Designing Control Rooms for Humans

When the Science of Ergonomics Enters the Control Room Safety and Efficiency Soon Follow

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Today's work environment has been revolutionized by PC's and PC workstations. The most dramatic changes have taken place in industrial control centers and control rooms. Control rooms, traditionally used for sharing instrumentation information, have evolved from large panels with support instrumentation in adjacent rooms, to modern control buildings that support people interfacing with computers. This change has impacted the way these buildings are designed and has introduced a new discipline called Human Factor Engineering (HFE).

Listen to: Podcast: The Control Room of the Future

In the past, the only human factor influencing control room design was the grouping of  instruments to support pattern recognition. This scheme allowed operators and engineers to maintain the "big picture" of the process under control. Sometimes the designers followed another simple human factors guideline that dictated a minimum and maximum height for instrument mounting, somewhere between 40—70 in. from the floor, so the typical operator could read all the instruments without having to stoop or stretch.

Unfortunately for processors, the vast majority of the control panels were not designed by human factors engineers, but by instrumentation engineers, unfamiliar with the finer points of ergonomics.

Instrument engineer-designed panels do have some redeeming features—many of which readers should be familiar with, including the ability to recognize patterns and quickly identify process changes. Similarly well-known to veteran processors was the ability to identify trends by pen marks in the folds of plotter paper, and the enforcement of a low number of alarms due to cost and space limitations.

Unfortunately, most did not recognize these positive aspects of traditional control interfaces during the transition from analog instrument-based control to digital (computer) control. Much of this was lost during the transition to first and second-generation Distributed Control System (DCS) control room designs. During that period, some processors also lost the ability to effectively share control and process information among operators (both field and control room), supervisors, engineers and managers.

The House Instruments Built

The building that housed the control room was designed with the instrumentation in mind, and then, later, DCS equipment. The primary and secondary users of the building were often an afterthought and had to live within the constraints of the design. Often kitchens, and even restrooms, were not originally planned, so space for operator comfort was adapted where available.

First generation DCS-based control room plans were adapted from buildings designed to accommodate the 50-year old control panel. The result? Long, thin, crowded control rooms with poor console adjacencies and poor traffic patterns. Typically, these control rooms were located in the field, with the redundant instrument panel in the background (Figure 1).

Second-generation control rooms were often characterized by their independence from field instrumentation; as witnessed by the appearance of the first consolidated control rooms. The advent of electronics permitted greater distances between the field instruments and the previous-generation control rooms, but the instrument engineer still dominated their design.

Operating consoles were usually off-the-shelf designs supplied by the same instrumentation vendors who produced DCS equipment. This technology was big, bulky, noisy, and did not adhere to modern ergonomic design considerations. Hence, support equipment such as hardwired alarms, phones, public address systems, and PC's were difficult to incorporate into the layout of the room. All of these things were just bad add-on accessories.

It was during this stage of control room design evolution that industry trade associations and regulators began to realize that the layout of the room, the control interfaces it encompasses and the building it's housed in, can have a great impact on an operator's performance.

Read Also: Control Center Design Can Boost Operator Performance

When we look at human reliability we discover that even on a good day, seemingly innocuous elements of the work environment can stress the operator. Common maladies such as headaches, eye strain and sleep-related problems often have root causes traceable to such factors as glare from poorly designed lighting systems; poor temperature and humidity control; bad air quality; and poorly maintained buildings.

Adding to the woes of the operator are poor workspace design, an environment aggravated by uncomfortable consoles, keyboards, chairs and noise. Often excessive, noise generated by console fans, panel alarms, radio/PA speaker interference and constant radio communications all contribute to poor ambient conditions.

These environmental factors are exacerbated by a poorly implemented DCSs. Many systems are plagued with issues that make it very difficult for an operator to detect, diagnose and respond to in an abnormal situation. These issues commonly include excessive and undisciplined use of alarms that obscure more critical alarms; poor user interfaces that make it difficult to recognize changes and perceive important deviations; and poor navigation, forcing operators to spend precious time flipping through displays to find critical data.

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