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Bourdon Tube Pressure Gauge for Ships

Shipboard machinery must operate within certain desired parameters. Instrumentation enables the parameters—pressure, temperature, and so on—to be measured or displayed against a scale. A means of control is also required in order to change or alter the displayed readings to meet particular requirements.

Bourdon tube pressure gauge is probably the most commonly used gauge pressure measuring instrument and is shown in Figure . It is made up of an elliptical section tube formed into a C-shape and sealed at one end. The sealed end, which is free to move, has a linkage arrangement which will move a pointer over a scale. The applied pressure acts within the tube entering through the open end, which is fixed in place.

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The pressure within the tube causes it to change in cross section and attempt to straighten out with a resultant movement of the free end, which registers as a needle movement on the scale. Other arrangements of the tube in a helical or spiral form are sometimes used, with the operating principle being the same.

Bourdon tube pressure gauge
Fig:Bourdon tube pressure gauge

While the reference or zero value is usually atmospheric, to give gauge pressure readings, this gauge can be used to read vacuum pressure values.

The Bourdon tube is also an elastic-element type of pressure transducer. It is relatively cheap and is commonly used for measuring the gauge pressure of both gaseous and liquid fluids. It consists of a specially shaped piece of oval-section, flexible, metal tube that is fixed at one end and free to move at the other end. When pressure is applied at the open, fixed end of the tube, the oval cross-section becomes more circular. In consequence, there is a displacement of the free end of the tube. This displacement is measured by some form of displacement transducer, which is commonly a potentiometer or LVDT. Capacitive and optical sensors are also sometimes used to measure the displacement.



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