Design Standards for High-Pressure Machines

From the above facts, it may therefore be concluded that notches and other irregularities in the cross-section areas as well as small and smallest dents in the surface (roughnesses) should be avoided. This is why polished surfaces and cross sections as smooth as possible are a basic requirement for construction as well. The easiest way to realize this requirement is to keep the space that is under pressure as small as possible ( small is beautiful ) and to lead the pressure-generated forces to the energy consumption point not circuitously but as directly as possible. Furthermore, shrinked designs as well as the use of autofrettage decisively increase fatigue life (see Chapter 12). 

It is therefore recommended to have the same dimensions for the cross section of the groove and the cross section of the O-ring (tolerances to be considered). An O-ring is acceptable where the cross section is only slightly bigger. 

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