Human Centered Design for the Operating Plant-Part 2

by | Sep 6, 2012 | Asset Management | 0 comments

In our continuing series on why and how technologies developed with a human centered design (HCD) approach, Emerson’s Tom Wallace looks more closely at guided configuration and setup as well as leveraging productivity across different device types and protocols.

Traditionally, different devices have different configuration and setup parameters and processes. Since configuration and setup is generally done once for a device, the variety of device types, configuration options, and configuration processes, provide high potential for human error. Incorrectly configured devices can appear to be operating correctly, but be giving incorrect information.

This incorrect device setup can result in abnormal process conditions ranging from increased production costs to compromised safety. The obviously incorrect process variable is actually the easiest to correct since it is the easiest to detect. Process information that looks approximately correct but is not is more problematic.

Guided configuration and setup eliminates many errors by providing a step-by-step process where success in the current step is required to go to the next step. This step-by-step process should do two things. The first is to make sure the proper steps are done in the proper order, and that no steps are accidentally skipped.

The second is that steps that require human action or decision-making are guided in order to minimize human error. Guiding information should include a clear description of what the step does, and ranges or types of entries that are appropriate.

The following pictorial example will show how human centered design addresses different human error types. A zero trim on a Rosemount 3051S pressure transmitter with Foundation fieldbus protocol will show the points.

All calibration options as well as information used during calibration are on this single screen. A zero trim will be performed to show how HCD is used and how it eliminates human error.

Steps that should be done prior to starting the task are shown. Here the user is reminded to take the loop out of automatic control so a potential process upset is eliminated.

The user is given information verifying the task to be done and the effect of the task. The user can terminate an incorrect task before the device is changed.

Foundation fieldbus has blocks with modes. One of the most common FF errors is placing unnecessary blocks out of service, or leaving blocks out of service. By automatically managing modes these errors are eliminated.

The sensor can be calibrated in a number of ways. A dropdown menu containing all the appropriate choices for the specific transmitter type helps prevent the wrong option from being selected.

The user is advised to perform external steps at the specific point in the task where the step is needed. This eliminates errors caused by steps being omitted or performed at the wrong time.

If a step is not done correctly the error could prevent a good outcome. Here the user didn’t properly zero the transmitter so the pressure is too high for a zero trim. The error condition is automatically detected, the step is aborted, and the user informed.

In steps not shown the error is corrected, the task continued and completed from the point where is previously failed. All blocks are returned to auto mode automatically. By eliminating the need to repeat steps time is saved and potential errors eliminated.

Leverage productivity across different device types. The people who deal with field devices deal with them one at a time, but they may deal with a hundred different device types in a facility. Human centered design principles must be applied in consistent ways across the entire range of devices used in the plant in order to derive maximum benefit from HCD.

In other words, every different device type, and every different device revision should have a human – technology interface that functions and is used in as similar a way as possible. This allows the user to leverage what is learned in dealing with one device type to other device types or device revisions. The key benefit is that human error is substantially reduced or eliminated when dealing with new device types or device revisions. In addition, the risk of loss of experienced resources is at least partly mitigated. The net effect is more predictable success with more variable levels of personnel experience.

Leverage productivity across protocols. Devices communicate with automation systems using a variety of communications protocols. In some cases, differences in communications protocol will drive substantial changes in device capability and how users must interact with the devices for many of the tasks listed above.

For example, in many communications protocols, device functionality is determined and accessible from a single, monolithic structure. When the device is accessed, all functionality is accessible. Other communications protocols subdivide device functionality into multiple software structures that are typically addressed individually. These are often referred to as blocks. Some functions may require activities across multiple blocks in order to complete successfully. As much as possible, human centered design should automatically handle navigation and coordination across multiple blocks in a way that is transparent to the user. This will again reduce the learning curve, reduce human error, and help the user achieve predictable success.

We’ll conclude this series with a closer look at ways of estimating the cost of human error in projects.

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The opinions expressed here are the personal opinions of the authors. Content published here is not read or approved by Emerson before it is posted and does not necessarily represent the views and opinions of Emerson.

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