ASME BPVC Section VIII Div. 1 Pressure Vessels, Taylor-Forge Flanges & Gasket Seating
ASME Bolted Flange Gasket m & y Bolt-Load Formula
Calculate Hydrostatic End Force H (kN), Operating Pressurized Bolt Load Wm1 = H + Hp (kN), Ambient Initial Gasket-Seating Bolt Load Wm2 (kN), and Governing Total Bolt Root Area Am (mm²).
On low-pressure flanges, ambient initial gasket-seating crush Wm2—not internal fluid pressure Wm1—governs stud bolt sizing!
Under the ASME Boiler & Pressure Vessel Code Section VIII Division 1 Mandatory Appendix 2 (Taylor-Forge method), a bolted ring/raised-face flange with Gasket Load Reaction Diameter `G` (mm) and Effective Gasket Seating Width `b` (mm) must satisfy TWO independent bolt-load states: (1) **Operating Pressurized State `W_m1 = H + H_p`**, resisting both Hydrostatic End Force `H = ((PI()/4) * G^2 * P) / 1,000` (kN) trying to blow the blind/pipe apart AND Residual Contact Force `H_p = (2 * b * PI() * G * m * P) / 1,000` (kN) keeping the gasket compressed by Gasket Maintenance Factor `m` (`~2.0–3.0` for spiral-wound stainless/graphite) times Design Pressure `P` (MPa); and (2) **Ambient Initial Gasket-Seating State `W_m2 = (PI() * b * G * y) / 1,000`** (kN), crushing the virgin gasket at zero internal pressure above Minimum Design Seating Stress `y` (MPa, e.g. `69` MPa = `10,000` psi for spiral-wound)! Governing Total Bolt Root Area is `A_m = MAX(W_m1, W_m2) * 1,000 / S_b` (mm²)!
Verify on a 10-Inch High-Pressure Spiral-Wound Raised-Face Flange—Gasket_Reaction_Diameter `G` = 285.0 mm (B2), Effective_Seating_Width `b` = 6.40 mm (B3), Design_Internal_Pressure `P` = 4.20 MPa (`42` bar, B4 -> Hydrostatic Force `H = 267.93` kN in E2), Gasket_Factor `m` = 3.00 (B5 -> Operating Bolt Load `W_m1 = 412.34` kN in E3), Minimum_Seating_Stress `y` = 69.0 MPa (B6 -> Ambient Seating Load `W_m2 = 395.39` kN in E4), and SA-193 B7 Allowable_Bolt_Stress `S_b` = 172.0 MPa (B7): Operating `W_m1` governs, requiring `2,397.3` mm² total tensile root area (E5)!
| ASME Appendix 2 Flange KPI (G=285 mm, b=6.4 mm, P=4.2 MPa, m=3.0, y=69 MPa) | Formula | Verified Output |
|---|---|---|
| Hydrostatic End Force H (kN) | ((PI() / 4) * (G^2) * P_MPa) / 1000 | 267.93 kN (51.04 kN @ low 0.8 MPa) |
| Operating Bolt Load Wm1 (kN) | H_kN + (2 * b * PI() * G * m * P) / 1000 | 412.34 kN (78.54 kN @ low 0.8 MPa) |
| Gasket-Seating Load Wm2 (kN) | (PI() * b * G * y_MPa) / 1000 | 395.39 kN (GOVERNS @ low 0.8 MPa!) |
| Governing Bolt Root Area Am (mm²) | (MAX(Wm1_kN, Wm2_kN) * 1000) / Sb_MPa | 2,397.3 mm² (2,298.8 mm² @ 0.8 MPa) |
ASME Appendix 2 Taylor-Forge Wm1 vs Wm2 Governing Bolt Area Formula
Validate `Reaction_Diam G > 20` mm, `Effective_Width b` in `(1, G/4]` mm, `Pressure P > 0` MPa, `Gasket_Factor m >= 0.5`, `Seating_Stress y > 0` MPa, and `Allowable_Bolt_Stress S_b > 20` MPa!
=LET(gd_m, B2, bw_m, B3, pr_m, B4, mf_g, B5, ys_m, B6, sb_m, B7, IF(OR(gd_m <= 20, bw_m <= 1, bw_m > gd_m / 4, pr_m <= 0, mf_g < 0.5, ys_m <= 0, sb_m <= 20), "Invalid Flange Input", LET(hf_k, ((PI() / 4) * (gd_m ^ 2) * pr_m) / 1000, hp_k, (2 * bw_m * PI() * gd_m * mf_g * pr_m) / 1000, wo_k, hf_k + hp_k, ws_k, (PI() * bw_m * gd_m * ys_m) / 1000, ROUND((MAX(wo_k, ws_k) * 1000) / sb_m, 1))))Low-Pressure 0.80 MPa Steam Line Seating-Governed Crossover Check (Set Pressure P B4 = 0.80 MPa)
Drop Design Pressure `B4` from `4.20` down to `0.80` MPa (`8` bar): Operating Load `W_m1` E3 plunges `81%` to `78.54` kN (`H = 51.04` kN in E2), yet Initial Spiral-Wound Seating Crush `W_m2` E4 stays `395.39` kN—completely governing Bolt Area `A_m = 2,298.8` mm² (E5) so the stiff metal-wound gasket still seals!
=IF(ISTEXT(E5), E5, ROUND((((PI() / 4) * (B2 ^ 2) * B4) + (2 * B3 * PI() * B2 * B5 * B4)) / 1000, 2))Try the example
Use the original values or change them to test your understanding.