Bourdon tube pressure gauges are the most frequently used mechanical pressure measuring instruments. Their pressure element is often known as a Bourdon tube: The French engineer Eug�ne Bourdon made use of this functional principle in the middle of the 19th century. It really is predicated on an elastic spring, a c-shaped, bent tube with an oval cross-section.
The effect of pressure on a Bourdon tube
When the internal space of the Bourdon tube is pressurised, the cross-section is thus altered towards a circular shape. The hoop stresses that are created in this process raise the radius of the c-shaped tube. As a result, the end of the tube moves by around two or three millimetres. Thankful is really a measure of the pressure. It is transferred to a movement, which turns the linear deflection right into a rotary movement and, with a pointer, makes this visible on a scale.
Bourdon tube variants
With the c-shaped bent Bourdon tubes, pressures around 60 bar can be displayed. For higher pressures, helical or spiral-type Bourdon tubes are employed. Based on the geometry, material and material thickness, pressures up to 7,000 bar could be realised. With regards to the requirement, the pressure elements are constructed with copper alloys, stainless steels or special materials such as for example Monel.
Note
Further information on Bourdon tube pressure gauges are available on the WIKA website.