Auxiliary Valve Control (AVC)

The Auxiliary Valve Control (AVC) instruction controls an auxiliary valve that is used with the main clutch or brake valves of a press. This instruction is used when a delay is desired between the enabling or disabling of the main clutch or brake valves and an auxiliary valve (for example, a soft clutch or brake application). The clutch or brake can then be engaged in a two-step sequence providing pressure relief for smoother starting or stopping of the press. One AVC instruction is required for each function that is to be implemented. For example, if a delay is needed when starting and stopping a press, one AVC instruction controls the start delay and another AVC instruction controls the stop delay.

The timing of the auxiliary valve reaction is configurable. Also, the instruction can be set up to handle different valve types and positive or negative feedback signals.

Available Languages

Ladder Diagram

Function Block

This instruction is not available in function block.

Structured Text

This instruction is not available in Structured Text.

Operands

The following table provides the operands used to configure the instruction. These operands cannot be changed at runtime.

The following table explains the instruction inputs. The inputs may be field device signals from input devices or derived from user logic.

(1)

ISO 13849-1 stipulates instruction reset functions must occur on falling edge signals. To comply with ISO 13849-1 requirements, add this logic immediately before this instruction.

Rename the “Reset_Signal” tag in this example to the reset signal tagname. Then use the OSF instruction Output Bit tag as the instruction’s reset source.

The following table explains the instruction outputs. The outputs may be field device signals, or may be derived from user logic.

Operation

Normal Auxiliary Valve Reaction (Delay Type = On)

The following diagram shows a typical soft clutch setup where the auxiliary valve instruction is configured for an On-delay. When Actuate transitions from OFF (0) to ON (1) at (A), the delay timer starts if the Delay Enable input is ON (1). If the Output Follows Actuate input is True, Output 1 energizes once the delay period is over at (B). If the Output Follows Actuate input is False, Output 1 is energized only during the delay period. When the Actuate input transitions from ON (1) to OFF (0), Output 1 follows it and is de-energized immediately if the Output Follows Actuate input is True.

In a soft clutch application, the time period from (A) to (B) indicates the ‘soft’ part of the clutch engagement where there is pressure relief through the auxiliary valve. During this period, the main clutch valve is choked yielding a smoother clutch engagement.

Normal Auxiliary Valve Reaction (Delay Type = Off)

This example shows a typical brake setup where the auxiliary valve instruction is configured for an Off-delay. When the Acutate input transitions from OFF (0) to ON (1) at (A), Output 1 energizes immediately if the Output Follows Acutate input is True. When the Actuate input transitions from ON (1) to OFF (0) at (B), the delay timer starts if the Delay Enabled input is ON (1). If the Output Follows Actuate input is True, Output 1 remains energized until the delay period ends at (C). Output 1 is then de-energized. If the Output Follows Actuate input is False, Output 1 is energized only during the delay period.

In a soft brake application, the time period from (B) to (C) indicates the ‘soft’ part of the brake engagement, where there is pressure relief from the auxiliary valve. During this period, the brake valve is choked, yielding a smoother brake engagement.

Immediate Auxiliary Valve Reaction (Delay Type = On)

This example shows the Delay Enable input changing from ON (1) to OFF (0) during the On-delay phase. When the Actuate input transitions from OFF (0) to ON (1) at (A), the delay timer starts. Then, the Delay Enable input transitions from ON (1) to OFF (0) before the delay timer expires and Output 1 is immediately energized at (B).

Immediate Auxiliary Valve Reaction (Delay Type = Off)

This example shows the Delay Enable input changing from ON (1) to OFF (0) during the Off-delay phase. When the Actuate input transitions from ON (1) to OFF (0) at (A), the delay timer starts. Then, the Delay Enable input transitions from ON (1) to OFF (0) before the delay timer expires and Output 1 is immediately de-energized at (B).

Auxiliary Valve Feedback Fault

This timing diagram shows an example of a Feedback fault where the auxiliary valve did not react within the specified time with Delay Type = ON (1), Output Follows Acutate = True, and Feedback Type = Positive. When the Actuate input transitions from OFF (0) to ON (1) at (A), the delay timer begins. After the delay timer expires at (B), Output 1 is energized. At (C), the Feedback 1 input has not reacted within the specified Feedback Reaction Time, causing a fault. Output 1 is de-energized.

The Fault Present output is cleared at (D) because the Reset input has been asserted and the Feedback 1 input is in the correct state. However, Output 1 cannot be energized again until (E), when the Actuate input turns OFF (0).

False Rung State Behavior

When the instruction is executed on a false rung, all instruction outputs are de-energized.

Fault Codes and Corrective Alarms

The fault codes are listed in hexadecimal format followed by decimal format.

Diagnostic Codes and Corrective Actions

The diagnostic codes are listed in hexadecimal format followed by decimal format.

Affects Math Status Flags

No

Major/Minor Faults

None specific to this instruction. See Index Through Arrays for array-indexing faults.

Execution