The Pipeline Hazards and Materials Safety Administration (PHMSA) regularly audits pipeline companies to see if they comply with API 1165 as it’s important not only for effectively monitoring and controlling your systems but also for safety reasons.

Still, what is API 1165?

Well, this is part two of our blog series of everything you need to know about API 1165. In part 1, What Is API 1165 and Why Is It Important for My SCADA System?, you learned what is API 1165 plus its advantages and disadvantages. While in this post, we’ll explore the API 1165 recommended practices in more detail and their connection to Human Factors Engineering (HFE).

Gestalt Principles to Organize Information on Screens

As API 1165 is a recommended practice for HMI (human-machine interface) design, it’s important to understand the Gestalt principles. These principles revolve around how the human brain organizes designs with multiple elements and consequently should be considered by designers in organizing and presenting graphical information on a screen. By taking these principles into account, users can find the information they need with less effort, which is an important factor in environments where timely decisions are crucial.


Here are the Gestalt principles to present and organize information on a screen:

A figure representing the Gestalt principle of Similarity


This principle states the human brain groups similar elements together despite their proximity to each other. We group these elements together when they share color, shape, or size.

The Gestalt Principle of Continuity


The human brain perceives elements organized on a line or pattern to be related to each other while elements that don’t follow the line or continuity don’t belong.

The Gestalt Principle of Good Figure

Symmetry or good figure

When you see a set of complex objects together, your brain tries to shape these objects in the simplest way possible. For example, in the above image, the example of good figure shows the logo of the Olympic games.

A figure representing the Gestalt principle of Closure


This principle states that if you see an image with missing parts, your brain tries to fill in the spaces to create a whole image.

A figure representing the Gestalt principle of Proximity


This refers to how close elements are to each other. The closer elements are to each other, the stronger the relationship. The proximity principle influences the human brain so much that even if objects share size, color, or shape, their relationship isn’t as strong as when they’re close.

A figure representing the Gestalt principle of Common Region

Common region

If elements are in the same closed region, the human brain perceives that they’re grouped together.

What Principles Underly API 1165?

Now that the basics of visual elements are clear, you’re ready to learn the set of rules that makes API 1165 so important for HMI screens.

Here are the key elements to designing a screen with a clean and user-friendly interface.

Consistency and Coding

Consistency and coding refer to HMI screens looking and working the same everywhere in your facility. When your HMI has a consistent interface design, the human-machine interaction with your operators becomes easier.

Here’s a breakdown of how to follow consistency and coding for screens:

  • Screen should follow consistency throughout the system: Meaning the placement of objects, shapes, color, or presentation of dynamic and static objects should be consistent across the whole system, not just one screen.
  • Screen should follow consistency in text: Screens should share the same font style, size, and shading.
  • Screens should incorporate consistent coding: This involves many elements like the colors of normal or abnormal conditions, the size and shape of symbols (pumps, valves, tanks, etc.), and acronyms or abbreviations. All of these elements should be the same across the system.

Consistency and coding ensure that even if you change your operators to different stations, they would still know exactly how to operate and understand your HMIs.

Screen Layout and Navigation

Screen layout and navigation ensure that the HMI screen is accessible and usable. This helps operators get the information they need as quickly as possible.

Here’s how to have a user-friendly layout and navigation screen:

  • Screens should have a reasonable call-up time and refresh date: This refers to how much time it takes for a new screen to open or for data to refresh. A response time between two to five seconds is a substantial factor in the user experience. If your screen takes too long to open, operators may start to lose focus and it may be difficult for them to resume their task.
  • Screens should NOT contain unnecessary data: Unnecessary data is referred to as clutter. This includes elements with no data points and locally operated equipment.
  • Screens should follow a hierarchy: There should be multiple levels or types of operational screens. You can have general information about a facility or more detailed information about a pump.
  • Navigation should be intuitive: To achieve this, provide multiple ways of accessing data (menus, button bars, hot spots, or navigation buttons). Also, menus should be logical to operators.

Objects, Colors, and Text

The objects, colors, and text of an interface have the potential of catching your attention and alert you about the status of the system.

Here’s how objects, colors, and text can give a meaningful message to your operators:

  • Screens should incorporate color: You should keep a minimum of 11 colors and be consistent about the meaning of every single one of them. But don’t use colors excessively on a screen as it can decrease their effectiveness for control.
  • Screens should incorporate symbols: Symbols add more comprehension to a screen than text. Create a standard and consistent set of symbols that are simple for your operators to understand and avoid distorted images. Also, keep the animations to a minimum as they can be distracting.
  • Text and format should be consistent: Font, size, and formatting should be consistent across screens. Some general recommendations include using Arial 9 for text and a bold larger font size for the main headers on screens.
  • Messages should be relevant: Pop-up messages should show up at setpoints. In these situations, your operator has to give feedback to the system (“yes” or “no” buttons), so keep messages short and simple.

Object Dynamics and Data Attributes

Object dynamics and data attributes relate to how operators can identify changes in the system.

Here’s how object dynamics and data attributes help your operators stay informed about the status of your system:

  • Object characteristics should change with related data points: For example, if a valve is open, it should have a different color than closed valves. Or if a tank is full, it should have a color that distinguishes it from empty tanks. Characteristics that could change include shape, size, color, and text.
  • Data attributes and the state of data points should be easy to tell: Your operators should be able to differentiate alarms by severity. This indicates how serious an issue is and if it needs immediate action.

Control Techniques and Administration

Control techniques and administration elements are important to guarantee that your processes run smoothly. If they don’t, you can take corrective actions from your HMI screen.

Here are the factors you should consider in having effective control and administration of your systems with HMI screens:

  • Control points: For starters, control points should have a reasonable size, so they can be accurately selected. Also, operators should be able to differentiate controllable points from non-controllable points. Best practices for this are to make sure control points are highlighted, have a border around them, and for the mouse pointer to change when hovering over them.
  • Command execution: The screen should require two or more commands before a new value or instruction is set. Operators must ensure the value they want to enter is correct, reducing human error.
  • Error management: When there’s an error, a message should pop up. Examples of errors include incorrect and out of range values. The message should allow operators to cancel the command.
  • Administration: All your screens should follow a Management of Change (MOC) process. You should have documentation of all the changes made to your SCADA screens and provide training on these changes to your personnel.

Follow HMI Screen Best Practices

Implementing API 1165 makes a lot of sense when you understand why it helps promote the success of your operators. But even when you know all the rules, taking the first step towards implementation is difficult when analysis paralysis gets in the way.

If you want to learn the steps to effectively implement API 1165 RP in your SCADA system displays, go to part 3, How to implement API 1165 RP in your SCADA system, where we share a useful framework.

In the meantime, if you’re considering anything from migrating to a new SCADA system, implementing API 1165, or have a few specific questions, we’re here to help. Contact us at or fill out the form below.

Have API 1165 Questions?

If there’s a specific API 1165 project or question you’d like to discuss, contact us today.