Addressing Batch Process Control with S88 Recipes
I received a lot of feedback on my recent posts on recipes and specifications. I was asked why I didn???t mention the S88 definitions for recipes and how it fits with the point I was trying to make.
Well, I think that???s a pretty fair point and I wanted to get into that a little bit today. If you recall, I was making a couple of major points about recipes and specifications.
First, there are a lot of people throughout the company that use some part of the recipes and/or specifications in their jobs from time to time. In fact, there???s probably a lot more people that use the recipes and specifications that anybody has ever really considered.
Secondly, there???s more problems out there than you realize when it comes to pushing out new recipes or specifications and ensuring everyone has the most up-to-date versions of the recipes and specifications they need.
So, with those points in mind, let???s look at the S88 definitions for recipes and see if we can bring this all together. The following are summarized definitions of recipes from the S88 standard.
- General Recipe ??? Contains product-specific information. Typically one for each product and is independent of any specific site that makes the product.
- Site Recipe ??? Contains site-specific information. Typically one for each product at each site and is independent of any specific process cell that makes the product.
- Master Recipe ??? (also referred to a process cell recipe) ??? Contains process cell-specific information. Typically one for each process cell at each site for each product but is independent of a specific batch.
- Control Recipe ??? (also referred to as a batch recipe) ??? Contains batch-specific information. One for each batch that is made at each process cell. Normally created when the batch is scheduled or created.
So, that???s the definition of the S88 recipes. One point to make right off the bat is that a lot of people don???t necessarily look at the S88 recipe information and instead look at what might be referred to as specification data that resides outside of the S88 recipes. This is especially true for the QA specification, raw material specifications, WIP material specifications, finished product specifications, and so on. Just something to keep in mind.
But, to get back to our question of recipe management, dissemination and viewing in this S88 recipe environment. First of all, most of the batch execution engines that are out there keep copies of Master Recipes and create copies of Control Recipes when a batch is created or scheduled. Rarely does a batch execution system have anything in it but Master Recipes as configuration information and Control Recipes as execution information. The batch engine simply creates a Control Recipe from the Master Recipe and then executes that Control Recipe.
Secondly, most of the General Recipes and Site Recipes are managed centrally by the R&D groups. In fact, in a lot of cases, most companies don???t make a distinction between General Recipes and Site Recipes and in lots of cases that have one or the other but not both. Just something that makes the S88 world a little more complicated.
But, that means you still have the same issues with recipe dissemination that we???ve talked about before. Have you ever executed a batch using your batch engine using the Master Recipe only to find out later that the General Recipe had been changed and you didn???t know about it? That happens all the time. It fact, in most companies there???s a big disconnect between the people that manage the General Recipes and the people that manage and use the Master Recipes and Control Recipes.
I???m sure you???ve been in the middle of it. You find out about a recipe change and you update the Master Recipe in your batch engine, or DCS system, or HMI/SCADA system, or PLC, and start using it. And then you find out that the change was made days or weeks ago and nobody told you. Now you???ve made several days (or weeks) worth of batches using the old recipe. So, now, what do you do?
It happens all the time but it shouldn???t and it doesn???t have to. But, you do need to do a couple of things here. First, put some processes in place so that when changes are made there are some rudimentary notifications if nothing else. Some e-mails, some phone calls, or something to let everyone know that some recipe changes are being made. Especially if the General Recipe and/or Site Recipe is managed and changed by a completely different group.
Secondly, look at some ways to automatically update the Master Recipe when the General Recipe and/or Site Recipe changes. The good news here is just about all the current batch engines, DCS systems, PLC systems, HMI/SCADA systems all have mechanisms that make this very doable. You just need to look at it and figure out exactly what you want it to do. But, the good news is that the tools to do it are probably already there.
Well, I probably didn???t come close to answering all the questions related to S88 recipes. But, I think I???ve given you a little food for thought here. And, of course, there???s lots of resources out there. Thanks again for all the feedback on this topic. Keep it coming. I like to hear from you.