The Piping Stress Analysis skill provides capabilities for analyzing piping system stresses per ASME B31 codes, ensuring code compliance and equipment protection through proper flexibility analysis.
Capabilities
Piping flexibility analysis
Thermal expansion stress calculation
Support and restraint design
Nozzle load verification
Flange leakage assessment
Code compliance verification (B31.1, B31.3)
CAESAR II integration
Piping isometric review
Usage Guidelines
ASME B31 Code Overview
Code Selection
Code
Application
관련 스킬
B31.1
Power piping
B31.3
Process piping
B31.4
Liquid transportation
B31.5
Refrigeration piping
B31.8
Gas transmission
B31.9
Building services
Stress Categories
B31.3 Stress equations:
Sustained stress:
S_L = (P*D)/(4*t) + (0.75*i*M_A)/Z <= S_h
Expansion stress:
S_E = sqrt(S_b^2 + 4*S_t^2) <= S_A
Occasional stress:
S_L + S_occ <= k*S_h
Where:
P = pressure
D = outside diameter
t = wall thickness
i = stress intensification factor (SIF)
M_A = sustained moment
Z = section modulus
S_h = hot allowable stress
S_A = allowable stress range
k = occasional load factor
Thermal Expansion Analysis
Thermal Movement
Linear expansion:
delta_L = alpha * L * (T2 - T1)
Where:
alpha = coefficient of thermal expansion
L = pipe length
T2 - T1 = temperature change
Typical alpha values (in/in/F):
Carbon steel: 6.5 x 10^-6
Stainless steel: 9.5 x 10^-6
Copper: 9.3 x 10^-6
Flexibility Analysis
Key principles:
1. Piping expands when heated
2. Expansion induces stress if restrained
3. Flexibility (bends, loops) reduces stress
4. Over-constrained systems have high stress
5. Under-constrained systems have excessive movement
Stress Intensification Factors
Common SIF Values
Component
i-factor (approx)
Straight pipe
1.0
Long radius elbow
0.9/h^(2/3)
Short radius elbow
0.75/h^(2/3)
Miter bend (1 cut)
1.52/h^(5/6)
Welding tee
0.9/h^(2/3)
Reinforced fabricated tee
Variable
Branch connection
Variable
Flexibility characteristic:
h = t*R/(r^2)
Where:
t = wall thickness
R = bend radius
r = mean radius of pipe
Nozzle load limits:
- Equipment vendor provides allowables
- Common standards: API 610, API 617, NEMA SM23
- Consider sustained and thermal loads separately
- Combined loads may use interaction formula
Typical check:
sqrt((F_x^2 + F_y^2 + F_z^2)/(F_allow^2) +
(M_x^2 + M_y^2 + M_z^2)/(M_allow^2)) <= 1.0
Load Combinations
Operating case:
W + P + T + D
Hydrotest case:
W + H + D
Where:
W = Weight
P = Pressure
T = Thermal
D = Displacement
H = Hydrotest pressure
Flange Leakage
Assessment Methods
ASME B16.5 flange rating:
- Check P-T rating at operating conditions
- Include pressure equivalent from moments
Equivalent pressure method:
P_eq = P + (16*M)/(pi*G^3)
Where:
M = bending moment at flange
G = flange gasket diameter
NC(T)MF method:
Uses ASME VIII Appendix 2 calculations
More accurate for high moment cases
Modeling Guidelines
Model Building
Key elements:
1. Include all pipe runs
2. Model equipment properly (rigid/flexible)
3. Define support locations accurately
4. Include all branch connections
5. Apply correct operating conditions
6. Model spring hangers if used