ISA101: Toward a More Effective HMI Strategy

ISA101 is in its final stages of becoming a standard. It is designed to develop and establish a consistent approach to effective HMI development and implementation for manufacturing and especially process industries. End users, automation suppliers and system integrators can use this standard to create more effective HMIs, which will lead to higher productivity and a safer operating environment.

Before getting into a discussion of what the standard involves, what are the characteristics of an effective HMI? There is no “perfect” solution for a given situation, but there are common expectations of what an operator should be able to determine quickly by looking at control room screens:

• Is the process stable, or in an upset situation?

• Is the plant running where it should be for effective production?

• Are key process variables currently changing, or stable?

• How have the most critical variables been running over the past few hours?

• Are there alarms or upsets? Where are they, what is their source and what should I be doing to fix the problems?

Designers have always tried to provide the best available HMI displays. As technology has moved from panel boards with individual meters, gages and pen recorders to digital control systems with electronic displays—designers have used expanded capabilities to develop new approaches for the benefit of operators and other users.

But some companies began to try and outdo each other by adding more capabilities and “bells and whistles” as new technologies emerged, and some are still doing this today. While these can make for very impressive demonstrations, they don’t always help operators understand the current state of the process, nor do they necessarily help operators make quick well-reasoned decisions in response to abnormal conditions.

From Panel Board to P&ID

Retaining an approach first developed back in panel board days, control system designers typically begin with a detailed P&ID (piping and instrumentation diagram) as the basis of operator displays when creating HMIs. This is very effective if the main objective is showing the instrumentation layout in a process environment, and in some applications it is desirable.

However, if used for basic operator screens, it typically leads to a very congested and confusing picture without sufficient emphasis on the information operators need to perform their tasks efficiently. P&IDs follow the geographical positioning of processes in small chunks, not necessarily the process flow. Consequently, when trying to respond to an abnormal condition, an operator may have to search through multiple screens without ever having an overall picture of the affected processes. 

In most plants, the number of console operators in our post-recession world today has been reduced to the barest minimum. Consequently, those remaining are inundated with information from many sources and need to perform a long list of other functions at the same time. While monitoring the status of the process, the operator may need to communicate with field operators, fill out work orders, check the latest laboratory results, and maybe more. A congested and confusing HMI adds to the stress level and makes quick decisions difficult. It can also lead to errors and unsafe operation.

Figure 1 is an example of a traditional HMI display based on a P&ID. It provides lots of detailed information, but little to identify which items are important. Is the process running well at the moment? Is the plant about to explode? When a pump is shown as red, is it running, shut off or in alarm?

Figure 1: This screen graphic for a distillation tower provides much information, but does not indicate the relative importance of any specific reading. Is the process running just fine, or is the tower about to explode?

Moreover, if a plant considers it important for operators to have a high-fidelity picture of the equipment and instrumentation via HMI screens, it has to commit itself to maintaining such a level of accuracy. Any change in the plant—relocation of a pressure sensor, modification to pump piping, and so forth—needs to be updated on the HMI. However, most sites lack a systematic way to keep displays up-to-date or lack management of change (MOC) procedures to address this problem.

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Taking a Lifecycle Approach

Creating and maintaining an effective HMI strategy is a multi-step process, and the entire process can span decades from initial concepts to decommissioning. ISA101 takes a lifecycle approach to effective HMI management and seeks to identify, define and address different needs across this time span. Figure 2 shows the steps as the standard organizes them.

Figure 2: Creating an effective HMI strategy goes far beyond snazzy screen graphics. The process of looking for ways to improve performance should never stop.

The main HMI lifecycle stages are Design, Implement and Operate. HMI Philosophy, Style Guide and Toolkits provide a set of consistent documentation for HMI management at the site or company wide. Continuous work processes—including MOC, Audit and Validation—can occur throughout the lifecycle.

ISA101 stresses human factor aspects of engineering and ergonomics in HMI development. Human factors include considerations of sensory and cognitive limits of operators when using the HMIs. Human factor-based displays provide situation awareness for the operator in a consistent manner, without distractions. If operators are less stressed and more focused when performing their tasks, they can work more efficiently with fewer errors.

ISA101 has been developed by a committee of experienced users, system integrators and automation suppliers over many years through many review and comment cycles. It provides recommendations and best practices for effective HMI systems which will be easy to operate and maintain in the long run.   

End users, automation suppliers and system integrators have embraced a group of HMI management tools and processes proposed by ISA101. Some sites will want to implement these through internal efforts, and others may want to engage the supplier or integrator.

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