Resolving Missing Engineering Units on APL Block Icons in PCS 7 Web Navigator Client

Missing engineering units on APL block icons on SIMATIC PCS 7 Web Navigator clients—while displaying correctly on the Web Server—occur when the client workstation lacks the dedicated APL Web Client plugin or when Internet Explorer security settings block custom font downloads. Standard Web Navigator core installations deliver WinCC graphics engines but do not install APL-specific ActiveX controls, custom glyph fonts, and unit rendering components. To resolve this, install the 'Siemens APL Web Plugin' on the client machine, re-publish the Web project using the Web View Publisher on the server, and enable 'Font download' in the Internet Explorer Trusted Sites zone.

Client-Server Architecture of PCS 7 Web Navigator and APL Rendering

SIMATIC PCS 7 Web Navigator enables remote operators and plant supervisors to monitor and control processes using Microsoft Internet Explorer or the dedicated WinCC WebViewer. The architecture consists of a Web Server (collocated with an OS Server or OS Single Station) and remote Web Clients.

The Advanced Process Library (APL) employs advanced graphic objects, dynamic faceplates, and custom font glyphs to display engineering units, status icons, and alarm indicators. When an operator views an APL block icon (e.g., MotL, VlvL, or PIDConL), the Web Server executes server-side scripts and serves published process graphics (*.pdl transformed into Web format). However, the actual rendering of unit text and vector glyphs on the client canvas depends on local client plugins and Internet Explorer ActiveX execution privileges.

Root Causes of Missing Engineering Units on Web Clients

When units appear properly on the Web Server but remain blank on Web Clients, the problem is traced to three primary causes:
1. Missing APL Web Client Plugin: The standard Web Navigator installation (WebClient.exec) installs basic WinCC controls but omits the APL Web Client plugin (Siemens.Simatic.Pcs7.Apl.WebClient.exe). Without this plugin, APL faceplate controls cannot evaluate internal unit properties (PV_Unit, Unit).
2. Outdated Web Publication: If block icons or APL libraries were updated on the OS Server, but the Web View Publisher was not re-run with complete publishing enabled, the web cache retains outdated symbol templates.
3. Internet Explorer Security Zone Restrictions: Internet Explorer security settings for Trusted Sites may block font downloads or ActiveX initialization, preventing custom fonts used for engineering units from rendering.

Web Navigator Client Plugin and Security Matrix

The table below outlines the software components, plugins, and browser configuration requirements for APL Web Navigator clients:

Component / SettingTarget WorkstationRequired Version / ConfigurationPurposeWeb Navigator Client CoreWeb Client PCSame version as Web Server (e.g., V9.0)Provides foundational WinCC web runtime environment.Siemens APL Web PluginWeb Client PCMatches PCS 7 APL version installed on OSDelivers APL-specific ActiveX controls, faceplates, and unit display.Web View PublisherWeb Server / ESExecuted after every OS project modificationConverts WinCC PDLs into optimized Web Navigator web graphics.Font Download SettingWeb Client BrowserTrusted Sites -> Custom Level -> EnablePermits downloading embedded fonts and custom unit symbols.ActiveX Controls and PluginsWeb Client BrowserTrusted Sites -> Download signed ActiveX -> EnableAllows execution of PCS 7 graphic controls on the client.Protected ModeWeb Client BrowserTrusted Sites -> Enable Protected Mode: UncheckedEnsures seamless inter-process communication between plugins and browser.

Step-by-Step Configuration and Plugin Installation Procedure

Re-publish Project on Web Server: On the Web Server, open WinCC Explorer and launch Web View Publisher. Select Publish complete project (or select the APL screen templates and block icons). Complete the wizard and restart the Internet Information Services (IIS) web service (iisreset via administrative command prompt).
Download APL Plugin from Web Server: On the client PC, open Internet Explorer and navigate to the Web Server main page (http://<Server_IP_or_Hostname>). Navigate to the Download section.
Install Siemens APL Web Plugin: Locate and download the setup package Siemens.Simatic.Pcs7.Apl.WebClient.exe (or APL Web Client Plugin). Close all Internet Explorer sessions and run the installer with administrative privileges.
Configure Internet Explorer Security Options:
- Open Internet Explorer Internet Options -> Security -> Trusted Sites -> Sites and add http://<Web_Server_Address>.
- Click Custom level... for Trusted Sites:
- Set Downloads -> Font download to Enable.
- Set ActiveX controls and plugins -> Run ActiveX controls and plug-ins to Enable.
- Set ActiveX controls and plugins -> Script ActiveX controls marked safe for scripting to Enable.
Relaunch Web Navigator Client: Restart Internet Explorer or launch WinCC WebViewer. Connect to the server and verify that engineering units (e.g., m3/h, bar, degC) appear crisply on all APL block icons.

Verification

Verify correct operation using the following checkpoints:
1. Open a process screen containing analog indicators (PIDConL, MonAnL): confirm that the engineering unit string appears directly adjacent to the process value field.
2. Click the block icon to open the APL standard faceplate: confirm that the unit is visible in the faceplate header, setpoint fields, and operating limit displays.
3. Verify across multiple client machines with different Windows OS builds (e.g., Windows 7 and Windows 10) that unit rendering remains consistent.

Limitations and Operational Precautions

Modern browsers such as Google Chrome, Mozilla Firefox, or Microsoft Edge in standard mode do not support native ActiveX controls required by SIMATIC PCS 7 V9.0 Web Navigator. Clients must utilize Microsoft Internet Explorer 11 or Microsoft Edge in IE Mode with the appropriate Enterprise Mode site list configured. Ensure that antivirus or corporate endpoint security software does not block ActiveX execution or DLL injection for Siemens.Simatic.Pcs7.Apl.WebClient.exe.