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How to Configure the C_GROUP Block for Route and Group Control in PCS 7 CEMAT

How to Configure the C_GROUP Block for Route and Group Control in PCS 7 CEMAT

In the SIMATIC PCS 7 CEMAT mineral and cement automation library, the C_GROUP block (FB1010) serves as the central coordinating module that controls and supervises technological groups of drives, dampers, and process signals. To configure C_GROUP correctly, you must establish sequential start and stop interlocks (GEVG, GVG), interconnect child drive run signals to the group feedback vector (GRE), and link group command pulses to individual motor control blocks (C_DRV_1D, C_DRV_2D). The block evaluates safety interlocks, manages operator start/stop sequences with configurable pre-warning horn timers, and aggregates child equipment fault states into a single unified group faceplate on the WinCC operator station.

Table of Contents

Role of the C_GROUP Module in CEMAT Plant Hierarchy

In heavy processing industries (such as cement, mining, and bulk materials handling), equipment operates as interdependent production lines (e.g., raw mill feed, clinker transport conveyors, kiln exhaust). The SIMATIC PCS 7 CEMAT library structures automation into three hierarchical tiers:
1. Drive and Valve Layer: Individual actuators controlled by C_DRV_1D (unidirectional drives), C_DRV_2D (bidirectional drives), and C_VALVE (solenoid/motor valves).
2. Route Layer (C_ROUTE): Selects material flow paths and diverters.
3. Group Layer (C_GROUP): Commands and supervises the entire collection of drives and routes assigned to a functional process stage.

C_GROUP ensures that conveyor belts and crushing mills start strictly in reverse material flow order (preventing material piling) and stop in normal flow order (allowing equipment to purge).

Signal Architecture: Group Commands vs. Drive Feedbacks

The C_GROUP block coordinates child equipment through dedicated interface vectors:

ParameterDirectionData TypeFunction in CEMAT ArchitectureGEVGInputBOOLStart Interlock: Group start is blocked unless this condition evaluates to TRUE.GVGInputBOOLOperating Interlock: Deasserting stops the group immediately during RUN.GREInputBOOLGroup Feedback ON: Logical sum of all child equipment running confirmations.GABOutputBOOLGroup ON Command: Pulse signal distributed to drive blocks to trigger starting.GAUOutputBOOLGroup OFF Command: Distributed to drive blocks to trigger shutdown.HORNOutputBOOLActivates audible pre-start warning horn for plant floor safety.

Configuring Start/Stop Sequences and Pre-Warning Horns

Heavy industrial safety standards mandate audible and visual warnings before automated machinery starts:
* Pre-Warning Horn Phase: When an operator presses Start on the C_GROUP faceplate, C_GROUP asserts the HORN output and starts the internal timer HORN_TIM (typically set to 15 to 30 seconds).
* Waiting for Acknowledgment: The sequence can require field personnel acknowledgment or proceed automatically after the timer elapses.
* Cascaded Drive Startup: Once the pre-warning phase completes, C_GROUP pulses GAB. Individual drives evaluate their local sequence delay timers (STARTDEL), starting sequentially from downstream to upstream.
* Startup Supervision: C_GROUP monitors the RUN_TIM parameter. If all child drives do not report running status via GRE before RUN_TIM expires, C_GROUP aborts the startup, trips already running drives, and raises a group startup fault alarm.

Method: Interconnecting C_GROUP with Child Equipment Blocks

To implement a complete equipment group in CFC:

  1. In SIMATIC Manager, open the CFC chart corresponding to the target plant section.
  2. Insert an instance of C_GROUP (FB1010) from the CEMAT library into cyclic interrupt task OB35.
  3. Place child drive blocks (e.g., three instances of C_DRV_1D representing Conveyor 1, Conveyor 2, and Feeder 1).
  4. Interconnect the starting commands:
    - Connect C_GROUP.GAB to C_DRV_1D.EB1 (Group Start Input) on all child drives.
    - Connect C_GROUP.GAU to C_DRV_1D.EB2 (Group Stop Input) on all child drives.
  5. Interconnect feedback signals:
    - Connect each drive's running status output (EBM) through an AND block, and connect the result to C_GROUP.GRE.
  6. Configure Drive Startup Delays:
    - In Conveyor 1 (downstream), set STARTDEL := T#0s.
    - In Conveyor 2 (intermediate), set STARTDEL := T#5s.
    - In Feeder 1 (upstream), set STARTDEL := T#10s.
  7. Configure Interlocks:
    - Interconnect upstream safety switches, emergency pull-cords, and lube oil permissions to GEVG and GVG.
  8. Compile CFC and compile OS to generate group block icons and faceplates.

Verification

To verify that the C_GROUP logic functions safely and reliably:

  1. Open the C_GROUP faceplate in WinCC Runtime.
  2. Confirm that with all safety interlocks healthy, the faceplate status indicates Interlocks OK and the Start button is active.
  3. Click Start:
    - Verify that output HORN activates immediately and the acoustic pre-warning timer counts down.
    - Confirm that Conveyor 1 starts at 0 s, Conveyor 2 starts at 5 s, and Feeder 1 starts at 10 s.
    - Confirm that the group status transitions from Starting to Running (green).
  4. Trigger a fault on Conveyor 2 (e.g., simulate a motor overload or belt misalignment):
    - Confirm that Conveyor 2 and Feeder 1 stop immediately.
    - Confirm that C_GROUP generates a group alarm and displays the faulted drive tag on the group faceplate.

Limitations and Operational Precautions

  • Emergency Stop Wiring: C_GROUP software interlocks must never replace hardwired safety circuits. Emergency stop pull-cords and safety relays must directly cut coil power to motor contactors or VFD Safe Torque Off (STO) terminals.
  • Manual Local Mode: Drives switched to Local Manual mode via local control stations (C_DRV_1D.ESPO) are decoupled from C_GROUP automation commands. Ensure C_GROUP is configured to tolerate local operation without tripping the entire line if required by process rules.
  • Process Object Count: Each C_GROUP and child C_DRV_1D block consumes PCS 7 process object (PO) licenses. Budget license allocations during engineering.

Engineer FAQ

What is the difference between GEVG and GVG on C_GROUP?
GEVG (Start Interlock) is evaluated only while starting the group; once running, a loss of GEVG does not trip the group. GVG (Operating Interlock) is continuous; if GVG drops at any time, the group trips immediately.

Can a single drive belong to multiple C_GROUP blocks?
No. In standard CEMAT architecture, a drive is assigned strictly to one parent group. If a drive must be commanded by different operational paths, use C_ROUTE modules to arbitrate ownership.

Why does C_GROUP show 'Startup Fault' even though all motors started?
This occurs if the running feedbacks (EBM) were not correctly interconnected to the group feedback input (GRE), or if RUN_TIM expired before the final motor reported running.

Technical References

  • Siemens Industry Online Support Entry ID 109742323: SIMATIC PCS 7 CEMAT Engineering Manual
  • CEMAT Mineral Processing Function Block Reference Manual (Document No. A5E42478546)
  • Siemens Industry Online Support Entry ID 109809264: CEMAT Group and Route Management Guidelines

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