Basic Load Cases used for Piping Stress Analysis

Following steps shall be carried for Piping Stress Analysis of any system,

1.      Identify the Critical lines from the P&ID based on the criteria mentioned in the Piping Stress Analysis Design Basis.

2.      Prepare a Stress Critical Line list

3.      Categorize the lines as Category-1 (Extensive computer analysis required), Category-2 (Visual Analysis or by Nomo graphs, etc.) and Category-3 (Non-critical lines)

4.      Segregate the Category-1 lines and identify Stress systems. Segregation should be made in such a way that proper boundary conditions can be defined for those lines. Also lines which can affect the behavior of the system significantly should be selected. Depending on the configurations Category-2 and Category-3 lines may also be included in the Piping system

5.      Select a system for the analysis based on the priority or project requirement

6.      List down the lines to be included in the system

7.      Check if all the parameters of the lines are available,

A.      Maximum Design Temperature & Pressure

B.      Operating Temperature & Pressure

C.      Minimum Design Temperature & Pressure

D.     Test Pressure

1.      Check if any Occasional loading is applicable for the selected system,

A.      Wind Loading

B.      Seismic Loading

C.      PSV reaction forces

1.      Note down environmental Data of the project,

A.      Ambient Temperature

1.      Once the modeling of the system is done in the Caesar-II using all the above data, next important activity is to formulate the load cases for which the system is to be analyzed

2.      List down all the possible conditions the selected system may experience.

3.      Load Cases for a piping system is given below,’

CASE: 1 Basic parameters and no occasional loading

Following parameters will be used for formulating the load cases,

WW    =       Water filled weight

HP      =       Hydro test Pressure

W       =       Dead weight of the Piping system

P1      =       Maximum Design Pressure

P2      =       Operating Pressure

P3      =       Minimum Design Pressure

T1      =       Maximum Design Temperature

T2      =       Operating Temperature

T3      =       Minimum Design Temperature

Case No.Load CaseStress Type
L1WW+HPHYDRO
L2W+T1+P1OPE
L3W+T2+P2 (P1 can be used in this case)OPE
L4W+T3+P3 (P1 can be used in this case)OPE
L5W+P1SUS
L6L2-L5EXP
L7L3-L5EXP
L8L4-L5EXP
L9L2-L4EXP

CASE: 2 Basic Parameters with Wind loading

Following parameters will be used for formulating the load cases,

WW    =       Water filled weight

HP      =       Hydro test Pressure

W       =       Dead weight of the Piping system

P1      =       Maximum Design Pressure

P2      =       Operating Pressure

P3      =       Minimum Design Pressure

T1      =       Maximum Design Temperature

T2      =       Operating Temperature

T3      =       Minimum Design Temperature

WIN1  =       Wind Load in +X direction (direction is just for example user can use this

terminology for any other direction as per his ease)

WIN2  =       Wind Load in –X direction (direction is just for example user can use this

terminology for any other direction as per his ease)

WIN3  =       Wind Load in +Z direction (direction is just for example user can use this

terminology for any other direction as per his ease)

WIN4  =       Wind Load in –Z direction (direction is just for example user can use this

terminology for any other direction as per his ease)

Case No.Load CaseStress TypeCombination Type
L1WW+HPHYDROAlgebraic
L2W+T1+P1OPEAlgebraic
L3W+T2+P2 (P1 can be used in this case)OPEAlgebraic
L4W+T3+P3 (P1 can be used in this case)OPEAlgebraic
L5W+P1SUSAlgebraic
L6W+T1+P1+WIN1OPEAlgebraic
L7W+T1+P1+WIN2OPEAlgebraic
L8W+T1+P1+WIN3OPEAlgebraic
L9W+T1+P1+WIN4OPEAlgebraic
L10L6-L2OCCAlgebraic
L11L7-L2OCCAlgebraic
L12L8-L2OCCAlgebraic
L13L9-L2OCCAlgebraic
L14L5+L10OCCScalar
L15L5+L11OCCScalar
L16L5+L12OCCScalar
L17L5+L13OCCScalar
L18L2-L5EXPAlgebraic
L19L3-L5EXPAlgebraic
L20L4-L5EXPAlgebraic
L21L2-L4EXPAlgebraic

CASE: 3 Basic Parameters with Seismic loading

Following parameters will be used for formulating the load cases,

WW    =       Water filled weight

HP      =       Hydro test Pressure

W       =       Dead weight of the Piping system

P1      =       Maximum Design Pressure

P2      =       Operating Pressure

P3      =       Minimum Design Pressure

T1      =       Maximum Design Temperature

T2      =       Operating Temperature

T3      =       Minimum Design Temperature

U1      =       Seismic loads also known as Uniform loads in terms of ‘g’ in North-South

Direction (direction is just for example user can use this terminology for any other direction as per his ease)

U2      =       Seismic loads also known as Uniform loads in terms of ‘g’ in East-West

Direction (direction is just for example user can use this terminology for any other direction as per his ease)

U3      =       Seismic loads also known as Uniform loads in terms of ‘g’ in Vertical

Direction (direction is just for example user can use this terminology for any other direction as per his ease).

Generally vertical load due to seismic is negligible and not included in the Load case formation.

Case No.Load CaseStress TypeCombination Type
L1WW+HPHYDROAlgebraic
L2W+T1+P1OPEAlgebraic
L3W+T2+P2 (P1 can be used in this case)OPEAlgebraic
L4W+T3+P3 (P1 can be used in this case)OPEAlgebraic
L5W+P1SUSAlgebraic
L6W+T1+P1+U1OPEAlgebraic
L7W+T1+P1-U1OPEAlgebraic
L8W+T1+P1+U2OPEAlgebraic
L9W+T1+P1-U2OPEAlgebraic
L10L6-L2OCCAlgebraic
L11L7-L2OCCAlgebraic
L12L8-L2OCCAlgebraic
L13L9-L2OCCAlgebraic
L14L5+L10OCCScalar
L15L5+L11OCCScalar
L16L5+L12OCCScalar
L17L5+L13OCCScalar
L18L2-L5EXPAlgebraic
L19L3-L5EXPAlgebraic
L20L4-L5EXPAlgebraic
L21L2-L4EXPAlgebraic

CASE: 4 Basic Parameters with Wind &Seismic loading

Following parameters will be used for formulating the load cases,

WW    =       Water filled weight

HP      =       Hydro test Pressure

W       =       Dead weight of the Piping system

P1      =       Maximum Design Pressure

P2      =       Operating Pressure

P3      =       Minimum Design Pressure

T1      =       Maximum Design Temperature

T2      =       Operating Temperature

T3      =       Minimum Design Temperature

WIN1  =       Wind Load in +X direction (direction is just for example user can use this

terminology for any other direction as per his ease)

WIN2  =       Wind Load in –X direction (direction is just for example user can use this

terminology for any other direction as per his ease)

WIN3  =       Wind Load in +Z direction (direction is just for example user can use this

terminology for any other direction as per his ease)

WIN4  =       Wind Load in –Z direction (direction is just for example user can use this

terminology for any other direction as per his ease)

U1      =       Seismic loads also known as Uniform loads in terms of ‘g’ in North-South

Direction (direction is just for example user can use this terminology for any other direction as per his ease)

U2      =       Seismic loads also known as Uniform loads in terms of ‘g’ in East-West

Direction (direction is just for example user can use this terminology for any other direction as per his ease)

U3      =       Seismic loads also known as Uniform loads in terms of ‘g’ in Vertical

Direction (direction is just for example user can use this terminology for any other direction as per his ease).

Generally vertical load due to seismic is negligible and not included in the Load case formation.

Case No.Load CaseStress TypeCombination Type
L1WW+HPHYDROAlgebraic
L2W+T1+P1OPEAlgebraic
L3W+T2+P2 (P1 can be used in this case)OPEAlgebraic
L4W+T3+P3 (P1 can be used in this case)OPEAlgebraic
L5W+P1SUSAlgebraic
L6W+T1+P1+WIN1OPEAlgebraic
L7W+T1+P1+WIN2OPEAlgebraic
L8W+T1+P1+WIN3OPEAlgebraic
L9W+T1+P1+WIN4OPEAlgebraic
L10W+T1+P1+U1OPEAlgebraic
L11W+T1+P1-U1OPEAlgebraic
L12W+T1+P1+U2OPEAlgebraic
L13W+T1+P1-U2OPEAlgebraic
L14L6-L2OCCAlgebraic
L15L7-L2OCCAlgebraic
L16L8-L2OCCAlgebraic
L17L9-L2OCCAlgebraic
L18L10-L2OCCAlgebraic
L19L11-L2OCCAlgebraic
L20L12-L2OCCAlgebraic
L21L13-L2OCCAlgebraic
L22L5+L14OCCScalar
L23L5+L15OCCScalar
L24L5+L16OCCScalar
L25L5+L17OCCScalar
L26L5+L18OCCScalar
L27L5+L19OCCScalar
L28L5+L20OCCScalar
L29L5+L21OCCScalar
L30L2-L5EXPAlgebraic
L31L3-L5EXPAlgebraic
L32L4-L5EXPAlgebraic
L33L2-L4EXPAlgebraic

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