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How to Configure Monitoring-Only Motor Modes and Suppress Faceplate Controls in PCS 7 APL

How to Configure Monitoring-Only Motor Modes and Suppress Faceplate Controls in PCS 7 APL

In SIMATIC PCS 7 Advanced Process Library (APL), configuring a motor block (such as MotL or VlvMotL) for monitoring-only equipment—where only Run and Trip feedbacks exist without DCS start/stop control—is achieved by restricting operator permissions via the 'OS_Perm' parameter and configuring APL 'Feature' bits. In CFC, de-asserting the start/stop permission bits in OS_Perm (OS_Perm.Bit0 = 0) disables manual control buttons on the WinCC faceplate, while de-asserting mode change permissions locks the block into Local or Out of Service mode. Alternatively, a customized block icon variant can be created in '@PCS7TypicalsAPLV8.pdl' to display only operational status icons while hiding command buttons.

Table of Contents

Monitoring-Only Equipment Challenges in Standard APL Libraries

In process automation facilities, certain field equipment is operated strictly locally or by independent mechanical packages (e.g., vendor chillers, lubrication skids, manual sump pumps):
* The Operational Requirement:
* The DCS must monitor and display equipment running state (FbkRun) and electrical fault state (Trip).
* The DCS must NOT permit operators to issue Start or Stop commands from WinCC faceplates, which would cause operator confusion or false command alarms.
* The Architectural Dilemma: Standard APL motor blocks (MotL, VlvMotL) default to active command outputs and operator control buttons.
* The APL Solution: APL provides built-in parameterization mechanisms (OS_Perm, Feature, block icon variants) to transform full control blocks into passive monitoring indicators without writing custom code.

Configuring Operator Permissions (OS_Perm) in Continuous Function Charts

The primary method to inhibit operator control is parameter OS_Perm (Operator Permissions):

  • What Is OS_Perm?: A 32-bit structured word on the block interface where each bit grants or revokes specific operator actions on the WinCC faceplate.
  • Inhibiting Motor Control Actions:
  • In CFC, open the object properties for MotL.
  • Open parameter OS_Perm:
    • Bit 0: 1 = Operator can switch to Manual mode -> Set to 0
    • Bit 1: 1 = Operator can switch to Auto mode -> Set to 0
    • Bit 2: 1 = Operator can switch to Out of service -> Set to 0
    • Bit 4: 1 = Operator can start motor -> Set to 0
    • Bit 5: 1 = Operator can stop motor -> Set to 0
    • Bit 6: 1 = Operator can reset motor -> Keep 1 if fault reset is needed.
  • When these bits are zeroed, the corresponding buttons on the WinCC faceplate are permanently disabled (greyed out).

Manipulating APL Feature Bits for Alarm and Mode Suppression

The Feature parameter (32-bit DWORD) governs fundamental block execution logic:

  • Setting Constant Local Mode:
  • Interconnect input LocalAct := TRUE to permanently place the block in Local mode.
  • In WinCC, the faceplate will display the 'Local' hand icon, indicating that control authority resides in the field.
  • Disabling Command Output Warnings:
  • Configure parameter MonTiDynamic := 0.0 to disable dynamic stroke/start monitoring alarms.
  • Connect the electrical fault contact directly to Trip.Value.
  • Alarm Suppression:
  • Set input MsgLock := TRUE if process alarm logging is not desired, or configure message priorities in the Message Configuration dialog.

Customizing Dedicated Monitoring Block Icons in @PCS7TypicalsAPLV8.pdl

To achieve a completely streamlined block icon that visually depicts only status:

  1. Open Template in Graphics Designer:
    * Open @PCS7TypicalsAPLV8.pdl in Graphics Designer.
  2. Duplicate and Customize Icon:
    * Copy the standard MotL block icon (e.g., variant 1).
    * Rename the customized icon object to: @MotL/Monitor.
    * In the customized icon, delete the manual mode indicator, alarm bell, and setpoint fields, leaving only the motor symbol and tag label.
  3. Assign Variant in CFC:
    * In the CFC chart, select the MotL block: open Object Properties.
    * Set Block icon: enter the custom identifier (e.g., Monitor).
  4. Compile OS:
    * Execute Compile OS. The AS-OS compiler instantiates the clean 'Monitor' icon across the process graphics.

Comparison of Monitoring-Only Configuration Approaches

The table below compares techniques for implementing monitoring-only equipment in PCS 7 APL.

TechniqueFaceplate StateIcon VisualsEngineering EffortUpgradabilityOS_Perm ZeroingButtons visible but disabledStandard APL iconMinimal (CFC setting)100% Migration-ProofCustom Block Icon VariantStandard APL faceplateClean status-only iconLow (Edit typicals)HighMonDiL Digital MonitoringDigital status faceplateDigital alarm badgeMinimalStandard APL blockCustom SCL BlockFully customized faceplateCustom graphicsHighModerate

Verification

To confirm that monitoring-only operation is achieved:
1. In CFC, verify that MotL.OS_Perm bits for start, stop, and mode selection are set to 0.
2. Interconnect motor running feedback to FbkRun.Value and electrical trip to Trip.Value.
3. In WinCC Runtime, click the motor block icon to open the faceplate.
4. Verify that the Start, Stop, Auto, and Manual buttons are visibly disabled and reject mouse clicks.
5. In the field, start the motor: verify that the block icon animates from gray (stopped) to solid green (running).
6. Simulate a motor overload trip: confirm that the block icon turns flashing red and the faceplate displays the Trip alarm.

Limitations and Operational Precautions

  • Never leave command outputs (Start, Stop) connected to field contactors if the motor is intended for monitoring only; disconnect the physical outputs in CFC.
  • Ensure that the Trip input is wired with fail-safe logic (normally open vs normally closed) matching the physical thermal overload relay.
  • If customizing @PCS7TypicalsAPLV8.pdl, always preserve backup copies of typical files to prevent OS Project Editor overwrite.
  • Always validate final software licensing and system documentation against the applicable Siemens catalog and authorized distributor quotation.

Engineer FAQ

Why not just use the MonDiL block instead of MotL?

MonDiL is ideal for raw digital status. However, plants often mandate using MotL for all rotating equipment to ensure consistent motor graphic symbols, operating hour accumulation, and standard operator faceplate layouts.

Can an operator change modes if OS_Perm is zeroed?

No. Setting OS_Perm.Bit0 = 0 and OS_Perm.Bit1 = 0 removes the operator's right to toggle between Auto and Manual modes from the faceplate.

Where can I find the complete bit mapping for OS_Perm?

The full 32-bit layout for OS_Perm is documented in the Siemens PCS 7 Advanced Process Library (APL) manual under the specific block section.

Technical References

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Related Tags

  • MotL
  • OS_Perm
  • Feature Bits
  • Monitoring Only
  • Block Icons
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