NAMUR
6.1 Control Activities
The control activities are listed below, starting with those furthest from the process:
• Recipe Management – Provides recipes as required; performs translations and editing with add, modify, delete.
• Production Planning and Scheduling – Provides batch schedules to the process cell.
• Production Information Management – Digests raw process data and provides the results to other activities.
Note:The above three activities were defined before SP95 existed, so there is con- siderable overlap with 95. At the time, SP88 as a group had only cursory knowledge of the business functions and no time to learn. The focus was on Batch Process Control, not business functions.
• Process Management – Manages the functions of the process cell.
• Unit Supervision – Supervises unit functions and executes unit recipes; functions as a combined supervisor and operator.
• Process Control – Operates the equipment and control modules.
• Personnel and Environmental Protection – Provides separate control actions that prevent bad things from happening, regardless of what Process Control may be telling the unit to do. This activity is outside the scope of this standard because SP88 had no qualified experts. Protection is the work of other standards groups, such as 84.
The four activities above will be covered in Chapter 12.
The word managementis used in three of the activities. It does not refer to people management in the sense of leading a group of functions. It is closer to the kind of management that you find in computer books, such as File Manager and Device Man- ager. Process Management actually coordinates the functions of the process cell. It does not make business decisions.
6.1.1 Control Activity Model
The figure that follows shows the seven control activities defined by 88.01. Each is connected by lines representing the relationship of each activity to the others. These relationships will be discussed, along with each activity, in this chapter and the next.
The figure resembles Figure 19 in 88.01. A dashed horizontal line is used to separate the business functions from their counterparts in Operations (also called Manufac- turing or Production). The activities discussed in 88.01 are not restricted by physical boundaries. Some of the things associated with the first three activities—Recipe Man- agement, Production Planning and Scheduling, and Production Information
Management—may actually be business functions. Business functions are outside the scope of this standard.
The first three activities meet the following needs of the batch manufacturing environment:
• Recipe Management – Recipes must be stored securely somewhere, new recipes must be able to be added, and existing recipes must be copied to the process cell in order to make the batch specified by the schedule.
• Production Planning and Scheduling – The functions of this activity are divided between business and manufacturing. The dividing line may vary by industry or plant. The end result must be a schedule for making batches in each process cell, with enough additional information to be able to satisfy customer requirements.
Figure 11-1 Control Activity Model
• Information Management – The information from the operation of the process cell has to be stored somewhere. Various bits of process, product, and material knowl- edge must be made available to manufacturing functions. Special algorithms are used to compress and summarize continuous and event data. Trending may be turned on and off by procedural control.
The next three activities meet the needs of the process cell:
• Process Management – Generates control recipes for specific batches, initiates batches after assigning resources, coordinates transfers and equipment, and gener- ates reports or passes the information to Information Management.
• Unit Supervision – Execute recipe procedures, acquire resources, may coordinate Process Control activities.
• Process Control – Execute equipment procedures, perform Basic control tasks.
Note that executing procedures is really not a supervisory function—it is a control function. If there is no automation then it is the operator, not the supervisor, that reads the recipe procedure and follows its instructions.
There is a dashed horizontal line between Process Control and Personnel and Envi- ronmental Protection because Protection is outside the scope of this standard.
Protection used to be called a “Safety Shutdown System,” but “Safety” now has special meaning for trial lawyers.
The activity model did not always look like this. During a SP88 meeting in Phoenix, Arizona, it bore a strong resemblance to a tall cactus with two arms representing Recipe Management and Information Management. Above the cactus was the clear blue sky, with some fluffy white clouds. Three of those clouds appeared to be attached to the top of the cactus and its arms. Later, the clouds were identified as vapor that condensed into 95.
6.1.2 Information Handling
All of the activities communicate in one way or another. That’s how relationships are formed. There are some common information handling aspects that apply to all six activities, whether done by people or machines. These are:
• Reference information
• Security
• Availability
• Archives
• Change management
• Reference tracking Reference information
This is information that must be requested from another activity, as opposed to the stream of information within an activity or that which is published by control instru- mentation.
There are more activities in a plant than are shown in the control activity model.
Communication with those other activities is required in order to request and receive information that is external to batch process control. Each source of reference infor- mation must organize and store it, and act as a server for client requests. Each control activity, as a client, should be able to get the reference information that it requires.
Examples of reference information include master recipes, maintenance schedules, inventory control reports, benchmark consumptions, and yields. 88.01 provides a more extensive list of examples of reference information. The information may be restricted to one process cell, one area, one site, or one enterprise.
Security
In the exciting days that followed the discovery of digital control and networks, some boasted that a person in the boardroom could open a valve in any manufacturing
facility. This is a very bad idea. A manufacturing area maintains control over a number of process cells by endless safety training and the diligent application of safety principles by the operators. They keep the hazardous stuff contained. Anyone outside of manufacturing, and especially at the boardroom level, is unlikely to have had any safety training. It is essential that the ability to directly alter control settings be restricted to those who have been trained in the consequences of such actions.
The business side may include individuals who have an exaggerated need for the power to change anything, so it is necessary to put a control firewall between manu- facturing and business, particularly Information Technology. Of course, business must be able to direct manufacturing activities, but it must do so by going through procedures that protect the people who must work in close proximity to the process—
like Scotty:
Captain Kirk:“More power, Scotty!”
Scotty:“She canna take much more, Captain! I’m giving yer all she’s got!”
The captain can demand, but the engineer (operator) knows the limits of what can be done.
Availability
Information must be available in a timely manner. Process control information has a useful life of milliseconds to minutes, so it is used directly and not captured, stored, and referenced. One of the direct uses may be to capture it for historical storage.
Redundant systems may be required to assure a continuous stream of process data.
Stored data requires periodic backups, even if storage is redundant. The timing of the backups depends on the control time horizon of the information. Don’t forget that busi- ness makes control decisions based on digested process control data. If a source of stored data fails, will you be able to get that information back on line in a timely manner?
The following three activities may be changed by 88.00.04 when it is published.
Archival
Nothing is more constant in manufacturing than change, especially if the principle of
“continuous improvement” has any value to the enterprise. Regulatory commission rules and attack lawyers make it a very good idea to be able to reconstruct how a
product was made, even though the facility may no longer make it that way. That makes it necessary to archive information that is no longer useful for current production. Of course, the physical archive media must be updated to keep up with storage technology.
Change management
The changes to the ways in which products are produced should originate with someone who submits the proposed change to an approval process. The control activities must prohibit unauthorized changes so that there is no one who is unaware of the change. An approved change must alter the header description of the informa- tion in some way, usually by changing a version number. The reasons for the change and the methods for making it must be documented and tied to the version number of the changed information.
Some regulations require that the change be validated before it is put into production.
If so, then the validation procedure and results must be documented and referenced to the information that implements the change. When any document is changed, the change should be logged with the time and date in a summary list, which acts as a directory of changes. The new document should be a new file instead of an alteration of the original, as was done when documents and drawings were created manually.
This assures that each change will be archived without losing the previous changes and their dates.
The paragraph above refers to static information. Sometimes dynamic information must be changed, like a lab analysis or data that is entered to simulate readings from a bad transmitter. An audit trail that lists “why who did what and when” is more appro- priate than a formal change order process. The audit trail must be reviewed in a timely manner to catch any changes that should not have been made. Access to change dynamic information must be restricted.
Reference tracking
A large amount of data from different sources may be needed to reconstruct the way that a product was made. This usually starts with a batch or lot ID from the product or its invoice. That must be tracked to find the date and time when the batch was made.
Change logs and audit trails must be reviewed for events within a time range. If any are found, they must be tracked back to their change descriptions to see if they affected the batch in question. It may be necessary to look at events weeks away from when the batch was made. Perhaps someone found a problem caused by a change to the process a month before, but no one else noticed it. The change logs include recipe changes as well as changes to equipment entities. Perhaps maintenance logs must also be searched to see if some equipment event may have dropped something into the batch.
Tracking may be necessary to find the reason for a change in production performance that is not readily apparent from trend and event data. Tracking may be used to demonstrate the absence of evidence that anything had changed during the produc- tion of a batch. This demonstration may be necessary before the customer will pay for the product.
Some of the references that need to be tracked may have been archived, so there must be a reasonable way to search for and recover the archived information.
6.1.3 Process and Control Engineering
There is no doubt that engineering is required in order to design batch processes. The only question is one of engineering specialties and coordination. Even if lawyers have replaced your engineers, you should have some understanding of how the outsourced engineering will be done so that you will have some chance of getting what you require.
Design engineering is one part of the life cycle. Engineering is required to start up, maintain, and dismantle both equipment and software, but this section is only con- cerned with design.
The design of General and Site recipes does not include specific equipment, but it does include process functions that will be performed by equipment entities. These recipes instruct the Master recipe engineers in the chemistry and procedure that is required to make a product.
There are two sides to the development process for new master recipes. These are shown in Figure 11-2, which is redrawn from Figure 20 in 88.01.
Figure 11-2 Concurrent Definition/Selection
One side (the left) concerns the design of the recipe building blocks. The other side (the right) concerns the process functionality of equipment entities, because the recipe must be able to direct the equipment entities to make a product. Assuming that there is more than one engineer, one must take the recipe side and determine what procedural elements and equipment are needed to satisfy a range of product requirements that are appropriate for the facility. The other engineer must take the equipment entity side and determine what equipment and control is needed to pro- vide the required process functionality. The two engineers actually represent engineering functions that may be accomplished by one person or two teams.
“Processing Considerations” include the General or Site recipe, product specifications, and any process exception handling that is not done by the equipment entities.
“Equipment Considerations” include the General or Site definition of Process Func- tions, the available equipment entities, and equipment exception handling. There are always equipment exceptions to be predicted and handled.
The recipe orders the procedural elements, among other things. Similarly, the path orders the equipment entities. The degree of flexibility of the path depends on the requirements of the range of products being manufactured.
This is an iterative process. If some equipment entities exist, then the recipe engineer fits them in as available process functions and asks the entity engineer to design new entities as required. If the facility is presently a green field with grass roots, then the recipe engineer begins the design by discovering the required process functionality and requesting it. The entity engineer designs entities that are constrained by tech- nology, availability, and cost. This means that they may not exactly meet the process functionality requirements. The engineers meet to resolve the differences and pro- duce a set of recipe building blocks that will work in a particular cell. Each recipe phase, operation, or unit procedure that connects to an equipment entity must match an equipment phase, operation, or unit procedure. These blocks are used to build Master recipes from Site or General recipes.
Similar engineering is required at the site and general recipe levels. Although there are no equipment entities, the process designers must make an effort to choose process functions that are available at the target facility or facilities. Meetings with the engi- neers who do master recipe building blocks are required in order to reduce the work that is necessary to translate a site or general recipe into a master recipe. Careful engi- neering may allow future translations to be automated, if the relationship between a process function and an equipment phase can be reduced to an algorithm.
If possible, the equipment entities should be designed to maximize the things that can be done with each entity. If the design staff can develop a complete list of process functions that might be encountered at a particular facility or cell, then work can begin on creating equipment entities in isolation from recipe development. Manage- ment may order the construction of a facility to make a class of product before recipe development has even started.
It is a rare engineer who builds something that cannot be improved. Version 1 is never the last version. For this reason, the engineers at a facility will have work to do as improvements become evident, but only if they cut costs.