August 2003
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BATCH AUTOM BATCH AUTOMA ATION TION::
Make S88 Work For You A Chemical Chemical Week Week Associate Associates s Publication Publication
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Writing a Functional Specification for an S88 Batch Project Define the requirements first, or you’ll pay for it later Christie Deitz, Todd Ham and Steve Murray Emerson Process Management
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This article focuses on industry accepted definitions of functional specification, S88 terminology and models; a methodology for using S88 to specify automation requirements; and a proposed structure for the functional specification. In addition, some common challenges that the authors have encountered are addressed. Tips learned from successfully creating functional specifications are also provided.
88*, a standard addressing the automation engineers. As a result, batch control, is well known in the functional-specification effort is the process-automation world. usually the first time that the process It is a design philosophy for requirements are translated to S88 software, equipment, and pro- batch-process-control requirements. Further complicating matters, many cedures. S88 provides a consistent set of standards and terminology for manufacturing facilities these days batch control. Typically, following S88 must produce multiple products in Functional specification varying quantities (see Multiproduct A functional specification “defines on a project means: • Defining the physical model Plant Design, CE, July, pp. 42–49). The what the system should do, and what • Defining the procedures and recipes requirements for flexibility and quick functions and facilities are to be proThe first step of a process-automa- time-to-market have become important vided. It provides a list of design obtion project is to define the require- business drivers in many industries. jectives for the system” [ 1]. ments. Typically, the main deliverable Process automation and “flexibleThe GAMP (good automation manuof this effort is a functional specifica- batch” control can enable a manufac- facturing practice) life cycle for comtion. In regulated industries (such as turer to quickly produce a new product puter-system development is shown in pharmaceutical), a written and ap- in customer-required quantities. How- Figure 1. According to GAMP, the proved functional specification is re- ever, the modularity and flexibility functional specification is based on a quired for computer system valida- should be designed in from the begin- user-requirement specification, which tion. In other industries, it may not be ning. The S88 standard provides a identifies the system requirements required for regulatory compliance, framework for addressing these needs with regard to data, interfaces, envibut the same requirements must be in the design and implementation of a ronment and constraints. The funcdefined in order to provide the devel- process-automation project. tional specification defines the opment team with the information it Using the S88 standard for an au- process-automation requirements and needs to do the design and implemen- tomation project can provide many becomes the basis for the design spectation of the process automation. benefits, including these: ifications. System-acceptance testing Traditionally, the process-automa- • The standard terminology facili- confirms that the requirements in the tion requirements that are documented tates clear communications between functional specification are met. in the functional specification flow from automation, quality control, manuFrom a development team’s perthe process design. Process engineers, facturing and management spective, the functional specification who define the process sequences and • The S88 standard facilitates object- is the basis for design. It defines what critical control parameters for each oriented, class-based designs. Class- the system will do, but does not say unit, hand over their information to aubased equipment and procedures how to do it. Usually it becomes a contomation engineers; however, the can save time and money because tractual document defining the scope process engineers are typically not as the software is reusable. This will be of a project. Inputs to the functional familiar with the S88 concepts as are discussed in more detail later specification include the process de• Modular design allows for easier re- scription, piping and instrumentation *S88 is shorthand for ISA-S88.01-1995. For configuration and redeployment of diagrams (P&IDs), process-flow diamore information on S88, see CE March 2000, pp. 66–72. the facility grams (PFDs), and an instrument list.
User requirements specification
GAMP Life Cycle
Functional specification
System acceptance testing OQ
Hardware design specification
Hardware acceptance testing
Software design specification Software module specification
Enterprise
Software integration testing Software module testing Code modules
Review and test modules
FIGURE 1. The functional specifications are one of the first steps in the good automation manufacturing practice (GAMP) life cycle for developing a computer system
Site
FIGURE 2 (left). The physical model in an S88 project defines the hierarchy of equipment used in the batch process
Procedural control model
Physical model (lower 4 levels)
Procedure
Process cell
Process cell
Unit procedure
Unit
Unit
Operation
Unit
Phase
Unit
Phase
Equipment module
Area
Equipment module
Control module
FIGURE 3. The procedural model defines the control that enables the equipment in the physical model to perform a process task
tional-specification development. S88 Unit Procedure is a sequence of Opdoes not address the batch control erations. It controls the function of a boundaries for these levels. single Unit. A Unit may have more Area defines a specific section of the than one Unit Procedure, but only one Site, such as a building name. The Unit Procedure may control the Unit Area may contain one or many Process at a time. Cells. S88 does not address the batch- Operation is a sequence of Phases. control boundaries for this level. Typically, an operation controls a por Process Cell contains all of the pro- tion of the Unit function. duction and supporting equipment A Unit Phase performs a unique or inUNDERSTANDING S88 (Units, Equipment Modules, and Con- dependent process function on a Unit. The S88 standard was approved by ISA trol Modules) necessary to make a It coordinates the control of Equipment in 1995 and provides models and termi- batch of product. Modules and Control Modules. nology that an engineer can use to spec- Unit is a major piece of equipment that An Equipment Phase performs a ify automation requirements in a mod- performs a specific task within the simple process function on an Equipular fashion. This section attempts to batch process. A Unit consists of Equip- ment Module. It coordinates the conintroduce the S88 models and terminol- ment Modules and Control Modules. trol of Control Modules. ogy that is most relevant to functional- Equipment Module is a group of specification development. Further S88 equipment that can carry out minor States and commands information can be found in the S88 processing activities. It can be subor- S88 provides a convenient matrix of specification itself. Additionally, there dinate to a Unit, or it can stand alone. states and commands for the elements are several published texts that provide Typically, an Equipment Module con- in the procedural model. Procedural detailed discussions on the S88 models sists of Control Modules and does not states can either be transient or quiesand their real-life implementation. cent. Transient states typically condirectly interface to plant I/O. Control Module is a single entity that tain a sequence of actions that must Physical model performs state-oriented or regulatory be completed in order to proceed to a The physical model defines the hierar- control. It can be subordinate to a Unit corresponding quiescent state (for exchy of equipment used in the batch or an Equipment Module or it can ample, Running and Complete.) process, as shown in Figure 2. This stand alone. A Control Module typiProcedural commands cause the model provides a means to organize cally interfaces directly to plant I/O. state of the procedural element to and define the equipment used to conchange (for example, Start and Stop.) trol the process. The levels are briefly Procedural model An operator or another procedural eledefined as: The procedural model defines the con- ment can issue these commands. Fig Enterprise defines the company that trol that enables the equipment in the ure 4 diagrams a control-system venphysical model to perform a process dor’s interpretation of the S88 owns the facility (plant). Site defines the location of the facil- task. This is shown graphically in Fig- procedural state and command maity. These first two levels provide a ure 3, with definitions following below. trix. The procedural states can be delink to business systems, regulatory Procedure is the sequence of Unit fined as follows: compliance requirements and, possi- Procedures required to make a batch. Idle : Waits for a Start command to bly, engineering standards that must It orchestrates the control of the transition to Running. Running: Begins when the Start be considered as part of the func- equipment in the Process Cell. Failure to develop a comprehensive functional specification can make pro ject-scope management difficult, can cause the project to exceed the budgeted hours and can potentially lead to unsafe process-automation implementation. Using S88 and the ideas that follow can help ensure the creation of useful and accurate project specifications.
Sequence done
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Aborting
Aborted
Abort
Abort
command is received. Normal operation actions are executed. Complete: The Running State has completed. Waits for a Reset command to transition to Idle. Pausing : (Not pictured.) A Pause command was received in the Running State. The Running State logic progresses to the next defined pause point. At the pause point the state transitions to Paused. Paused: (Not pictured.) Used for short-term stops to the procedural element. The state returns to Running once the Resume command is issued. The Running State logic continues from the pause point. Holding: Equipment is placed in a safe state. The Running State is disrupted and placed in Holding when an exception to normal operation is detected or the operator issues the Hold command. Held: Holding State has completed. No actions are taken. At this point, the operator or a batch recipe can issue a Hold, Restart, Stop or Abort command. Restarting: The Restart command has been issued by the operator when the state is Held. Takes action to return equipment to normal operation. Once Restarting finishes, it transitions to the Running State. Stopping: Equipment is placed in a safe state. The current state is disrupted when the operator issues the Stop command. Stopped: Stopping State has completed. At this point, the recipe cannot be restarted. Aborting : Equipment is placed in a safe state. The current state is disrupted when the operator issues the Abort command. Aborted: Aborting State has completed. At this point, the recipe cannot be restarted.
APPLY S88 TO THE PROCESS The first step is to break down process-automation requirements into modules following the S88 standard. Use the S88 models to begin to modularize the physical elements and their corresponding procedural requirements at a conceptual level. Typically, this exercise starts by using P&IDs and process descriptions. The goal is to identify and organize the modules
Fail– hold
Abort Abort Reset
Holding
Sequence done
Held
Stop Fail– hold
Idle
Start and not fail
Reset
Running
Stop
Stop
Restart and not fail
Restarting Sequence done Stop
Stopping Abort
Sequence done
Sequence done
Complete
Stopped
Reset FIGURE 4. Here is one vendor’s interpretation of the S88 procedural state and command matrix
according to their automation requirements. It is not critical at this stage to define details. Some guidelines for this exercise are: • Mark up the P&IDs to define the boundaries of the modules. If necessary, create separate drawings to simplify module boundaries • Focus on the function of the module. Does the module boundary drawn include the appropriate equipment to carry-out the function? Can the module act independent of others? • When identifying the function and the boundary of a module, ensure that the module can handle exceptions to its own normal operation • Identify how the module interacts with other modules. Does the module belong to a unit? Or, can it be shared by multiple units, as might be the case with a supply header? • Identify what information the module must pass to other modules • Begin to establish classes of modules. Do other modules perform the same or similar function? This is probably the single most important task when trying to achieve reuse or flexibility of automation requirements • Organize the modules into a hierarchy that defines their relationship to each other. This is a top-down exercise that follows the S88 Physical Model and Procedural Model
Example makes things clearer For example, you might modularize control of a buffer-preparation vessel (Figure 5) as follows: 1. Define the unit boundary. In this
case, we will draw the unit boundary (the blue boundary in Figure 5) around the entire buffer prep vessel upstream to the water (WFI) and cleaning solution (CIPS) inlet valves and downstream to the valve that allows transfer from the inline mixertransfer pump to the next vessel. This unit performs the task of making buffer for use in other plant areas. 2. Define the control modules. The authors prefer to define the control modules, or entities that perform state-oriented or regulatory control, before defining the equipment modules. For the buffer prep vessel, the control modules include the individual valves, the mixer motor, the agitator motor, and the analog indicators. These are circled in green in Figure 5. 3. Define the equipment modules. For the buffer prep vessel, the equipment modules, or modules that work together to perform a minor function, might include the following, shown in Figure 6: Charge equipment module: The boundary is drawn to include discrete valves used to charge the vessel with either water (WFI) or cleaning solution (CIPS). Only one valve can be opened at any given time. Pressure-control equipment module: The boundary includes pressure indicator, control valve, and discrete valves used to control the pressure of the vessel. Discharge equipment module: The boundary includes the in-line mixertransfer pump and discrete valves used to either recirculate back to the
Vent
WFI
Charge equipment module Air
CIPS
Pressure control equipment module
WFI
Air
Vent
CIPS PIC-101 PT-101
Unit boundary
Filter
PIC-101 Discharge equipment module
PT-101 Drain
Drain Buffer prep tank 101
In-line mixertransfer pump
CWR Buffer prep tank 101
TT-101
TIC-101
CWS
In-line mixertransfer pump
TT-101
Hold tank KEY:
TT = Temperature transmitter WFI = Water for injection TIC = Temperature indication and control CIPS = Clean-in-place supply CWR = Chilled water return PIC = Pressure indication and control CWS = Chilled water supply PT = Pressure transmitter LI = Level indication
FIGURE 5. For this buffer-preparation vessel, the unit boundary is shown in blue. The control modules are circled in green
Temperature control equipment module CWR
LI-101
CWS LI-101
Filter
TIC-101
Hold tank KEY: WFI = Water for injection CIPS = Clean-in-place supply PIC = Pressure indication and control PT = Pressure transmitter
TT = Temperature transmitter TIC = Temperature indication and control CWR = Chilled water return CWS = Chilled water supply LI = Level indication
FIGURE 6. The equipment modules for the buffer prep vessel are defined here
vessel for mixing or to transfer to a a batch in order to define the process cell and the philosophy for running downstream vessel. Temperature-control equipment mod- equipment in order to define the units. ule: The boundary includes the tem- 2. Consider how production wants perature indicator and valves used to to operate the facility. Consider procedures that may run as part of norcontrol vessel temperature. Typically, identifying modules and mal operation, for maintenance, or for organizing them is an iterative cycle. other reasons when drawing phase, Don’t worry too much about the first operation, unit procedure and procepass. Just get started and reconsider dure boundaries. everything after you have a first draft. 3. Where functionality is similar Once you have a draft, it is time to but not identical, consult with procollect further details and refine the duction and process engineering. contents. Now is the time to make sure Possibly, the requirements could be all of the involved people sign off on the modified to allow you to use a classproposed model. This functional-speci- based approach, as described in the folfication effort will be most successful if lowing section. its authors involve all of the stakehold- 4. Identify recipe parameters, ers, including people in automation, which will be passed down from the process engineering, production and recipe, and unit parameters, which quality. The document should be writ- are fixed for the unit. Generally, paten so that all of these disciplines can rameters that change based on the understand it; and all of the stakehold- product or the formula are recipe paraers should agree to the level of detail meters (for example, reaction time), and content of the document. This ap- whereas parameters that are based on proach may also allow it to serve as a the physical characteristics of the training tool for new plant engineers, equipment are unit parameters (for exchemists, operations personnel, and ample, drain time). 5. Identify opportunities to push other plant personnel. When you get these people involved, control as far down the hierarchy as possible. For example, define agiinclude the following considerations: 1. What is the operating philoso- tator control as an equipment module phy at the plant? To what extent will rather than as a phase at the unit automation be required? You will level. In general, this is a good pracneed to know what will be considered tice because it provides modular con-
trol, streamlines the unit phase, and increases the chance of reuse. Once this exercise is complete, it is time to formally define the requirements and structure the functional specification. This leads to the question of how to specify these automation requirements. The following section shows how to take the concepts discussed in this section and capture them in a functional specification that fully defines the automation requirements.
Class-based requirements A functional specification that uses the S88 model is beneficial because it uses standard terminology and concepts. However, the principal benefit is typically the streamlined design, implementation, and testing effort that comes from using a class-based approach to defining the automation requirements. The S88 standard does not address the concept of class-based control. However, class-based control is a logical extension of S88 and is one obvious way to simplify the functional specification (In other words, don’t write the same functionality more than once). In a purely “unit-based” functional specification, there is not much consideration given to standardizing functionality. Consider a fermentation suite that has four production-class fermenters. Each fermenter has identical equip-
Cover Story
OUTLINE FOR A FUNCTIONAL SPECIFICATION OF THE BUFFER-PREP VESSEL EXAMPLE 1. Introduction 2. Equipment Modules i. Charge Equipment Module 1. CIP Phase Class 2. WFI Phase Class ii. Pressure Control Equipment Module 1. CIP Phase Class 2. Pressurize Phase Class 3. Vent Phase Class iii. Discharge Equipment Module 1. Mix Phase Class 2. Transfer Phase Class
iv. Temperature Control Equipment Module 1. Cool Phase Class 3. Buffer Prep Unit Definition i. Alias Definitions ii. Process Alarms and Batch Failure Handling iii. Parameters iv. Phase Classes 1. CIP 2. Charge WFI 3. Add Raw Material 4. Transfer Buffer
ment and performs standard functions, such as pressure testing, clean-in-place (CIP), and sterilize-in-place (SIP). A unit-based functional specification would define each of the four units and three phases on each unit, possibly repeating the same or similar information. This approach allows unintentional deviations from one unit to another. But it may also raise the potential for long-term problems. For in- • Add Raw Material: manually add a tages for dividing up the documents stance, process engineering or maintespecified amount of raw material to must be weighed for each project. For a nance could specify a change for one of the vessel small project, it probably makes sense the four units without considering the • Transfer Buffer: Transfer the con- to use a single document to keep all of others. But if the units were instead tents of the vessel to another vessel the information in a single location. part of the same class, the class-based Note that this class-based approach For larger projects, a single document design would force the engineers to con- allows three units to be reduced to one could easily become unmanageable. sider the impact on the other units. unit class, twelve equipment modules The authors’ preference for large As an example, consider the buffer- to be reduced into four equipment projects is to create a functional-specipreparation vessel discussed above. module classes, and many control fication document for each area. This You might define class-based control modules to be reduced into a few con- approach typically allows classes to be for this buffer prep vessel as follows: trol module classes. Also, instead of described within a single document 1. Group the control modules into twelve phase definitions (four phases because classes often fall within a classes. Control-module classes might times three units), only four phase process area. Yet it allows for a liminclude analog input, discrete input, classes need to be defined. ited number of documents. Typically discrete valve, PID loop, and motor. The modular approach forces the five to ten process areas exist on a 2. Group the equipment modules writer to evaluate deviations among process. The authors also typically into classes. For the buffer prep vessel, the three units to determine if inconsis- create one functional specification the equipment modules classes become: tencies exist. It may also reduce design, early in the project to describe mod• Charge equipment module implementation, and testing time. ules that exist across all areas such as • Pressure-control equipment module But keep in mind that forcing items the agitator control equipment mod• Discharge equipment module that are not truly similar into a class ule, temperature control equipment • Temperature-control equipment may cause more headaches than good. module, and so on. module An example outline for a buffer prep Items forced into a class will often di 3. Identify phase classes for the verge as the project moves forward, area functional specification docuequipment-module classes. Based creating delays and costs. In a class- ment is shown in the box above. on the process description, the pres- based analysis, as with everything else, sure-control equipment module may you must weigh the advantages versus Involve all stakeholders Once the functional specification is have the following phase classes: the disadvantages. written, it is time to get the right peo• CIP: clean the equipment (Figure 7A) • Vent: Vent the vessel to atmosphere Organizing the specifications ple together again. All of the stake(Figure 7B) The writer of the functional specifica- holders that played a part in the func• Pressurize: Control the vessel pres- tion will need to decide where to draw tional specifications development sure (Figure 7C) the boundary between functional- should also take part in reviewing and 4. Group the units into classes. In specification documents. The two ex- ultimately approving the document. It our example plant, we have three tremes are is important to build a consensus so buffer prep vessels that are identical. 1. One functional-specification docu- that all parties agree on the requireTherefore, we will create a unit class ment for the entire facility. ments before you proceed to software called Buffer Prep Vessel with three 2. Smaller functional-specification doc- design and implementation. This does instances: Buffer Prep Tank 101, uments for each individual module. not guarantee there will be no arguBuffer Prep Tank 102, and Buffer The benefits of the single functional- ments in the future but, it does proPrep Tank 103. specification document for the entire vide a solid starting point and a stable 5. Identify phase classes for the facility are that it provides one source platform for change control. unit classes. Based on the process de- of reference and a “big picture” of how scription, the Buffer Prep Unit Class the facility works and that it can be OTHER CONSIDERATIONS may have the following phases: more convenient for approvals and Exception handling • CIP: Clean the vessel maintenance. A benefit of smaller doc- The S88 standard defines exception • Charge WFI: Charge a specified uments is that they are more manage- handling as “those functions that deal amount of purified water to the vessel able. The advantages and disadvan- with plant or process contingencies
Pressure control equipment module (A) WFI
Vent
Air
Pressure control equipment module (B) Vent
Air
CIPS PIC-101
PIC-101
Modularize the equipment To this point, the functional-specification discusDrain Drain sion has been limited to Pressure control equipment module (C) modularizing the automaCWR tion requirements. There Buffer prep Air tank 101 Vent has been limited discussion LI-101 on the physical plant equipCWS ment and its relationship to automation requirements. TIC-101 TT-101 PIC-101 Raw Filter However, the plant equipmaterial PT-101 ment used to execute the mixer process certainly has a direct impact on the automaDrain tion requirements. Hold tank Accordingly, it makes KEY sense to examine how the WFI = Water for injection PT = Pressure transmitter CWR = Chilled water return S88 models might be used CIPS = Clean-in-place supply TT = Temperature transmitter CWS = Chilled water supply PIC = Pressure indication and control TIC = Temperature indication and control LI = Level indication to modularize the physical plant. If the physical plant FIGURE 7. Shown here are three different phase classes for the pressure-control equipment can be modularized, then it module of the buffer-preparation-vessel example. These are clean the equipment (A), vent the ves- is more likely that areas of sel to atmosphere (B), and control the vessel pressure (C) reuse and flexibility can be identified. For example, an equipand other events which occur outside tion as when the process is stable. Third, for Phase logic, consider not ment module may include an agitator the normal or desired behavior of batch control.” In addition, S88 pro- only how to react to an exception but motor and a weigh scale to indicate vides models, such as the procedural also how to recover from that excep- when vessel level is low, causing the state matrix, and terminology that tion. For some exceptions, recovery agitator motor to turn off. If the same provide the fundamentals to address may be as simple as taking an alter- agitator motor and weigh scale types exception handling. However, the spe- nate action in the Running logic. How- are used throughout the plant, then cific details of identifying the excep- ever, other exceptions may be more se- only one equipment module class is tions and determining the appropriate vere and their recovery complicated. needed to specify the automation rereaction are left to those specifying the The most complicated recovery is from quirements for agitators in the plant. exceptions that require the Phase to The most benefit, however, comes automation requirements. There are several considerations go to a safe state such as Holding. when the modular approach is applied that must be made when specifying ex- This type of recovery can be labor in- at the unit level. If process vessels ception-handling requirements. First, tensive because one must logically co- with identical functions, or even simiexception handling must be considered ordinate the actions of the Running, lar functions, are designed with like as an integral part of the automation Holding, and Restarting states. equipment, then it is more likely that requirements. It cannot be left as an afTake, as an example, a Unit Phase the same set of software modules can terthought. One will find that a signifi- that charges material to a vessel. specify the automation requirements cant part of the specification develop- The Running logic can be divided for all the vessels. ment will be spent on this activity. If into three major tasks: 1) open vesOf course, there will always be situthis activity is not adequately ad- sel inlet, 2) wait for charged quan- ations in which a process requirement dressed, plant equipment and product tity to reach target, and 3) close ves- can only be satisfied by a unique piece integrity may be jeopardized. sel inlet. One must consider of equipment. But, the point is that a Second, an exception and its corre- exceptions relative to these tasks be- modular approach to plant equipment sponding reaction must be considered fore recovery can be specified. Re- will lead to modular specifications. as a pair. The reaction to an exception covery from an exception during the The less modular the physical equipshould fit the severity of the exception. “wait for charged quantity” task is ment is, the harder it is to create softIn some cases, an alarm sent to the op- different than recovery from the ware modules that can be used across erator is sufficient. Other exceptions “close vessel inlet” task. For the for- the plant. may require that a batch be aborted. mer, the charge is incomplete so reThis raises the question: When Additionally, the reaction may change covery involves completing the should automation people get inrelative to the current step of the charge. For the latter, the charge volved? Typically, these people are process. A high-temperature alarm has already completed so recovery called in after the process design and that occurs while the process is ramp- involves ensuring that no additional P&IDs are complete. However, foring-up may not require the same reac- charge is executed. ward thinking would suggest that getPT-101
Filter
PT-101
Filter
SUMMARIZING THE TERMINOLOGY PHYSICAL MODELS Process cells Also referred to as trains, these define the logical grouping of equipment necessary to produce one or more batches, though not necessarily a final product. Defining process cells makes production scheduling easier. Things to consider when defining process cells include: • Establish clear boundaries • Functions performed must be consistent regardless of what product is being produced • Interact with other process cells minimally and, when necessary, conducted at the same or higher entity level; that is, from process cell to process cell • Maintain consistency so operators interacting with similar entities do so naturally and without confusion Units are a collection of
equipment and control modules in which major processing activities, such as react, distill, crystallize, make solution, and so on, can be conducted. Unit characteristics are: • Operate on only one batch at a time • Cannot acquire another unit • Operate independent of other units
and limit switches combined can form Off/On valve control modules, and transmitters and valves can be combined into PID control modules.
Procedural Models Phases accomplish a specific process-oriented task, can be executed sequentially or in parallel, can be self-terminating, and need to account for excepEquipment modules are func- tion condition handling. When tional groups centered around defining phases, a few of the a piece of processing equip- considerations include: ment that carry out defined ac- • Consistent use of predefined tivities, such as header control, states, such as holding, held, dosing, weighing, jacket serrestarting, failing vice management, scrubber • Consistent use of predefined control, and so on. A collection commands, such as hold, of control modules can become stop, abort an equipment module if the col- • Definition of the modes for lection executes one or more each phase, and how the equipment phases. phase will respond to each mode. For example, is a sinControl modules are the lowest grouping of equipment cagle-step mode needed for pable of carrying out basic troubleshooting? control. For example, solenoids • Definition of exception han-
ting these people involved earlier would allow the process design to take a more modular approach. Theoretically, the time that the automation engineer spends up-front, diminishes the time that must be spent in the end. This is for two reasons: 1) He or she has an intimate knowledge of the process by the time specification begins; 2) Some of the modularization issues have already been resolved so less time is spent trying manufacture modularity in the software.
and testing efforts by streamlining many instances into one class A functional specification defines the batch automation requirements. Some factors that help ensure the accuracy and the usefulness of the functional specification include 1. Getting automation or other S88knowledgeable people involved early in process design in order to facilitate modular process design, which will enable more modular automation. 2. Involving all of the different stakeholders of including automation, Conclusions process engineering, production, and Developing the requirements for quality in the Functional Specification batch process automation can be a effort in order to understand the oper very complicated task. Using the S88 ating philosophy and to get buy-in on model for batch control provides a the content. common structure and terminology 3. Organizing the documents so that from which to start. Generally, you they are a manageable number and take a stepwise approach to identify- size for the project. Avoid oversized ing and organizing the modules and documents and excessive numbers defining the procedural requirements. of documents. Usually several iterations are re- 4. Identifying exception handing quired before you arrive at a model Investing time and effort into the with which you are happy. functional specification will help to In addition to the common structure streamline the design, implementation and terminology, S88 facilitates class- and testing efforts and will minimize based definition of the batch control. changes due to early misunderstandBy using the class-based approach, ings between stakeholders as the pro■ you can ject moves forward into startup. • Minimize documentation by defin Edited by Gerald Ondrey ing requirements only once for the References entire class 1. GAMP Guide for Validation of Automated • Improve consistency Systems in Pharmaceutical Manufacture. V4.0, Good Aurtomated Manufacturing • Reduce the design, implementation, Practice Forum, 2001.
dling and recovery mechanisms • Data collection of phase-related activities Operations are independent processing activities that usually result in a chemical or physical change in the material being handled. Operations include the instructions necessary for the initiation, organization, and completion of activities such as prepare reactor, charge, heat, cool, and react. Unit procedures provide a strategy for carrying out operations and methods in a contiguous manner within a single unit. A unit procedure can execute concurrently on different units. Procedures are the strategy for carrying out batch activities within a process cell. Procedures, such as clean-inplace, do not always produce a product or a product intermediate. ❏
Authors Christie Deitz is a consultant and project leader for Emerson Process Management’s Life Sciences Industry Center, (8301 Cameron Road, Austin, Tex. 78754; Phone: 512-832-3240; Fax: 512-8323785; Email: christie.deitz @emersonprocess.com) which specializes in process automation for the pharmaceutical and biotech industries. She has worked for Emerson for fifteen years as a technical lead for design and implementation teams providing FDA validatable computer systems for several large pharmaceutical and biopharmaceutical processes. She is also a consultant on computer systems validation issues and a member of the core team of the PDA Part 11 Task Group. Deitz holds a B.S. in chemical engineering from Texas A&M University as well as an M.S. in chemical engineering from the University of Texas. Todd Ham is a consultant and project leader for Emerson Process Management’s Life Sciences Industry Center (Phone: 512-832-7136; Fax: 512-8323785; Email: todd.ham @emer sonprocess.com). He has eleven years of experience in process control as a technical lead for batch automation pro jects in the pharmaceutical, biopharmaceutical, chemical, and food and beverage industries. His experience also includes plant startups and support. He is currently the lead engineer and primary batch architect for a 9,000 point batch biotech facility. Ham holds a B.S. in mechanical engineering from the University of Notre Dame. Steve Murray is a consultant and project leader for Emerson Process Management’s Life Sciences Industry Center, (Phone: 512-832-3909; Fax: 512-832-3785; Email: steve
[email protected]). He has ten years of experience in process control including six years of experience in batch automation. He was recently the lead engineer and batch architect for a 5,000-point batch biotech facility. Murray holds a B.S. in electrical engineering f rom the University of Dayton.
Reprinted from CHEMICAL ENGINEERING , August 2003, copyright 2003 by Chemical Week Associates, L.L.C. with all rights reserved. Additional reprints may be ordered by calling Chemical Engineering Reprint Department (212) 621-4631. To subscribe to Chemical Engineering, call (212) 621-4656.
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