CM 3310 Process Control, Spring Lecture 20

Transcription

1 Introduction to S88 CM 3310 Process Control, Spring 2017 Instructor: Dr. Tom Co Lecture 20 Recommended references: 1. J. Parshall and L. Lamb, Applying S88: Batch Control from a User s Perspective. ISA, Research Triangle Park, NC, ANSI/ISA-S , Batch Control Part 1: Models and Terminology( available via ) CM3310 Lecture 20 Page 1 What is S88? - (shorthand for ANSI/ISA-88) is a standard to address batch process control, including software, equipment and procedures. - also becomes a design philosophy for easier development of recipes and increased flexibility, modularity and reliability Features: - common standards easier communication among recipe developers, process engineers, customers and vendors across different levels - modularity increased reusability of recipes and equipment as well as easier validation - added values: 1) guidelines for handling abnormal events, 2) standards for tracking historical data CM3310 Lecture 20 Page 2

2 Three main S88 models : 1. Physical Models 2. Procedural Models 3. Process Models CM3310 Lecture 20 Page 3 Physical Models Figure 1. S88 Physical Model. CM3310 Lecture 20 Page 4

3 Enterprise: Company, division or business unit Site: Specific plant/factory Area: Sections in a site based on either physical layout or business function Process Cell: Grouping of all equipment necessary to make batches. o Specifies collective membership of equipment for designed batches, i.e. a batch process is not allowed (or in some implementation, relaxed to strongly discouraged ) to cross cell boundaries. o May provide one or more trains of equipment for different batches, where train (aka line ) means a set of equipment for making a batch, while path (aka stream ) is the order of equipment to make a particular batch. o Types of process cells based on number of products: 1) Single Product one product for each batch 2) Multi Product : a) using same procedure but different formula or b) using different procedures CM3310 Lecture 20 Page 5 o Types of process cells based on paths: 1) Single Path several units (to be described later) in sequence 2) Multiple-Path several single-path trains in parallel (no product transfer between them) 3) Network a. Fixed: same units used in same sequence b. Variable: may change as the batch is being produced Unit: subgrouping of equipment necessary to handle one or more major processing activities (e.g. mix, react, crystallize, etc.). o Usual criteria: does it require a recipe for the operation of the unit (e.g. storage tanks and pumps are often not considered as units) o Can only work on one batch at a time (no mixing of batches for improved batch tracking) o Often contain the whole batch or in some cases just portion of a batch o Units should be defined such that they can operate independently of each other CM3310 Lecture 20 Page 6

4 Equipment Module: subgrouping of equipment inside a unit that coordinates the action of control modules (to be described later) or other equipment modules to carry out a finite number of specific minor processing activities (e.g. dosing, weighing, filling, draining, etc.). o Executes equipment phases, but do not execute higher level procedure o Coordinates one or more control modules to address (or arbitrate requests ) from units. Thus, equipment modules have procedural control that requires complex set of logic that carry out sequencing. o The finite number of equipment capabilities and the minor processing activities need to be set ( for matching with states within control recipes ). o Can be shared by different units ( shared-resource ) or not ( exclusive-useresource ). CM3310 Lecture 20 Page 7 Comparison between Units (U) and Equipment Modules (EM) 1 U: centered on major equipment EM: centered on auxiliary equipment 2 U: can run multiple procedures EM: often has one phase (procedure) 3 U: can get different recipes EM: same command for any product 4 U: intended to stand alone EM: bound to units (or other EMs) 5 U: can communicate with other units EM: receives commands and only responds CM3310 Lecture 20 Page 8

5 Control Module : a collection of sensors, actuators, other control modules, and other associated equipment that is operated as a single entity. o Control modules are typically given a command and then drive the equipment to a state and can provide information (for performance assessment or alarm conditions) o Can also contain other control modules (example: a header CM containing several on/off block CM valves ) o Can contain field or non-field components such as PID loop, PLC commands or DCS commands. o A device should only be controlled by only one control module o Can include additional functions such as: - Modes ( manual, automatic, simulation ) - Permissives - State transition logic - Error detection and failure logic CM3310 Lecture 20 Page 9 Comparison between Equipment Module (EM) and Control Modules (CM) 1 EM: runs sequencing logic CM: provides basic control only 2 EM: connects to equipment via CM CM: connects directly to equipment 3 EM: can be a shared equipment CM: dedicated to an EM or other CMs CM3310 Lecture 20 Page 10

6 Recall: Discussion of Recipes (in Lecture 7) 1. Recipe development sequence: General Recipe Site Recipe Master Recipe Control Recipe 2. Control Recipes contain the following: Recipe header Version/Revision number Author, basis References to policies, procedures Equipment definition List of approved units Materials definition (or Formula) Raw material standards Process material specifications (filters, decolorizers, etc.) Procedures Phase definition for normal operation Abnormal condition handlers Other Information Safety and compliance information CM3310 Lecture 20 Page 11 Procedural Model Figure 2. S88 Procedural Model (Used in Master and Control Recipes) CM3310 Lecture 20 Page 12

7 Procedure: Unit Procedure: Operation: Provides the ordered set of unit procedures under a specified path to produce a batch Contains an ordered set of operations to address the needs of the main procedure. Only one operation is presumed to be active at any time with a unit. An ordered set of phases that defines a major processing sequence, that takes the materials being processed from one state to another (usually involving a chemical or physical change). Note: It is recommended to locate operation boundaries where normal operation can be safely suspended. CM3310 Lecture 20 Page 13 Phase: Provides actions that a) Enable/disable regulating and state-oriented types of basic control b) Specification of set points and initial output values c) Setting and modifying alarm and limits d) Reading/monitoring/data collection of process variables e) Are executed via commands to basic control and other phases CM3310 Lecture 20 Page 14

8 Process Models Figure 3. S88 Process Model (Used in General and Site Recipes) Remarks: Process models are not locked to any particular set of equipment. Its main focus is in the sequence of transformation of the raw material to manufacture the product. Thus, there is no need to worry about the physical models yet (e.g. often developed by chemists and/or process development department). CM3310 Lecture 20 Page 15 Linking of Physical, Procedural Control and Process Models Figure 4. Linking among the models. CM3310 Lecture 20 Page 16

9 States and Commands (suggested by S88) - States are used to specify the current condition of a procedural element or equipment entity, while commands are one method for moving a procedural element or equipment entity from one state to another Figure 5. State Transition for Procedural Elements CM3310 Lecture 20 Page 17 Commands for Discontinuation of Normal Run: Full/Final Discontinuation 1. Stop : executes Stopping Logic, i.e. a normal stop. can commence during the following states: Running Holding, Held, Restarting Pausing, Paused 2. Abort : executes Abort Logic, which is quicker, not necessarily controlled, abnormal stop. can commence during the following states: Running Holding, Held, Restarting Pausing, Paused Stopping, Stopped CM3310 Lecture 20 Page 18

10 Partial/Temporary Discontinuation 1. Pause : freezes current activity at the next defined safe or stable location of the Running state. It returns at the spot where activity was frozen (i.e. last safe state) after Resume command is given. 2. Hold : executes Hold Logic. Returns to the spot in the activity specified by the Restarting logic. CM3310 Lecture 20 Page 19 Observation/Notes: 1. S88 requires batch recipe management to be separate from equipment control (e.g. S88 software such as OpenBatch for recipe control/batch management while PLC/DCS used for equipment control) 2. Process cells inventories available units and other equipment to determine match with recipe procedure coordination, arbitration and scheduling 3. Operations need to be chunked at the right level to allow for timely monitoring and potential overrides or interruptions. 4. Units and unit procedures are determined based on the need for recipes and independent operation also activity latched to only one batch 5. Equipment modules are designed for modularity and reusability can be attached to different units when needed 6. Control modules are focused on actions rather than sequential logic CM3310 Lecture 20 Page 20