Architecting SIMATIC PCS 7 Maintenance Stations - Standalone MS Single Station vs Distributed MS Server-Client

In SIMATIC PCS 7, running a separate non-redundant Maintenance Station (MS) Server and MS Client on a single physical PC is supported using the standardized 'MS Single Station' configuration. In an MS Single Station architecture, WinCC Runtime executes locally as a single-user system hosting both asset diagnostic processing and the operator maintenance faceplates on one machine. A standalone MS Single Station communicating directly with automation stations over the Industrial Ethernet Plant Bus does not require a connection to the Terminal Bus unless external web clients or peer operator stations need access.

Role of the Maintenance Station (MS) in Plant Asset Management

The SIMATIC PCS 7 Maintenance Station (MS) provides plant-wide asset management, predictive health monitoring, and standardized diagnostics (in accordance with NAMUR NE 107).

The Maintenance Station continuously interrogates:
1. Automation System Hardware: S7-400 CPUs, power supplies, communications processors, and ET 200 distributed I/O racks.
2. Network Infrastructure: SCALANCE industrial Ethernet switches, wireless access points, and security routers via SNMP.
3. Intelligent Field Devices: HART, PROFIBUS PA, and Foundation Fieldbus transmitters and valve positioners using EDD (Electronic Device Description).
4. PC Stations: Operating system health, disk space, and license status across OS Servers and Clients.

Architectural Models - MS Single Station vs Distributed MS Server-Client

When designing the Maintenance Station infrastructure, engineers select from three manufacturer-supported topologies:

Topology ModelPhysical PC CountLicense RequirementTerminal Bus Needed?Best Suited ForMS Single Station1 Dedicated PCPCS 7 MS Single StationOnly if external web clients connectSmall to medium plants; localized maintenance shops.Distributed MS Server / Client2+ Dedicated PCsMS Server + MS ClientYes (Mandatory)Large multi-unit plants with separate maintenance control rooms.Combined ES / MS Client1 PC (MS Server) + ESMS Server (ES runs MS Client)Yes (Mandatory)Cost-optimized systems utilizing the ES for maintenance screens.

An MS Single Station completely combines the diagnostic data collector and the operator visualization onto a single physical PC housing.

Terminal Bus vs Plant Bus Connectivity Requirements

Network requirements depend directly on the chosen topology:
* Plant Bus Connection (Mandatory): Every MS Server or MS Single Station must have a direct connection to the Industrial Ethernet Plant Bus (via CP 1623 6GK1162-3AA00 or standard network adapter with SOFTNET-IE). This interface interrogates the automation stations and receives hardware diagnostic interrupts (OB82, OB83, OB86).
* Terminal Bus Connection (Conditional):
- In an MS Single Station: If maintenance personnel interact exclusively on that single local monitor, no Terminal Bus interface card is required.
- In a Distributed Architecture: The MS Server requires a Terminal Bus card to transmit diagnostic screen data and server packages to remote MS Clients or Web Viewers.

Engineering Station as an MS Client Workstation

For facilities seeking to avoid purchasing an additional client PC while maintaining a separate MS Server:
* The existing Engineering Station (ES) can simultaneously function as the MS Client.
* During project engineering in SIMATIC Manager, insert an OS Client object under the ES PC Station, assign the MS Server data package, and download the client project.
* Maintenance personnel can open the Maintenance Station views directly from the engineering console without hardware expansion.

Verification

To confirm that the Maintenance Station is operational:
1. Launch WinCC Runtime on the MS Single Station or MS Client.
2. Verify that the Maintenance Overview Screen renders the complete plant asset hierarchy without missing component icons.
3. Check the communication status indicator in the top toolbar; confirm active communication with the plant bus.
4. Deliberately disconnect an auxiliary sensor or trigger an I/O diagnostic interrupt; verify that the maintenance status icon changes to yellow ('Maintenance Required') or orange ('Maintenance Demanded') within 3 seconds.
5. In the asset view, click on the faulted module; confirm that the diagnostic faceplate opens and displays the exact slot and channel fault description.

Limitations and Operational Precautions

Do not combine an MS Server and an OS Process Server on the same single station PC in medium or large plants. Merging production process visualization and heavy SNMP/fieldbus asset diagnostics onto one machine causes CPU resource contention and risks slowing operator alarm response times during plant upsets. Use dedicated hardware for production OS Servers and Maintenance Stations.

Engineer FAQ

Can an MS Single Station be made redundant?

No. By definition, a Single Station is a standalone, non-redundant unit. If high availability is required for maintenance asset monitoring, you must deploy a redundant MS Server pair.

Does the Maintenance Station require separate Process Object (PO) licenses?

Yes. The Maintenance Station utilizes MS Runtime Basic Package licenses and consumes asset objects (counting monitored field devices, modules, and PCs) distinct from standard AS/OS Process Objects.

Can operators view maintenance screens on standard OS Clients?

Yes. By assigning the MS Server Data package to standard OS Clients, production operators can navigate to maintenance faceplates directly from their existing screens.

What protocol does the Maintenance Station use to monitor SCALANCE switches?

The Maintenance Station utilizes the SNMP (Simple Network Management Protocol) OPC Server to poll switch port status, link loss, and power supply health.