By Mr. Phichit.B Piping Stress Engineer: Toyo-Thai Thai Corporation Public Company Limited
Pipe Wall Thickness Calculation ASME B31.1 Vs. ASME B31.3 Internal Pressure
ASME B31.1
ASME B31. B31.3
Same as B31.1
tm = t + c tm =
+c
tm =
(1)
+c
(2)
1|P age
By Mr. Phichit.B Piping Stress Engineer: Toyo-Thai Thai Corporation Public Company Limited
ASME B31.1
ASME B31. B31.3
2|P age
By Mr. Phichit.B Piping Stress Engineer: Toyo-Thai Thai Corporation Public Company Limited
ASME B31.1
ASME B31. B31.3
3|P age
By Mr. Phichit.B Piping Stress Engineer: Toyo-Thai Thai Corporation Public Company Limited
ASME B31.1
ASME B31. B31.3
4|P age
By Mr. Phichit.B Piping Stress Engineer: Toyo-Thai Thai Corporation Public Company Limited
ASME B31.1
ASME B31.3
SE
SE
S
E
5|P age
By Mr. Phichit.B Piping Stress Engineer: Toyo-Thai Corporation Public Company Limited
ASME B31.1
ASME B31.3
Para. 102.4.7 Weld Strength Reduction Factors. At elevated temperatures, seam welds on longitudinal-welded or spiral-welded pipe can have lower creep strength than the base material. This reduction is a factor in determining the minimum wall thickness for longitudinal-welded or spiralwelded pipe (i.e., not seamless), whether fabricated in accordance with a material specification or fabricated in accordance with the rules of this Code. The weld strength reduction factor, W, is given in Table 102.4.7. The designer is responsible to assess application of weld strength reduction factor requirements for welds other than longitudinal and spiral, as applicable (e.g., circumferential welds).
302.3.5 (e) Weld Joint Strength Reduction Factor, W. At elevated temperatures, the long-term strength of weld joints may be lower than the long-term strength of the base material. For longitudinal or spiral (helical seam) welded piping components, the product of the allowable stress and the applicable weld quality factor, SE, shall be multiplied by the weld joint strength reduction factor, W, when determining the required wall thickness for internal pressure in accordance with para. 304. The designer is responsible for the application of weld joint strength reduction factors to welds other than longitudinal and spiral (helical seam) (e.g., circumferential). The weld joint strength reduction factor, W, is equal to 1.0 when evaluating occasional loads such as wind and earthquake, or when evaluating permissible variations in accordance with para. 302.2.4. The pressure rating or allowable stress for the occasional load or variation condition is not required to be reduced by the weld joint strength reduction factor. It is also not required when calculating the allowable stress range for displacement stresses, S A , in para. 302.3.5(d). The weld joint strength reduction factor only applies at weld locations. The weld joint strength reduction factor is the ratio of the nominal stress to cause failure of the weld joint to that of the base material for the same duration. Except as provided in (f) below, the weld joint strength reduction factor, W, shall be in accordance with Table 302.3.5.
6|P age
By Mr. Phichit.B Piping Stress Engineer: Toyo-Thai Thai Corporation Public Company Limited
More Discussion ===>> Creep Range (move move slowly or deform permanently) ก" #$ก% Stress # & '( ) *) ก+ , * Stress -) ก%),, 1"ก yield strength ( ก1% Stress ก% Yield) -) .& #/ ( Creep ก% & '( 1 ASME CODE *1( Creep is of concern for Carbon steels above ~357 to 412°C, (700 to 800°F). Stainless steels above ~950ºF (~510ºC) Aluminum alloys above ~300ºF (~150ºC) W , W = 1.0 ก 0" ) Creep range ' Seamless " 0$ % # Creep range ( ' ), ก && 1+& ก 0#* W 2 ก1 . ' Code # " &ก + 1 ก ก% Creep ก & + % Temp W 1" 4(# "0 % ), 1 W (( ASME B31.1 2 (Para. 104.1.4) ก ASME B31.3 ก ก B31.1 Safety factor ก B31.3
" & W (1 ก 0 • •
W = 1.0 ก 0" ) creep range ' Seamless W = Table 102.4.7 (B31.1) or Table 302.3.5 (B31.3) ก 0" # creep range ( # Seamless
***** 1 , ASME B31.1 Table 102.4.7 NOTES: (1) NP = not permitted. (# ,0$ % &) # ASME B31.3 1 ก NOTES: (a) Weld joint strength reduction factors at temperatures above the upper temperature limit listed in Appendix A for the base metal or outside side of the applicable range in Table 302.3.5 302.3.5 are the responsibility of the designer. At temperatures below those where weld joint strength reduction factors are tabulated, a value of 1.0 shall be used for the factor W where required; however, the additional rules of this Table and Notes do not app apply. " & Y ก+# 1 B31.1 B31.3 ( 1 B31.1 (ก B31.3 % A = additional thickness (B31.1) & ก& c = sum of the mechanical allowances (thread or groove depth) plus corrosion and erosion allowances ( B31.3 ) ( S = maximum allowable stress in material E = joint efficiency (or casting quality factor) at the design temperature >> # ASME B31.1 ก & ' SE SF 2 ก1 # Appendix A (Code& S 0 E # & ) 1 1 * . กก Material ( 1 ' ), && ก #1 ก& 1 ก # >> ASME B31.3 ,กก S 2# Table A-1 E 2# Table A-1A or A-1B
7|P age
By Mr. Phichit.B Piping Stress Engineer: Toyo-Thai Thai Corporation Public Company Limited
Additional Information For Straight Pipe under External Pressure
ASME B31.1
ASME B31.3 B31.
8|P age
