Dear my colleagues,
Today, I will start the series of sequence and phase PLC programming.
Firstly what is sequence?
Sequence describe a flow or a sequence of operation, example a production operation such as: making cookie, CIP, produce soft drink bottle, pasteurizing.
TO understand more about sequence, I will share about S88, it stands for ANSI/ISA-88, is a standard addressing batch process control. It is a design philosophy for describing equipment, and procedures.
The scope of the ISA/ANSI S88 is to provide guidelines for the design and specifications of batch control systems:
- Firstly, To define terminology specific to batch control systems that will encourage understanding between manufacturers and users.
- Secondly,To define Physical model; a hierarchical physical model of batch system
- Next, To define Procedure; a hierarchical software model of batch system
- Next, To define recipes that link the Procedure to the Physical model
Next, I will share about S88 Physical Model, we have 4 layers:
Process Cell : The entire collection of equipment needed to execute a single recipe from start to finish batch
Unit :
– Usually centered on a major piece of process equipment
– Frequently operates on or contains the complete batch
– May operate on or contain only a portion of the complete batch
– Cannot operate on or contain more than one batch at a time
Equipment module: Group devices for performing one or more specific processing activities
Control module: “connect” software to the process through actuators and sensors with all elements treated as a single entity
Next is Procedural Model that is forming for our program structure for sequence and phase.
We have 4 levels:
Procedure (recipe level):
– The overall strategy for making a batch
– Consists of an ordered sequence of unit procedures
Unit Procedure:
– The subset of a procedure that occurs within a single unit
– Consists of an ordered sequence of (one or more) operations
Operation:
– A sequence that causes a significant physical or chemical change within the batch
– Consists of an ordered sequence of (one or more) phases
Phase:
– The smallest element of procedural control, capable of causing one or more actions
More detail explanation: https://www.youtube.com/watch?v=8X-ZKS45zZk
Flexbitautomation.com
