Motorized Butterfly Valve Control

Motorized Butterfly Valve Control(Old-fashion)

Your mission (should you choose to accept it)

Create a control strategy for the butterfly valve w/ motorized damper actuator.

Damper w/ Motorized Actuator

Actuator

Butterfly valveMechanical linkage

Motorized Actuator

Components inside the motorized actuator.

This is not of the same type as shown in the previous slide, but it shows similar componentsAnyway.

Motorized Actuator

Input/Outputs

DO – Command Open

DO – Command Close

AI – Position feedback 0-100%

DI – Valve Fully Closed Limit Switch

DI – Valve Fully Open Limit Switch

PLCActuator

Command Open

Input/Outputs

DO – Command OpenPLC

Actuator

When the PLC turns this Digital Outputsignal ON, power is applied to the forward commandof the motor inside the actuator. The forward rotationof the motor then turns the butterfly valve open.

Command Close

Input/Outputs

DO – Command ClosePLC

Actuator

When the PLC turns this Digital Outputsignal ON, power is applied to the reverse commandof the motor inside the actuator. The reverse rotationof the motor then turns the butterfly valve close.

Actual Position feedback

Input/Outputs

AI – Position feedback 0-100%

PLCActuator

The PLC receives 4-20mA as the valve position feedback. This signal is required so thatthe PLC can monitor the actual position of the valve and compare it with the setpoint position.For example, if the setpoint is 50% and the actual position is only at 25%, then the PLC shouldgive an open command (forward motor) until the actual position equals the setpoint. If the setpointis lower than the actual position, then the PLC should command a close command (reverse motor)until the actual position equals the setpoint.

Limit switches

Input/Outputs

DI – Valve Fully Closed Limit Switch

DI – Valve Fully Open Limit Switch

PLCActuator

If the mechanical limit of the actuator is reached, the any command to the actuator must be OFF. This functions as safety switches so that the motor inside the actuator prevents any further rotation once the fully open/closed limits were reached.

Modes of ControlManual When operator presses the “Command Open” button from the HMI, the

PLC activates the “Command Open” DO, making the motor actuator rotate forward. When the operator presses the “Command Close” button from the HMI, the PLC activates the “Command Close” DO, making the motor actuator rotate in reverse. These buttons are momentary. As the buttons are pressed, the command to the actuator activates. As the buttons are released, the command to the actuator de-activates.

Auto The operator only enters a setpoint, then the program automatically opens/closes the valve until the setpoint equals the actual position.

Input/Output ListHardware Outputs• YS1 – Command Open. When this is active, actuator moves forward, opening the

valve.• YS2 – Command Close. When this is active, actuator moves in reverse, closing the

valve.

Hardware inputs• ZSO – Fully Open Limit Switch. When this is active, then the mechanical limit of the

actuator rotation is reached and any command open to the actuator must be deactivated.

• ZSC – Fully Closed Limit Switch. When this is active, then the mechanical limit of the actuator rotation is reached and any command close to the actuator must be deactivated.

• PV – Actual Position of the Valve in %.

Input/Output ListSoftware Outputs• YSA – Open Fault Timeout. Command Open has been active for 30 seconds and SP

is still greater than PV. Latches on fault, reset required. Disables any valve command open.

• YSB – Close Fault Timeout. Command Close has been active for 30 seconds and SP is still less than PV. Latches on fault, reset required. Disables any valve command close.

• YSC – Position fault. Both ZSO and ZSC are active. No latching logic and therefore no reset required.

Software inputs• HSA – Auto/Man Selection• HSB – Manual Command Open• HSC – Manual Command Close• HSD – Manual Command reset

Logic DiagramWhen in Manual, the Operator pressesThe HSB button to open the valve.

When in Manual, the Operator pressesThe HSC button to close the valve.

Manual comman open/closeNote that the YS1 and YS2 are non-latching. Which means, when the

operator releases the HSB and HSC buttons, the valve remains at its last position. This is a safer control rather than latching YS1 or YS2 where in once the HSB or HSC button is pressed, then the valve will continuously open/close. If that happens and the operator forgets to cancel the command, then the valve will go fully open/close.

In this logic, we prefer that the valve stays at last position if there are no command open/close from the operator is active.

Logic DiagramWhen in Auto, the PLC compares the actual (PV)from the setpoint (SP) position.

This is your Auto Open Command

This is your Auto Close Command

Auto open/closeSP is an analog value where the PV is compared to. If the SP is greater than PV, then

the SP>PV is True. If the SP is less than the PV, the SP<PV is True.If the setpoint position is greater than the actual position, the open the valve more. If

the setpoint is less than the actual position, then close the valve more.

Function of limit switchesWhen the open limit switch is active, stop activatingOpen command.

When the closed limit switch is active, stop activatingclose command.

Open fault timeout

If command open is active and the actual valve position is still less than the setpoint for 30 seconds, then the valve might have a problem because it is taking to long to open.

Close fault timeout

If command close is active and the actual valve position is still greater than the setpoint for 30 seconds, then the valve might have a problem because it is taking to long to close.

Fault timeout deactivates command open.

Fault timeout deactivates command close.