Bourdon tube pressure gauges 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 made use of this functional principle in the middle of the 19th century. It is based on an elastic spring, a c-shaped, bent tube with an oval cross-section.
The effect of pressure on a Bourdon tube
Once 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 increase the radius of the c-shaped tube. Subsequently, pressure gauge octa of the tube moves by around two or three millimetres. This deflection is really a way of measuring the pressure. It really 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 up to 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. Depending on the requirement, the pressure elements are created from copper alloys, stainless steels or special materials such as for example Monel.
Note
More info on Bourdon tube pressure gauges are available on the WIKA website.