Per RD 10-249-98 sections 5.1 and 5.2, the maximum initial ovalization factor for elliptical cross-sections is defined as:
When actual measured ovality data from bent pipes is unavailable (such as during design phase), perform two separate analyses:
One analysis with ovalization factor a = 0%
One analysis with the maximum a value from manufacturing specifications or supplier data (see section 5.2.6.8)
Apply the ovalization factor in these analyses:
Bend wall thickness pressure rating calculations
Bend stress analysis
Bourdon effect evaluation in bends (pressure-induced straightening)
Note: According to RD 10-249-98 section 5.2.6.8, multiply the initial ovality factor a by 1.8 for low-temperature piping systems. PASS/START-PROF automatically applies this multiplier when using RD 10-249-98 section 5.2 criteria.
When initial ovality measures less than 3% per section 5.2.6.8, omit ovality considerations from stress analysis. PASS/START-PROF does not automatically apply this exclusion.