I am often asked questions about the ISA standards like – What is the difference between ISA-95 and ISA-88? and What is the relationship between ISA-88 and ISA-95 standards?

In this article I will only focus on answering these questions.

If we look at history, ISA-88 standard was developed before ISA-95. ISA-88’s focus was purely batch processing. Looking at the effectiveness of the standard, industry asked for a similar standard for not only the ‘Continuous’ and ‘Discrete’ manufacturing but the data model and integration with the layers above including MES and ERP applications and processes.

Then ISA came up with the new standard called ISA-95.

ISA-95 defines 4 levels for an enterprise manufacturing plant. Level 0, 1 and 2 are the levels of process control. Their objective is the control of equipment, in order to execute production processes that end in one or more products.

Level 3 could be called the level of MES (manufacturing execution system) activities. Level 3 consists of several activities that must be executed to prepare, monitor and complete the production process that is executed at level 0, 1 and 2. For example activities like detailed scheduling, quality management, maintenance, production tracking, and so on.

The highest level (level 4) could be called the level of ERP (Enterprise Resource Planning) systems. At this level financial and logistic activities are executed. These activities are not directly related to production. For example Long term planning, Marketing and sales, Procurement.

Enterprise Manufacturing – Data Modeling

ISA-88 defines the Physical model, which structures the Enterprise hierarchically from the highest to the lowest level: Enterprise, Site, Area, Process cell, Unit, Equipment Module and Control module. ISA-88 is especially focused on the level of the Process Cell and the lower levels.

ISA-95 is focused on the boundary between the Area and the Site.

ISA-95 is based on the hierarchical structuring of ISA-88 of the physical assets of the industrial company. But ISA-88 focuses on the Process cell and ISA-95 focuses on the Site and the Area. For ISA-95 the levels of the Process cell and Unit are only of interest if it is necessary to exchange information between enterprise and control systems about these levels. It might be necessary for the business logistic system to have information about the process cell, to be able to schedule long-term activities in this process cell.

ISA-95 also adopts the ISA-88 terminology. It uses terms like Enterprise, Site, Area, Process cell, and so on, as attributes of the Production Schedule. If you have structured your product information based on ISA-88, it will be easier to use the ISA-95 object models for product information. There are a lot more similarities to be mentioned, which is not strange; a lot of SP95 committee members are also ISA-88 committee members.

In short: It is not strictly necessary to have basic knowledge about ISA-88 if you want to understand ISA-95. But it makes it a lot easier. It will also be less complicated to apply ISA-95 if your company is already using ISA-88. But it is not strictly necessary.

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