ISA-88

What is ISA-88?

ISA-88 (also S88) is the globally used standard for batch control that uses fixed models and terminology to describe how you separate the equipment, procedures and recipes of a batch process, so that the same plant can produce different recipes safely and repeatably. The standard was developed by the International Society of Automation (ISA), approved in 1995 as ANSI/ISA-S88.01 and adopted by the IEC in 1997 as IEC 61512-1. ISA-88 is not a software standard but a design philosophy: it applies to manual processes just as much as to fully automated batch systems in a DCS, SCADA or MES.

ISA-88 separates the what (the product recipe) from the how (the control of the equipment), making batch control modular, reusable and scalable.

🧠 What exactly does ISA-88 cover?

A batch process converts a measured quantity of raw material into a finished product through a fixed sequence of steps; it is one of the three process types alongside discrete and continuous production (see Discrete, Batch and Continuous Processes). Before ISA-88, every vendor and every project built batch software in its own way. The standard tackled four problems: there was no universal model, user requirements were hard to communicate, systems from different vendors were difficult to integrate and batch software was hard to configure.

ISA-88 therefore defines:

• Models - a physical model, a process model, a procedural control model and a recipe model
• Terminology - unambiguous terms such as unit, phase and control recipe, so that process engineers, vendors and quality departments speak the same language
• Separation of recipe and equipment - recipes are product-specific but not equipment-specific; equipment control is equipment-specific but product-neutral
• Modes and states - how procedures and equipment start, pause, hold and abort
• Data structures and batch records - in the later parts, as the basis for recipe exchange and traceability

📚 How is the ISA-88 series structured?

The series consists of four parts and several technical reports. The IEC adopted the parts as the IEC 61512 series.

The 2010 revision made the physical model more flexible: since then a process cell may contain equipment modules or control modules directly alongside its units, for example for shared equipment, and a unit may contain control modules directly.

🧱 Which models does ISA-88 define?

The physical model divides the plant into seven levels: enterprise, site, area, process cell, unit, equipment module and control module. A company organises the top three levels itself; from the process cell downwards the structure is batch-specific. Levels may be omitted, but the unit is mandatory: it is the vessel, such as a reactor or mixing kettle, in which one batch at a time undergoes processing.

The procedural control model breaks a recipe down into procedure, unit procedure, operation and phase. The phase is the smallest reusable building block, for example Dose, Heat to, Agitate or Transfer. In addition, the process model describes the same production without equipment, as process, process stage, process operation and process action. R&D and process development use this model before it is known on which plant the product will be made.

Basic control such as interlocks and control loops belongs in the control modules and equipment modules, usually in a PLC or DCS following IEC 61131. Sequencing and product logic belong in phases and recipes, often worked out as SFC.

🔄 How do recipes, modes and states work?

ISA-88 has four recipe levels running from general to specific:

Every recipe contains five kinds of information: a header (identification and version), the formula (raw materials, quantities and process parameters), the equipment requirements, the procedure and other information such as safety and quality instructions.

For execution, Part 1 describes modes (automatic, semi-automatic and manual) and an example state model including Idle, Running, Complete, Held, Stopped and Aborted, reached through commands such as Start, Hold, Restart, Stop, Abort and Reset. This state model later reappeared in PackML and in the service model of Module Type Package.

📦 Example: chocolate according to ISA-88

A manufacturer makes dark and milk chocolate in two identical mixing kettles. The master recipe Dark chocolate 70% contains the formula (cocoa mass, sugar, cocoa butter, melting temperature 45 °C, mixing time 10 minutes) and the procedure. The procedure calls four phases: Dose, Heat to, Agitate and Cool. The milk chocolate recipe uses the same phases, only with different parameters.

When an order starts, the batch system creates a control recipe, allocates a free mixing kettle and logs every step with time, temperature and quantity. A new flavour therefore needs only a new recipe, not new PLC code. The CIP cleaning between two batches is often set up as an ISA-88 procedure of its own as well.

🔧 How do you implement ISA-88 in a project?

1. Map the plant - classify equipment according to the physical model and define units, equipment modules and control modules, for example based on the P&ID.
2. Define phases as a library - describe for each phase the parameters, limits, interlocks, alarms and the data that is logged.
3. Build basic control separately from recipes - program control modules and equipment modules in a product-neutral way and test them separately, for example during the FAT.
4. Write the recipes - translate the process description into master recipes; let process experts manage recipes without changing code.
5. Connect upwards - link the batch system to MES and ERP for orders, materials and release using ISA-95 structures.
6. Control changes - manage recipes and phase logic under change management with versioning and approval.

A common mistake is to make phases too large or product-specific; that destroys the reusability that ISA-88 is all about.

🤖 Which systems support ISA-88?

Most batch packages are based on ISA-88, such as SIMATIC BATCH from Siemens (within PCS 7 and PCS neo), FactoryTalk Batch from Rockwell Automation, DeltaV Batch from Emerson, 800xA Batch Management from ABB and Batch Management from AVEVA. They provide recipe management, unit allocation, phase execution and electronic batch records. ISA-88 reduces dependence on a single vendor but does not eliminate it: in practice recipes and phase logic remain tied to the chosen package.

🔁 How does ISA-88 relate to ISA-95, PackML and MTP?

🔐 What does ISA-88 mean for validation and security?

In pharmaceuticals and food, every batch must demonstrably be made according to the recipe. Part 4 therefore structures the batch production record, the basis for electronic batch records and tracking and tracing. Under GMP and EU GMP Annex 11 for computerised systems, and for exports to the US under 21 CFR Part 11 of the FDA, those records need an audit trail and electronic signatures. Because phases are tested separately and reused, validation following GAMP becomes simpler. In the food industry, fixed critical steps such as pasteurisation align with the HACCP plan.

For cybersecurity, the physical model offers a natural division into zones under IEC 62443: a process cell with its units often forms a single zone. Recipe servers and batch servers are valuable targets, because a manipulated recipe directly affects product quality or safety.

❓ Frequently asked questions

What is the difference between ISA-88 and S88?

ISA-88 and S88 are two names for the same batch control standard. S88 derives from the original designation ISA-S88.01 and is still widely used in practice. The international counterpart of ISA-88 is the IEC 61512 series.

Is ISA-88 only intended for batch processes?

ISA-88 was written for batch processes, but its models are also used outside batch. The ISA-88 state model underlies PackML for machines and Module Type Package for modular plants. For continuous processes, ISA-106 is the related standard.

What is a phase in ISA-88?

A phase in ISA-88 is the smallest procedural building block that performs a process-oriented task, such as dosing, heating or agitating. A recipe calls phases with parameters, while the phase itself runs in the equipment control. Well-designed phases are product-neutral and can therefore be reused in many recipes.

What is the difference between a master recipe and a control recipe?

A master recipe in ISA-88 is the approved template for a product on a particular process cell. A control recipe is its copy for a single batch, with actual units, quantities and a batch number. Changes during the batch are recorded in the control recipe and the batch record, not in the master recipe.

Is ISA-88 mandatory?

ISA-88 is a voluntary standard and not a legal requirement. In pharmaceuticals, food and fine chemicals, however, ISA-88 is the de facto norm, because batch software is built on it and its structure makes validation and traceability easier. Clients therefore often specify ISA-88 in their user requirements.

Which version of ISA-88 is current?

The current Part 1 of ISA-88 is ISA-88.00.01-2010, a revision of the original ANSI/ISA-S88.01 from 1995. Parts 2, 3 and 4 date from 2001, 2003 and 2006. The technical report on machine and unit states, ISA-TR88.00.02, appeared in a new edition in 2022.

📌 In summary

ISA-88 is the standard that structures batch control by separating recipe, procedure and equipment.

With the physical model, the procedural model and four recipe levels, ISA-88 makes process automation modular: reusable phases, product-neutral equipment control and recipes that process experts manage themselves. This delivers faster product changeovers, simpler validation and full traceability per batch, and together with ISA-95 forms a reusable architecture from process control up to business systems.