Displaying Active Interlock Bypasses in PCS 7 Measuring Point Browser

Displaying Active Interlock Bypasses in PCS 7 Measuring Point Browser

In SIMATIC PCS 7 V9.0, active interlock bypasses on Advanced Process Library (APL) blocks like Intlk02, Intlk04, or Intlk08 fail to display under the Bypass category in the Measuring Point Browser when the block's Feature Bit 2 ('Separate evaluation for excluded and simulated interlock signals') or channel bypass enable bits (BypEn.Inx) are disabled. Without Feature Bit 2 set to 1, the interlock block treats bypassed signals as standard operator manipulations or simulation flags, routing them to the 'Manipulated value' filter rather than 'Bypassed'. Setting Feature.Bit2 = 1, setting BypEn.In01..In08 = 1, and compiling the OS ensures active bypasses generate the specific status word bits required for proper Measuring Point Browser classification.

Table of Contents

• Measuring Point Browser Architecture and Asset Filtering
• Interlock Bypass Mechanics in APL (Intlk02, Intlk04, Intlk08)
• Feature Bit 2 and Bypass Signal Classification Matrix
• Step-by-Step Configuration to Display Bypasses in the Browser
• Verification
• Limitations and Operational Precautions
• Engineer FAQ
• Technical References
• Related Articles
• Related Tags

Measuring Point Browser Architecture and Asset Filtering

The SIMATIC PCS 7 Measuring Point Browser (Messstellen-Browser) is a centralized operational diagnostic tool embedded in WinCC Runtime. It provides operators and maintenance supervisors with instantaneous plant-wide overviews of anomalous process conditions, allowing users to filter tags across categories such as Alarms, Warnings, Tolerances, In Service, Simulation, Manipulated Value, and Bypassed.

To populate these categories dynamically, the Measuring Point Browser queries standardized status words exported by APL blocks to WinCC Tag Management. In APL V8.x and V9.0, interlock blocks (Intlk02, Intlk04, Intlk08) communicate their active condition using the status outputs Status1 and Status2. If the block's internal bypass state machine is not fully enabled, the interlock signal's bypass bit is not evaluated, causing the Measuring Point Browser to misclassify or completely overlook active bypasses.

Interlock Bypass Mechanics in APL (Intlk02, Intlk04, Intlk08)

An interlock block bypass allows an authorized operator or maintenance technician to temporarily ignore a trip or interlock condition on a specific input signal (e.g., bypassing a high-vibration sensor during motor startup). For an interlock signal to be recognized as bypassed in the supervisory system, three prerequisites must be satisfied in the controller:

1. Bypass Enable Assignment (BypEn.Inx): Each individual input pin In01 through In08 has a corresponding boolean configuration parameter BypEn.In01 through BypEn.In08. If BypEn.Inx = FALSE, bypass operations on that specific channel are prohibited and ignored.
2. Feature Bit 2 Activation: By default in standard APL templates, Feature.Bit2 ('Separate evaluation for excluded and simulated interlock signals') is set to 0. Under this default setting, bypassed signals are evaluated under the legacy simulation model and are mapped to WinCC as Manipulated Value.
3. Bypass State Activation (BypAct): Setting Feature.Bit2 = 1 activates the dedicated bypass evaluation logic. When an input is placed in bypass, the block sets output BypAct = 1 and sets the corresponding channel bypass bit in Status2, which the Measuring Point Browser explicitly queries for the Bypass filter category.

Feature Bit 2 and Bypass Signal Classification Matrix

The following table demonstrates how Feature Bit settings and input states govern Measuring Point Browser display behavior:

Step-by-Step Configuration to Display Bypasses in the Browser

To configure APL interlock blocks to correctly report active bypasses in the PCS 7 Measuring Point Browser:

1. Enable Channel Bypass Permissions in CFC:
   - In the CFC chart, locate the interlock block (Intlk02, Intlk04, or Intlk08).
   - Open the block properties or unhide the input pins BypEn.In01 .. BypEn.In08.
   - Set the BypEn pin to 1 (TRUE) for each channel permitted to undergo maintenance bypass.

2. Configure Feature Bit 2 on Interlock Block:
   - Locate the input parameter Feature on the interlock block.
   - Open the Feature Bit structure configuration.
   - Set Bit 2 ('Separate evaluation for excluded and simulated interlock signals') to 1.

3. Compile and Download AS:
   - Compile the CFC chart folder (Scope: Changes Only).
   - Download changes to the S7-400 CPU in RUN mode.

4. Compile OS and Verify Tag Transmission:
   - Perform an OS Compile (Changes Only) to ensure WinCC Tag Management captures the updated APL block status structures.

5. Filter in Measuring Point Browser:
   - In WinCC Runtime, open the Measuring Point Browser from the top overview toolbar.
   - In the filter criteria pane, deselect all status categories and check Bypassed.
   - The active interlock tag will now appear in the list with tag name, description, and bypass timestamp.

Verification

To verify proper bypass detection:
1. Open the process graphic containing the interlock block faceplate in WinCC Runtime.
2. Click the interlock icon to open the faceplate. Select a permissible input and activate Bypass.
3. Confirm that a blue bypass indicator symbol appears next to the input in the faceplate.
4. Open the Measuring Point Browser, select only the Bypassed filter checkbox, and click Apply.
5. Verify that the interlock block measuring point appears in the table with state Bypassed.
6. Deactivate the bypass and confirm that the measuring point clears immediately from the browser window.

Limitations and Operational Precautions

• Plant Safety Governance: Bypassing an interlock disables a functional safety barrier. Ensure plant administrative bypass management procedures (e.g., permit-to-work systems) are strictly enforced.
• Feature Bit Scope: In standardized projects utilizing Control Module Types (CMT), modifying Feature.Bit2 should be performed in the Master Data Library to prevent desynchronization.
• Operator Permissions: Interlock bypass commands in WinCC require high-level authorization (typically Level 6: Process Controlling or Level 11: Higher Process Controlling).

Engineer FAQ

Why did my bypassed interlock show up under Manipulated Value instead of Bypass?

Because Feature Bit 2 was set to 0. Without Feature Bit 2 enabled, the interlock block classifies bypasses as operator manipulated values rather than distinct bypass conditions.

Can an interlock block bypass an input if BypEn is set to 0?

No. The BypEn.Inx parameter acts as an engineering interlock. If BypEn.Inx = 0, the operator faceplate disables and greys out the bypass checkbox for that channel.

Does setting Feature Bit 2 require a CPU restart?

No. Modifying Feature bits in CFC can be downloaded to the S7-400 CPU online in RUN mode using standard Changes-Only download.

Are motor or valve blocks also displayed in the Measuring Point Browser when interlocked?

Yes, drive blocks (MotL, VlvL) appear in the browser under 'Interlocked' when their interlock conditions are actively preventing operation.

Technical References

• SIMATIC Process Control System PCS 7 Advanced Process Library (V9.0 SP1) Programming and Operating Manual (A5E39140304-AB)
• SIMATIC Process Control System PCS 7 Operator Station (V9.0) Manual
• Siemens Industry Online Support: Using the PCS 7 Measuring Point Browser (Entry ID: 109759590)

Related Articles

• Capturing First-In Motor Trip Signals Using APL Interlock Blocks in PCS 7
• Suppressing APL MotL Start-Stop Pulse Outputs in Local Mode on PCS 7
• Configuring User Authorization and Authorization Levels in PCS 7 APL Faceplates

Related Tags

• Measuring Point Browser
• Intlk04
• Intlk08
• Feature Bit 2
• Interlock Bypass