152: Control/Display/Alarm Integration/Arrangement Issue
Definition/Typical Issues
Was there a failure to arrange related controls and displays close to each other? Was a display arranged so that it was obscured during manipulation of the related control? Were control/display relationships unclear to the user? Was the response of a display to control movements inconsistent, unpredictable, or incompatible with populational stereotypes or with the user's expectations? Was there difficulty with multiple displays being affected by a single control? Was there a failure to develop a clear relationship between the controls and the displays? Was there a failure to locate controls near the displays they affected? Is it difficult for the operator to read the display while adjusting the control? Are control/display arrangements inconsistent with populational stereotypes?
Did differences in controls, displays, or alarms between different processes or areas contribute to the event?
Were similar controls indistinguishable from one another?
Examples
Example 1
- The temperature control had numbers on the dial that ranged from 0 to 100. The temperature indication ranged from 0 to 100°C. However, setting the dial to 75 did not result in a temperature of 75°C.
Example 2
- The operator incorrectly started pump D instead of pump B. The pump controls are all identical and arranged in reverse alphabetical order from left to right like this: E D C B A. This violates an expectation that controls will be in alphabetical order from left to right.
Example 3
- The controls for three pumps were arranged differently than the pumps themselves. As a result, the wrong pump was often started.
Example 4
- There were three sections of lights in the room (front, middle, and back). However, the light switches were not in the same arrangement. The light switch for the back lights was located closest to the front of the room.
Example 5
- Two computer systems, located side-by-side in the facility, were programmed using different color schemes. On the first system, the color red indicated an open valve and green indicated a closed valve. On the second system, green indicated normal and red indicated an abnormal condition. Because of the inconsistency in color-coding between the two systems, an operator who normally worked on the first system allowed a tank to overflow when he was temporarily assigned to the second system. His mindset was that green indicated lack of flow.
Example 6
- An operator inadvertently started the wrong pump. The cooling water pumps are arranged alphabetically (A-D) from left to right. However, the control panel has the controls arranged as follows:
A C
B D
Example 7
- In one processing plant, two units performed the same function. Each unit had a separate control room. The control rooms were identical except that they were mirror images of one another. An operator, normally assigned to the first unit, caused a serious process upset when he was assigned to work in the second unit.
Typical Recommendations
- Configure the control panel so that it is easy to locate related controls and displays.
- Locate displays so that the related control can be manipulated while watching the display.
- Ensure that the control and its displays are directly related to one another (i.e., if pressure is displayed, the corresponding control should directly affect pressure as opposed to another parameter, like temperature).
- Ensure that each display responds consistently with populational stereotypes when the control is manipulated (e.g., the display shows a quantitative increase when a control is turned clockwise).
- Ensure that one display is provided for every control.
- Ensure that there is clear mapping between the controls and displays.
- Ensure that color codes consistently have the same meaning on all control boards in the facility.
- Ensure that identical units have identical control configurations.
- Label components in sequential order: ABC not ACB.
- Ensure that similar controls have distinguishable features.
Cross-References
| Version 10 Element(s) | |
|---|---|
| Node ID | Node Name |
| 143 | Control/Display Integration/Arrangement LTA |
| 145 | Conflicting Layout |
| Maritime Element(s) | |
|---|---|
| Node ID | Node Name |
| 167 | Control/Display/Alarm Integration/Arrangement Issue |