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,’
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 |
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 |
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 |
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 |