Process Historian Overview
The idea of a Process Historian can sound confusing. But, they are necessary for collecting and tracking historical data.
There are three main approaches to Process Historians:
Built-in Trending with an HMI
A Database-backed storage option
A Full-Blown Process Historian.
In this post, we’ll review all three options in depth. Plus you can check out the video below for the highlights. An example of one of Corso Systems’ Process Historian included in the video.
Built-in Trending on an HMI
Virtually all modern HMI platforms have some form of built-in trending. This feature stores values for various datapoints and displays them for operators on a built-in trending component. This option is extremely valuable for providing information to operators while they are on the plant floor. A common use case is displaying pump speeds for the current shift, or tank levels for the last 24 hours. But, these interfaces are not well suited for navigating large datasets. They are more designed to show a static number of tags on a trend for a particular time period.
If you need to collect a larger number of tags, or make data available to another interface—such as a third-party trending tool, a reporting back-end, or Excel—the next step would be to move towards a database backed system. Using scripting, you can generally get data from an HMI system into a database. And some HMI packages natively utilize SQL databases for storage. Alternately, OPC-HDA or dataloggers can take data from your process to a database.
Database-Backed Storage Solutions
Databases provide easier access to data—including the ability for more advanced analytics than you can do in an HMI trending tool. Additionally Database-backed options make the data available for use in third party tools, and even web-based systems. The example video above details a database-backed solution that Corso Systems implemented exposing historical data for a golf-course pump station manufacturer. The database-backed system allows users on mobile devices (via a website with a powerful trending and reporting package not available in a standard HMI interface) to access historical data. This extremely popular feature can be replicated for virtually every application. For more information, please see our Remote Viewing Application.
The downside to database-backed systems is that they don’t utilize compression. As your dataset grows, it can impact performance when accessing the data. This can be an extreme detractor if you are creating a huge data set, have a lot of tags, and/or are collecting the data in close intervals. A database-backed option can also require working with someone who knows how to extract the data and turn it into useful information. If you will be collecting more than a few thousand datapoints, or want to collect data on the level of milliseconds (or even faster), consider a full-blown Process Historian.
Full Process Historian
Process Historians generally utilize data compression techniques to reduce the overall file sizes of your stored data. They can also limit the data stored to values that have changed outside of deadband to prevent storing duplicate values over and over. Process Historians are also usually paired with an analysis tool designed to work directly with the data to turn it into useful information. These tools can include basic trending, reporting backends, and various data mining tools for understanding operations in more detail.
Many process Historians also offer an SQL Query Interface. This brings the power of the Historian’s compression together with the open-ended nature of a database. This also makes the Process Historian easier to integrate with other systems. Process Historians are usually an added expense beyond the SCADA system, and can be cumbersome to configure before you’re familiar with the interfaces. But, they provide a robust and powerful solution for turning data into information.
Layering the Options
For many facilities, a common solution to the Process Historian conundrum is to layer the options. This solution is common in facilities where staff require multiple layers of information. Operators and plant floor level staff use the built-in trending tools for a more real-time view of the data. Process Engineers and design/optimization staff will use the database to have an “all-time” view. Additionally, this approach allows the comparison of various process conditions against each other to find optimal process conditions.
Your Next Steps with Process Historians
Like most everything, it is about having the right tool for the job—and sometimes you will need more than one tool. For more information on Process Historians, read about our Remote Viewing Application. Need help with Process Historians? Contact us!