How to Select and Configure PCS 7 APL and Industry Library Blocks for Single and Double-Acting Cylinders

In SIMATIC PCS 7, controlling pneumatic and hydraulic cylinders in sequential machine applications is achieved using standard Advanced Process Library (APL) blocks or the specialized SIMATIC PCS 7 Industry Library (IL). For single-acting cylinders with spring return, the standard APL 'ValveL' block is deployed. For double-acting cylinders with two energized solenoid positions and discrete end-limit switches (Retracted / Extended), the APL 'Vlv2WayL' block or Industry Library 'VlvPosL' / 'VlvDiv' block is selected. While standard APL blocks require no extra software licenses, deploying Industry Library blocks requires separate engineering and runtime licenses per automation station.

Cylinder Kinematics and Control Requirements in Process Skids

In automated packaging lines, reactor discharge chutes, and filter presses:
* Single-Acting Cylinders: Actuated by a single solenoid valve. Applying pneumatic pressure drives the piston forward; removing pressure allows an internal mechanical spring to return the piston to its rest position. Feedback consists of one or two limit switches (FbkOpen, FbkClose).
* Double-Acting Cylinders: Actuated by dual solenoids (or a 5/2-way directional control valve). Solenoid A extends the rod, while Solenoid B retracts it. Both directions are powered actively. Feedback requires two discrete end-limit sensors.
* Multi-Position / Intermediate Cylinders: Cylinders with 3 to 8 discrete stopping positions or continuous analog positioning.

Single-Acting Cylinders: Configuring APL ValveL with Spring Return

The standard ValveL block (FB1899) from the PCS 7 APL library perfectly matches single-acting cylinder physics:

Output Mapping:
* Connect output Ctrl.Value to the digital output channel driver driving the solenoid valve.
* Ctrl = 1: Solenoid energized -> Cylinder extends.
* Ctrl = 0: Solenoid de-energized -> Cylinder returns via spring.
Feedback Sensor Configuration:
* Connect the Extended limit switch to input FbkOpen.Value.
* Connect the Retracted limit switch to input FbkClose.Value.
Dynamic Monitoring Time:
* Configure parameter MonTiDynamic to the stroke travel duration plus a safety margin (e.g., 5.0 seconds).
* If the cylinder fails to reach the limit switch before MonTiDynamic expires, ValveL generates a monitoring error alarm.

Double-Acting Cylinders: Configuring APL Vlv2WayL and Interlocks

For double-acting cylinders where both extend and retract strokes are driven actively by separate solenoid outputs:

Deploying APL Vlv2WayL (FB1898):
* Provides dual independent control outputs: Ctrl1 (Drive to Position 1 / Retract) and Ctrl2 (Drive to Position 2 / Extend).
* Features built-in hardware anti-collision interlocks ensuring Ctrl1 and Ctrl2 are never energized simultaneously.
Neutral State Management:
* In 5/3-way center-closed valve configurations, setting both Ctrl1 = 0 and Ctrl2 = 0 freezes the cylinder in its current mechanical position.
Travel Monitoring:
* Connect retracted limit switch to Fbk1 and extended limit switch to Fbk2.
* Separate monitoring timers (MonTi1, MonTi2) can be tuned to reflect differing extend vs retract stroke speeds.

Multi-Position Cylinders: SIMATIC PCS 7 Industry Library (IL)

When cylinders feature multiple intermediate mechanical stops or proportional pneumatic positioning:

Industry Library Blocks:
VlvPosL: Controls proportional pneumatic cylinders with 4-20 mA analog feedback and positioning solenoids.
VlvDiv (Diverter Valve / Multi-Way): Supports up to 8 discrete operational positions, ideal for rotating indexing cylinders or multi-stage pneumatic diverters.
Industry Library Licensing Guardrails:
The SIMATIC PCS 7 Industry Library is a separately orderable software package.
Requires an Engineering License (SIMATIC PCS 7 Industry Library Engineering) on the ES and Runtime PO Licenses on each automation station where IL blocks execute.
In contrast, standard APL blocks (ValveL, Vlv2WayL) are fully included in the base PCS 7 license.

Comparison of Cylinder Control Blocks in PCS 7

The table below outlines block selection criteria for cylinder control across standard APL and the Industry Library.

Cylinder TypeRecommended BlockLibrary SourceSolenoid OutputsFeedback InputsLicensing RequirementSingle-Acting (Spring Return)ValveL (FB1899)APL Base1x DO (Ctrl)2x DI (FbkOpen, FbkClose)Base PCS 7 AS/OS PODouble-Acting (2 Solenoids)Vlv2WayL (FB1898)APL Base2x DO (Ctrl1, Ctrl2)2x DI (Fbk1, Fbk2)Base PCS 7 AS/OS POMulti-Position (3-8 Stops)VlvDivIndustry LibraryUp to 8 DO/CodesUp to 8 discrete inputsIL Runtime LicenseProportional Analog CylinderVlvPosLIndustry LibraryAnalog AO / Step DOAnalog AI (Position %)IL Runtime LicenseCustom SCL Cylinder FBUser DevelopedCustom ProjectFlexibleFlexibleZero extra license

Verification

To confirm cylinder operation and monitoring:
1. In CFC, insert Vlv2WayL into OB35 and interconnect Ctrl1 (Retract) and Ctrl2 (Extend) to output channel drivers.
2. Connect proximity switches to Fbk1 and Fbk2.
3. Open WinCC Runtime: click the cylinder block icon to open the faceplate.
4. Command the cylinder to Extend: verify Ctrl2 activates, the cylinder moves forward, and Fbk2 asserts within the configured monitoring time.
5. Command the cylinder to Retract: confirm Ctrl2 de-energizes, Ctrl1 energizes, and Fbk1 confirms arrival.
6. Disconnect a feedback sensor wire: command a stroke and verify that a dynamic monitoring fault triggers exactly upon timer expiry.

Limitations and Operational Precautions

Ensure physical mechanical interlocks and pneumatic dump valves prevent cylinder over-travel or crushing hazards during manual faceplate operation.
When using double-acting cylinders, verify that directional valves do not cause hydraulic lock or pressure intensification if both ports are closed under load.
If deploying Industry Library blocks, verify that valid IL runtime licenses are installed in Automation License Manager; missing licenses will trigger recurring demo mode alerts.
Always validate final software licensing, Industry Library packages, and hardware ordering numbers against the applicable Siemens catalog and authorized distributor quotation.

Engineer FAQ

Can I use standard ValveL for a double-acting cylinder?

Only if the cylinder uses a single 5/2-way solenoid with spring return. If the cylinder uses a dual-solenoid 5/2 or 5/3-way valve requiring separate extend and retract electrical signals, you must use Vlv2WayL.

What block icon does Vlv2WayL use in WinCC?

By default, Vlv2WayL generates a two-way diverter valve block icon. For cylinders, engineers typically customize the bitmap symbols in Graphics Designer to depict a linear pneumatic actuator.

Does the Industry Library require separate WinCC faceplates?

Yes. The Industry Library installs its own dedicated WinCC faceplates, block icons, and @PG_IL_* picture files into the project via the OS Project Editor.