Diagnosing SIMIT Simulation License Overrun - You Have Exceeded the Licensed Model Size

In Siemens SIMIT simulation software, the error dialog 'You have exceeded the licensed model size. Engineering no longer possible' occurs when the total number of simulation tags (variables) or component calculation entities across all active diagrams exceeds the tag limit permitted by the installed license dongle or software container. For instance, retrieving complex application examples such as SIMIT Contec Flownet into an installation licensed with a SIMIT Small package (limited to 2,500 simulation tags) exceeds the license quota because detailed hydrodynamic or conveyor components consume thousands of tags. To resolve the issue, verify current tag utilization under Project Properties, deactivate or delete non-essential sub-diagrams, replace detailed physical components with simplified behavioral blocks, or upgrade to a SIMIT Medium or Large license through authorized Siemens sales channels.

Executive Summary

Virtual commissioning with Siemens SIMIT enables realistic plant modeling by simulating field sensors, actuators, and mechanical behavior alongside virtual controllers. However, SIMIT employs tiered capacity licensing tied to simulation complexity, categorized into Small, Medium, Large, and Engineering packages. When control engineers import comprehensive Siemens application templates or multi-unit process models into a workstation equipped with an entry-level license, SIMIT enforces license limits upon compilation or simulation startup. The software halts engineering modifications and prevents the simulation engine from starting. Understanding tag calculation metrics and model optimization allows engineers to right-size their simulations or select appropriate license packages.

Architecture and Fundamental Mechanics

The licensing and tag counting mechanics of Siemens SIMIT operate through defined runtime metrics:

SIMIT Capacity Licensing Tiers:
* SIMIT software licensing is scaled according to maximum model capacity, governed by Automation License Manager (ALM) and a USB hardware dongle or software license key:
- SIMIT Small: Supports up to 2,500 simulation tags.
- SIMIT Medium: Supports up to 15,000 simulation tags.
- SIMIT Large: Supports up to 40,000 simulation tags.
- SIMIT Professional / Unlimited: Removes tag limitations for massive multi-controller enterprise models.
What Constitutes a SIMIT Simulation Tag?:
* A simulation tag is not merely an external I/O signal mapped to the PLC.
* Every internal variable, chart connection, mathematical parameter, and state memory variable instantiated within a SIMIT component block consumes simulation tag capacity.
* Specialized library components from the FLOWNET (hydrodynamic/pneumatic piping networks) and CONTEC (material handling and conveyor logistics) libraries are computationally intensive; a single detailed pipe node, valve manifold, or conveyor segment can generate dozens of internal state variables.
License Evaluation at Model Startup:
* When an engineer opens or retrieves an archived project (.simit or .zip), SIMIT compiles the topological diagrams into an internal execution matrix.
* If the aggregated tag count exceeds the license entitlement, SIMIT locks the simulation engine. The user can inspect the project structure, but clicking Start triggers the 'exceeded licensed model size' error dialog.

Step-by-Step Implementation Procedure

Follow these procedures to diagnose tag consumption and resolve model size overruns in SIMIT:

Check Actual Tag Consumption in Project Properties:
* In SIMIT, navigate to the Project Navigation pane.
* Right-click the root project node and select Properties.
* In the Properties window, examine the Statistics or Sizing tab.
* Note the values for Total Simulation Tags (e.g., 3,840 tags) versus Licensed Tags (e.g., 2,500 tags).
Identify High-Density Simulation Diagrams:
* Expand the Diagrams folder in Project Navigation.
* Review individual sub-diagrams. Large hydrodynamic networks (FLOWNET), complex 3D virtual reality components, and multi-lane conveyor matrices (CONTEC) are typical contributors to tag bloat.
Deactivate or Delete Non-Critical Diagrams:
* If the full application model is not required for your specific controller test scope:
* Right-click unnecessary sub-diagrams and select Delete (or move them to an uncompiled scratch folder).
* Alternatively, select auxiliary components on the diagram and delete them to reduce the variable count below 2,500.
Replace Complex Physical Models with Macro Behavioral Blocks:
* Where detailed FLOWNET thermodynamic calculations are not strictly required, replace pipe segments and pressure-flow solvers with basic standard library analog ramp or lag blocks (PT1, INTEGRAL).
* Standard mathematical blocks consume a fraction of the tags generated by physical simulation solvers.
Procure a SIMIT Capacity Upgrade Package:
* If the complete simulation model must be executed as designed, initiate a license upgrade:
* Identify the required tier (e.g., SIMIT Medium 15,000 tags or Large 40,000 tags).
* Consult an authorized Siemens distributor or the Siemens Industry Mall to validate official order numbers and license transfer procedures.
* Transfer the upgrade license key onto the SIMIT USB dongle using Automation License Manager.

Verification

In SIMIT, reopen the Project Properties dialog and verify that the Total Simulation Tags figure is lower than your licensed tag threshold. Click the Start (Play) button in the top toolbar. Confirm that the simulation engine starts smoothly, the status indicator turns green, and no license warning dialogs appear.

Limitations and Operational Precautions

Deleting components from an application example may invalidate coupled process interlocks; ensure that all signals required by the PLC controller program remain actively driven. License quantities cannot be expanded dynamically without purchasing authorized upgrade packages through Siemens sales channels.

Engineer FAQ

What is the tag limit for a SIMIT Small license?

A SIMIT Small license allows up to 2,500 simulation tags.

Do internal variables in custom SIMIT component types count as tags?

Yes. Every declared input, output, and internal state variable in a SIMIT Component Type Editor (CTE) block counts toward the total tag quota.

Can I run SIMIT in demo mode if I exceed the tag limit?

No. When the tag limit of an installed license is exceeded, SIMIT blocks starting the simulation entirely; running larger models requires upgrading the license.

How do FLOWNET components affect tag consumption?

FLOWNET components model physical pressure, enthalpy, flow, and density across pipe grids, generating numerous internal thermodynamic equations and state tags per component.