How to Improve Plant Operations through Better HMI


A better-customised HMI system can help to have a good application of engineering best practices throughout the design, panel layout, production, testing, and quality assurance processes. Five areas are primarily in the successful design of a good HMI screen system. They are:

  • Situation Awareness

  • Using Color Effectively

  • Interpreting the data

  • Depicting Device State

  • HMI Display Organization

Situation Awareness:

Situation awareness is specific for each function. The designer or engineer should know about the process. The situation can easily be understood from:

  • P&ID representations

  • From trending data

  • The plant operator can provide data for HMI design.

Using trending an operator can see where the process is heading. The operator can then be proactive and recognize impending problems, rather than being reactive and responding to alarms and problems after the fact.

Using Color Effectively:

Use different colours to represent activities. Seven to 10 % of males are Red-Green colour blind. Also, avoid using color alone to express information. Only attract attention to an area of the display if there is an Abnormal Situation.

Interpreting the data are:

  • Is this process healthy?

  • How long does it take you to scan and interpret the information?

  • What should the numbers be?

  • Are the numbers actually meaningful?

  • How much training would you require before you could interpret the numbers?

Upper and lower limit of these values should show:

  • How long does it take you to scan and compare these numbers?

  • How much longer does it take you to calculate by how much they are within range?

  • This is data that requires examining and processing (Level 1 SA)

  • Data should be presented that supports comprehension (Level 2 SA)

Depicting Device State:

  • Use colours only to represent the abnormal situation. Do not use red for stopped or closed and green for running or opened.

  • Consider using a visually different shape within the object to represent running/ open.

  • Use status words that describe the device state that is running and stopped.

  • The device should not be too slow (ASM states 3 seconds) and the operator may think the command wasn’t executed.

  • And if Too fast (ASM states 0.5 seconds) and the operator may miss the change.

HMI Display Organization:

  • Provide information that helps the operator retain the data in short-term memory.

  • Group related information together so that it can be processed as one chunk

  • The average short-term memory can hold seven items plus or minus 2, so group data together to facilitate this fact.

  • If you have a vessel that has three specific values related to it, then show it inside the ship, this allows the operator to see them as a piece of data instead of placing them outside the ship where the operator will see them as three individual pieces of data.