Setup of Programs in Accord Builder
A Program is an automated activity in the Process Plant. Plant conditions are evaluated and Valves and Motors are activated automatically depending on plant conditions and operator commands. Programs may have one or more steps in a Sequence. Programs usually contain setpoints and selection decisions. In Builder a program consists of Conditions, Operations, Alarms, Setpoints, Decisions, and Steps and the Steps contain Automatic Activations and Alarms and Operations. The Item types have various options which are explained in the sections for each type.
Inserting a Program:
A Program is configured by adding or inserting the Program into the Program Group, and adding Equipment to Equipment Units and adding Conditions, Operations, Alarms, Setpoints, Decisions and Steps and a Step Order as required. Operations and Alarms and Activations are enabled by being listed in the Steps.
When a new Program is inserted into the Program group then the component holders are automatically generated.
Individual Program Properties:
Single Step: This is for a ‘Background Program’ which is to run continuously. These programs run Common or Safety functions.
Step On in Hold: The default setting is that a program will not step on automatically if it is in hold or Alarm. This means the Operator must acknowledge the Alarm or restart the program manually. The Enable setting will allow the program to step on Automatically if a Critical Alarm has occurred or if the program is put in Hold by operator.
Power Recovery: If the PLC fails all the information for the system is retained until the PLC is powered up again. The program may be configured to restart in any case or be configured to go into Hold, and then will require Operator to restart the program.
Unit Selection: Normally a program will ‘Reserve’ or Select units when it is Active. This means that another program attempting to start using those units will go into Alarm, assuming the Unit Selected Alarms are still in the First Step. However some programs for background or common functions may not be required to ‘Reserve’ or select units.
PreStart operator Actions notes – this information will be used in project documentation.
Variables and Constants:
These are global registers whose values are available to all programs Conditions and Operations.
Variable: This is a PLC Register whose Floating Pt value is written by the PLC as a result of an Operation. These can be read in Operations and Conditions.
Constant: This is a PLC Register which has a constant Floating Pt value in the PLC, it is written during configuration in Builder. Constants can be read in Conditions and Operations.
Within a Program the Setpoints are Registers which hold Floating Pt values which can also be read during conditions and Operations.