Operating safety gate (Modified)
Depth at or below 80%, and operating pressure at or below P'_Mod
SAFE AT OPERATING PRESSURE
Operating pressure 9,930 kPa is at or below Modified B31G safe pressure 13,007 kPa.
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ASME B31G & Modified B31G Remaining Strength
Estimate remaining strength for a blunt metal-loss defect using original B31G and Modified B31G. Defaults are a 508 mm, 9.5 mm WT, Grade 483 metric example at F=0.72, with a 2.5 mm deep, 150 mm long defect at 9930 kPa operating pressure. Switch to US Customary to convert those inputs. Results update as you edit.
Section 1
Units
Unit system
Switching units converts the numbers already in the form. Design factor F stays the same.
Section 2
Pipe & Defect Parameters
mm
mm
MPa
factor
Dimensionless. Typical liquid or Class 1 Div 2 value is 0.72. Does not convert.
mm
mm
kPa
Compared with Modified B31G safe pressure for the operating safety gate.
Section 3
Remaining Strength
Uncorroded MAOP
13,007 kPa
Barlow: 2 x WT x SMYS x F / OD
Depth ratio d/t
26.3%
Rejects above 80 percent metal loss
B31G safe pressure P'_B31G
13,007 kPa
Original B31G parabolic / Folias A, capped at MAOP
Modified B31G safe pressure P'_Mod
13,007 kPa
0.85dL / RSTRENG-style Folias z, capped at MAOP
Modified RSF factor
100.0%
P'_Mod / uncorroded MAOP
What this tool calculates
Uncorroded MAOP is the Barlow hoop-stress pressure 2 x WT x SMYS x F / OD. Depth ratio is d/t. Original B31G uses a parabolic metal-loss area (about 2/3 dL) and a Folias factor based on A = 0.893 L / sqrt(OD x WT), with flow stress 1.1 x SMYS. If A is greater than 4, the long-defect form uses (1 - d/t).
Modified B31G uses a 0.85dL rectangular area and an RSTRENG-style Folias factor based on z = L^2 / (OD x WT). Metric flow stress is (SMYS + 68.95) MPa. US flow stress is SMYS + 10,000 PSI. Both safe pressures are capped at uncorroded MAOP. Modified RSF is P'_Mod divided by that MAOP.
The operating safety gate uses Modified B31G. Depth ratio above 80% is REJECT (>80% DEPTH). Otherwise the gate is SAFE AT OPERATING PRESSURE when current operating pressure is at or below P'_Mod, or DERATING REQUIRED when it is above.
Switching the unit toggle converts values already in the form: OD, wall, defect depth, and defect length by 25.4, SMYS by 145.038, and operating pressure by 0.145038. Design factor F is dimensionless and does not convert. Metric uses mm, kPa, and MPa. US Customary uses inches and PSI.