Engineering task and calculation objective
The ESMC912 module performs the load transformation of nozzle loads for horizontal vessels on two saddle supports according to the BASF works standard E-S-MC 912 (April 2016 edition). Individual nozzle loads — forces and moments from connected piping, defined for example via the NozzleSpecApp — are transformed from their local point of application at the nozzle/shell intersection into the support plane of the vessel and combined there into superimposed reaction forces and reaction moments of all nozzles.
These transformed section forces are the input values for the actual strength verifications: the saddle calculation of the horizontal vessel (e.g. according to Zick or the relevant code sections) and the local checks at the nozzle attachment. Without a clean load transformation, piping loads from the stress analysis cannot be transferred consistently to the vessel supports.
The module captures the vessel geometry with the cylinder diameter, the saddle spacing and the lever arms between vessel centerline, saddle attachment and saddle base point, as well as the position of each nozzle in the x, y and z directions including the radius and angular position of the load application point on the cylinder or on a dished end.
Standard and calculation basis: BASF E-S-MC 912: 2016-04
Calculation workflow
- Define vessel and saddle geometry: The diameter of the cylinder, the distance between the fixed and the sliding saddle, and the distances between the vessel centerline and the saddle base point or the saddle attachment to the shell establish the support plane and the lever arms of the transformation.
- Position the nozzles: For each nozzle, the position in the x, y and z directions and the radius and angular position of the load application point are specified — on the cylinder via the cylinder radius, on dished ends via the crown radius of the end.
- Enter local nozzle loads: The forces and moments acting locally at the intersection of each nozzle are entered in the nozzle-fixed coordinate system, typically as specified values from the piping analysis or the NozzleSpecApp.
- Transform into the support plane: Each local load is converted into the global vessel coordinate system via the lever arms of its point of application; forces thereby generate additional offset moments with respect to the support plane of the saddles.
- Superimpose and output the loads: The contributions of all nozzles are superimposed with correct signs. The result is the superimposed reaction forces and reaction moments in the support plane, split between the fixed and the sliding saddle, as input quantities for the saddle and shell verifications. A completeness check indicates whether all entries are consistent.
Input quantities
| Quantity | Symbol | Unit |
|---|---|---|
| Cylinder diameter | da | mm |
| Distance between fixed and unfixed saddle | ls | mm |
| Distance between vessel center line and saddle base point | hs | mm |
| Distance between vessel center line and connection of saddle to the shell (da / 2) | hv | mm |
| Number of nozzles | Stutzen | - |
| Nozzle position | Typ | – |
| Position of nozzle in x-direction | x | mm |
| Position of nozzle in y-direction | y | mm |
| Position of nozzle in z-direction | z | mm |
| Radius of loading point (cylinder radius, reference radius of head) | ra | mm |
| Angular position of loading point | φ | ° |
| Forces on nozzle that act locally at intersection point | P | N |
| Forces on nozzle that act locally at intersection point | VL / V1 | N |
| Forces on nozzle that act locally at intersection point | VC / V2 | N |
| Moments on nozzle that act locally at intersection point | ML / M1 | N·mm |
| Moments on nozzle that act locally at intersection point | MC / M2 | N·mm |
| Moments on nozzle that act locally at intersection point | MT | N·mm |
| Nozzle position | Typ | – |
| Position of nozzle in x-direction | x | mm |
| Position of nozzle in y-direction | y | mm |
| Position of nozzle in z-direction | z | mm |
| Radius of loading point (cylinder radius, reference radius of head) | ra | mm |
| Angular position of loading point | φ | ° |
| Forces on nozzle that act locally at intersection point | P | N |
Calculated results
| Quantity | Symbol | Unit |
|---|---|---|
| Reaction force of a nozzle at the support level | Pxq | N |
| Reaction force of a nozzle at the support level | Pyq | N |
| Reaction force of a nozzle at the support level | Pzq | N |
| Reaction moment of a nozzle at the support level | MPxq | N·mm |
| Reaction moment of a nozzle at the support level | MPxVq | N·mm |
| Reaction force of a nozzle at the support level | Pxql | N |
| Reaction force of a nozzle at the support level | Pyql | N |
| Reaction force of a nozzle at the support level | Pzql | N |
| Reaction moment of a nozzle at the support level | MPxql | N·mm |
| Reaction moment of a nozzle at the support level | MPxVql | N·mm |
Calculation options
Nozzle position
Nozzle in the cylinder · Nozzle in the head
Nozzle position
Nozzle in the cylinder · Nozzle in the head
Nozzle position
Nozzle in the cylinder · Nozzle in the head
Nozzle position
Nozzle in the cylinder · Nozzle in the head
Nozzle position
Nozzle in the cylinder · Nozzle in the head
Nozzle position
Nozzle in the cylinder · Nozzle in the head
Nozzle position
Nozzle in the cylinder · Nozzle in the head
Nozzle position
Nozzle in the cylinder · Nozzle in the head
Frequently asked questions
Does the load transformation replace the strength verification of the saddles or nozzles?
No. The module provides only the statically correct conversion and superposition of the nozzle loads into the support plane. The verifications themselves — the saddle check of the horizontal vessel, the local membrane and bending stresses at the nozzle attachment — are subsequently carried out with the transformed section forces in the calculation modules or code sections intended for that purpose.
Why is a distinction made between the fixed and the sliding saddle?
The fixed saddle takes longitudinal forces in addition to vertical loads, whereas the sliding saddle releases the axial thermal expansion of the vessel and by design carries only transverse and vertical loads. Axial nozzle loads therefore run entirely into the fixed saddle; the transformation must separate these load paths correctly, otherwise the saddles and foundations will be sized incorrectly.
Is BASF E-S-MC 912 applicable outside BASF plants?
It is a works standard that is contractually specified in BASF projects. The underlying mechanics — transformation and superposition of nozzle loads into the support plane — is universally valid, but the specific sign conventions, load cases and interfaces (such as to the NozzleSpecApp) follow the works standard. For projects without a BASF connection, it must be clarified which load-transfer concept the end customer requires.
Which input error is the most critical?
Sign and coordinate errors: the local nozzle loads must be given in the agreed nozzle-fixed system, and the angular position and radius of the application point must match the actual installed position. An angle set 180° wrong reverses lever arms and can simulate relieving instead of loading superpositions — the results should therefore always be checked for plausibility against a hand estimate of the dominant loads.