Filtering System Diagnostic Messages and Managing Safety Partial Shutdown Alarms in SIMATIC PCS 7

System-generated alarms such as hardware rack diagnostics can be filtered or hidden in SIMATIC PCS 7 using OS Project Editor settings, Alarm Logging suppression, or WinCC Smart Alarm Hiding. However, high-priority safety alarms like 'Safety program: partial shutdown' (Event Class 16) represent critical safety state changes that cannot and must not be completely deleted or suppressed. Regulatory and safety standards mandate that shutdown alarms remain logged. To eliminate nuisance alarms during controller downloads, engineers must optimize download procedures, configure maintenance states on F-channel drivers, and utilize standard alarm hiding matrices.

System Diagnostic Alarms vs Safety Program Shutdown Events

During program commissioning, controller downloads, or rack power cycling, SIMATIC PCS 7 generates two distinct categories of automated alarms:
1. Hardware and System Diagnostics: Alarms generated by module driver blocks (MOD_D1, RACK_NO, OB_BEGIN) reporting module pulled, power supply redundancy lost, or bus communication interruptions.
2. Safety Program Diagnostics: High-priority fail-safe alarms generated directly by S7 F-Systems runtime blocks (F_SHUTDN, F_START, F_CYC_CO).

The alarm 'Safety program: partial shutdown' is triggered when an F-runtime group detects a severe fault—such as an F-cycle time overrun in OB35, an unacknowledged F-communication failure, or excessive F-I/O passivations—causing the safety logic to shut down a specific safety group while keeping others operational.

Regulatory and Functional Safety Standards for Alarm Suppression

Under international functional safety standards (IEC 61508, IEC 61511) and ISA-18.2 / EEMUA 191 alarm management guidelines:
* Mandatory Visibility: Critical safety trips, partial shutdowns, and interlock trips must be presented to operators unambiguously. They cannot be permanently silenced or removed from the system audit trail.
* Prohibition of Deletion: Attempting to delete safety messages from the WinCC Alarm Logging editor will result in automatic regeneration during the next AS-OS Compilation (Compile OS), because message configurations originate in the safety CFC blocks.
* Controlled Hiding: While permanent suppression is forbidden, PCS 7 provides Smart Alarm Hiding to temporarily suppress alarms based on plant state (e.g., during planned unit outages or maintenance overrides) while preserving full audit logging in the Chronological List.

Configuring OS Project Editor and WinCC Smart Alarm Hiding

To manage nuisance system messages legitimately without violating safety compliance:

[WinCC Explorer -> OS Project Editor]
   │
   ├─► Navigate to Tab: "Message Display"
   ├─► Select: "Hide system messages in the short-term alarm list"
   │     • Redirects hardware driver warnings to the dedicated "System" or "Diagnostic" list
   │     • Keeps process operator screen free of background rack noise
   └─► Click Apply / OK
         │
         ▼
[Implementing WinCC Smart Alarm Hiding (ISA-18.2 Compliant)]
   │
   ├─► Open Alarm Logging -> Tools -> Alarm Hiding Configuration
   ├─► Define Hiding Mask / Matrix based on plant operational state tag (e.g., Plant_State = MAINTENANCE)
   ├─► Link nuisance hardware alarms to the hiding condition
   └─► When active: Alarms do not flash on banner but record silently to Chronological List

This ensures full auditability without cluttering active operator display banners.

Suppressing Download Clutter and Nuisance Rack Alarms

The following table outlines strategies for handling specific alarm categories during engineering downloads:

Alarm Event MessageSource Block / ComponentSuppression Allowed?Recommended Handling StrategySafety program: partial shutdownF_SHUTDN / F-RuntimeNo (Safety Critical)Resolve root cause: increase F-cycle time in OB35 or fix F-module communication.Safety program: full shutdownS7 F-Systems CPU CoreNo (Safety Critical)Requires CPU inspection; investigate F-CRC mismatches or safety logic corruption.Module failure / Rack faultMOD_D1 / RACK_NOYes (Display only)In OS Project Editor, deselect "Display in Process Alarm Window"; retain in System Window.I/O channel passivated / depassivatedF_CH_DO / F_CH_DITemporary (Maintenance)Use Maintenance Station / SWC_MOS override during active loop testing.AS-OS Download Delta DiscrepanciesWinCC Alarm LoggingYesPerform AS delta download during low-activity windows; use MsgLock on impacted charts.

Verification

To verify that alarm filtering is operating correctly and safely:
1. In WinCC Runtime, open the Alarm Logging display and verify that standard process alarm banners show only operational alarms.
2. Click on the dedicated System Alarm List tab (or Maintenance List); verify that system diagnostic messages are present and properly categorized.
3. Simulate an auxiliary hardware module fault (e.g., disconnect an unused ET 200M channel); confirm the diagnostic alarm records in the background archive without triggering audible horns on the operator console.
4. Verify that critical safety alarms (such as Safety program: partial shutdown) remain visible with high-priority flashing headers in the primary alarm list if deliberately simulated.

Limitations and Operational Precautions

Never modify message attributes directly within the WinCC Alarm Logging database tables. Any manual edits made inside WinCC Explorer will be overwritten during the next AS-OS Compilation from SIMATIC Manager. All permanent alarm filtering, class assignments, and priority adjustments must be configured at the CFC block level (MsgLock, block properties) or within the OS Project Editor.

Engineer FAQ

Can I delete the 'Safety program: partial shutdown' alarm in Alarm Logging?

No. The alarm is generated automatically by the F-runtime system blocks during AS-OS compilation. Even if deleted in WinCC, it will be recreated during the next compile.

How do I prevent nuisance alarms during online software downloads?

Set the MsgLock = 1 input parameter on major APL technological blocks prior to downloading changes, or use the PCS 7 Maintenance Station bypass features.

Where does WinCC store hidden alarms?

Hidden alarms are stored in the WinCC alarm archive and are accessible in runtime via the 'Hidden Messages' list button on the standard PCS 7 alarm toolbar.

Why did a 'Safety program: partial shutdown' occur during download?

Downloading changes in RUN mode while an F-OB cycle time is borderline can cause the CPU to momentarily exceed the configured maximum F-cycle time, tripping the safety runtime group shutdown.