Bourdon tube pressure gauge s are the most regularly used mechanical pressure measuring instruments. Their pressure element is frequently referred to as a Bourdon tube: The French engineer Eug�ne Bourdon used this functional principle in the center of the 19th century. It is based on an elastic spring, a c-shaped, bent tube having an oval cross-section.
The result 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 which are created in this technique raise the radius of the c-shaped tube. Therefore, the end of the tube moves by around two or three millimetres. This deflection is really a measure of the pressure. It is used in a movement, which turns the linear deflection 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 used. According to the geometry, material and material thickness, pressures around 7,000 bar could be realised. Depending on requirement, the pressure elements are constructed of 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.