How does a Bourdon tube pressure gauge measure pressure?

Fluid like air or water goes through the process connection and up into the Bourdon tube. As pressure inside increases, the tube straightens out. A gear transfers the motion to the dial pointer. In fancy engineering terms, the tube deflects, and the movement converts that deflection into a rotary movement of the pointer.

Why do pressure gauges come in standard ranges of 15, 30, 60, and 100 PSI?

A Frenchman named Eugene Bourdon invented the Bourdon tube in the mid-1800s. To this day, most Bourdon tubes are made in Europe where pressure is measured in bar or atmospheres. This is why the standard pressure gauge ranges in PSI tend to have equivalent bar denominations. For example, 15 PSI is equal to 1 bar, 30 PSI to 2 bar, and 60 PSI to 4 bar, and so on.

What about the Bourdon tube is different for different ranges of measurement?

A Bourdon tube’s size and wall thickness determine the range of a gauge. Larger, thin-wall tubes are used to measure lower pressures. Smaller, thicker-wall tubes are used to measure higher pressures. For very high pressures, thick-wall tubing is used to create a helical Bourdon tube within a gauge series. The mechanical movement is the same from as low as 10 PSI to as high as 10,000 PSI.

How long do Bourdon tube pressure gauges last?

The Bourdon tube is incredibly robust and can last millions of cycles and decades of operation under normal conditions. Conditions that lead to shorter lifespan include over-pressuring, extreme temperatures, shock, pulsation, vibration, corrosion, and clogging.

Can you recalibrate or replace the Bourdon tube?

Most pressure gauges can be calibrated by adjusting the pointer or gear inside. This can correct small changes in the movement or tube over time. However, if the Bourdon tube stretches, cracks, or breaks, the entire pressure gauge is not repairable.