Local Stresses WRC107

Local Stress Analysis Techniques: Nozzle Loads Mandeep Singh Intergraph CAS February 21st, 2011

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Piping to Nozzle to Vessel

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Piping Engineer vs. Vessel Fabricator Did you check the nozzle for loads My Nozzle is good for Pressure Alright.., Give me actual loads But, the analysis is not finished yet Ok, give me Maximum Loads your nozzle can withstand What !, there are infinite combinations... 3

Saga of Nozzle loads ƒ What came first,

Or

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Some Ideas for resolution ƒ Use “standard” Nozzle Loads

ƒ Provides a “standard” level of strength 5

Some Ideas for resolution ƒ Get a “Maximum” Nozzle load set

ƒ Indicate if you want a bigger Mx, My etc.. 6

Resolutions …. ƒ Model Nozzle flexibilities in Piping model

ƒ Preferably re-check the nozzle with actual loads – but may be too late in the game

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A look at CAESAR II load cases Sustained

Thermal Expansion

Occasional – only the delta

Operating

ƒ Specify the loads as SUS, EXP, OCC – Thermal Expansion – Self-limiting, so higher allowable – Occasional – 20% increase in allowable

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Stresses near Nozzles

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WRC107 ƒ 1965, updated in 1979, Prof. Bijlaard work ƒ Provides stress in Cylinder and Spheres ƒ Based on Un-penetrated shell ƒ Gives stresses in header only ƒ Consists of charts and fill in tables.

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Lots of charts to look up

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Then fill in tables

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New Update to WRC 107 -> WRC 537

• • format

Same results Easier to read Format

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Stress Combinations ƒ Next, Combine stresses in categories – General Primary Membrane (Pm) – Local Primary Membrane (Pl) – Secondary Stresses (Q)

ƒ Compare to allowables

Primary Stresses ƒ “load-controlled” – pressure, weight ƒ Not self-limiting ƒ Tighter limits (1.5*S)

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Secondary Stresses – “Strain-controlled” – thermal Exp., bending at gross discontinuities – Self-limiting – stress can reduce after local yielding. – Higher allowable (approx 3*Savg)

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Some limitations of WRC107 ƒ Re-pad not considered ƒ Assumes a 90° (radial nozzle) ƒ Spherical Shells – – – –

di/Di ≤ 1/3 but less if Dm/T between 20-55 U ≤ 2.2 (U = ro / ((Rm T)0.5, for nozzle) 0.25 ≤ t /T ≤ 10 5 ≤ rm /t ≤ 50

ƒ Cylindrical Shells: – – – –

d/D ≤ ¼ for cylinders or < 0.6 with significant warnings D/T ≤ 600 L/D ≥ 1.5 ¼ ≤ C1 /C2 ≤ 4

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WRC 297 ƒ Based a different, thin shell theory (Prof. Steele) ƒ For cylindrical nozzles on cylinders ƒ Extends the range of WRC 107 (d/D ≤ 0.5) ƒ Gives stresses both in header and branch ƒ Also provides Nozzle Flexibilities

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Software Demonstration CAESAR II demonstration ƒ

Adding Nozzle Flexibility

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Utilizing the Nozzle/Equipment limits – Actual or “standard” loads

PV Elite demonstration ƒ

Using nozzle loads - Actual or “standard” loads

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Import the loads from CAESAR II pipe stress run.

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