Troubleshooting Disabled Interlock and Permission Buttons on APL Faceplates

Interlock and Permission buttons remain disabled on APL faceplates in the Operator Station (OS) when the technological block has no interlock blocks interconnected to its Permit, Intlck, or Protect pins in CFC, or when the logged-on operator lacks Authorization Level 5 ('Process Controlling') or Level 6 ('Higher Process Controlling') in WinCC User Administrator. Additionally, if the OS Client cannot access interlock faceplate templates (such as 'PG_Intlk02_Standard.pdl') across the server share, the faceplate script grays out navigation buttons to prevent runtime navigation errors.

Mechanics of APL Interlock Navigation and Faceplate Scripting

In the SIMATIC PCS 7 Advanced Process Library (APL), motor (MotL) and valve (VlvL) faceplates include dedicated buttons for interlocking navigation:
* Permit: Navigates to activation permissions required before starting.
* Interlock (Intlck): Navigates to operational interlocks active during running.
* Protect: Navigates to safety shutdown interlocks.

When clicked, internal C-scripts read the block's input parameters and open secondary child faceplates (PG_Intlk02_Standard.pdl, PG_Intlk04_Standard.pdl, or PG_Intlk08_Standard.pdl).

The enabled/disabled state of these buttons is evaluated dynamically during faceplate initialization based on three criteria:
1. Signal interconnection existence (is an interlock block linked in CFC?).
2. Operating authorizations in WinCC User Administrator.
3. Feature bit settings in the AS block algorithm.

Root Causes of Disabled Interlock and Permission Buttons

When operators report that Start, Stop, and Auto/Manual buttons function normally but Interlock and Permission buttons remain permanently grayed out on the OS:

Absence of CFC Interlock Interconnections: If the Permit, Intlock, or Protect input pins on the MotL block in CFC are left unconnected (or connected to static binary constants rather than an Intlk02 / Intlk04 / Intlk08 block), the block's internal structure flag reports no child faceplate. The script immediately disables the button because there is no child screen to display.
WinCC User Authorization Level Restrictions: Standard operational commands (start/stop) require only Authorization Level 5 (Process Controlling). However, bypassing interlocks, inspecting detailed interlock logic trees, or changing interlock parameters requires Authorization Level 6 (Higher Process Controlling). If the user possesses only Level 5 (or basic Level 1), the interlock inspection buttons are locked.
Terminal Bus Share and Missing Interlock PDLs: In a distributed client-server architecture, if the OS Project Editor was not run completely on the OS Server, or if the client cannot read PG_Intlk*.pdl files from the server's GraCS share, the faceplate script detects missing template files and disables the buttons.
Feature Bit Suppression: Feature.Bit21 ("Show interlock buttons in faceplate") was toggled to 0 in CFC.

Step-by-Step Resolution and User Authorization Setup

Follow this troubleshooting sequence to restore interlock button operation:

Verify CFC Interconnections:
* Open the CFC chart containing the motor or valve block.
* Verify that an interlock block (e.g., Intlk04 - FB 1824) is placed on the chart.
* Ensure Intlk04.Out is connected to MotL.Permit, MotL.Intlock, or MotL.Protect.
* Compile and download CFC changes.
Configure WinCC User Administrator Permissions:
* Open the OS project in WinCC Explorer.
* Double-click User Administrator.
* Select the operator user account (or operator group).
* Ensure that authorizations include:
- Authorization 5: Process Controlling
- Authorization 6: Higher Process Controlling
- Save changes. On the OS Client, log off and log back in to WinCC Runtime.
Execute OS Project Editor and Verify GraCS Share:
* On the OS Server, open WinCC Explorer and run the OS Project Editor with Complete configuration.
* Compile the OS and download to the target OS station.
* Verify that PG_Intlk02_Standard.pdl exists inside the server's GraCS directory.

Verification

In WinCC Runtime, open the faceplate for the motor.
Verify that:
The Permission and Interlock buttons in the faceplate header are fully enabled (not grayed out).
The small padlock or key icon reflects the current interlock health (green unlocked vs. red locked).
Clicking the Interlock button immediately opens the child interlock faceplate showing the individual input conditions and bypass states.

Limitations and Operational Precautions

Granting Authorization Level 6 allows operators to bypass interlocks if Feature.Bit2 is enabled. Ensure plant operating procedures strictly regulate who is granted higher process controlling privileges.
If testing on an Engineering Station where Windows Administrator is logged in, permissions are bypassed by default; always validate user rights under the actual restricted operator account.

Engineer FAQ

Can an interlock button open a custom graphic screen instead of an APL interlock faceplate?
Yes, but it requires customizing the C-script behind the button or linking the block's OS_Permit tag to a custom picture window.
Why did the buttons work on the ES but not on the OS PC?
The user logged in on the ES had full engineering administrator rights (Authorizations 1 through 19), whereas the operator account logged in on the OS station only had basic Level 5 privileges.
What is the difference between Permit, Interlock, and Protect?
Permit allows a motor to start (checked only during startup). Interlock trips a running motor if conditions fail. Protect is a safety interlock that cannot be bypassed and overrides all manual commands.

Technical References

SIMATIC PCS 7 Advanced Process Library (APL) Function Manual: Interlock Blocks (A5E43360408-AA).
SIMATIC WinCC V7/V8 User Administrator and Security Guidelines.
Siemens Industry Online Support Entry ID 109801081: Interlock Configuration and Faceplate Navigation in PCS 7.

Related Tags

PCS 7, APL, Faceplates, Interlocks, Permission, User Administrator, WinCC, MotL

Troubleshooting Disabled Interlock and Permission Buttons on APL Faceplates