PCS 7 OS Single Station Architectures: How Standalone Stations Operate Without Central ES NetPro Configuration

In SIMATIC PCS 7 systems (such as PCS 7 V5.2 or V6.x), two physical OS Single Stations can operate correctly on the plant floor even when only a single 'SIMATIC PC Station' is configured in the Engineering Station's NetPro. This occurs when the facility deploys a 'Minimal Configuration' or cloned station architecture: the single OS project defined on the ES is duplicated onto secondary physical PCs using the WinCC Project Duplicator (ProjectDuplicator.exe) rather than maintaining distinct PC stations in SIMATIC Manager. Each physical PC runs an identical, autonomous local copy of the WinCC runtime project referencing the same controller S7 connections.

PCS 7 Engineering Paradigms: Centralized vs Duplicated OS Stations

In standard SIMATIC PCS 7 design guidelines, every physical computer participating in a DCS facility is modeled as a distinct SIMATIC PC Station in the Component View and NetPro (e.g., ES01, OS_SRV01, OS_SRV02, CLIENT01..05). Each station possesses its own hardware configuration, network cards, and target download paths.

However, in smaller facilities or legacy installations (e.g., PCS 7 V5.2 / V6.0), engineers frequently encounter systems where three physical computers exist (1 Engineering Station and 2 independent Operator Stations), yet opening NetPro reveals only one single SIMATIC PC Station.

How the WinCC Project Duplicator Enables Standalone Multi-Station Runtimes

The secret to this architecture is the WinCC Project Duplicator (ProjectDuplicator.exe):

Single Project Authoring: The engineer creates and compiles only one OS project on the Engineering Station. This OS is configured as an OS Single Station.
Duplication via Network: Rather than using SIMATIC Manager's 'Target OS Download', the engineer shares the project folder and uses the WinCC Project Duplicator to clone the project directly onto the hard drives of Operator Station 1 and Operator Station 2.
Local Computer Name Adaptation: During duplication, the tool automatically updates the WinCC Computer Name to match the local Windows hostname of the receiving PC.

Why Only One PC Station Exists in the ES NetPro Configuration

Because both physical OS machines run identical graphics, alarm logs, and tag configurations, the original system integrator chose not to duplicate station definitions in the ES Multiproject. In Siemens documentation PCS 7 Minimal Configurations (SIOS Entry ID: 24023824), this approach was officially documented as an acceptable deployment method for small, cost-sensitive installations that do not require server redundancy or multi-client partitioning.

Network and Communication Architecture: S7 Connection Multiplexing

How do both independent OS stations communicate with the PLC simultaneously?:

In NetPro, the configured S7 connection binds to the AS CPU via Industrial Ethernet.
When the project is cloned to PC 1 and PC 2, both computers open an S7 connection to the same S7-400 controller using identical TSAP / connection parameters.
The S7-400 CPU communication processor (CP 443-1) accepts both incoming S7 connections as independent client sessions, multiplexing communication work memory across both stations.

Centralized Multiproject vs Project Duplicator Architecture Comparison

The following table compares the official centralized architecture against the cloned minimal configuration:

| Engineering Dimension | Standard Centralized Architecture | Cloned Single-Station Architecture |
|---|---|---|---|
| NetPro Configuration | Separate PC Station per physical PC | Single PC Station configured on ES |
| Project Distribution | SIMATIC Manager PLC > Download | WinCC Project Duplicator (ProjectDuplicator.exe) |
| Engineering Maintenance | Central delta compilation & download | Must re-duplicate project to all PCs on changes |
| Historical Data Storage | Shared Redundant OS Servers | Fragmented (Each station logs its own SQL data) |
| Alarm Acknowledgment | Plant-wide synchronized acknowledgment | Local acknowledgment (Does not sync across stations) |
| Reference Manual | SIMATIC PCS 7 Engineering System Manual | PCS 7 Minimal Configurations (Entry ID 24023824) |

Verification

Verify cloned single-station operation through the following steps:

Log onto Operator Station 1. Open WinCC Explorer; confirm that under Computer, the computer name matches PC 1's hostname.
Log onto Operator Station 2. Confirm that its WinCC Computer name matches PC 2's hostname.
Open WinCC Channel Diagnosis on both stations during runtime; verify that both maintain active S7 connections to the PLC.
Toggle a digital valve on PC 1; confirm that the state change updates on the PC 2 process graphic within 500 ms.
Trigger a process alarm; observe whether alarm acknowledgment is local or synchronized.

Limitations and Operational Precautions

Consider these operational rules when maintaining cloned single stations:

Fragmented Alarm and Archive History: Because these stations operate as independent single stations rather than a server-client pair, alarms acknowledged on Station 1 will NOT be acknowledged on Station 2, and tag archives remain separate.
Double S7 Connection Load: Each duplicated station consumes independent communication resources on the S7-400 CPU; verify that total S7 connections do not exceed the CPU limit.
Modern Migration Recommendation: In modern PCS 7 versions (V8.x, V9.x), migrate to a proper OS Single Station plus OS Client or redundant OS Server architecture to ensure unified alarming and central engineering.

Engineer FAQ

How do I deploy logic changes to both stations in this architecture?

You must compile the OS project on the ES and then use the WinCC Project Duplicator to copy the updated project to each physical station individually.