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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,
    1. Maximum Design Temperature & Pressure
    2. Operating Temperature & Pressure
    3. Minimum Design Temperature & Pressure
    4. Test Pressure



  8. Check if any Occasional loading is applicable for the selected system,
    1. Wind Loading
    2. Seismic Loading
    3. PSV reaction forces
  9. Note down environmental Data of the project,
    1. Ambient Temperature
  10. 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
  11. List down all the possible conditions the selected system may experience.
  12. 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 Case Stress Type
L1 WW+HP HYDRO
L2 W+T1+P1 OPE
L3 W+T2+P2 (P1 can be used in this case) OPE
L4 W+T3+P3 (P1 can be used in this case) OPE
L5 W+P1 SUS
L6 L2-L5 EXP
L7 L3-L5 EXP
L8 L4-L5 EXP
L9 L2-L4 EXP

 




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 Case Stress Type Combination Type
L1 WW+HP HYDRO Algebraic
L2 W+T1+P1 OPE Algebraic
L3 W+T2+P2 (P1 can be used in this case) OPE Algebraic
L4 W+T3+P3 (P1 can be used in this case) OPE Algebraic
L5 W+P1 SUS Algebraic
L6 W+T1+P1+WIN1 OPE Algebraic
L7 W+T1+P1+WIN2 OPE Algebraic
L8 W+T1+P1+WIN3 OPE Algebraic
L9 W+T1+P1+WIN4 OPE Algebraic
L10 L6-L2 OCC Algebraic
L11 L7-L2 OCC Algebraic
L12 L8-L2 OCC Algebraic
L13 L9-L2 OCC Algebraic
L14 L5+L10 OCC Scalar
L15 L5+L11 OCC Scalar
L16 L5+L12 OCC Scalar
L17 L5+L13 OCC Scalar
L18 L2-L5 EXP Algebraic
L19 L3-L5 EXP Algebraic
L20 L4-L5 EXP Algebraic
L21 L2-L4 EXP Algebraic

 

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 Case Stress Type Combination Type
L1 WW+HP HYDRO Algebraic
L2 W+T1+P1 OPE Algebraic
L3 W+T2+P2 (P1 can be used in this case) OPE Algebraic
L4 W+T3+P3 (P1 can be used in this case) OPE Algebraic
L5 W+P1 SUS Algebraic
L6 W+T1+P1+U1 OPE Algebraic
L7 W+T1+P1-U1 OPE Algebraic
L8 W+T1+P1+U2 OPE Algebraic
L9 W+T1+P1-U2 OPE Algebraic
L10 L6-L2 OCC Algebraic
L11 L7-L2 OCC Algebraic
L12 L8-L2 OCC Algebraic
L13 L9-L2 OCC Algebraic
L14 L5+L10 OCC Scalar
L15 L5+L11 OCC Scalar
L16 L5+L12 OCC Scalar
L17 L5+L13 OCC Scalar
L18 L2-L5 EXP Algebraic
L19 L3-L5 EXP Algebraic
L20 L4-L5 EXP Algebraic
L21 L2-L4 EXP Algebraic

 

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 Case Stress Type Combination Type
L1 WW+HP HYDRO Algebraic
L2 W+T1+P1 OPE Algebraic
L3 W+T2+P2 (P1 can be used in this case) OPE Algebraic
L4 W+T3+P3 (P1 can be used in this case) OPE Algebraic
L5 W+P1 SUS Algebraic
L6 W+T1+P1+WIN1 OPE Algebraic
L7 W+T1+P1+WIN2 OPE Algebraic
L8 W+T1+P1+WIN3 OPE Algebraic
L9 W+T1+P1+WIN4 OPE Algebraic
L10 W+T1+P1+U1 OPE Algebraic
L11 W+T1+P1-U1 OPE Algebraic
L12 W+T1+P1+U2 OPE Algebraic
L13 W+T1+P1-U2 OPE Algebraic
L14 L6-L2 OCC Algebraic
L15 L7-L2 OCC Algebraic
L16 L8-L2 OCC Algebraic
L17 L9-L2 OCC Algebraic
L18 L10-L2 OCC Algebraic
L19 L11-L2 OCC Algebraic
L20 L12-L2 OCC Algebraic
L21 L13-L2 OCC Algebraic
L22 L5+L14 OCC Scalar
L23 L5+L15 OCC Scalar
L24 L5+L16 OCC Scalar
L25 L5+L17 OCC Scalar
L26 L5+L18 OCC Scalar
L27 L5+L19 OCC Scalar
L28 L5+L20 OCC Scalar
L29 L5+L21 OCC Scalar
L30 L2-L5 EXP Algebraic
L31 L3-L5 EXP Algebraic
L32 L4-L5 EXP Algebraic
L33 L2-L4 EXP Algebraic

 

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  1. thank you for your support about basic load cases used for piping stress

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