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Configuring Double-Acting Two-Way Valves with Dual Outputs Using APL VlvMotL in SIMATIC PCS 7

Configuring Double-Acting Two-Way Valves with Dual Outputs Using APL VlvMotL in SIMATIC PCS 7

To control a 2-way valve equipped with a double-acting actuator requiring two distinct control outputs (Open Command and Close Command) and two end-position feedbacks (Open and Closed) in SIMATIC PCS 7 APL, deploy the standard technological block VlvMotL (Motorized Valve, FB1849) instead of VlvL or Vlv2Way. While VlvL is designed for single-solenoid valves with one continuous output and Vlv2Way is designed for 3-port diverter valves with intermediate neutral positions, VlvMotL natively provides independent Open and Close digital outputs with configurable traveling monitoring, intermediate stopping options, and full interlock protection. If intermediate stopping is not required, configure block parameters to execute direct end-to-end travel.

Table of Contents

Executive Summary

In industrial process engineering, fluid control valves utilize various actuator mechanisms depending on plant safety and motive power requirements. While standard fail-safe process valves utilize spring-return single-solenoid actuators (energize to open, spring to close), large process lines, heavy slurry conduits, and gas isolation manifolds frequently deploy double-acting pneumatic actuators or electric motorized actuators. These devices require two active command outputs from the automation system: one digital output to drive the valve open (Open_Cmd), and an independent digital output to drive the valve closed (Close_Cmd), along with dual limit switches for end-position verification (FbkOpen and FbkClose). Engineers attempting to model these devices often struggle because standard VlvL provides only a single output, while Vlv2Way is tailored for 3-way diverter splitters. Understanding how VlvMotL natively resolves this requirement eliminates the need for custom logic blocks.

Technological Valve Architectures in SIMATIC PCS 7 APL

The Advanced Process Library (APL) provides specialized technological blocks for specific valve physical typologies:

  • VlvL (Basic Valve, FB1899): Engineered for single-solenoid spring-return valves. Features a single continuous binary control output (Ctrl) where 1 = Open and 0 = Closed.
  • Vlv2Way (Two-Way Diverter Valve, FB1898): Engineered for diverter valves switching process fluids between two distinct discharge ports. Features three states: Position 1, Position 2, and Neutral/Closed, with three separate command outputs.
  • VlvMotL (Motorized Valve, FB1849): Engineered for valves driven by motorized gearheads, reversing contactors, or dual-solenoid 5/2-way and 5/3-way pneumatic spool valves. Features separate Open and Close command outputs.

Why VlvL and Vlv2Way Are Ill-Suited for Double-Acting Two-Way Valves

Attempting to force other APL blocks to fit dual-output valves creates maintenance problems:

  • Using VlvL with External Inverters: Inverting Ctrl to create a Close_Cmd via an external NOT gate or RS flip-flop in CFC bypasses block monitoring; if both feedbacks fail, the external logic may leave Close_Cmd energized indefinitely, burning out actuator coils or causing pneumatic pressure lockups.
  • Using Vlv2Way: Exposes unnecessary faceplate controls (Position 1 / Position 2 / Neutral) that confuse operators managing a simple Open/Closed pipeline valve.

Deploying VlvMotL for Dual-Output Actuators

VlvMotL resolves the requirement natively:

  • Provides independent outputs: Open (FB output pin) and Close (FB output pin).
  • Monitors runtime travel limits: Parameters MonTiDynamic and MonTiStatic detect transit stalls and end-position timeouts.
  • Configurable via Feature Bits: Can be configured for continuous command signals or pulse outputs, and intermediate stopping can be enabled or suppressed.

APL Valve Block Selection Matrix

The following table compares APL valve blocks across key mechanical actuation criteria:

Valve Physical TypeRecommended APL BlockCommand OutputsPosition Feedback InputsIntermediate Stopping?Single Solenoid (Spring Return)VlvL (FB1899)1 (Ctrl)2 (FbkOpen, FbkClose)No (Open or Closed)Double Acting (Dual Command)VlvMotL (FB1849)2 (Open, Close)2 (FbkOpen, FbkClose)Configurable (Feature.Bit8)3-Port Diverter / SplitterVlv2Way (FB1898)3 (Pos1, Pos2, Stop)3 (FbkPos1, FbkPos2, FbkNeutral)Yes (Neutral State)Modulating Control ValveVlvAnL (FB1896)1 Analog (MV)1 Analog (PosReal)Continuous 0-100%Safety Isolation Valve (ESD)VlvL with F-Driver1 Fail-Safe Output2 Proximity SensorsNo (Spring Safety Trip)

Step-by-Step Procedure to Configure VlvMotL for Double-Acting Valves

Method: CFC Implementation and Parameterization

  1. Open the target CFC chart in the CFC Editor.
  2. Drag block VlvMotL (FB1849) from the APL library catalog into the chart.
  3. Connect digital channel driver blocks (Pcs7DiIn) for the Open limit switch to input FbkOpen and Closed limit switch to FbkClose.
  4. Connect output parameter Open to the digital output driver (Pcs7DiOu) for the open solenoid/contactor.
  5. Connect output parameter Close to the digital output driver (Pcs7DiOu) for the close solenoid/contactor.
  6. Configure traveling time monitoring: Set MonTiDynamic (e.g. T#15s) to match actuator stroke time plus safety margin.
  7. If intermediate stopping is NOT desired (valve must always stroke fully to end limit):
    * Set Feature.Bit8 = 0 (No separate stop command in manual mode; selecting Open or Close strokes fully).
  8. If pulse commands are required for latching pneumatic valves, configure Feature.Bit4 = 1 (Pulse output signals).
  9. Compile CFC charts and execute delta download.

Verification

To verify double-acting valve control:

  1. Open Command Test: In WinCC faceplate, issue an OPEN command. Confirm that output Open asserts, output Close remains 0, and the valve travels toward Open.
  2. Feedback Transition: When FbkOpen asserts, confirm that output Open de-energizes (if pulse mode) or remains active (if continuous), and faceplate status indicates 'Open' with green icon.
  3. Close Command Test: Issue a CLOSE command. Confirm that output Close asserts, Open remains 0, and valve strokes to full closure.
  4. Travel Time Fault Check: Artificially disconnect feedback and command Open. Confirm that after MonTiDynamic expires, the block trips, issues alarm 'Monitoring Error: Open', and de-energizes outputs.

Limitations and Operational Precautions

  • Simultaneous Command Prevention: VlvMotL has built-in hardware protection preventing Open and Close from asserting simultaneously; however, hardwired electrical interlocks should always be wired at the contactor / MCC level for motor drives.
  • Pulse Duration Sizing: If using pulse outputs, ensure the pulse duration (PulseWidth) is long enough for the pneumatic spool valve to latch completely.
  • Faceplate Icon Styling: If using VlvMotL for a pneumatic valve, the default WinCC block icon may show motor arrows; customize the block icon variant (@VlvMotL/1 vs /2) in Graphic Designer to render standard 2-way valve symbols.

Engineer FAQ

Can I use VlvMotL for valves that do not have an electric motor?

Yes. VlvMotL is widely used for double-acting pneumatic and hydraulic valves because it natively provides dual Open/Close outputs.

How can I prevent operators from stopping the valve midway between Open and Close?

Disable Feature Bit 8 (Feature.Bit8 = 0). This removes the 'Stop' button from the faceplate, forcing complete travel.

Does VlvMotL support runtime interlocks (Permit, Intlock, Protect)?

Yes, VlvMotL includes the complete suite of APL interlocks: Permit (start permissive), Intlock (unlatched trip), and Protect (latched protective trip).

Technical References

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Related Tags

  • https://industrialautomation.net/search?query=simatic-pcs7
  • https://industrialautomation.net/search?query=advanced-process-library
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  • https://industrialautomation.net/search?query=cfc-editor
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