Bourdon effect

[triplea]

Could somebody help me to describe Bourdon effect for a straight pipe and for a bend?
Can you tell me also the calculation formulas?

Thaks!

 

[electricpete]

There is a pressure-sensing device called a bourdon tube which is a coiled flexible tube with fluid pressure on the inside. As pressure increases, the coil tends to want to straighten out against spring pressure (since there is a bigger surface area around the outside curve of the coil than the inside curve of the coil... with same pressure applied on both).

I would assume that a piping elbow wants to straighten out for the same reason. The higher the pressure, the higher the force... also probably depends on the geometry of the elbow.

 

[lakshmi]

the bourdon effect is the difference between the pressure inside the tube or pipe in relation to the pressure outside the tube or pipe. If the inside presurer is greater than the outside presure the tube or pipe will expand. And if the tube or pipe is bent in a circular form, the expansion is noticable and can be converted to a calibrated reading as in a pressure gauge.

 

Electricpete is correct. Internal pressure can affect the pipe bend or elbow in 2 ways. The Bourdon effect describes the tendency for the pipe bend to "open" under internal pressure and "close" under external pressure. The reason is as described by Electricpete. The other effect is the "stiffening" of pipe bends and elbows as internal pressure is increased. The stiffening results from the internal pressure resisting the "ovalization" of the cross section that normally occurs when a bending moment is applied to the bend. One or both of these effects can occur in large diameter pipe with large D/t ratios. Reference B31.3, Appendix D, Table D300 and note (7). If you have piping systems of moderate diameter but are designing to B31.3, Chapter IX (high pressure - Class 2500 or higher) you will want to consider these effects. Good pipe stress computer programs (e.g., Caesar II) will give you the option of "toggling" these effects off or on.

Regards, John.