NAMUR
5.3 Recipes
88 Batch Control Concepts, Part 2
This chapter covers the entire recipe part of 88.01 Section 5, Batch Control Concepts.
Figure 8-1 Recipe Types
A recipe created at the enterprise level may cause intermediate products to be made at different sites, with final processing being done at other sites. One general recipe may create several site recipes, which in turn create several master recipes, which are copied to many control recipes. It must be possible to trace a control recipe back through the genealogy of recipes to discover the parent general recipe.
A recipe contains the process-related information needed to make the product. A recipe does not contain information about the estimated time required for procedural elements. Such information varies with events that are outside the scope of the recipe. Many recipes have change control procedures that are designed to discourage change. If the timing changes because a process improvement has shortened the time to do an operation then that should not be a reason to change the recipe and go back through the approval process. Save the timing statistics in a separate file, organized by procedural element and normalized as required. An elapsed time specification in a formula value is a requirement, not an estimate.
The master and control recipe procedures are designed to operate specific equipment.
The general and site recipe procedures can not be specific to equipment because they will be used at many sites and many process cells. As 88.01 says, the difference is between describing the technique (without being specific about the equipment) and describing the task that specific equipment must perform.
The need for four types of recipes arises in a distributed enterprise that has multiple manufacturing sites. This is the most complex situation. This book will start with the simplest situation and work up, rather than from the enterprise down. Not everyone will need all four types in order to live long and prosper in their business.
5.3.1.4 Control Recipe
The recipe closest to the controlled equipment that will do the processing is called the control recipe. This recipe is essential to making a batch because it contains the details necessary to command the equipment. The control recipe at least identifies the unit in which processing will start and must identify all units and material selec- tions that cannot be chosen while running.
A control recipe may be modified as processing progresses. Modifications may include adjustments to the procedure as actual units become known, if they are not all prearranged. Some formula values may be modified based on analysis of the product in progress. The control recipe does not become the complete record of what actually happened because it does not contain time. A separate information system creates that record as a batch report.
Then there is the problem of translating the report for a “golden” batch back into a recipe so that the golden batch may be repeated. But if you think about it, if the system allowed enough variance for a random golden batch to happen then that system is unlikely to be able to duplicate it. If the golden batch was not random but was created by deliberate variations in successive control recipes then the information required to create a new recipe is owned by the experimenter.
Each control recipe for each batch is translated from the master recipe for the desired product. The control recipe is a copy of the master except for a unique batch ID and the tailoring required for specific equipment entities or material sources.
5.3.1.3 Master Recipe
The master recipe is created for one process cell using knowledge of the equipment entities within the cell. There may be more than one master recipe per product if the differences in controlled equipment require that distinction. Generally, process cells have enough variation that a master recipe must be specific to one cell.
A master recipe may be useful for several cells when designers become accustomed to creating identical operating interfaces that conceal the differences in equipment. Fur- ther, the control recipe may become a simple copy of the master recipe, with formula values adjusted by simple calculations for the size of the batch, and a unique batch ID.
The master recipe is required for batch production. Even a plant that has just one unit requires a master recipe for each product in order to create control recipes for each batch of that product.
The following are some additional characteristics of master recipes:
• A master recipe fails in its purpose if control recipes generated from it do not operate the equipment properly. The control recipe procedure is a duplicate of the master recipe procedure, unless somebody changes the control recipe. Generally, changes are made to the control recipe to choose specific equipment within the cell, not to alter the procedure.
• A master recipe must contain product-specific information required for equipment and material selection if a selection exists. This information may be used by a scheduler to select materials and equipment for future batches.
• Formula data relating to batch size may be normalized to a base batch size or it may be calculated from specified equations or simple fixed values, depending on the equipment control requirements.
• A master recipe may be created for equipment that has manual control, some auto- matic control, or full automation.
• A master recipe is created by translating the requirements of a general or site recipe into something that the cell can do, if there is a general or site recipe. If not, then the master recipe can be created from a sketch on the back of an envelope or as a modification of another master recipe.
The relationship of master recipe to general or site recipes is not limited to one to one.
There will be as many master recipes as there are different process cells or sets of equipment that can make the product specified by the site recipe.
5.3.1.2 Site Recipe
The site recipe is a recipe that is specific to a site but not to specific equipment at the site. It teaches the technique but not the task. The site recipe describes the process functionality that is required to make a product, in the local language of the site. The processing may be modified to match the materials that are available at the site, for example, solid material from a local mine instead of powdered or dissolved material.
Also, local materials may vary in concentration and impurities enough to require pre- processing or changes in the formula.
The site recipe contains information that may be used for site business planning, such as material and energy production and consumption.
If site recipes exist then master recipes must be derived from them. Even if there is only one site, the site recipe can assure consistency of multiple master recipes. If there is only one process cell in only one site then the site recipe level is not required.
Remember that site means anything that the enterprise wants it to mean. Mostly it means a manufacturing facility, but it can mean a country or a region.
The site recipe may be derived from a general recipe and may be one of several site recipes required by that general recipe. If no general recipe exists then the site recipe is created at the site, which can then be transferred to a few other sites for adaptation to those sites. If the number of sites is larger than two (or maybe three) then man- aging the consistency of the site recipes may not be possible without having a general recipe to set the standard.
5.3.1.1 General Recipe
The general recipe is required for an enterprise that has more than a few sites, and especially for an enterprise with a corporate research center. The general recipe becomes the standard from which all site recipes are derived. A general recipe is not written for specific equipment but uses process stages, operations, and actions to refer to process functions. You saw how equipment entities are related to process functions in the previous chapter. Again, the general recipe teaches the technique but not the specific task.
NE 33 calls the general recipe the source recipe, with no site recipes. It is written by a chemist, biologist, or other scientist using process functions for the procedure. In NE 33, a source recipe may be used to derive a basis recipe (corresponding to a master recipe) that may be used by a laboratory, pilot plant, or production plant. SP88 devel- oped the opinion that this was too broad because the available technologies are so different. The process functions used to write the 88 general recipe are those that are or could be implemented by equipment entities in any production facility. This view simplifies the task of translating a general recipe into a site recipe.
The general recipe contains formula values that are related to batch size as normal- ized values, for example, percentages of a unit measure of product. Pressure,
temperature, and analysis values are fixed because they do not change with batch size.
For specialty chemicals, there may be equipment requirements related to materials of construction that would either catalyze unwanted reactions or corrode enough to affect the product. Bioreactors tend to be stainless steel, although not all cells of interest thrive on a pH of about 7 in a medium that is mostly water.
The general recipe contains information that may be used for high-level business planning, such as exact normalized quantities of materials and enough information to estimate the cost of equipment. Regulatory agencies may be interested in the
overview of the process and materials that an edited general recipe can provide—
edited, that is, in the sense that the process operations and actions are removed.
5.3.2 Recipe Contents
The first edition of this book described four categories of recipe information—header, equipment requirements, formula, and procedure. SP88 decided that other categories were also required, so we compromised on a category called Other Information.
Some categories are treated differently depending on the type of recipe that contains them, as noted below.
5.3.2.1 Header
The header contains information needed to manage recipes but not to produce a product. The header contains a category of information that identifies the product to be made with this recipe. For example, it includes information that traces the
genealogy of this recipe, including authors and the version numbers of parents. The header grows larger as you go down the recipe hierarchy. It includes information that
contains the details of the approval process and the level of progress toward a status of
“released to production.” A site, master, or control recipe will include information naming the location where that information is valid. SP88 did not even try to stan- dardize the contents of the header because there are so many variations in use.
5.3.2.2 Formula
The formula was discussed in general in Chapter 5. A formula contains three cate- gories of information that group values for easy searching. They are process inputs, process parameters, and process outputs.
Process Inputs may be subdivided into materials, energy, and people. Material data may include more than name and amount, and may include possible alternate sources for a material. Energy and material are specified as a ratio to the product output so that they are independent of batch size. A control recipe will have actual amounts because the batch size is known. The number of people required to make a batch is not known in a general recipe, possibly known in a site recipe, and certainly known in a master recipe and control recipe.
Process Outputs may be subdivided into products, by-products, and waste products.
These may be materials or energy, but so far there is no industrial process that makes people. One of the products is selected as the one to which all other batch size values will be normalized. This is the major product of the recipe.
Process Parameters contain anything that is not an input or an output. Constant values may be used for values like temperature, pressure, pH, and time. The values are always associated with a procedural element, but 88.01 does not provide a way to make the association because it is not an implementation standard. SP88 would have had to describe an implementation in order to deal with parameters that are split among procedural elements. There is also the problem of dealing with a procedural element that is used more than once in a sequence.
The information for process inputs is like the ingredient list for a cooking recipe. The ingredients must be on hand or you’d better not start breaking eggs. Substitutions may be suggested, like chicken instead of meat from an endangered species. Cooking time and temperature are in the procedure paragraphs, as are instructions to split an ingredient for different parts of the procedure. There is one output, which is the title of the recipe. That is, one output if you don’t count the waste products, like eggshells.
5.3.2.3 Equipment Requirements
If there is no choice of wetted materials (e.g., glass, 304 stainless, tantalum), strength of materials, or other capabilities in process equipment then this category of informa- tion of a general or site recipe may be empty. Master and control recipes must be specific about equipment. A multipurpose batch process cell is likely to have a selec- tion of wetted materials, pressure ratings, agitator designs, and other equipment capabilities. If the process cell contains units that are constrained by transfer piping,
then the equipment requirements category must contain enough information to choose the correct train. (Perhaps trainis a contraction of constrainand should be written as ‘train. More likely, the major equipment looks like coupled railroad cars.) The equipment requirements category of the recipe contains the information neces- sary to choose the proper equipment entities to make a batch. A scheduler may use this information to select the specific equipment that might be available at the right time. The process cell may use this information to choose the unit that will start the recipe, and it may allocate or reserve other units as required as the recipe procedure progresses. Other cells may be designed to choose transfer destinations when needed. One user who attended SP88 meetings wanted to be absolutely certain that the standard did not require procedural elements for transfers. In his plant, when a unit procedure ended, control was passed back to the cell. The cell accomplished the transfer and started the next unit procedure in the selected unit. Of course, other processes usually require that the destination unit start its unit procedure before the transfer takes place.
The equipment requirements category of a general and site recipe cannot refer to spe- cific equipment. It must offer guidance and constraints for the selection of actual equipment. For example, “reactor must vent non-condensable gasses to a flare stack because they are poisonous” or “agitator must provide at least x joules per liter during reaction.” A master recipe may be able to condense the guidance into “use R-xx3 or R- xx4 for unit procedure React.” A control recipe may say “use R-743 for unit procedure React,” or it may leave the master recipe choices in place until the batch is started by the process cell. If the process cell has been designed with trains then the designa- tions for the allowable trains may be all that is in equipment requirements.
5.3.2.4 Recipe Procedure
The recipe procedure defines the plan of action for making a product. General and site recipe procedures are constructed using the stages, operations, and actions of the process model described in Section 4.1.3 and Figure 6-1 in Chapter 6. These elements describe process functions without making any reference to actual equipment.
Master and control recipe procedures are built using the procedural elements of Sec- tion 5.1.2 and Figure 7-1. These elements describe functions of controlled equipment, which are related to process functions as described in Section 5.2.1 and Figure 7-2.
A general recipe author is constrained to use process functions that are generally available at the sites. It would require a business decision to create a new process function at one or more sites to enable the author to use a new function. A master recipe author is constrained to use equipment functions that are available in the process cell. Constraints may be reduced or eliminated by carefully matching the enterprise process stages with a process cell’s unit procedures, and so on down the hierarchies of process functions and procedural elements.
General Recipe
As stated above, the general recipe procedure consists of the three process functions—
stages, operations, and actions. The procedure consists of an ordered set of stages.
Each stage consists of an ordered set of operations. Each operation consists of an ordered set of actions, as shown on the left side of Figure 8-2. We will deal with the other relationships shortly.
Process stages, operations, and actions do not have to fit within unit or even process cell boundaries in the target production facilities. This is because the general recipe must be independent of the various manufacturing facilities. A general recipe may call for processing that has to be done in different facilities. In this case, the general recipe leads to several site recipes, and Figure 8-2 applies not to the general recipe but to one of the site recipes.
Site Recipe
The site recipe procedure is a copy of that part of the general recipe procedure that applies to the site. Normally, there is no change in the process functions. Authorized alterations may be made to the copy in order to accommodate the peculiarities of the site. There was a time when corporate engineering could make the sites reasonably uniform, but now the fashion is to buy out your competition and so some of the pur- chased sites are quite peculiar.
Master Recipe
The master recipe procedure consists of the three procedural control elements—unit procedures, operations, and phases. See the right side of Figure 8-2. The procedure may be an ordered set of unit procedures, and so on down the hierarchy. The words
“may be” are used instead of “is” because some SP88 members wanted the model to be collapsible. The reason for this will become apparent in Section 5.3.3.
The relationships between a general or site recipe and a master recipe are complex, as shown in Figure 8-2. This is because the abstract meaning on the left becomes con- crete on the right. A master recipe procedure must be able to operate equipment entities when it is copied to a control recipe. The figure shows that the relationship may be that one process function translates to one or more procedural elements or that several process functions may become one procedural element.
There is always the possibility that the equipment design may require more or fewer procedural elements than the occurrence of each process function in the site or gen- eral recipe procedure. There is also the possibility that a process stage may be just another set of operations to be carried out in the same unit, or that a process opera- tion becomes a set of phases added to an existing equipment operation. All things are possible, provided that the master recipe procedure makes the product that is
described by the general or site recipe.