows returns to its original shape and the switch contact returns to its original position.
The expansion movement of a metal bellows has a high linearity. The switch differential, that is precisely adjusted with a specific calibrated spring system, remains correspondingly constant. This ensures the accuracy of pressure control and switching, even over a long period of time.
Note
Detailed information on pressure switches with metal bellows, e.g. models PSM-520, PSM-550 and PSM-700, are available on the WIKA website. Comfortable would like to buy pressure switches with metal bellows? Inside our WIKA online-shop you will find a few of our standard designs. In case you have any questions, your contact will gladly assist you to.