The Site for Gas and Liquid Chromatography
Estimation of the Maximum Allowable Working Pressure for Tubing
There are two possible pressures. The maximum allowable working pressure (MAWP), which is a safe pressure to work with, without the possibility of ruptures or bursting. And there is the burst pressure; the name stands for itself. Normally a factor four is assumed between the two. If you quadruple the maximum allowable working pressure, you get the burst pressure for temperatures of the materials' chromatographic application areas. Estimations are based on Barlow's formula:
| PMAWP = (OD - ID)/OD · σUTS/SF = 2 dW/OD · σUTS/SF | |
| ID = Internal Diameter of the Pipe OD = Outside Diameter of the Pipe dW = Wall Thickness of the Pipe |
SF = Safety Factor (1 for burst pressure, 4 for MAWP) |
The burst pressure is dependent on the wall thickness and the diameter of a pipe. The larger the diameter and the thinner the wall, the less pressure it needs to burst a pipe. Thin walls mean a ID/OD ratio close to 1.0 Also the tensile strength of the pipe material plays a role. A plastic tube will burst long before a metal tube will. And within the metals soft copper will burst before strong steel. The factor (OD - ID)/OD can also be expressed as 1 - ID/OD, this is 1 minus the ratio between internal and outside diameter of the tubing. |
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