What is the minimum required thickness of a welding neck flange as shown in Fig. 10.14a with the following design data? (Note: These data are the same as those used for the blind flange in Example 10.8. In Fig. 10.15 is a sample calculation of a welding neck flange. Design pressure, p, = 2,500 psi.

Question

What is the minimum required thickness of a welding neck flange as shown in Fig. 10.14a with the following design data? (Note: These data are the same as those used for the blind flange in Example 10.8. In Fig. 10.15 is a sample calculation of a welding neck flange.

Design pressure, p, = 2,500 psi.

Design temperature = 250°F.

Bolt-up and gasket seating temperature = 70°F.

Flange material is SA-105.

Bolting material is SA-325 Grade 1 .

Gasket details are spiral-wound metal, fiber filled, stainless steel, inside diameter is 13.75 in. and width is 1.0 in.

Accepted Answer

1 . Allowable bolt stress at design and seating temperatures = [latex]S_{b}[/latex] = 19,200 psi.

2 . Allowable flange stress at design and seating temperatures = [latex]S_{f}[/latex] = 17,500 psi.

3 . Gasket dimensions are

[latex]b_{o}=N / 2=0.5 \ in[/latex]. and [latex]b=0.5 \sqrt{b_{0}}=0.3535[/latex]

G = 13.75 + (2 × 1) - (2 × 0.3535) = 15.043 in.

4 . Determine bolt loadings and sizing of bolts with N = 1 ; b = 0.3535; y = 10,000 ; m = 3.0.

[latex]H=\frac{\pi}{4} G^{2} p=\frac{\pi}{4}(15.043)^{2}(2500)=444,323[/latex]

[latex]H_{p}=2 b \pi G m p=2(0.3535) \pi(15.043)(3.0)(2500)=250,591[/latex]

[latex]W_{m 1}=H+H_{p}=(444,323)+(250,591)=694,914[/latex]

[latex]W_{m 2}=\pi b G y=\pi(0.3535)(15.043)(10,000)=167,060[/latex]

[latex]A_{m}= ext { the greater of } W_{m 1} / S_{b h}=(694,914) /(19,200)=36.2 ext { in.}^{2}[/latex]

[latex] ext { or } W_{m 2} / S_{b c}=(167,060) /(19,200)=8.7 ext { in. }^{2}[/latex]

[latex]A_{b}[/latex] = actual bolt area = 36.8 in.² 16 bolts at 2-in. diameter

[latex]W_{a}=0.5\left(A_{m}+A_{b} ight) S_{b c}=0.5(36.2+36.8)(19,200)=700,800[/latex]

[latex]W_{0}=W_{m 1}=694,914[/latex]

5 . Calculate total flange moment for the design condition.

Flange Loads

[latex]H_{D}=\frac{\pi}{4} B^{2} p=\frac{\pi}{4}(10.75)^{2}(2500)=226,906[/latex]

[latex]H_{G}=H_{p}=250,591[/latex]

[latex]H_{T}=H-H_{D}=(444,323)-(226,906)=217,417[/latex]

Lever Arms

[latex]h_{D}=R+0.5 g_{1}=(2.5)+0.5(3.375)=4.1875[/latex]

[latex]h_{G}=0.5(C-G)=0.5(22.5-15.043)=3.7285[/latex]

[latex]h_{T}=0.5\left(R+g_{1}+h_{G} ight)=0.5(2.5+3.375+3.7285)=4.8018[/latex]

Flange Moments

[latex]M_{D}=H_{D} imes h_{D}=(226,910)(4.1875)=950,170[/latex]

[latex]M_{G}=H_{G} imes h_{G}=(250,590)(3.7285)=934,330[/latex]

[latex]M_{T}=H_{T} imes h_{T}=(217,420)(4.8018)=1,043,990[/latex]

[latex]M_{d e}=M_{D}+M_{G}+M_{T}=2,928,490[/latex]

6 . Calculate total flange moment for bolt-up condition.

Flange Load

[latex]H_{G}=W_{a}=700,800[/latex]

Lever Arm

[latex]h_{G}=0.5(C-G)=3.7285[/latex]

Flange Moment

[latex]M_{b u}=H_{G} imes h_{G}=(700,800)(3.7285)=2,612,930[/latex]

7 . Use the greater of [latex]M_{d e}[/latex] or [latex]M_{bu}\left(S_{h} / S_{c} ight) ; M_{0}=2,928,490[/latex].

8 . Shape constants from the ASME Code, VIII-1, Appendix 2: K = A/B = (26.5)/(10.75) = 2.465. From Fig. 2-7.1, Section VIII-1;

T = 1.35 Z = 1.39 Y = 2.29 U = 2.51.

[latex]g_{1} / g_{0}=3.375 / 1.0=3.375[/latex]

[latex]h_{0}=\sqrt{B g_{0}}=\sqrt{(10.75)(1.0)}=3.279[/latex]

From Fig. 2-7.2, Section VIII-1, F = 0.57.

From Fig. 2-7.3, Section VIII-1, V = 0.04.

From Fig. 2-7.6, Section VIII-1; f = 1.0.

[latex]e=F / h_{0}=(.57) /(3.279)=0.1738[/latex]

[latex]d=(U / V) h_{0} g_{0}^{2}=(2.51 / .04)(3.279)(1)^{2}=205.76[/latex]

9 . Calculate stresses. Assume a flange thickness t = 4.5 in.

L = (te + 1) / T + t³ / d = (1.320) + (0.443) = 1.763

Longitudinal Hub Stress

[latex]S_{H}=f M_{0} / \operatorname{Lg}_{1}^{2} B=(1)(2,928,490) /(1.763)(3.375)^{2}(10.75)[/latex]

[latex]S_{H}=13,570 \ psi[/latex]

Radial Flange Stress

[latex]S_{R}=\left(\frac{4}{3} t e+1 ight) M_{0} / L t^{2} B=(2.0428)(2,928,490) /(1.763)(4.5)^{2}(10.75)[/latex]

[latex]S_{R}=15,590 \ psi[/latex]

Tangential Flange Stress

[latex]\begin{aligned}S_{T} &=\left(Y M_{0} / t^{2} B ight)-Z S_{R} \&=(2.29)(2,928,490) /(4.5)^{2}(10.75)-(1.39)(15,590)\end{aligned}[/latex]

[latex]S_{T}=9140 \ psi[/latex]

10 . Allowable stresses

[latex]S_{H} \leq 1.5 S_{f}:(1.5)(17,500)=26,250>13,570 \ psi[/latex]

[latex]S_{R} \leq S_{f}: 17,500>15,590 \ psi[/latex]

[latex]S_{T} \leq S_{f}: 17,500>9140 \ psi[/latex]

Question 10.9: What is the minimum required thickness of a welding neck fla...

Related Answered Questions

Verified Answer:

A welding-neck flange with the same geometry as that in Example 10.9 except for the thickness is used with a full-face gasket. The design pressure is 320 psi and the “soft” gasket is vegetable fiber with m = 1.75 and y = 1100. What is the minimum required thickness? ...

Verified Answer:

Verified Answer:

Determine the minimum corner radius to make Example 10.1 acceptable (valid) to be used. ...

Verified Answer:

With the reverse flange given in Example 10.11, what is the minimum required thickness based on an allowable flange stress of 17,500 psi ? ...

Verified Answer:

A reverse flange is joined to a regular ring-type joint flange to form a reducing connection. The total bolt-up moment is controlling and equal to M0 = 2,613,000. The flange bore B´= 13.25 in.; the outside diameter A = 26.5 in.; and the flange thickness t = 5 in. What is the tangential flange ...

Verified Answer:

Considering the pressure vessel described in Example 10.5, the vessel is to have one end closed by a blind flange. What is the minimum required thickness of the blind flange? Design data are the following: Design pressure p = 2500 psi. Design temperature = 250°F. Flange material is SA-105. ...

Verified Answer:

Suppose a vessel requires 24-2 ½-in. diameter bolts on a flange that is 5.5 in. thick. What is the maximum bolt circle that will not cause secondary bending stresses? The minimum bolt spacing for 2 ½-in. diameter bolts is 5 ¼ in. ...

Verified Answer:

A vessel flange uses 16 -2-in. diameter bolts. Flange stress calculations indicate that a flange thickness of t = 4.5 in. is adequate. The bolt circle diameter is C = 22.5 in. Will secondary bending stresses be developed? ...

Verified Answer:

A vessel has the following design data: design pressure p = 2500 psi; design temperature = 250°F; a spiral-wound metal, fiber-filled stainless steel gasket with an inside diameter of 13.75 in. and width N = 1.0 in. The gasket factors are m = 3.0 and y = 10,000. Bolts are SA-325 Grade 1 with ...

Verified Answer: